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• gunicorn + django + nginx unix://socket failed (11: Resource temporarily unavailable)

  - by user1068118

  Running very high volume traffic on these servers configured with django, gunicorn, supervisor and nginx. But a lot of times I tend to see 502 errors. So I checked the nginx logs to see what error and this is what is recorded: [error] 2388#0: *208027 connect() to unix:/tmp/gunicorn-ourapp.socket failed (11: Resource temporarily unavailable) while connecting to upstream Can anyone help debug what might be causing this to happen? This is our nginx configuration: sendfile on; tcp_nopush on; tcp_nodelay off; listen 80 default_server; server_name imp.ourapp.com; access_log /mnt/ebs/nginx-log/ourapp-access.log; error_log /mnt/ebs/nginx-log/ourapp-error.log; charset utf-8; keepalive_timeout 60; client_max_body_size 8m; gzip_types text/plain text/xml text/css application/javascript application/x-javascript application/json; location / { proxy_pass http://unix:/tmp/gunicorn-ourapp.socket; proxy_pass_request_headers on; proxy_read_timeout 600s; proxy_connect_timeout 600s; proxy_redirect http://localhost/ http://imp.ourapp.com/; #proxy_set_header Host $host; #proxy_set_header X-Real-IP $remote_addr; #proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; #proxy_set_header X-Forwarded-Proto $my_scheme; #proxy_set_header X-Forwarded-Ssl $my_ssl; } We have configure Django to run in Gunicorn as a generic WSGI application. Supervisord is used to launch the gunicorn workers: home/user/virtenv/bin/python2.7 /home/user/virtenv/bin/gunicorn --config /home/user/shared/etc/gunicorn.conf.py daggr.wsgi:application This is what the gunicorn.conf.py looks like: import multiprocessing bind = 'unix:/tmp/gunicorn-ourapp.socket' workers = multiprocessing.cpu_count() * 3 + 1 timeout = 600 graceful_timeout = 40 Does anyone know where I can start digging to see what might be causing the problem? This is what my ulimit -a output looks like on the server: core file size (blocks, -c) 0 data seg size (kbytes, -d) unlimited scheduling priority (-e) 0 file size (blocks, -f) unlimited pending signals (-i) 59481 max locked memory (kbytes, -l) 64 max memory size (kbytes, -m) unlimited open files (-n) 50000 pipe size (512 bytes, -p) 8 POSIX message queues (bytes, -q) 819200 real-time priority (-r) 0 stack size (kbytes, -s) 8192 cpu time (seconds, -t) unlimited max user processes (-u) 1024 virtual memory (kbytes, -v) unlimited file locks (-x) unlimited

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• Why is my new Phenom II 965 BE not significantly faster than my old Athlon 64 X2 4600+?

  - by Software Monkey

  I recently rebuilt my 5 year old computer. I upgraded all core components, in particular from an Athlon 64 X2 4600+ at 2.4 GHz with DDR2 800 to a Phenom II 965 BE (quad core) at 3.6 GHz with DDR3 1333 (actually 1600, but testing consistently detected memory errors at 1600). The motherboard is also much newer and better. The HDD's (x3), DVD writer and card reader are the same. The BIOS memory config is auto-everything except the base timing which I overrode to 1T instead of 2T. The BIOS CPU multiplier is slightly over-clocked to 3.6 GHz from the stock 3.4 GHz. I noticed compiling Java is slower than I expected. As it happens I have some (single-threaded) Java pattern-matching code which is CPU and memory bound and for which I have performance numbers recorded on a number of hardware platforms, including my old system. So I did a test run on the new equipment and was stunned to find that the numbers are only slightly better than my old system, about 25%. The data set it is operating on is a 148,975 character array, which should easily fit in caches, but in any event the new CPU has larger caches all around. The system was, of course, otherwise idle for the test and the test run is a timed 10 seconds to eliminate scheduling anomalies. A long while ago, when I upgraded only memory from DD2 667 to DDR2 800 there was no change in performance of this test, which subjectively supports that the test cycle does not need to (significantly) access main memory, but yes it is creating and garbage collecting a large number of objects in the process of this test (low millions of matches are found for the pattern set). I am about 99.999% certain the code hasn't changed since I last ran it on 2009-03-17 - but I can't easily retest the old hardware, because it is currently in pieces on my work-bench waiting to be built into a new computer for my kids. Note that Windows (XP) reports a CPU speed of 795 MHz unless I have some thing running. With stuff running it seems to jump all over the place each time I use ALT-Pause to display the system properties, everywhere from 795 MHz to 3.4 Ghz. So why might my shiny new hardware under-performing so badly? EDIT: The old memory was Mushkin DDR2 800 with timings set for auto which should have been 5-5-5-12. The new memory is Corsair DDR3 1600, running at 1333 with timings also auto which are 9-9-9-21. In both cases they are a paired set of dual channel DIMMs. I was waiting to ensure my system was stable before tweaking with memory timings.

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• Linux per-process resource limits - a deep Red Hat Mystery

  - by BobBanana

  I have my own multithreaded C program which scales in speed smoothly with the number of CPU cores.. I can run it with 1, 2, 3, etc threads and get linear speedup.. up to about 5.5x speed on a 6-core CPU on a Ubuntu Linux box. I had an opportunity to run the program on a very high end Sunfire x4450 with 4 quad-core Xeon processors, running Red Hat Enterprise Linux. I was eagerly anticipating seeing how fast the 16 cores could run my program with 16 threads.. But it runs at the same speed as just TWO threads! Much hair-pulling and debugging later, I see that my program really is creating all the threads, they really are running simultaneously, but the threads themselves are slower than they should be. 2 threads runs about 1.7x faster than 1, but 3, 4, 8, 10, 16 threads all run at just net 1.9x! I can see all the threads are running (not stalled or sleeping), they're just slow. To check that the HARDWARE wasn't at fault, I ran SIXTEEN copies of my program independently, simultaneously. They all ran at full speed. There really are 16 cores and they really do run at full speed and there really is enough RAM (in fact this machine has 64GB, and I only use 1GB per process). So, my question is if there's some OPERATING SYSTEM explanation, perhaps some per-process resource limit which automatically scales back thread scheduling to keep one process from hogging the machine. Clues are: My program does not access the disk or network. It's CPU limited. Its speed scales linearly on a single CPU box in Ubuntu Linux with a hexacore i7 for 1-6 threads. 6 threads is effectively 6x speedup. My program never runs faster than 2x speedup on this 16 core Sunfire Xeon box, for any number of threads from 2-16. Running 16 copies of my program single threaded runs perfectly, all 16 running at once at full speed. top shows 1600% of CPUs allocated. /proc/cpuinfo shows all 16 cores running at full 2.9GHz speed (not low frequency idle speed of 1.6GHz) There's 48GB of RAM free, it is not swapping. What's happening? Is there some process CPU limit policy? How could I measure it if so? What else could explain this behavior? Thanks for your ideas to solve this, the Great Xeon Slowdown Mystery of 2010!

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• Windows 7 & Virtual PC and Internet (gateway) problems on host PC

  - by Mufasa

  I upgraded to Windows 7 on a PC that is a few years old. The CPU was one revision away from having Hyper-V on it. So, I had to install Microsoft Virtual PC 2007 (v6.0.156.0) to run full XP instances instead of the seamless XP virtualization that is advertised so much. That's fine though; the 'older' version is useful since I use it to run different versions of the whole XP/IE stack for testing. (I'm a web developer.) ...And for the one 16-bit application we still use at the office for scheduling. * sigh * The virtual instances work fine, including networking. My issue is that after a reboot or coming out of sleep mode, my host Windows 7 won't connect to the Internet. It will connect to the local network fine. If I disable the "Virtual Machine Network Services" item (I'll call "VMNS" from here on) in the LAN Connection properties box, it starts working. But than the Virtual PC instances lose their network connectivity. If I re-enable VMNS again in the same instance, everything works (Internet on host and in the virtualized instances). But after the next reboot/sleep cycle this starts over. The route table gave me a clue though. When doing a cycle w/ VMNS enabled: IPv4 Route Table =========================================================================== Active Routes: Network Destination Netmask Gateway Interface Metric 0.0.0.0 0.0.0.0 On-link 10.0.3.51 20 0.0.0.0 0.0.0.0 10.0.10.10 10.0.3.51 276 ... After VMNS is disabled, the first route goes away. I assume that is for VMNS to intercept virtualized instance's network connections and forward them correctly? Just a guess though. More info: I checked my Firewall settings and Services (because I'm sort of a control nazi and turn off a lot) but couldn't find anything that made sense and if turned on changed anything. So it might be something there I'm missing, but I don't know what. My current hacked solution: So, I figured I'd mess with the routes myself to see if that helped, it did. If I run a route delete 0.0.0.0 on the universal (0.0.0.0) gateway routes, and add back in just the 2nd line with route add 0.0.0.0 mask 0.0.0.0 10.0.10.10--the one that points to my actual gateway (10.0.10.10)--then I don't have to mess with the disable/enable cycle of VMNS, and everything works. Running those two commands is faster then bringing up connection options and disabling and re-enabling VMNS, but I still don't want to have use that hack script every boot either. (Oh, and I also tried messing with hard-coding TCP/IP settings in my network adapter, including setting high metrics, etc., but that didn't help either.) Any suggestions on the right way to fix this?

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• Parallelism in .NET – Part 16, Creating Tasks via a TaskFactory

  - by Reed

  The Task class in the Task Parallel Library supplies a large set of features.  However, when creating the task, and assigning it to a TaskScheduler, and starting the Task, there are quite a few steps involved.  This gets even more cumbersome when multiple tasks are involved.  Each task must be constructed, duplicating any options required, then started individually, potentially on a specific scheduler.  At first glance, this makes the new Task class seem like more work than ThreadPool.QueueUserWorkItem in .NET 3.5. In order to simplify this process, and make Tasks simple to use in simple cases, without sacrificing their power and flexibility, the Task Parallel Library added a new class: TaskFactory. The TaskFactory class is intended to “Provide support for creating and scheduling Task objects.”  Its entire purpose is to simplify development when working with Task instances.  The Task class provides access to the default TaskFactory via the Task.Factory static property.  By default, TaskFactory uses the default TaskScheduler to schedule tasks on a ThreadPool thread.  By using Task.Factory, we can automatically create and start a task in a single “fire and forget” manner, similar to how we did with ThreadPool.QueueUserWorkItem: Task.Factory.StartNew(() => this.ExecuteBackgroundWork(myData) ); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This provides us with the same level of simplicity we had with ThreadPool.QueueUserWorkItem, but even more power.  For example, we can now easily wait on the task: // Start our task on a background thread var task = Task.Factory.StartNew(() => this.ExecuteBackgroundWork(myData) ); // Do other work on the main thread, // while the task above executes in the background this.ExecuteWorkSynchronously(); // Wait for the background task to finish task.Wait(); TaskFactory simplifies creation and startup of simple background tasks dramatically. In addition to using the default TaskFactory, it’s often useful to construct a custom TaskFactory.  The TaskFactory class includes an entire set of constructors which allow you to specify the default configuration for every Task instance created by that factory.  This is particularly useful when using a custom TaskScheduler.  For example, look at the sample code for starting a task on the UI thread in Part 15: // Given the following, constructed on the UI thread // TaskScheduler uiScheduler = TaskScheduler.FromCurrentSynchronizationContext(); // When inside a background task, we can do string status = GetUpdatedStatus(); (new Task(() => { statusLabel.Text = status; })) .Start(uiScheduler); This is actually quite a bit more complicated than necessary.  When we create the uiScheduler instance, we can use that to construct a TaskFactory that will automatically schedule tasks on the UI thread.  To do that, we’d create the following on our main thread, prior to constructing our background tasks: // Construct a task scheduler from the current SynchronizationContext (UI thread) var uiScheduler = TaskScheduler.FromCurrentSynchronizationContext(); // Construct a new TaskFactory using our UI scheduler var uiTaskFactory = new TaskFactory(uiScheduler); If we do this, when we’re on a background thread, we can use this new TaskFactory to marshal a Task back onto the UI thread.  Our previous code simplifies to: // When inside a background task, we can do string status = GetUpdatedStatus(); // Update our UI uiTaskFactory.StartNew( () => statusLabel.Text = status); Notice how much simpler this becomes!  By taking advantage of the convenience provided by a custom TaskFactory, we can now marshal to set data on the UI thread in a single, clear line of code!

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• Backup options in SharePoint 2007

  - by sreejukg

  It is very important to make sure the server farm backup is taking properly, making sure that in case of any disaster, the administrator has the latest backup that can be used to restore. This articles addresses some of the options available for backup/restore in SharePoint 2007 Backup There are two options that can be utilized to take backup of SharePoint sites. Using SharePoint Central Administration website Using SharePoint central administration website, you can do backup/restore from user interface. Using central administration website you can back up the following · Server farm · Web application · Content databases Follow these steps to take backup of the server farm using central administration 1. Open Central administration website 2. Navigate to Operations -> Backup and Restore -> Perform a backup 3. Here you will have options to choose the item to back up. Select Farm (the top most item in the list) 4. Once you select the items to backup, click on “Continue to backup options” 5. Select “Full” as type of backup. 6. In the backup file location, enter the path where you need to store the backup. The path should be according to the UNC, for e.g. for c drive you may use \\server\c$\mybackupFolder 7. Click ok 8. Now you will be redirected to Backup and Restore Status page. This page shows the progress for the backup operation. You can use the refresh button to update the status of backup(this page will automatically refresh in every 30 seconds). Once completed you can find the files in the specified folder. Using STSADM website SharePoint comes with a STSADM command line tool. STSADM provides lot of administrative operations that can be performed on SharePoint 2007 sites. You can find STSADM command from the following location C:\Program Files\Common Files\Microsoft shared\web server extensions\12\bin (You may change the drive letter according to your installation) STSADM provides a method for performing the Office SharePoint Server 2007 administration tasks at the command line or by using batch files or scripts. STSADM provides access to operations not available by using the Central Administration site The general syntax for STSADM is as follows STSADM -operation Operation Name –parameter1 value1 –parameter2 value2 ……….. Using STSADM you can back up the following · Server farm · Web application · Content databases To perform any STSADM, operation you need to be a member of administrators group. Follow these steps to take backup of SharePoint server farm using STSADM tool. Note: make sure you are logged in to the computer where central administration website is installed. 1. Open the Command prompt (You should run command prompt with administrator privileges) 2. Change the working directory to C:\Program Files\Common Files\Microsoft shared\web server extensions\12\bin 3. Enter the command, then press enter Stsadm –o backup -directory <UNC path> -backupmethod full 4. You will get success / failure message once the command finishes. How to schedule the backup There is no option to schedule a backup using central administration site. Also there is no operation provided by STSADM to automate the backup. The farm administrators need to take backup in regular intervals. To achieve this, you can write a batch file that includes STSADM command to take full backup of the server. This batch file can be scheduled using windows task scheduler to execute in certain intervals. Sample of the batch file 1. Open notepad(or any other text editor) 2. Enter the following commands @echo off echo =============================================================== echo Back up the farm to <C:\backup> echo =============================================================== cd %COMMONPROGRAMFILES%\Microsoft Shared\web server extensions\12\BIN @echo off stsadm.exe -o backup -directory "<\backup>" -backupmethod full echo completed 3. Save the file with .bat extension You can schedule this batch file as you require. Other Options Using STSADM tool, you will be able to take backup for individual site collection. The syntax for this is stsadm -o backup -url <URL name for site collection> -filename <file name> [-overwrite] The explanations for the parameters are as follows. -url The url of the site collection you need to backup -filename The name of the backup file. E.g. c:\backup.bak -overwrite optional. Indicates if the filename specified exists, whether to overwrite or not. If you are creating the batch file for scheduling the backup for a site collection, you may need to specify the backup filename automatically created. It is an option that you can generate the filename with date so that you can keep backup for each day. e.g. The following commands can be utilized create a site collection backup. @echo off echo =============================================================== echo Back up the farm to <C:\backup> echo =============================================================== echo =============================================================== echo getting todays date to a variable echo =============================================================== @For /F "tokens=1,2,3 delims=/ " %%A in (‘Date /t’) do @( Set Day=%%A Set Month=%%B Set Year=%%C Set todayDate=%%C%%B%%A ) cd %COMMONPROGRAMFILES%\Microsoft Shared\web server extensions\12\BIN @echo off stsadm -o backup -url <sitecollection url> -filename \\ServerName\ShareName\Backup_%todayDate%.bak -overwrite echo completed To read more about backup STSADM operation, read this http://technet.microsoft.com/en-us/library/cc263441.aspx

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• On Contract Employment

  - by kerry

  I am going to post about something I don’t post about a lot, the business side of development.  Scott at the antipimp does a good job of explaining how contracts work from a business perspective.  I am going to give a view from the ground. First, a little background on myself.  I have recently taken a 6 month contract after about 8 years of fulltime employment.  I have 2 kids, and a stay at home wife.  I took this contract opportunity because I wanted to try it on for size.  I have always wondered whether I would like doing contracts over fulltime employment.  So, in keeping with the theme of this blog I will write this down now so that I may reference it later. ALL jobs are temporary! Right now you may not realize it, most people simply ignore it, but EVERY job is temporary.  Everyone should be planning for life after the money stops coming in.  Sadly, most people do not.  Contracting pushes this issue to the forefront, making you deal with it.  After a month on a contract, I am happy to say that I am saving more than I ever saved in a fulltime position.  Hopefully, I will be ready in case of an extended window of unemployment between contracts. Networking I find it extremely gratifying getting to know people.  It is especially beneficial when moving to a new city.  What better way to go out and meet people in your field than to work a few contracts?  6 months of working beside someone and you get to know them pretty well.  This is one of my favorite aspects. Technical Agility Moving between IS shops takes (or molds you into) a flexible person.  You have to be able to go in and hit the ground running.  This means you need to be able to sit down and start work on a large codebase working in a language that you may or may not have that much experience in.  It is also an excellent way to learn new languages and broaden your technical skill set.  I took my current position to learn Ruby.  A month ago, I had only used it in passing, but now I am using it every day.  It’s a tragedy in this field when people start coding for the joy and love of coding, then become deeply entrenched in their companies methods and technologies that it becomes a just a job. Less Stress I am not talking about the kind of stress you get from a jackass boss.  I am talking about the kind of stress I (or others) experience about planning and future proofing your code.  Not saying I stay up at night worrying whether we have done it right, if that code I wrote today is going to bite me later, but it still creeps around in the dark recesses of my mind.  Careful though, I am not suggesting you write sloppy code; just defer any large architectural or design decisions to the ‘code owners’. Flexible Scheduling It makes me very happy to be able to cut out a few hours early on a Friday (provided the work is done) and start the weekend off early by going to the pool, or taking the kids to the park.  Contracting provides you this opportunity (mileage may vary).  Most of your fulltime brethren will not care, they will be jealous that they’re corporate policy prevents them from doing the same.  However, you must be mindful of situations where this is not appropriate, and don’t over do it.  You are there to work after all. Affirmation of Need Have you ever been stuck in a job where you thought you were underpaid?  Have you ever been in a position where you felt like there was not enough workload for you?  This is not a problem for contractors.  When you start a contract it is understood that you are needed, and the employer knows that you are happy with the terms. Contracting may not be for everyone.  But, if you develop a relationship with a good consulting firm, keep their clients happy, then they will keep you happy.  They want you to work almost as much as you do.  Just be sure and plan financially for any windows of unemployment.

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• Parallelism in .NET – Part 8, PLINQ’s ForAll Method

  - by Reed

  Parallel LINQ extends LINQ to Objects, and is typically very similar.  However, as I previously discussed, there are some differences.  Although the standard way to handle simple Data Parellelism is via Parallel.ForEach, it’s possible to do the same thing via PLINQ. PLINQ adds a new method unavailable in standard LINQ which provides new functionality… LINQ is designed to provide a much simpler way of handling querying, including filtering, ordering, grouping, and many other benefits.  Reading the description in LINQ to Objects on MSDN, it becomes clear that the thinking behind LINQ deals with retrieval of data.  LINQ works by adding a functional programming style on top of .NET, allowing us to express filters in terms of predicate functions, for example. PLINQ is, generally, very similar.  Typically, when using PLINQ, we write declarative statements to filter a dataset or perform an aggregation.  However, PLINQ adds one new method, which provides a very different purpose: ForAll. The ForAll method is defined on ParallelEnumerable, and will work upon any ParallelQuery<T>.  Unlike the sequence operators in LINQ and PLINQ, ForAll is intended to cause side effects.  It does not filter a collection, but rather invokes an action on each element of the collection. At first glance, this seems like a bad idea.  For example, Eric Lippert clearly explained two philosophical objections to providing an IEnumerable<T>.ForEach extension method, one of which still applies when parallelized.  The sole purpose of this method is to cause side effects, and as such, I agree that the ForAll method “violates the functional programming principles that all the other sequence operators are based upon”, in exactly the same manner an IEnumerable<T>.ForEach extension method would violate these principles.  Eric Lippert’s second reason for disliking a ForEach extension method does not necessarily apply to ForAll – replacing ForAll with a call to Parallel.ForEach has the same closure semantics, so there is no loss there. Although ForAll may have philosophical issues, there is a pragmatic reason to include this method.  Without ForAll, we would take a fairly serious performance hit in many situations.  Often, we need to perform some filtering or grouping, then perform an action using the results of our filter.  Using a standard foreach statement to perform our action would avoid this philosophical issue: // Filter our collection var filteredItems = collection.AsParallel().Where( i => i.SomePredicate() ); // Now perform an action foreach (var item in filteredItems) { // These will now run serially item.DoSomething(); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This would cause a loss in performance, since we lose any parallelism in place, and cause all of our actions to be run serially. We could easily use a Parallel.ForEach instead, which adds parallelism to the actions: // Filter our collection var filteredItems = collection.AsParallel().Where( i => i.SomePredicate() ); // Now perform an action once the filter completes Parallel.ForEach(filteredItems, item => { // These will now run in parallel item.DoSomething(); }); This is a noticeable improvement, since both our filtering and our actions run parallelized.  However, there is still a large bottleneck in place here.  The problem lies with my comment “perform an action once the filter completes”.  Here, we’re parallelizing the filter, then collecting all of the results, blocking until the filter completes.  Once the filtering of every element is completed, we then repartition the results of the filter, reschedule into multiple threads, and perform the action on each element.  By moving this into two separate statements, we potentially double our parallelization overhead, since we’re forcing the work to be partitioned and scheduled twice as many times. This is where the pragmatism comes into play.  By violating our functional principles, we gain the ability to avoid the overhead and cost of rescheduling the work: // Perform an action on the results of our filter collection .AsParallel() .Where( i => i.SomePredicate() ) .ForAll( i => i.DoSomething() ); The ability to avoid the scheduling overhead is a compelling reason to use ForAll.  This really goes back to one of the key points I discussed in data parallelism: Partition your problem in a way to place the most work possible into each task.  Here, this means leaving the statement attached to the expression, even though it causes side effects and is not standard usage for LINQ. This leads to my one guideline for using ForAll: The ForAll extension method should only be used to process the results of a parallel query, as returned by a PLINQ expression. Any other usage scenario should use Parallel.ForEach, instead.

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• CLR via C# 3rd Edition is out

  - by Abhijeet Patel

  Time for some book news update. CLR via C#, 3rd Edition seems to have been out for a little while now. The book was released in early Feb this year, and needless to say my copy is on it’s way. I can barely wait to dig in and chew on the goodies that one of the best technical authors and software professionals I respect has in store. The 2nd edition of the book was an absolute treat and this edition promises to be no less. Here is a brief description of what’s new and updated from the 2nd edition. Part I – CLR Basics Chapter 1-The CLR’s Execution Model Added about discussion about C#’s /optimize and /debug switches and how they relate to each other. Chapter 2-Building, Packaging, Deploying, and Administering Applications and Types Improved discussion about Win32 manifest information and version resource information. Chapter 3-Shared Assemblies and Strongly Named Assemblies Added discussion of TypeForwardedToAttribute and TypeForwardedFromAttribute. Part II – Designing Types Chapter 4-Type Fundamentals No new topics. Chapter 5-Primitive, Reference, and Value Types Enhanced discussion of checked and unchecked code and added discussion of new BigInteger type. Also added discussion of C# 4.0’s dynamic primitive type. Chapter 6-Type and Member Basics No new topics. Chapter 7-Constants and Fields No new topics. Chapter 8-Methods Added discussion of extension methods and partial methods. Chapter 9-Parameters Added discussion of optional/named parameters and implicitly-typed local variables. Chapter 10-Properties Added discussion of automatically-implemented properties, properties and the Visual Studio debugger, object and collection initializers, anonymous types, the System.Tuple type and the ExpandoObject type. Chapter 11-Events Added discussion of events and thread-safety as well as showing a cool extension method to simplify the raising of an event. Chapter 12-Generics Added discussion of delegate and interface generic type argument variance. Chapter 13-Interfaces No new topics. Part III – Essential Types Chapter 14-Chars, Strings, and Working with Text No new topics. Chapter 15-Enums Added coverage of new Enum and Type methods to access enumerated type instances. Chapter 16-Arrays Added new section on initializing array elements. Chapter 17-Delegates Added discussion of using generic delegates to avoid defining new delegate types. Also added discussion of lambda expressions. Chapter 18-Attributes No new topics. Chapter 19-Nullable Value Types Added discussion on performance. Part IV – CLR Facilities Chapter 20-Exception Handling and State Management This chapter has been completely rewritten. It is now about exception handling and state management. It includes discussions of code contracts and constrained execution regions (CERs). It also includes a new section on trade-offs between writing productive code and reliable code. Chapter 21-Automatic Memory Management Added discussion of C#’s fixed state and how it works to pin objects in the heap. Rewrote the code for weak delegates so you can use them with any class that exposes an event (the class doesn’t have to support weak delegates itself). Added discussion on the new ConditionalWeakTable class, GC Collection modes, Full GC notifications, garbage collection modes and latency modes. I also include a new sample showing how your application can receive notifications whenever Generation 0 or 2 collections occur. Chapter 22-CLR Hosting and AppDomains Added discussion of side-by-side support allowing multiple CLRs to be loaded in a single process. Added section on the performance of using MarshalByRefObject-derived types. Substantially rewrote the section on cross-AppDomain communication. Added section on AppDomain Monitoring and first chance exception notifications. Updated the section on the AppDomainManager class. Chapter 23-Assembly Loading and Reflection Added section on how to deploy a single file with dependent assemblies embedded inside it. Added section comparing reflection invoke vs bind/invoke vs bind/create delegate/invoke vs C#’s dynamic type. Chapter 24-Runtime Serialization This is a whole new chapter that was not in the 2nd Edition. Part V – Threading Chapter 25-Threading Basics Whole new chapter motivating why Windows supports threads, thread overhead, CPU trends, NUMA Architectures, the relationship between CLR threads and Windows threads, the Thread class, reasons to use threads, thread scheduling and priorities, foreground thread vs background threads. Chapter 26-Performing Compute-Bound Asynchronous Operations Whole new chapter explaining the CLR’s thread pool. This chapter covers all the new .NET 4.0 constructs including cooperative cancelation, Tasks, the aralle class, parallel language integrated query, timers, how the thread pool manages its threads, cache lines and false sharing. Chapter 27-Performing I/O-Bound Asynchronous Operations Whole new chapter explaining how Windows performs synchronous and asynchronous I/O operations. Then, I go into the CLR’s Asynchronous Programming Model, my AsyncEnumerator class, the APM and exceptions, Applications and their threading models, implementing a service asynchronously, the APM and Compute-bound operations, APM considerations, I/O request priorities, converting the APM to a Task, the event-based Asynchronous Pattern, programming model soup. Chapter 28-Primitive Thread Synchronization Constructs Whole new chapter discusses class libraries and thread safety, primitive user-mode, kernel-mode constructs, and data alignment. Chapter 29-Hybrid Thread Synchronization Constructs Whole new chapter discussion various hybrid constructs such as ManualResetEventSlim, SemaphoreSlim, CountdownEvent, Barrier, ReaderWriterLock(Slim), OneManyResourceLock, Monitor, 3 ways to solve the double-check locking technique, .NET 4.0’s Lazy and LazyInitializer classes, the condition variable pattern, .NET 4.0’s concurrent collection classes, the ReaderWriterGate and SyncGate classes.

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• Oracle Linux and Oracle VM pricing guide

  - by wcoekaer

  A few days ago someone showed me a pricing guide from a Linux vendor and I was a bit surprised at the complexity of it. Especially when you look at larger servers (4 or 8 sockets) and when adding virtual machine use into the mix. I think we have a very compelling and simple pricing model for both Oracle Linux and Oracle VM. Let me see if I can explain it in 1 page, not 10 pages. This pricing information is publicly available on the Oracle store, I am using the current public list prices. Also keep in mind that this is for customers using non-oracle x86 servers. When a customer purchases an Oracle x86 server, the annual systems support includes full use (all you can eat) of Oracle Linux, Oracle VM and Oracle Solaris (no matter how many VMs you run on that server, in case you deploy guests on a hypervisor). This support level is the equivalent of premier support in the list below. Let's start with Oracle VM (x86) : Oracle VM support subscriptions are per physical server on which you deploy the Oracle VM Server product. (1) Oracle VM Premier Limited - 1- or 2 socket server : $599 per server per year (2) Oracle VM Premier - more than 2 socket server (4, or 8 or whatever more) : $1199 per server per year The above includes the use of Oracle VM Manager and Oracle Enterprise Manager Cloud Control's Virtualization management pack (including self service cloud portal, etc..) 24x7 support, access to bugfixes, updates and new releases. It also includes all options, live migrate, dynamic resource scheduling, high availability, dynamic power management, etc If you want to play with the product, or even use the product without access to support services, the product is freely downloadable from edelivery. Next, Oracle Linux : Oracle Linux support subscriptions are per physical server. If you plan to run Oracle Linux as a guest on Oracle VM, VMWare or Hyper-v, you only have to pay for a single subscription per system, we do not charge per guest or per number of guests. In other words, you can run any number of Oracle Linux guests per physical server and count it as just a single subscription. (1) Oracle Linux Network Support - any number of sockets per server : $119 per server per year Network support does not offer support services. It provides access to the Unbreakable Linux Network and also offers full indemnification for Oracle Linux. (2) Oracle Linux Basic Limited Support - 1- or 2 socket servers : $499 per server per year This subscription provides 24x7 support services, access to the Unbreakable Linux Network and the Oracle Support portal, indemnification, use of Oracle Clusterware for Linux HA and use of Oracle Enterprise Manager Cloud control for Linux OS management. It includes ocfs2 as a clustered filesystem. (3) Oracle Linux Basic Support - more than 2 socket server (4, or 8 or more) : $1199 per server per year This subscription provides 24x7 support services, access to the Unbreakable Linux Network and the Oracle Support portal, indemnification, use of Oracle Clusterware for Linux HA and use of Oracle Enterprise Manager Cloud control for Linux OS management. It includes ocfs2 as a clustered filesystem (4) Oracle Linux Premier Limited Support - 1- or 2 socket servers : $1399 per server per year This subscription provides 24x7 support services, access to the Unbreakable Linux Network and the Oracle Support portal, indemnification, use of Oracle Clusterware for Linux HA and use of Oracle Enterprise Manager Cloud control for Linux OS management, XFS filesystem support. It also offers Oracle Lifetime support, backporting of patches for critical customers in previous versions of package and ksplice zero-downtime updates. (5) Oracle Linux Premier Support - more than 2 socket servers : $2299 per server per year This subscription provides 24x7 support services, access to the Unbreakable Linux Network and the Oracle Support portal, indemnification, use of Oracle Clusterware for Linux HA and use of Oracle Enterprise Manager Cloud control for Linux OS management, XFS filesystem support. It also offers Oracle Lifetime support, backporting of patches for critical customers in previous versions of package and ksplice zero-downtime updates. (6) Freely available Oracle Linux - any number of sockets You can freely download Oracle Linux, install it on any number of servers and use it for any reason, without support, without right to use of these extra features like Oracle Clusterware or ksplice, without indemnification. However, you do have full access to all errata as well. Need support? then use options (1)..(5) So that's it. Count number of 2 socket boxes, more than 2 socket boxes, decide on basic or premier support level and you are done. You don't have to worry about different levels based on how many virtual instance you deploy or want to deploy. A very simple menu of choices. We offer, inclusive, Linux OS clusterware, Linux OS Management, provisioning and monitoring, cluster filesystem (ocfs), high performance filesystem (xfs), dtrace, ksplice, ofed (infiniband stack for high performance networking). No separate add-on menus. NOTE : socket/cpu can have any number of cores. So whether you have a 4,6,8,10 or 12 core CPU doesn't matter, we count the number of physical CPUs.

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• Big Data – Buzz Words: What is Hadoop – Day 6 of 21

  - by Pinal Dave

  In yesterday’s blog post we learned what is NoSQL. In this article we will take a quick look at one of the four most important buzz words which goes around Big Data – Hadoop. What is Hadoop? Apache Hadoop is an open-source, free and Java based software framework offers a powerful distributed platform to store and manage Big Data. It is licensed under an Apache V2 license. It runs applications on large clusters of commodity hardware and it processes thousands of terabytes of data on thousands of the nodes. Hadoop is inspired from Google’s MapReduce and Google File System (GFS) papers. The major advantage of Hadoop framework is that it provides reliability and high availability. What are the core components of Hadoop? There are two major components of the Hadoop framework and both fo them does two of the important task for it. Hadoop MapReduce is the method to split a larger data problem into smaller chunk and distribute it to many different commodity servers. Each server have their own set of resources and they have processed them locally. Once the commodity server has processed the data they send it back collectively to main server. This is effectively a process where we process large data effectively and efficiently. (We will understand this in tomorrow’s blog post). Hadoop Distributed File System (HDFS) is a virtual file system. There is a big difference between any other file system and Hadoop. When we move a file on HDFS, it is automatically split into many small pieces. These small chunks of the file are replicated and stored on other servers (usually 3) for the fault tolerance or high availability. (We will understand this in the day after tomorrow’s blog post). Besides above two core components Hadoop project also contains following modules as well. Hadoop Common: Common utilities for the other Hadoop modules Hadoop Yarn: A framework for job scheduling and cluster resource management There are a few other projects (like Pig, Hive) related to above Hadoop as well which we will gradually explore in later blog posts. A Multi-node Hadoop Cluster Architecture Now let us quickly see the architecture of the a multi-node Hadoop cluster. A small Hadoop cluster includes a single master node and multiple worker or slave node. As discussed earlier, the entire cluster contains two layers. One of the layer of MapReduce Layer and another is of HDFC Layer. Each of these layer have its own relevant component. The master node consists of a JobTracker, TaskTracker, NameNode and DataNode. A slave or worker node consists of a DataNode and TaskTracker. It is also possible that slave node or worker node is only data or compute node. The matter of the fact that is the key feature of the Hadoop. In this introductory blog post we will stop here while describing the architecture of Hadoop. In a future blog post of this 31 day series we will explore various components of Hadoop Architecture in Detail. Why Use Hadoop? There are many advantages of using Hadoop. Let me quickly list them over here: Robust and Scalable – We can add new nodes as needed as well modify them. Affordable and Cost Effective – We do not need any special hardware for running Hadoop. We can just use commodity server. Adaptive and Flexible – Hadoop is built keeping in mind that it will handle structured and unstructured data. Highly Available and Fault Tolerant – When a node fails, the Hadoop framework automatically fails over to another node. Why Hadoop is named as Hadoop? In year 2005 Hadoop was created by Doug Cutting and Mike Cafarella while working at Yahoo. Doug Cutting named Hadoop after his son’s toy elephant. Tomorrow In tomorrow’s blog post we will discuss Buzz Word – MapReduce. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Big Data, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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• Silverlight Reporting Application Part 3.5 - Prism Background and WCF RIA [Series Intermission]

  Taking a step back before I dive into the details and full-on coding fun, I wanted to once again respond to a comment on my last post to clear up some things in regards to how I'm setting up my project and some of the choices I've made. Aka, thanks Ben. :) Prism Project Setup For starters, I'm not the ideal use case for a Prism application. In most cases where you've got a one-man team, Prism can be overkill as it is more intended for large teams who are geographically dispersed or in applications that have a larger scale than my Recruiting application in which you'll greatly benefit from modularity, delayed loading of xaps, etc. What Prism offers, though, is a manner for handling UI, commands, and events with the idea that, through a modular approach in which no parts really need to know about one another, I can update this application bit by bit as hiring needs change or requirements differ between offices without having to worry that changing something in the Jobs module will break something in, say, the Scheduling module. All that being said, here's a look at how our project breakdown for Recruit (MVVM/Prism implementation) looks: This could be a little misleading though, as each of those modules is actually another project in the overall Recruit solution. As far as what the projects actually are, that looks a bit like this: Recruiting Solution Recruit (Shell up there) - Main Silverlight Application .Web - Default .Web application to host the Silverlight app Infrastructure - Silverlight Class Library Project Modules - Silverlight Class Library Projects Infrastructure &Modules The Infrastructure project is probably something you'll see to some degree in any composite application. In this application, it is going to contain custom commands (you'll see the joy of these in a post or two down the road), events, helper classes, and any custom classes I need to share between different modules. Think of this as a handy little crossroad between any parts of your application. Modules on the other hand are the bread and butter of this application. Besides the shell, which holds the UI skeleton, and the infrastructure, which holds all those shared goodies, the modules are self-contained bundles of functionality to handle different concerns. In my scenario, I need a way to look up and edit Jobs, Applicants, and Schedule interviews, a Notification module to handle telling the user when different things are happening (i.e., loading from database), and a Menu to control interaction and moving between different views. All modules are going to follow the following pattern: The module class will inherit from IModule and handle initialization and loading the correct view into the correct region, whereas the Views and ViewModels folders will contain paired Silverlight user controls and ViewModel class backings. WCF RIA Services Since we've got all the projects in a single solution, we did not have to go the route of creating a WCR RIA Services Class Library. Every module has it's WCF RIA link back to the main .Web project, so the single Linq-2-SQL (yes, I said Linq-2-SQL, but I'll soon be switching to OpenAccess due to the new visual designer) context I'm using there works nicely with the scope of my project. If I were going for completely separating this project out and doing different, dynamically loaded elements, I'd probably go for the separate class library. Hope that clears that up. In the future though, I will be using that in a project that I've got in the "when I've got enough time to work on this" pipeline, so we'll get into that eventually- and hopefully when WCF RIA is in full release! Why Not use Silverlight Navigation/Business Template? The short answer- I'm a creature of habit, and having used Silverlight for a few years now, I'm used to doing lots of things manually. :) Plus, starting with a blank slate of a project I'm able to set up things exactly as I want them to be. In this case, rather than the navigation frame we would see in one of the templates, the MainRegion/ContentControl is working as our main navigation window. In many cases I will use theSilverlight navigation template to start things off, however in this case I did not need those features so I opted out of using that. Next time when I actually hit post #4, we're going to get into the modules and starting to get functionality into this application. Next week is also release week for the Q1 2010 release, so be sure to check out our annualWebinar Week (I might be biased, but Wednesday is my favorite out of the group). Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Cloud to On-Premise Connectivity Patterns

  - by Rajesh Raheja

  Do you have a requirement to convert an Opportunity in Salesforce.com to an Order/Quote in Oracle E-Business Suite? Or maybe you want the creation of an Oracle RightNow Incident to trigger an on-premise Oracle E-Business Suite Service Request creation for RMA and Field Scheduling? If so, read on. In a previous blog post, I discussed integrating TO cloud applications, however the use cases above are the reverse i.e. receiving data FROM cloud applications (SaaS) TO on-premise applications/databases that sit behind a firewall. Oracle SOA Suite is assumed to be on-premise with with Oracle Service Bus as the mediation and virtualization layer. The main considerations for the patterns are are security i.e. shielding enterprise resources; and scalability i.e. minimizing firewall latency. Let me use an analogy to help visualize the patterns: the on-premise system is your home - with your most valuable possessions - and the SaaS app is your favorite on-line store which regularly ships (inbound calls) various types of parcels/items (message types/service operations). You need the items at home (on-premise) but want to safe guard against misguided elements of society (internet threats) who may masquerade as postal workers and vandalize property (denial of service?). Let's look at the patterns. Pattern: Pull from Cloud The on-premise system polls from the SaaS apps and picks up the message instead of having it delivered. This may be done using Oracle RightNow Object Query Language or SOAP APIs. This is particularly suited for certain integration approaches wherein messages are trickling in, can be centralized and batched e.g. retrieving event notifications on an hourly schedule from the Oracle Messaging Service. To compare this pattern with the home analogy, you are avoiding any deliveries to your home and instead go to the post office/UPS/Fedex store to pick up your parcel. Every time. Pros: On-premise assets not exposed to the Internet, firewall issues avoided by only initiating outbound connections Cons: Polling mechanisms may affect performance, may not satisfy near real-time requirements Pattern: Open Firewall Ports The on-premise system exposes the web services that needs to be invoked by the cloud application. This requires opening up firewall ports, routing calls to the appropriate internal services behind the firewall. Fusion Applications uses this pattern, and auto-provisions the services on the various virtual hosts to secure the topology. This works well for service integration, but may not suffice for large volume data integration. Using the home analogy, you have now decided to receive parcels instead of going to the post office every time. A door mail slot cut out allows the postman can drop small parcels, but there is still concern about cutting new holes for larger packages. Pros: optimal pattern for near real-time needs, simpler administration once the service is provisioned Cons: Needs firewall ports to be opened up for new services, may not suffice for batch integration requiring direct database access Pattern: Virtual Private Networking The on-premise network is "extended" to the cloud (or an intermediary on-demand / managed service offering) using Virtual Private Networking (VPN) so that messages are delivered to the on-premise system in a trusted channel. Using the home analogy, you entrust a set of keys with a neighbor or property manager who receives the packages, and then drops it inside your home. Pros: Individual firewall ports don't need to be opened, more suited for high scalability needs, can support large volume data integration, easier management of one connection vs a multitude of open ports Cons: VPN setup, specific hardware support, requires cloud provider to support virtual private computing Pattern: Reverse Proxy / API Gateway The on-premise system uses a reverse proxy "API gateway" software on the DMZ to receive messages. The reverse proxy can be implemented using various mechanisms e.g. Oracle API Gateway provides firewall and proxy services along with comprehensive security, auditing, throttling benefits. If a firewall already exists, then Oracle Service Bus or Oracle HTTP Server virtual hosts can provide reverse proxy implementations on the DMZ. Custom built implementations are also possible if specific functionality (such as message store-n-forward) is needed. In the home analogy, this pattern sits in between cutting mail slots and handing over keys. Instead, you install (and maintain) a mailbox in your home premises outside your door. The post office delivers the parcels in your mailbox, from where you can securely retrieve it. Pros: Very secure, very flexible Cons: Introduces a new software component, needs DMZ deployment and management Pattern: On-Premise Agent (Tunneling) A light weight "agent" software sits behind the firewall and initiates the communication with the cloud, thereby avoiding firewall issues. It then maintains a bi-directional connection either with pull or push based approaches using (or abusing, depending on your viewpoint) the HTTP protocol. Programming protocols such as Comet, WebSockets, HTTP CONNECT, HTTP SSH Tunneling etc. are possible implementation options. In the home analogy, a resident receives the parcel from the postal worker by opening the door, however you still take precautions with chain locks and package inspections. Pros: Light weight software, IT doesn't need to setup anything Cons: May bypass critical firewall checks e.g. virus scans, separate software download, proliferation of non-IT managed software Conclusion The patterns above are some of the most commonly encountered ones for cloud to on-premise integration. Selecting the right pattern for your project involves looking at your scalability needs, security restrictions, sync vs asynchronous implementation, near real-time vs batch expectations, cloud provider capabilities, budget, and more. In some cases, the basic "Pull from Cloud" may be acceptable, whereas in others, an extensive VPN topology may be well justified. For more details on the Oracle cloud integration strategy, download this white paper.

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• Cloud to On-Premise Connectivity Patterns

  - by Rajesh Raheja

  Do you have a requirement to convert an Opportunity in Salesforce.com to an Order/Quote in Oracle E-Business Suite? Or maybe you want the creation of an Oracle RightNow Incident to trigger an on-premise Oracle E-Business Suite Service Request creation for RMA and Field Scheduling? If so, read on. In a previous blog post, I discussed integrating TO cloud applications, however the use cases above are the reverse i.e. receiving data FROM cloud applications (SaaS) TO on-premise applications/databases that sit behind a firewall. Oracle SOA Suite is assumed to be on-premise with with Oracle Service Bus as the mediation and virtualization layer. The main considerations for the patterns are are security i.e. shielding enterprise resources; and scalability i.e. minimizing firewall latency. Let me use an analogy to help visualize the patterns: the on-premise system is your home - with your most valuable possessions - and the SaaS app is your favorite on-line store which regularly ships (inbound calls) various types of parcels/items (message types/service operations). You need the items at home (on-premise) but want to safe guard against misguided elements of society (internet threats) who may masquerade as postal workers and vandalize property (denial of service?). Let's look at the patterns. Pattern: Pull from Cloud The on-premise system polls from the SaaS apps and picks up the message instead of having it delivered. This may be done using Oracle RightNow Object Query Language or SOAP APIs. This is particularly suited for certain integration approaches wherein messages are trickling in, can be centralized and batched e.g. retrieving event notifications on an hourly schedule from the Oracle Messaging Service. To compare this pattern with the home analogy, you are avoiding any deliveries to your home and instead go to the post office/UPS/Fedex store to pick up your parcel. Every time. Pros: On-premise assets not exposed to the Internet, firewall issues avoided by only initiating outbound connections Cons: Polling mechanisms may affect performance, may not satisfy near real-time requirements Pattern: Open Firewall Ports The on-premise system exposes the web services that needs to be invoked by the cloud application. This requires opening up firewall ports, routing calls to the appropriate internal services behind the firewall. Fusion Applications uses this pattern, and auto-provisions the services on the various virtual hosts to secure the topology. This works well for service integration, but may not suffice for large volume data integration. Using the home analogy, you have now decided to receive parcels instead of going to the post office every time. A door mail slot cut out allows the postman can drop small parcels, but there is still concern about cutting new holes for larger packages. Pros: optimal pattern for near real-time needs, simpler administration once the service is provisioned Cons: Needs firewall ports to be opened up for new services, may not suffice for batch integration requiring direct database access Pattern: Virtual Private Networking The on-premise network is "extended" to the cloud (or an intermediary on-demand / managed service offering) using Virtual Private Networking (VPN) so that messages are delivered to the on-premise system in a trusted channel. Using the home analogy, you entrust a set of keys with a neighbor or property manager who receives the packages, and then drops it inside your home. Pros: Individual firewall ports don't need to be opened, more suited for high scalability needs, can support large volume data integration, easier management of one connection vs a multitude of open ports Cons: VPN setup, specific hardware support, requires cloud provider to support virtual private computing Pattern: Reverse Proxy / API Gateway The on-premise system uses a reverse proxy "API gateway" software on the DMZ to receive messages. The reverse proxy can be implemented using various mechanisms e.g. Oracle API Gateway provides firewall and proxy services along with comprehensive security, auditing, throttling benefits. If a firewall already exists, then Oracle Service Bus or Oracle HTTP Server virtual hosts can provide reverse proxy implementations on the DMZ. Custom built implementations are also possible if specific functionality (such as message store-n-forward) is needed. In the home analogy, this pattern sits in between cutting mail slots and handing over keys. Instead, you install (and maintain) a mailbox in your home premises outside your door. The post office delivers the parcels in your mailbox, from where you can securely retrieve it. Pros: Very secure, very flexible Cons: Introduces a new software component, needs DMZ deployment and management Pattern: On-Premise Agent (Tunneling) A light weight "agent" software sits behind the firewall and initiates the communication with the cloud, thereby avoiding firewall issues. It then maintains a bi-directional connection either with pull or push based approaches using (or abusing, depending on your viewpoint) the HTTP protocol. Programming protocols such as Comet, WebSockets, HTTP CONNECT, HTTP SSH Tunneling etc. are possible implementation options. In the home analogy, a resident receives the parcel from the postal worker by opening the door, however you still take precautions with chain locks and package inspections. Pros: Light weight software, IT doesn't need to setup anything Cons: May bypass critical firewall checks e.g. virus scans, separate software download, proliferation of non-IT managed software Conclusion The patterns above are some of the most commonly encountered ones for cloud to on-premise integration. Selecting the right pattern for your project involves looking at your scalability needs, security restrictions, sync vs asynchronous implementation, near real-time vs batch expectations, cloud provider capabilities, budget, and more. In some cases, the basic "Pull from Cloud" may be acceptable, whereas in others, an extensive VPN topology may be well justified. For more details on the Oracle cloud integration strategy, download this white paper.

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• World Backup Day

  - by red(at)work

  Here at Red Gate Towers, the SQL Backup development team have been hunkered down in their shed for the last few months, with the toolbox, blowtorch and chamois leather out, upgrading SQL Backup. When we started, autumn leaves were falling. Now we're about to finish, spring flowers are budding. If not quite a gleaming new machine, at the very least a familiar, reliable engine with some shiny new bits on it will trundle magnificently out of the workshop. One of the interesting things I've noticed about working on software development teams is that the team is together for so long 'implementing' stuff - designing, coding, testing, fixing bugs and so on - that you occasionally forget why you're doing what you're doing. Doubt creeps in. It feels like a long time since we launched this project in a fanfare of optimism and enthusiasm, and all that clarity of purpose and mission "yee-haw" has dissipated with the daily pressures of development. Every now and again, we look up from our bunker and notice all those thousands of users out there, with their different configurations and working practices and each with their own set of problems and requirements, and we ask ourselves "does anyone care about what we're doing?" Has the world moved on while we've been busy? Could we have been doing something more useful with the time and talent of all these excellent people we've assembled? In truth, you can research and test and validate all you like, but you never really know if you've done the right thing (or at least, something valuable for some users) until you release. All projects suffer this insecurity. If they don't, maybe you're not worrying enough about what you're building. The two enemies of software development are certainty and complacency. Oh, and of course, rival teams with Nerf guns. The goal of SQL Backup 7 is to make it so easy to schedule regular restores of your backups that you have no excuse not to. Why schedule a restore? Because your data is not as good as your last backup. It's only as good as your last successful restore. If you're not checking your backups by restoring them and running an integrity check on the database, you're only doing half the job. It seems that most DBAs know that this is best practice, but it can be tricky and time-consuming to set up, so it's one of those tasks that can get forgotten in the midst all the other demands on their time. Sometimes, they're just too busy firefighting. But if it was simple to do? That was our inspiration for SQL Backup 7. So it was heartening to read Brent Ozar's blog post the other day about World Backup Day. To be honest, I'd never heard of World Backup Day (Talk Like a Pirate Day, yes, but not this one); however, its emphasis on not just backing up your data but checking the validity of those backups was exactly the same message we had in mind when building SQL Backup 7. It's printed on a piece of A3 above our planning board - "Make backup verification so easy to do that no DBA has an excuse for not doing it" It's the missing piece that completes the puzzle. Simple idea, great concept, useful feature, but, as it turned out, far from straightforward to implement. The problem is the future. As Marty McFly discovered over the course of three movies, the future is uncertain and hard to predict - so when you are scheduling a restore to take place an hour, day, week or month after the backup, there are all kinds of questions that you wouldn't normally have to consider. Where will this backup live? Will it even exist at the time? Will it be split into multiple files? What will the file names be? Will it be encrypted? What files should it be restored to? SQL Backup needs to know what to expect at the time the restore job is actually run. Of course, a DBA will know the answer to all these questions, but to deliver the whole point of version 7, we wanted to make it easy for them to input that information into SQL Backup. We think we've done that. When you create your scheduled backup job, there is now an option to create a "reminder" to follow it up with a scheduled restore to verify the resulting backups. Actually, it's much more than a reminder, as it stores all the relevant data so you can click it and pre-populate the wizard with all the right settings to set up your verification restores. Simple. But, what do you think? We'd love you to try it. Post by Brian Harris

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• Trac vs. Redmine vs. JIRA vs. FogBugz for one-man shop?

  - by kizzx2

  Background I am a one-man freelancer looking for a project management software that can provide the following requirements. I have used Trac for about a year now. Tried Redmine and FogBugz on Demand for a couple of weeks. Never tried JIRA before. Basically, I'm looking for a piece of software that: Facilitates developer-client communication/collaboration Does time tracking Requirements Record time estimates/Time tracking Clients must be able to create/edit his own tickets/cases Clients must not see Developer created tickets/cases (internal) Affordable (price) with multiple clients Nice-to-haves Supports multiple projects in one installation Free eclipse integration (Mylyn) Easy time-tracking without using the Web UI (Trac's post commit hook or Redmine's commit message scanning) Clients can access the Wiki Export the data to standard formats My evaluation Trac can basically fulfill most of the above requirements, but with lots of customizations and plug-ins that it doesn't feel so clean. One downside is that the main trunk (0.11) has been around for a year or more and I still haven't seen much tendency of any upgrades coming up. Redmine has the cleanest Web UI. It's design philosophy seems to be the most elegant, with its innovative commit message scanning and stuff. However, the current version doesn't seem to be very mature and stable yet. It doesn't support internal (private) tickets and the time-tracking commit message patch doesn't support the trunk version. The good thing about it is that the main trunk still seems to be actively developed. FogBugz is actually a very well written piece of software. However the idea of paying $25/month for the client to be able to log-in to the system seems a little bit too far off for an individual developer. The free version supports letting clients create/view their own cases using email, which is a sub-optimal alternative to having a full-fledged list of the user's own cases. That also means clients can't read/write wiki pages. Its time-tracking approach is innovative and good though. However the fact that all the eclipse integration (Bugclipse, Foglyn) are commercial. Yet other investments before I can use my bug-tracker! If I revert back to the Web UI, it's not really a fast rendering Web service. Also, the in-built report functions are excellent (e.g. evidence based scheduling) JIRA is something I have zero experience with. Can someone with JIRA experience recommend why it might be a good fit for this particular situation? Question Can we share experience on this? Any specific plugins/customizations would that would best suit the requirements for this case?

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• C# - Alternative to System.Timers.Timer, to call a function at a specific time.

  - by Fábio Antunes

  Hello everybody. I want to call a specific function on my C# application at a specific time. At first i thought about using a Timer (System.Time.Timer), but that soon became impossible to use. Why? Simple. The Timer Class requires a Interval in milliseconds, but considering that i might want the function to be executed, lets says in a week that would mean: 7 Days = 168 hours; 168 Hours = 10,080 minutes; 10,080 Minutes = 6,048,000 seconds; 6,048,000 Seconds = 6,048,000,000 milliseconds; So the Interval would be 6,048,000,000; Now lets remember that the Interval accepted data type is int, and as we know int range goes from -2,147,483,648 to 2,147,483,647. That makes Timer useless in this case once we cannot set a Interval bigger that 2,147,483,647 milliseconds. So i need a solution where i could specify when the function should be called. Something like this: solution.ExecuteAt = "30-04-2010 15:10:00"; solution.Function = "functionName"; solution.Start(); So when the System Time would reach "30-04-2010 15:10:00" the function would be executed in the application. How can this problem be solved? Thanks just by taking the time to read my question. But if you could provide me with some help i would be most grateful. Additional Info: What these functions will do? Getting climate information and based on that info: Starting / Shutting down other Applications (most of them Console Based); Sending custom Commands to those Console Applications; Power down, Rebooting, Sleep, Hibernate the computer; And if possible schedule the BIOS to Power Up the Computer; EDIT: It would seem that the Interval accepted data type is double, however if you set a value bigger that an int to the Interval, and call Start() it throws a exception [0, Int32.MaxValue]. EDIT 2: Jørn Schou-Rode suggested using Ncron to handle the scheduling tasks, and at first look this seems a good solution, but i would like to hear about some who as worked with it.

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• How to Resolve Jason issue

  - by Mohammad Nezhad

  I am working in a web scheduling application which uses DayPilot component I started by reading the documentation and use the calendar control. but whenever I do some thing which (fires an event on the Daypilot control) I face with following error An exception was thrown in the server-side event handler: System.InvalidCastException: Instance Of JasonData doesn't hold a double at DayPilot.Jason.JasonData.op_Explicit(JasonData data) at DayPilot.Web.Ui.Events.EventMoveEventArgs..ctor(JasonData parameters, string[] fields, JasonData data) at DayPilot.Web.Ui.DayPilotCalendar.ExecuteEventJASON(String ea) at DayPilot.Web.Ui.DayPilotCalendar.System.Web.UI.ICallbackEventHandler.RaiseCallbackEvent(string ea) at System.Web.UI.Page.PrepareCallback(String callbackControlID) here is the completed code in the ASPX page <DayPilot:DayPilotCalendar ID="DayPilotCalendar1" runat="server" Direction="RTL" Days="7" DataStartField="eventstart" DataEndField="eventend" DataTextField="name" DataValueField="id" DataTagFields="State" EventMoveHandling="CallBack" OnEventMove="DayPilotCalendar1_EventMove" EventEditHandling="CallBack" OnEventEdit="DayPilotCalendar1_EventEdit" EventClickHandling="Edit" OnBeforeEventRender="DayPilotCalendar1_BeforeEventRender" EventResizeHandling="CallBack" OnEventResize="DayPilotCalendar1_EventResize" EventDoubleClickHandling="CallBack" OnEventDoubleClick="DayPilotCalendar1_EventDoubleClick" oncommand="DayPilotCalendar1_Command" and here is the complete codebehind protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) Initialization(); } private void dbUpdateEvent(string id, DateTime start, DateTime end) { // update for move using (SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["db"].ConnectionString)) { con.Open(); SqlCommand cmd = new SqlCommand("UPDATE [event] SET [eventstart] = @start, [eventend] = @end WHERE [id] = @id", con); cmd.Parameters.AddWithValue("id", id); cmd.Parameters.AddWithValue("start", start); cmd.Parameters.AddWithValue("end", end); cmd.ExecuteNonQuery(); } } private DataTable dbGetEvents(DateTime start, int days) { // get Data SqlDataAdapter da = new SqlDataAdapter("SELECT [id], [name], [eventstart], [eventend], [state], [other] FROM [event] WHERE NOT (([eventend] <= @start) OR ([eventstart] >= @end))", ConfigurationManager.ConnectionStrings["DayPilotTest"].ConnectionString); ; da.SelectCommand.Parameters.AddWithValue("start", start); da.SelectCommand.Parameters.AddWithValue("end", start.AddDays(days)); DataTable dt = new DataTable(); da.Fill(dt); return dt; } protected void DayPilotCalendar1_EventMove(object sender, DayPilot.Web.Ui.Events.EventMoveEventArgs e) { // Drag and Drop dbUpdateEvent(e.Value, e.NewStart, e.NewEnd); DayPilotCalendar1.DataSource = dbGetEvents(DayPilotCalendar1.StartDate, DayPilotCalendar1.Days); DayPilotCalendar1.DataBind(); DayPilotCalendar1.Update(); } private void Initialization() { // first bind DayPilotCalendar1.StartDate = DayPilot.Utils.Week.FirstDayOfWeek(new DateTime(2009, 1, 1)); DayPilotCalendar1.DataSource = dbGetEvents(DayPilotCalendar1.StartDate, DayPilotCalendar1.Days); DataBind(); } protected void DayPilotCalendar1_BeforeEventRender(object sender, BeforeEventRenderEventArgs e) { // change the color based on state if (e.Tag["State"] == "Fixed") { e.DurationBarColor = "Brown"; } } protected void DayPilotCalendar1_EventResize(object sender, DayPilot.Web.Ui.Events.EventResizeEventArgs e) { dbUpdateEvent(e.Value, e.NewStart, e.NewEnd); DayPilotCalendar1.DataSource = dbGetEvents(DayPilotCalendar1.StartDate, DayPilotCalendar1.Days); DayPilotCalendar1.DataBind(); DayPilotCalendar1.Update(); } protected void DayPilotCalendar1_EventDoubleClick(object sender, EventClickEventArgs e) { dbInsertEvent(e.Text , e.Start, e.End, "New", "New Meeting"); DayPilotCalendar1.DataSource = dbGetEvents(DayPilotCalendar1.StartDate, DayPilotCalendar1.Days); DayPilotCalendar1.DataBind(); DayPilotCalendar1.Update(); } note that I remove unnecessary code behinds

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• C# Confusing Results from Performance Test

  - by aip.cd.aish

  I am currently working on an image processing application. The application captures images from a webcam and then does some processing on it. The app needs to be real time responsive (ideally < 50ms to process each request). I have been doing some timing tests on the code I have and I found something very interesting (see below). clearLog(); log("Log cleared"); camera.QueryFrame(); camera.QueryFrame(); log("Camera buffer cleared"); Sensor s = t.val; log("Sx: " + S.X + " Sy: " + S.Y); Image<Bgr, Byte> cameraImage = camera.QueryFrame(); log("Camera output acuired for processing"); Each time the log is called the time since the beginning of the processing is displayed. Here is my log output: [3 ms]Log cleared [41 ms]Camera buffer cleared [41 ms]Sx: 589 Sy: 414 [112 ms]Camera output acuired for processing The timings are computed using a StopWatch from System.Diagonostics. QUESTION 1 I find this slightly interesting, since when the same method is called twice it executes in ~40ms and when it is called once the next time it took longer (~70ms). Assigning the value can't really be taking that long right? QUESTION 2 Also the timing for each step recorded above varies from time to time. The values for some steps are sometimes as low as 0ms and sometimes as high as 100ms. Though most of the numbers seem to be relatively consistent. I guess this may be because the CPU was used by some other process in the mean time? (If this is for some other reason, please let me know) Is there some way to ensure that when this function runs, it gets the highest priority? So that the speed test results will be consistently low (in terms of time). EDIT I change the code to remove the two blank query frames from above, so the code is now: clearLog(); log("Log cleared"); Sensor s = t.val; log("Sx: " + S.X + " Sy: " + S.Y); Image<Bgr, Byte> cameraImage = camera.QueryFrame(); log("Camera output acuired for processing"); The timing results are now: [2 ms]Log cleared [3 ms]Sx: 589 Sy: 414 [5 ms]Camera output acuired for processing The next steps now take longer (sometimes, the next step jumps to after 20-30ms, while the next step was previously almost instantaneous). I am guessing this is due to the CPU scheduling. Is there someway I can ensure the CPU does not get scheduled to do something else while it is running through this code?

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• Using commit monitors as a form of code review

  - by Jeff Dege

  I'm working in a small company - four developers, working on a variety of projects. We've been looking at what we can do as cost-effective methods of process improvement, and an idea came up. Given what we do, we often have single developers working on parts of a system, independently of the other developers. This can have a number of negative affects: A developer might not be fully aware of the context in which a change is being implemented, and make the change in a way that will meet the current customer's needs, but will break functionality that other customers depend on. A developer might make a change that breaks the current architectural design, introducing a dependency that will cause problems in future development. Other developers might not be aware of how the system has changed, in areas that they have not worked on. We've talked about doing code reviews, as a way of dealing with these issues. But we've not had much success when we tried. It takes a lot of time to prepare a change for a code review, and it takes everybody out of production while the review is being performed. And the benefits of any review we've tried has been minimal. We're using Subversion (with TortioseSVN) as our VCS. I've been looking at the SubVersion CommitMonitor tool, and wondering whether it might work as a sort of poor-man's code review. It lists every commit made on the repository, allowing someone to see the changes that have been made, the log messages made for that change, the files that were included in the change, and the specific lines in each file that were changed. Rather than scheduling a meeting, trying to get everybody together to review every change, we could just have every developer review every other developer's commits, at whatever time was convenient. This would keep every developer abreast of what changes were being made elsewhere in the system, and would have every change reviewed for customer conflicts and design consistency, at a fairly low cost. If someone saw a problem with the code that was being checked in, he could discuss it with the developer who did the commit, or more likely, schedule a meeting to discuss how the new feature could be implemented in a way that would not impact other users or screw up the architecture. Anyone else doing anything like this, using commit monitors for such a purpose?

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• crash in calloc

  - by mmd

  I'm trying to debug a program I wrote. I ran it inside gdb and I managed to catch a SIGABRT from inside calloc(). I'm completely confused about how this can arise. Can it be a bug in gcc or even libc?? More details: My program uses OpenMP. I ran it through valgrind in single-threaded mode with no errors. I also use mmap() to load a 40GB file, but I doubt that is relevant. Inside gdb, I'm running with 30 threads. Several identical runs (same input&CL) finished correctly, until the problematic one that I caught. On the surface this suggests there might be a race condition of some type. However, the SIGABRT comes from calloc() which is out of my control. Here is some relevant gdb output: (gdb) info threads [...] * 11 Thread 0x7ffff0056700 (LWP 73449) 0x00007ffff6a948a5 in raise () from /lib64/libc.so.6 [...] (gdb) thread 11 [Switching to thread 11 (Thread 0x7ffff0056700 (LWP 73449))]#0 0x00007ffff6a948a5 in raise () from /lib64/libc.so.6 (gdb) bt #0 0x00007ffff6a948a5 in raise () from /lib64/libc.so.6 #1 0x00007ffff6a96085 in abort () from /lib64/libc.so.6 #2 0x00007ffff6ad1fe7 in __libc_message () from /lib64/libc.so.6 #3 0x00007ffff6ad7916 in malloc_printerr () from /lib64/libc.so.6 #4 0x00007ffff6adb79f in _int_malloc () from /lib64/libc.so.6 #5 0x00007ffff6adbdd6 in calloc () from /lib64/libc.so.6 #6 0x000000000040e87f in my_calloc (re=0x7fff2867ef10, st=0, options=0x632020) at gmapper/../gmapper/../common/my-alloc.h:286 #7 read_get_hit_list_per_strand (re=0x7fff2867ef10, st=0, options=0x632020) at gmapper/mapping.c:1046 #8 0x000000000041308a in read_get_hit_list (re=<value optimized out>, options=0x632010, n_options=1) at gmapper/mapping.c:1239 #9 handle_read (re=<value optimized out>, options=0x632010, n_options=1) at gmapper/mapping.c:1806 #10 0x0000000000404f35 in launch_scan_threads (.omp_data_i=<value optimized out>) at gmapper/gmapper.c:557 #11 0x00007ffff7230502 in ?? () from /usr/lib64/libgomp.so.1 #12 0x00007ffff6dfc851 in start_thread () from /lib64/libpthread.so.0 #13 0x00007ffff6b4a11d in clone () from /lib64/libc.so.6 (gdb) f 6 #6 0x000000000040e87f in my_calloc (re=0x7fff2867ef10, st=0, options=0x632020) at gmapper/../gmapper/../common/my-alloc.h:286 286 res = calloc(size, 1); (gdb) p size $2 = 814080 (gdb) The function my_calloc() is just a wrapper, but the problem is not in there, as the real calloc() call looks legit. These are the limits set in the shell: $ ulimit -a core file size (blocks, -c) 0 data seg size (kbytes, -d) unlimited scheduling priority (-e) 0 file size (blocks, -f) unlimited pending signals (-i) 2067285 max locked memory (kbytes, -l) 64 max memory size (kbytes, -m) unlimited open files (-n) 1024 pipe size (512 bytes, -p) 8 POSIX message queues (bytes, -q) 819200 real-time priority (-r) 0 stack size (kbytes, -s) 10240 cpu time (seconds, -t) unlimited max user processes (-u) 1024 virtual memory (kbytes, -v) unlimited file locks (-x) unlimited The program is not out of memory, it's using 41GB on a machine with 256GB available: $ top -b -n 1 | grep gmapper 73437 user 20 0 41.5g 16g 15g T 0.0 6.6 55:17.24 gmapper-ls $ free -m total used free shared buffers cached Mem: 258437 195567 62869 0 82 189677 -/+ buffers/cache: 5807 252629 Swap: 0 0 0 I compiled using gcc (GCC) 4.4.6 20120305 (Red Hat 4.4.6-4), with flags -g -O2 -DNDEBUG -mmmx -msse -msse2 -fopenmp -Wall -Wno-deprecated -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS.

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• Unlocking a mutex from a different thread (C++)

  - by dan

  I'm using the C++ boost::thread library, which in my case means I'm using pthreads. Officially, a mutex must be unlocked from the same thread which locks it, and I want the effect of being able to lock in one thread and then unlock in another. There are many ways to accomplish this. One possibility would be to write a new mutex class which allows this behavior. For example: class inter_thread_mutex{ bool locked; boost::mutex mx; boost::condition_variable cv; public: void lock(){ boost::unique_lock<boost::mutex> lck(mx); while(locked) cv.wait(lck); locked=true; } void unlock(){ { boost::lock_guard<boost::mutex> lck(mx); if(!locked) error(); locked=false; } cv.notify_one(); } // bool try_lock(); void error(); etc. } I should point out that the above code doesn't guarantee FIFO access, since if one thread calls lock() while another calls unlock(), this first thread may acquire the lock ahead of other threads which are waiting. (Come to think of it, the boost::thread documentation doesn't appear to make any explicit scheduling guarantees for either mutexes or condition variables). But let's just ignore that (and any other bugs) for now. My question is, if I decide to go this route, would I be able to use such a mutex as a model for the boost Lockable concept. For example, would anything go wrong if I use a boost::unique_lock< inter_thread_mutex for RAII-style access, and then pass this lock to boost::condition_variable_any.wait(), etc. On one hand I don't see why not. On the other hand, "I don't see why not" is usually a very bad way of determining whether something will work. The reason I ask is that if it turns out that I have to write wrapper classes for RAII locks and condition variables and whatever else, then I'd rather just find some other way to achieve the same effect.

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• My style/control template out my calendar's blackout dates.

  - by Chris

  Howdy, My C#/WPF project needs a calendar. We're going to be using it to pick a range of dates for appointment scheduling. I'm told the default calendar is too small to be used by some of our reps so I've been working on resizing it. <toolkit:Calendar Grid.Row="1" x:Name="DateWindowCalendar" BorderBrush="White" BorderThickness="0" Style="{StaticResource PopupCalendarStyle}" DisplayMode="Month" SelectionMode="SingleRange" DisplayDateStart="{Binding FirstDayOfMonth}" AutomationProperties.AutomationId="ToolkitCalendarId" VerticalAlignment="Top"> </toolkit:Calendar> And I've created this styling: <Style x:Key="PopupCalendarStyle" TargetType="toolkit:Calendar"> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="toolkit:Calendar"> <StackPanel Margin="0" HorizontalAlignment="Center" x:Name="Root"> <toolkit:Calendar x:Name="Calendar" SelectedDate="{TemplateBinding SelectedDate}" DisplayDateStart="{TemplateBinding DisplayDateStart}" SelectionMode="{TemplateBinding SelectionMode}" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" SelectedDatesChanged="Calendar_SelectedDatesChanged"> <toolkit:Calendar.CalendarDayButtonStyle> <Style> <Setter Property="Button.Height" Value="34"/> <Setter Property="Button.Width" Value="34" /> <Setter Property="Button.FontSize" Value="16" /> </Style> </toolkit:Calendar.CalendarDayButtonStyle> <toolkit:Calendar.CalendarButtonStyle> <Style> <Setter Property="Button.Height" Value="34"/> <Setter Property="Button.Width" Value="34"/> <Setter Property="Button.FontSize" Value="16"/> </Style> </toolkit:Calendar.CalendarButtonStyle> </toolkit:Calendar> </StackPanel> </ControlTemplate> </Setter.Value> </Setter> </Style> Everything is almost perfect. I specify my range, I can track the selected dates (granted using the SelectedDatesChanged event instead of the SelectedDates property. The problem is I also need to be able to set blackout dates (usually the period between first of the month and today although sometimes first of the month to a few days from now). Without the styling, this works: DateWindowCalendar.BlackoutDates.Add(new CalendarDateRange( new DateTime(DateTime.Now.Year, DateTime.Now.Month, 01), DateTime.Now)); But when I add the style, I don't get the black out displays being displayed and worse its possible to select the blackout dates. I'm not sure what I missed but I'm hoping someone has an easy answer so that I don't have to rebuild the entire widget. Any help is appreciated. Thanks, Chris

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• Implementing coroutines in Java

  - by JUST MY correct OPINION

  This question is related to my question on existing coroutine implementations in Java. If, as I suspect, it turns out that there is no full implementation of coroutines currently available in Java, what would be required to implement them? As I said in that question, I know about the following: You can implement "coroutines" as threads/thread pools behind the scenes. You can do tricksy things with JVM bytecode behind the scenes to make coroutines possible. The so-called "Da Vinci Machine" JVM implementation has primitives that make coroutines doable without bytecode manipulation. There are various JNI-based approaches to coroutines also possible. I'll address each one's deficiencies in turn. Thread-based coroutines This "solution" is pathological. The whole point of coroutines is to avoid the overhead of threading, locking, kernel scheduling, etc. Coroutines are supposed to be light and fast and to execute only in user space. Implementing them in terms of full-tilt threads with tight restrictions gets rid of all the advantages. JVM bytecode manipulation This solution is more practical, albeit a bit difficult to pull off. This is roughly the same as jumping down into assembly language for coroutine libraries in C (which is how many of them work) with the advantage that you have only one architecture to worry about and get right. It also ties you down to only running your code on fully-compliant JVM stacks (which means, for example, no Android) unless you can find a way to do the same thing on the non-compliant stack. If you do find a way to do this, however, you have now doubled your system complexity and testing needs. The Da Vinci Machine The Da Vinci Machine is cool for experimentation, but since it is not a standard JVM its features aren't going to be available everywhere. Indeed I suspect most production environments would specifically forbid the use of the Da Vinci Machine. Thus I could use this to make cool experiments but not for any code I expect to release to the real world. This also has the added problem similar to the JVM bytecode manipulation solution above: won't work on alternative stacks (like Android's). JNI implementation This solution renders the point of doing this in Java at all moot. Each combination of CPU and operating system requires independent testing and each is a point of potentially frustrating subtle failure. Alternatively, of course, I could tie myself down to one platform entirely but this, too, makes the point of doing things in Java entirely moot. So... Is there any way to implement coroutines in Java without using one of these four techniques? Or will I be forced to use the one of those four that smells the least (JVM manipulation) instead?

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• How to interpret kernel panics?

  - by Owen

  Hi all, I'm new to linux kernel and could barely understand how to debug kernel panics. I have this error below and I don't know where in the C code should I start checking. I was thinking maybe I could echo what functions are being called so I could check where in the code is this null pointer dereferenced. What print function should I use ? How do you interpret the error message below? Unable to handle kernel NULL pointer dereference at virtual address 0000000d pgd = c7bdc000 [0000000d] *pgd=4785f031, *pte=00000000, *ppte=00000000 Internal error: Oops: 17 [#1] PREEMPT Modules linked in: bcm5892_secdom_fw(P) bcm5892_lcd snd_bcm5892 msr bcm5892_sci bcm589x_ohci_p12 bcm5892_skeypad hx_decoder(P) pinnacle hx_memalloc(P) bcm_udc_dwc scsi_mod g_serial sd_mod usb_storage CPU: 0 Tainted: P (2.6.27.39-WR3.0.2ax_standard #1) PC is at __kmalloc+0x70/0xdc LR is at __kmalloc+0x48/0xdc pc : [c0098cc8] lr : [c0098ca0] psr: 20000093 sp : c7a9fd50 ip : c03a4378 fp : c7a9fd7c r10: bf0708b4 r9 : c7a9e000 r8 : 00000040 r7 : bf06d03c r6 : 00000020 r5 : a0000093 r4 : 0000000d r3 : 00000000 r2 : 00000094 r1 : 00000020 r0 : c03a4378 Flags: nzCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment user Control: 00c5387d Table: 47bdc008 DAC: 00000015 Process sh (pid: 1088, stack limit = 0xc7a9e260) Stack: (0xc7a9fd50 to 0xc7aa0000) fd40: c7a6a1d0 00000020 c7a9fd7c c7ba8fc0 fd60: 00000040 c7a6a1d0 00000020 c71598c0 c7a9fd9c c7a9fd80 bf06d03c c0098c64 fd80: c71598c0 00000003 c7a6a1d0 bf06c83c c7a9fdbc c7a9fda0 bf06d098 bf06d008 fda0: c7159880 00000000 c7a6a2d8 c7159898 c7a9fde4 c7a9fdc0 bf06d130 bf06d078 fdc0: c79ca000 c7159880 00000000 00000000 c7afbc00 c7a9e000 c7a9fe0c c7a9fde8 fde0: bf06d4b4 bf06d0f0 00000000 c79fd280 00000000 0f700000 c7a9e000 00000241 fe00: c7a9fe3c c7a9fe10 c01c37b4 bf06d300 00000000 c7afbc00 00000000 00000000 fe20: c79cba84 c7463c78 c79fd280 c7473b00 c7a9fe6c c7a9fe40 c00a184c c01c35e4 fe40: 00000000 c7bb0005 c7a9fe64 c79fd280 c7463c78 00000000 c00a1640 c785e380 fe60: c7a9fe94 c7a9fe70 c009c438 c00a164c c79fd280 c7a9fed8 c7a9fed8 00000003 fe80: 00000242 00000000 c7a9feb4 c7a9fe98 c009c614 c009c2a4 00000000 c7a9fed8 fea0: c7a9fed8 00000000 c7a9ff64 c7a9feb8 c00aa6bc c009c5e8 00000242 000001b6 fec0: 000001b6 00000241 00000022 00000000 00000000 c7a9fee0 c785e380 c7473b00 fee0: d8666b0d 00000006 c7bb0005 00000300 00000000 00000000 00000001 40002000 ff00: c7a9ff70 c79b10a0 c79b10a0 00005402 00000003 c78d69c0 ffffff9c 00000242 ff20: 000001b6 c79fd280 c7a9ff64 c7a9ff38 c785e380 c7473b00 00000000 00000241 ff40: 000001b6 ffffff9c 00000003 c7bb0000 c7a9e000 00000000 c7a9ff94 c7a9ff68 ff60: c009c128 c00aa380 4d18b5f0 08000000 00000000 00071214 0007128c 00071214 ff80: 00000005 c0027ee4 c7a9ffa4 c7a9ff98 c009c274 c009c0d8 00000000 c7a9ffa8 ffa0: c0027d40 c009c25c 00071214 0007128c 0007128c 00000241 000001b6 00000000 ffc0: 00071214 0007128c 00071214 00000005 00073580 00000003 000713e0 400010d0 ffe0: 00000001 bef0c7b8 000269cc 4d214fec 60000010 0007128c 00000000 00000000 Backtrace: [] (__kmalloc+0x0/0xdc) from [] (gs_alloc_req+0x40/0x70 [g_serial]) r8:c71598c0 r7:00000020 r6:c7a6a1d0 r5:00000040 r4:c7ba8fc0 [] (gs_alloc_req+0x0/0x70 [g_serial]) from [] (gs_alloc_requests+0x2c/0x78 [g_serial]) r7:bf06c83c r6:c7a6a1d0 r5:00000003 r4:c71598c0 [] (gs_alloc_requests+0x0/0x78 [g_serial]) from [] (gs_start_io+0x4c/0xac [g_serial]) r7:c7159898 r6:c7a6a2d8 r5:00000000 r4:c7159880 [] (gs_start_io+0x0/0xac [g_serial]) from [] (gs_open+0x1c0/0x224 [g_serial]) r9:c7a9e000 r8:c7afbc00 r7:00000000 r6:00000000 r5:c7159880 r4:c79ca000 [] (gs_open+0x0/0x224 [g_serial]) from [] (tty_open+0x1dc/0x314) [] (tty_open+0x0/0x314) from [] (chrdev_open+0x20c/0x22c) [] (chrdev_open+0x0/0x22c) from [] (__dentry_open+0x1a0/0x2b8) r8:c785e380 r7:c00a1640 r6:00000000 r5:c7463c78 r4:c79fd280 [] (__dentry_open+0x0/0x2b8) from [] (nameidata_to_filp+0x38/0x50) [] (nameidata_to_filp+0x0/0x50) from [] (do_filp_open+0x348/0x6f4) r4:00000000 [] (do_filp_open+0x0/0x6f4) from [] (do_sys_open+0x5c/0x170) [] (do_sys_open+0x0/0x170) from [] (sys_open+0x24/0x28) r8:c0027ee4 r7:00000005 r6:00071214 r5:0007128c r4:00071214 [] (sys_open+0x0/0x28) from [] (ret_fast_syscall+0x0/0x2c) Code: e59c4080 e59c8090 e3540000 159c308c (17943103) ---[ end trace be196e7cee3cb1c9 ]--- note: sh[1088] exited with preempt_count 2 process '-/bin/sh' (pid 1088) exited. Scheduling for restart. Welcome to Wind River Linux

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