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• Whats the difference between Paxos and W+R>=N in Cassandra?

  - by user1128016

  Dynamo-like databases (e.g. Cassandra) provide ability to enforce consistency by means of quorum, i.e. a number of synchronously written replicas (W) and a number of replicas to read (R) should be chosen in such a way that W+RN where N is a replication factor. On the other hand, PAXOS-based systems like Zookeeper are also used as a consistent fault-tolerant storage. What is the difference between these two approaches? Does PAXOS provide guarantees that are not provided by W+RN schema?

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• wanting a good memory + disk caching solution

  - by brofield

  I'm currently storing generated HTML pages in a memcached in-memory cache. This works great, however I am wanting to increase the storage capacity of the cache beyond available memory. What I would really like is: memcached semantics (i.e. not reliable, just a cache) memcached api preferred (but not required) large in-memory first level cache (MRU) huge on-disk second level cache (main) evicted from on-disk cache at maximum storage using LRU or LFU proven implementation In searching for a solution I've found the following solutions but they all miss my marks in some way. Does anyone know of either: other options that I haven't considered a way to make memcachedb do evictions Already considered are: memcachedb best fit but doesn't do evictions: explicitly "not a cache" can't see any way to do evictions (either manual or automatic) tugela cache abandoned, no support don't want to recommend it to customers nmdb doesn't use memcache api new and unproven don't want to recommend it to customers

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• is MS Velocity ready for production?

  - by user80855

  I wonder if anyone has tried velocity in a production environment. It is in CTP2 version right now, and we are thinking of using it. Has anyone tried it? If yes was it a positive experience?

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• Connecting to an RMI object without registry

  - by Mark Probst

  I think I need to connect to a remote RMI object without going through the registry, but I don't know how. My situation is this: I'm implementing a simple job distribution service which consists of one distributor and multiple workers. The distributor has a registered RMI object to which clients connect to send jobs, and workers connect to accept jobs. Unfortunately the distributor and worker hosts are behind a firewall. To get to the distributor host I am tunneling two ports (one for the registry, one for the distributor object) via SSH, so I can get to the registry and the distributor from outside the firewall. To make that work I have to set "-Djava.rmi.server.hostname=localhost" on the distributor JVM so that the clients connect to their local, tunneled port, instead of the port on the actual distributor host, which is blocked. This creates a problem for the workers, though, because they need to connect to the distributor directly, but because of the "localhost" redirection they behave like clients and try to connect to a port on their own host, which is not available, because I'm not tunneling on the workers (it is impractical). Now, if I could connect to a remote object directly by giving the hostname and port, I could do away both with the registry on the distributor and the "localhost" hack, and make the workers connect properly. How do I do that? Or is there a different solution to this problem?

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• What should i do for accomodating large scale data storage and retrieval?

  - by kailashbuki

  There's two columns in the table inside mysql database. First column contains the fingerprint while the second one contains the list of documents which have that fingerprint. It's much like an inverted index built by search engines. An instance of a record inside the table is shown below; 34 "doc1, doc2, doc45" The number of fingerprints is very large(can range up to trillions). There are basically following operations in the database: inserting/updating the record & retrieving the record accoring to the match in fingerprint. The table definition python snippet is: self.cursor.execute("CREATE TABLE IF NOT EXISTS `fingerprint` (fp BIGINT, documents TEXT)") And the snippet for insert/update operation is: if self.cursor.execute("UPDATE `fingerprint` SET documents=CONCAT(documents,%s) WHERE fp=%s",(","+newDocId, thisFP))== 0L: self.cursor.execute("INSERT INTO `fingerprint` VALUES (%s, %s)", (thisFP,newDocId)) The only bottleneck i have observed so far is the query time in mysql. My whole application is web based. So time is a critical factor. I have also thought of using cassandra but have less knowledge of it. Please suggest me a better way to tackle this problem.

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• How do you export or release a Mac OS X program made in Xcode? Program does not load on other comput

  - by SolidSnake4444

  I made a program in Xcode, being a simple calculator that takes a first number, and a second number, and then either adds,subtracts,multiplies, or divides depending on the radio button. I build and run and the program comes up and works fine. When I went to show my friends on their macs, when you double click on the program the program pops in the tray for like .05 seconds and then disappears and we never can actually run the program. It still works perfect however on my computer. What am I doing wrong? How can I take the program I made, and run it on different macs? I have the release set to 10.5 but the active SDK to 10.6. It runs in both 10.5 and 10.6 simulators. One friend has 10.6.3 like me and the other has 10.5.x(cant remember the last part). To get the app, I changed from debug to release and set active SDK to 10.5. Then in the release folder I found the app and sent that over iChat. I feel this will be a problem in the future if I ever make a legit application to distribute. Thank you!

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• Is a Service Bus a good option to communicate with multiple external servers?

  - by PFreitas

  We are developing an application that communicates, via web services or TCP/IP sockets, with multiple servers (up to 50 different external companies). Basically, the exchanged messages are the same (XML), but depending on the inputs of our application we should call 1 or more external servers. The benefits we would expect of introducing a Service Bus in the architecture would be: 1- Remove the need to manage all point-to-point configurations (all the 50 endpoints); 2- Simplify the communication layer of our application by having only one server to talk to; Is a Service Bus a good architectural option for this scenario? What is the best (simplest) Service Bus for this kind of communication? I read a few MSDN articles on Azure Service Bus Relay, but it didn’t seem to fit our needs. Am I wrong? Thanks for your help.

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• C++ Winsock P2P

  - by Goober

  Scenario Does anyone have any good examples of peer-to-peer (p2p) networking in C++ using Winsock? It's a requirement I have for a client who specifically needs to use this technology (god knows why). I need to determine whether this is feasible. Any help would be greatly appreciated.

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• Condor job using DAG with some jobs needing to run the same host

  - by gurney alex

  I have a computation task which is split in several individual program executions, with dependencies. I'm using Condor 7 as task scheduler (with the Vanilla Universe, due do constraints on the programs beyond my reach, so no checkpointing is involved), so DAG looks like a natural solution. However some of the programs need to run on the same host. I could not find a reference on how to do this in the Condor manuals. Example DAG file: JOB A A.condor JOB B B.condor JOB C C.condor JOB D D.condor PARENT A CHILD B C PARENT B C CHILD D I need to express that B and D need to be run on the same computer node, without breaking the parallel execution of B and C. Thanks for your help.

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• How to make my Java Swing application a Client-Server application?

  - by Jonas

  I have made a Java Swing application. Now I would like to make it a Client-Server application. All clients should be notified when data on the server is changed, so I'm not looking for a Web Service. The Client-Server application will be run on a single LAN, it's a business application. The Server will contain a database, JavaDB. What technology and library is easiest to start with? Should I implement it from scratch using Sockets, or should I use Java RMI, or maybe JMS? Or are there other alternatives that are easier to start with? And is there any server library that I should use? Is Jetty an alternative?

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• How to bundle shell script and C code?

  - by eSKay

  I have a C shell script that calls two C programs - one after the another with some file handling before, in-between and afterwards. Now, as such I have three different files - one C shell script and 2 .c files. I need to give this script to other users. The problem is that I have to distribute three files - which the users must keep in the same folder and then execute the script. Is there some better way to do this? [I know I can make one C code file out of those two... but I will still be left with a shell script and a C code. Actually, the two C codes do entirely different things... so I want them to be separate]

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• Parallelizing a serial algorithm

  - by user643813

  Hej folks, I am working on porting a Text mining/Natural language application from single-core to a Map-Reduce style system. One of the steps involves a while loop similar to this: Queue<Element>; while (!queue.empty()) { Element e = queue.next(); Set<Element> result = calculateResultSet(e); if (!result.empty()) { queue.addAll(result); } } Each iteration depends on the result of the one before (kind of). There is no way of determining the number of iterations this loop will have to perform. Is there a way of parallelizing a serial algorithm such as this one? I am trying to think of a feedback mechanism, that is able to provide its own input, but how would one go about parallelizing it? Thanks for any help/remarks

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• How to bundle C/C++ code with C-shell-script?

  - by eSKay

  I have a C shell script that calls two C programs - one after the another with some file handling before, in-between and afterwards. Now, as such I have three different files - one C shell script and 2 .c files. I need to give this script to other users. The problem is that I have to distribute three files - which the users must keep in the same folder and then execute the script. Is there some better way to do this? [I know I can make one C code file out of those two... but I will still be left with a shell script and a C code. Actually, the two C codes do entirely different things... so I want them to be separate]

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• Split text files Accross threads

  - by Kevin

  The problem: I have a few text files (10) with numbers in them on every line. I need to have them split across some threads I create using the pthread library. these threads that are created (worker threads) are to find the largest prime number that gets sent to them (and over all the largest prime from all of the text files). My current thoughts on solutions: I am thinking myself to have two arrays and all of the text files in one array and the other array will contain a binary file that I can read say 1000 lines and send the pointer to the index of that binary file in a struct that contains the id, file pointer, and file position and let it crank through that. a little bit of what I am talking about pthread_create(&threads[index],NULL,calc_sqrt,(void *)threadFields[index]);//Pass struct to each worker Struct: typedef struct threadFields{ int *id, *position; FILE *Fin; }tField; If anyone has any insight or a better solution it would be greatly appreciated Thanks

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• How do I control output files name and content of an Hadoop streaming job?

  - by Eran Kampf

  Is there a way to control the output filenames of an Hadoop Streaming job? Specifically I would like my job's output files content and name to be organized by the ket the reducer outputs - each file would only contain values for one key and its name would be the key. Update: Just found the answer - Using a Java class that derives from MultipleOutputFormat as the jobs output format allows control of the output file names. http://hadoop.apache.org/core/docs/current/api/org/apache/hadoop/mapred/lib/MultipleOutputFormat.htmlhttp://hadoop.apache.org/core/docs/current/api/org/apache/hadoop/mapred/lib/MultipleOutputFormat.html I havent seen any samples for this out there... Can anyone point out to an Hadoop Streaming sample that makes use of a custom output format Java class?

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• How to bundle C code in C shell script?

  - by eSKay

  I have a C shell script that calls two C programs - one after the another with some file handling before, in-between and afterwards. Now, as such I have three different files - one C shell script and 2 .c files. I need to give this script to other users. The problem is that I have to distribute three files - which the users must keep in the same folder and then execute the script. Is there some better way to do this? [I know I can make one C code file out of those two... but I will still be left with a shell script and a C code. Actually, the two C codes do entirely different things... so I want them to be separate]

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• How to provide an API client with 1,000,000 database results?

  - by Chris Dutrow

  What is a good way to provide an API client with 1,000,000 database results? We are cureently using PostgreSQL. A few suggested methods: Paging using Cursors Paging using random numbers ( Add "GREATER THAN ORDER BY " to each query ) Save information to a file and let the client download it Iterate through results, then POST the data to the client server Return only keys to the client, then let the client request the objects from Cloud files like Amazon S3 (still may require paging just to get the file names ). What haven't I thought of that is stupidly simple and way better than any of these options?

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• Pseudorandom Number Generation with Specific Non-Uniform Distributions

  - by carnun

  Hello all, I'm writing a program that simulates various random walks (with differing distributions). At each timestep, I need randomly generated, two dimensional step distances and angles from the distribution of the random walk. I'm hoping someone can check my understanding of how to generate these random numbers. As I understand it I can use Inverse Transform Sampling as follows: If f(x) is the pdf of our random walk that has a non-uniform distribution, and y is a random number from a uniform distribution. Then if we let f(x) = y and solve to find x then we have a random number from the non-uniform distribution. Is this a feasible solution?

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• Oracle global_names DELETE problem

  - by jyzuz

  I'm using a database link to execute a DELETE statement on another DB, but the DB link name doesn't conform to global naming, and this requirement cannot change. Also I have global_names set to false, and cannot be changed either. When I try to use these links however, I receive: ORA-02069: - global_names parameter must be set to TRUE for this operation Cause: A remote mapping of the statement is required but cannot be achieved because GLOBAL_NAMES should be set to TRUE for it to be achieved. - Action: Issue `ALTER SESSION SET GLOBAL_NAMES = TRUE` (if possible) What is the alternative action when setting global_names=true is not possible? Cheers, Jean

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• DBA's say no to SQL Server DTC?

  - by NabilS

  I am trying to get our DBA's to enable DTC on a cluster of SQL Server 2005. Unfortunately they keep refusing. Their argument that they would need to set up a dedicated host for DTC (Could take months!!) as it is not a matter of ticking a few boxes. Is this true? How intrusive is DTC on a shared environment such as a SQL farm. Do I have an argument against this? Thanks

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• Using Git or Mercurial, how would you know when you do a clone or a pull, no one is checking in file

  - by Jian Lin

  Using Git or Mercurial, how would you know when you do a clone or a pull, no one is checking in files (pushing it)? It can be important that: 1) You never know it is in an inconsistent state, so you try for 2 hours trying to debug the code for what's wrong. 2) With all the framework code -- potentially hundreds of files -- if some files are inconsistent with the other, can't the rake db:migrate or script/generate controller cause some damage or inconsistencies to the code base?

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• Mesos slave not 'Running' multiple executors simultaneously

  - by user3084164

  I am using Mesos to distribute a bunch of tasks to different machines (mesos-slaves). Here is what happens: 1. My scheduler gets resource offers and accepts it. 2. Mesos stages multiple executors on the same mesos-slaves (each slave has 4 cpus) 3. Only ONE executor enters the 'Running' state on each of the slaves while the others are shown in 'Staging' state. 4. Only after the current executor finishes execution the other executor starts running. Given that I have 4 CPUs on each machine, shouldn't each slave be running 4 executors simultaneously? Each executor requires 1 CPU.

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• Distributed Application Environment and Web Services - What/How to learn?

  - by Dan

  I want to learn how to create distributed application environments and web services using spring, aspectj, hibernate, etc. rather than EJBs. Can anyone recommend a book or set of books that can help me (a single all-in-one book would be preferable)? Also, any advice regarding learning/creating distributed app environments and web services is appreciated.

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• Why does Process Explorer cause highly targeted failure of some applications / basic UI functions in a high-power EC2 Windows instance?

  - by Dan Nissenbaum

  Update: I have determined that Process Explorer itself - the program I am using to debug a performance issue - seems to be the cause of the issue. See note, with updated question, at end. I am running a high-power (cc2.8xlarge) Amazon AWS EC2 Windows instance off of a boot EBS volume, provisioned at 2500 PIOPS, which was created from a snapshot of a previous boot volume. My purpose with the instance is to use it as a development workstation with many developer tools installed, such as Visual Studio, a local XAMPP stack, etc. I have upwards of 40 programs installed on the machine. The usability of the instance as a development machine often works quite well. The RDP lag is adequately small. I have used it for hours on end without problems for some of my most intense development tasks. As a result, I have just purchased a reserved instance, and I opted to rebuild my development machine starting from scratch with a Windows Server 2012 AMI. After having installed all of my desired/required applications for development over this past week, again the machine seems to often work well and I have worked for up to an hour at a time without problems doing heavy development work. However, I continue to run into catastrophic OS usability issues that may prevent me from being able to rely on this machine as a development machine. I would like to track down the source of the problem, if there is an easily identifiable source. (Update: I have tracked down the source to be Process Explorer, the very program I was using to debug the problem. See update at end.) The issues are as follows. (These are some primary examples) Some applications, after a period of adequate responsiveness, suddenly begin to respond very, very slowly to basic user interface actions such as clicking on menus and pressing Ctrl-Tab to switch between open documents. Two examples are UltraEdit and PhpEd. It typically takes ~2 seconds for a menu to appear, and ~4 seconds to switch between open documents. Additionally, insertion point motion in the editor is lagged by upwards of ~2 seconds. Process Explorer, which I am using to help debug the problem, seems to run acceptably for a couple of minutes, but on multiple occasions Process Explorer itself hangs completely. It hangs at the same time as the problems noted above. When it hangs, it is 100% unresponsive. Clicking on its taskbar icon neither causes it to come to the top or go behind, and its viewable area is filled with nothing but a region partially containing pure white and partially containing incomplete windows widgets that are unreadable, and that never change. Waiting 10 minutes does not clear the problem. Attempting to force-quit Process Explorer by right-clicking on its taskbar icon and choosing "Close Window" takes about 5 full minutes to exit (Process Explorer itself can't be used to exit Process Explorer, and it is registered as a Task Manager substitute). Other programs work just fine during this time. For example, Chrome tabs flip very quickly back and forth, menus pop open instantly, web pages load quickly, and typing in forms/web applications inside the browser works promptly. Another example of an application that works crisply is Filemaker - its menus open instantly, and switching views in this application occurs promptly. Other applications also work without issue. Also, switching between applications occurs promptly as well. It is only a handful of applications that exhibit the problem, with some primary examples given above. At first I thought that EBS IOPS might be a problem. Therefore, I ran Performance Monitor, and watched the "Disk Transfers/sec" monitor in real time. At no point did this measure come anywhere close to hitting the 2500 PIOPS provisioned for the EBS volume. The RAM was also well under the limit (~10 GB used out of 60 GB). I did notice that one CPU core (out of 32 logical cores) was fully thrashing at 100% (i.e., ~3.1%) during the problematic periods. This seems to indicate that a single CPU core is handling the menus / flipping between open documents (for some applications only) / managing the Process Explorer user interface, and that this single core was hosed for some reason during the problematic periods. Also note that I have a desktop workstation (Windows 7) that I also use as a development machine, via a remote connection, with a nearly identical set of programs installed, and this desktop workstation does not exhibit any of the problems I've discussed above. I have been using it heavily for well over a year now. Any suggestions regarding either the source of the problem, or steps I might take to investigate the source of the problem, would be appreciated. Thanks. Note: After extensive testing & investigation, I have noticed that when I quit Process Explorer, the problem vanishes and the system performance returns to normal, and then reappears quickly when I run Process Explorer again (note: again, the performance problems only appear for a subset of applications - other applications work perfectly fine during the same period). My question is therefore (thankfully) more specific: Why does Process Explorer cause highly targeted failure of some applications (including itself) and basic UI functions, in a high-power EC2 Windows instance?

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• Iron Speed Designer 7.0 - the great gets greater!

  - by GGBlogger

  For Immediate Release Iron Speed, Inc. Kelly Fisher +1 (408) 228-3436 [email protected] http://www.ironspeed.com       Iron Speed Version 7.0 Generates SharePoint Applications New! Support for Microsoft SharePoint speeds application generation and deployment   San Jose, CA – June 8, 2010. Software development tools-maker Iron Speed, Inc. released Iron Speed Designer Version 7.0, the latest version of its popular Web 2.0 application generator. Iron Speed Designer generates rich, interactive database and reporting applications for .NET, Microsoft SharePoint and the Cloud.    In addition to .NET applications, Iron Speed Designer V7.0 generates database-driven SharePoint applications. The ability to quickly create database-driven applications for SharePoint eliminates a lot of work, helping IT departments generate productivity-enhancing applications in just a few hours.  Generated applications include integrated SharePoint application security and use SharePoint master pages.    “It’s virtually impossible to build database-driven application in SharePoint by hand. Iron Speed Designer V7.0 not only makes this possible, the tool makes it easy.” – Razi Mohiuddin, President, Iron Speed, Inc.     Integrated SharePoint application security Generated applications include integrated SharePoint application security. SharePoint sites and their groups are used to retrieve security roles. Iron Speed Designer validates the user against a Microsoft SharePoint server on your network by retrieving the logged in user’s credentials from the SharePoint Context.    “The Iron Speed Designer generated application integrates seamlessly with SharePoint security, removing the hassle of designing, testing and approving your own security layer.” -Michael Landi, Solutions Architect, Light Speed Solutions     SharePoint Solution Packages Iron Speed Designer V7.0 creates SharePoint Solution Packages (WSPs) for easy application deployment. Using the Deployment Wizard, a single application WSP is created and can be deployed to your SharePoint server.   “Iron Speed Designer is the first product on the market that allows easy and painless deployment of database-driven .NET web applications inside the SharePoint environment.” -Bryan Patrick, Developer, Pseudo Consulting     SharePoint master pages and themes In V7.0, generated applications use SharePoint master pages and contain the same content as other SharePoint pages. Generated applications use the current SharePoint color scheme and display standard SharePoint navigation controls on each page.   “Iron Speed Designer preserves the look and feel of the SharePoint environment in deployed database applications without additional hand-coding.” -Kirill Dmitriev, Software Developer, Iron Speed, Inc.     Iron Speed Designer Version 7.0 System Requirements Iron Speed Designer Version 7.0 runs on Microsoft Windows 7, Windows Vista, Windows XP, and Windows Server 2003 and 2008. It generates .NET Web applications for Microsoft SQL Server, Oracle, Microsoft Access and MySQL. These applications may be deployed on any machine running the .NET Framework. Iron Speed Designer supports Microsoft SharePoint 2007 and Windows SharePoint Services (WSS3). Find complete information about Iron Speed Designer Version 7.0 at www.ironspeed.com.     About Iron Speed, Inc. Iron Speed is the leader in enterprise-class application generation. Our software development tools generate database and reporting applications in significantly less time and cost than hand-coding. Our flagship product, Iron Speed Designer, is the fastest way to deliver applications for the Microsoft .NET and software-as-a-service cloud computing environments.   With products built on decades of experience in enterprise application development and large-scale e-commerce systems, Iron Speed products eliminate the need for developers to choose between "full featured" and "on schedule."   Founded in 1999, Iron Speed is well funded with a capital base of over $20M and strategic investors that include Arrow Electronics and Avnet, as well as executives from AMD, Excelan, Onsale, and Oracle. The company is based in San Jose, Calif., and is located online at www.ironspeed.com.

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