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  • Why the server is not responding?

    - by par
    Hello! Our server occasionally refuses to serve a simple HTML page. This is happening during a relatively high number of requests. However, the processor is not heavy loaded and there are a lot of free memory. The error seems to occure 1 out of 50 requests in average, depending on the server load. I need to find the source of the problem and take the appropriate actions to eliminate it. I have a suspicion that the problem source is a huge number of incoming network packets. There are 5000 packets per second on average. Traffic - 2 MBits/sec Can this be the cause of the error? There is an interesting thing, in case the server fails to respond, the request string is not logged to access.log by Apache. The error is repeatable from several client computers. DNS is not involved, since I have accessed the server by the IP. I have profiled the problem case with tcpdump utility. These are the good and bad sessions traced by tcpdump. The request is the same in both experiments. Good - server returns response. Bad - no response, time-out error. ---- Bad ---- 12:23:36.366292 IP 123.45.67.890.61749 > myserver.superbservers.com.www: S 2125316338:2125316338(0) win 8192 <mss 1460,nop,wscale 2,nop,nop,sackOK> 12:23:39.362394 IP 123.45.67.890.61749 > myserver.superbservers.com.www: S 2125316338:2125316338(0) win 8192 <mss 1460,nop,wscale 2,nop,nop,sackOK> 12:23:45.365567 IP 123.45.67.890.61749 > myserver.superbservers.com.www: S 2125316338:2125316338(0) win 8192 <mss 1460,nop,nop,sackOK> -------- ---- Good ---- 12:27:07.632229 IP 123.45.67.890.63914 > myserver.superbservers.com.www: S 3581365570:3581365570(0) win 8192 <mss 1460,nop,wscale 2,nop,nop,sackOK> 12:27:10.620946 IP 123.45.67.890.63914 > myserver.superbservers.com.www: S 3581365570:3581365570(0) win 8192 <mss 1460,nop,wscale 2,nop,nop,sackOK> 12:27:10.620969 IP myserver.superbservers.com.www > 123.45.67.890.63914: S 2654770980:2654770980(0) ack 3581365571 win 5840 <mss 1460,nop,nop,sackOK,nop,wscale 6> 12:27:10.838747 IP 123.45.67.890.63914 > myserver.superbservers.com.www: . ack 1 win 4380 12:27:10.957143 IP 123.45.67.890.63914 > myserver.superbservers.com.www: P 1:213(212) ack 1 win 4380 12:27:10.957152 IP myserver.superbservers.com.www > 123.45.67.890.63914: . ack 213 win 108 12:27:10.965543 IP myserver.superbservers.com.www > 123.45.67.890.63914: P 1:630(629) ack 213 win 108 12:27:10.965621 IP myserver.superbservers.com.www > 123.45.67.890.63914: F 630:630(0) ack 213 win 108 12:27:11.183540 IP 123.45.67.890.63914 > myserver.superbservers.com.www: . ack 631 win 4222 12:27:11.185657 IP 123.45.67.890.63914 > myserver.superbservers.com.www: F 213:213(0) ack 631 win 4222 12:27:11.185663 IP myserver.superbservers.com.www > 123.45.67.890.63914: . ack 214 win 108 -------- Hoster: SuperbHosting OS: Ubuntu Server parameters: E6300 CONROE 1.86GHZ 2 X 1MB CACHE 1066 1GB DDR2 667MHZ This is a link to apache configuration file we use http://repkin5.snow.prohosting.com/apache.txt This is server-status report taken right after time-out error. http://repkin5.snow.prohosting.com/server-status.htm There are only 10 Child Servers running out of 120, so enough space for new requests. VMSTAT procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu---- r b swpd free buff cache si so bi bo in cs us sy id wa 0 0 8900 725900 8468 65684 0 0 5 18 11 33 4 3 92 1

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  • What is Database Continuous Integration?

    - by David Atkinson
    Although not everyone is practicing continuous integration, many have at least heard of the concept. A recent poll on www.simple-talk.com indicates that 40% of respondents are employing the technique. It is widely accepted that the earlier issues are identified in the development process, the lower the cost to the development process. The worst case scenario, of course, is for the bug to be found by the customer following the product release. A number of Agile development best practices have evolved to combat this problem early in the development process, including pair programming, code inspections and unit testing. Continuous integration is one such Agile concept that tackles the problem at the point of committing a change to source control. This can alternatively be run on a regular schedule. This triggers a sequence of events that compiles the code and performs a variety of tests. Often the continuous integration process is regarded as a build validation test, and if issues were to be identified at this stage, the testers would simply not 'waste their time ' and touch the build at all. Such a ‘broken build’ will trigger an alert and the development team’s number one priority should be to resolve the issue. How application code is compiled and tested as part of continuous integration is well understood. However, this isn’t so clear for databases. Indeed, before I cover the mechanics of implementation, we need to decide what we mean by database continuous integration. For me, database continuous integration can be implemented as one or more of the following: 1)      Your application code is being compiled and tested. You therefore need a database to be maintained at the corresponding version. 2)      Just as a valid application should compile, so should the database. It should therefore be possible to build a new database from scratch. 3)     Likewise, it should be possible to generate an upgrade script to take your already deployed databases to the latest version. I will be covering these in further detail in future blogs. In the meantime, more information can be found in the whitepaper linked off www.red-gate.com/ci If you have any questions, feel free to contact me directly or post a comment to this blog post.

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  • How do I fix Google Earth 6.2.2 theme and fonts in 12.04?

    - by Joshua Robison
    Here is the problem. I would like to know how to get Google Earth using better fonts with anti-aliasing for English and Japanese. Don't know what these fonts are but they are hideous and completely different from my system fonts or Libre Office fonts or even QT apps like VLC and MiniTube. I'm using 12.04 LTS 32bit and almost had complete success with the 11.10 fix posted here Google Earth and Skype theme the theme and fonts will show up correctly for about 5 seconds before the program crashes.

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  • What is Database Continuous Integration?

    - by SQLDev
    Although not everyone is practicing continuous integration, many have at least heard of the concept. A recent poll on www.simple-talk.com indicates that 40% of respondents are employing the technique. It is widely accepted that the earlier issues are identified in the development process, the lower the cost to the development process. The worst case scenario, of course, is for the bug to be found by the customer following the product release. A number of Agile development best practices have evolved to combat this problem early in the development process, including pair programming, code inspections and unit testing. Continuous integration is one such Agile concept that tackles the problem at the point of committing a change to source control. This can alternatively be run on a regular schedule. This triggers a sequence of events that compiles the code and performs a variety of tests. Often the continuous integration process is regarded as a build validation test, and if issues were to be identified at this stage, the testers would simply not 'waste their time ' and touch the build at all. Such a ‘broken build’ will trigger an alert and the development team’s number one priority should be to resolve the issue. How application code is compiled and tested as part of continuous integration is well understood. However, this isn’t so clear for databases. Indeed, before I cover the mechanics of implementation, we need to decide what we mean by database continuous integration. For me, database continuous integration can be implemented as one or more of the following: 1)      Your application code is being compiled and tested. You therefore need a database to be maintained at the corresponding version. 2)      Just as a valid application should compile, so should the database. It should therefore be possible to build a new database from scratch. 3)     Likewise, it should be possible to generate an upgrade script to take your already deployed databases to the latest version. I will be covering these in further detail in future blogs. In the meantime, more information can be found in the whitepaper linked off www.red-gate.com/ci If you have any questions, feel free to contact me directly or post a comment to this blog post.

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  • Be Careful When Referencing SPList.Items

    - by Brian Jackett
    Be very careful how you reference your SPListItem objects through the SharePoint API.  I’ll say it again.  Be very careful how you reference your SPListItem objects through the SharePoint API.  Ok, now that you get the point that this will be a “learn from my mistakes and don’t do unsmart things like I did” post, let’s dig into what it was that I did poorly. Scenario     For the past year I’ve been building custom .Net applications that are hosted through SharePoint.  These application involve a number of SharePoint lists, external databases, custom web parts, and other SharePoint elements to provide functionality.  About two weeks ago I received a message from one of our end users that a custom application was performing slowly.  Specifically performance was slow when users were performing actions that interacted with the primary SharePoint list storing data for that app. The Problem     I took a copy of the production site into a dev environment to investigate the code that was executing.  After attaching the debugger and running through the code I quickly found pieces of code referencing SPListItem objects (like below) that were performing very poorly: SPListItem myItem = SPContext.Current.Web.Lists["List Name"].Items.GetItemById(value); // do updates on SPListItem retrieved     As it turns out the SPList I was referencing was fairly large at ~1000 items and weighing in over 150 MB.  You see the problem with my above code is that I retrieved the SPListItem by first (unnecessarily) going through the Items member of the list.  As I understand it, when doing so the executing code will attempt to resolve that entity and pull it from the database and into RAM (all 150 MB.)  This causes the equivalent of a 50 car pile up in terms of performance with a single update taking more than 15 seconds. The Solution     The solution is actually quite simple and I wish I had realized this during development.  Instead of going through the Items member it is possible to call GetItemById(…) directly on the SPList as in the example below: SPListItem myItem = SPContext.Current.Web.Lists["List Name"].GetItemById(value); // do updates on SPListItem retrieved     After making this simple change performance skyrocketed and updates were back to less than a second.   Conclusion     When given the option between two solutions, usually the simplest is the best solution.  In my scenario I was adding extra complexity going through the API the long way around to get to the objects I needed and it ended up hurting performance greatly.  Luckily we were able to find and resolve the performance issue in a relatively short amount of time.  Like I said at the beginning of the post, learn from my mistakes and hope it helps you.         -Frog Out   Image linked from http://www.freespirit.com/files/IMAGE/COVER/LARGE/BeCarefulSafe.jpg

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  • JavaOne Rock Star – Adam Bien

    - by Janice J. Heiss
    Among the most celebrated developers in recent years, especially in the domain of Java EE and JavaFX, is consultant Adam Bien, who, in addition to being a JavaOne Rock Star for Java EE sessions given in 2009 and 2011, is a Java Champion, the winner of Oracle Magazine’s 2011 Top Java Developer of the Year Award, and recently won a 2012 JAX Innovation Award as a top Java Ambassador. Bien will be presenting the following sessions: TUT3907 - Java EE 6/7: The Lean Parts CON3906 - Stress-Testing Java EE 6 Applications Without Stress CON3908 - Building Serious JavaFX 2 Applications CON3896 - Interactive Onstage Java EE Overengineering I spoke with Bien to get his take on Java today. He expressed excitement that the smallest companies and startups are showing increasing interest in Java EE. “This is a very good sign,” said Bien. “Only a few years ago J2EE was mostly used by larger companies -- now it becomes interesting even for one-person shows. Enterprise Java events are also extremely popular. On the Java SE side, I'm really excited about Project Nashorn.” Nashorn is an upcoming JavaScript engine, developed fully in Java by Oracle, and based on the Da Vinci Machine (JSR 292) which is expected to be available for Java 8.    Bien expressed concern about a common misconception regarding Java's mediocre productivity. “The problem is not Java,” explained Bien, “but rather systems built with ancient patterns and approaches. Sometimes it really is ‘Cargo Cult Programming.’ Java SE/EE can be incredibly productive and lean without the unnecessary and hard-to-maintain bloat. The real problems are ‘Ivory Towers’ and not Java’s lack of productivity.” Bien remarked that if there is one thing he wanted Java developers to understand it is that, "Premature optimization is the root of all evil. Or at least of some evil. Modern JVMs and application servers are hard to optimize upfront. It is far easier to write simple code and measure the results continuously. Identify the hotspots first, then optimize.”   He advised Java EE developers to, “Rethink everything you know about Enterprise Java. Before you implement anything, ask the question: ‘Why?’ If there is no clear answer -- just don't do it. Most well known best practices are outdated. Focus your efforts on the domain problem and not the technology.” Looking ahead, Bien remarked, “I would like to see open source application servers running directly on a hypervisor. Packaging the whole runtime in a single file would significantly simplify the deployment and operations.” Check out a recent Java Magazine interview with Bien about his Java EE 6 stress monitoring tool here.

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  • How do I fix a noisy input device (Internal Mic)? snd_hda_intel - debug included

    - by hazrpg
    As the title says, I'm having trouble with a very noisy audio input device - the internal mic or any plugged in mics. So far I've narrowed it down to an problem in ALSA since my debug info is showing a lot of "null" values. Can anyone help? Debug Info: http://www.alsa-project.org/db/?f=e0c6fb7e10624bf7691aa2b405cf0d3968e56c63 Exert from the debug: model : (null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null)

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  • Ubuntu server spontaneous reboot

    - by user1941407
    I have got two ubuntu 12.04 servers(xeon e3). Sometimes(several days) each server spontaneously reboots. HDDs and other hardware are ok. Which logfile can help find a reason of the problem? UPDATED. hardware: xeon e3 processor, intel server motherboard, 32gb ddr3 ecc, mdadm mirror hdd raid for system, mdadm ssd raid for database(postgres). Both servers have similar (not identical) components. Smart is OK. It seems that the problem is in the software. Python process and database are running on this servers. Syslog (time of reboot): Aug 23 13:42:23 xeon hddtemp[1411]: /dev/sdc: WDC WD15NPVT-00Z2TT0: 34 C Aug 23 13:42:23 xeon hddtemp[1411]: /dev/sdd: WDC WD15NPVT-00Z2TT0: 34 C Aug 23 13:43:24 xeon hddtemp[1411]: /dev/sdc: WDC WD15NPVT-00Z2TT0: 34 C Aug 23 13:43:24 xeon hddtemp[1411]: /dev/sdd: WDC WD15NPVT-00Z2TT0: 34 C Aug 23 13:44:14 xeon sensord: Chip: acpitz-virtual-0 Aug 23 13:44:14 xeon sensord: Adapter: Virtual device Aug 23 13:44:14 xeon sensord: temp1: 27.8 C Aug 23 13:44:14 xeon sensord: temp2: 29.8 C Aug 23 13:44:14 xeon sensord: Chip: coretemp-isa-0000 Aug 23 13:44:14 xeon sensord: Adapter: ISA adapter Aug 23 13:44:14 xeon sensord: Physical id 0: 37.0 C Aug 23 13:44:14 xeon sensord: Core 0: 37.0 C Aug 23 13:44:14 xeon sensord: Core 1: 37.0 C Aug 23 13:44:14 xeon sensord: Core 2: 37.0 C Aug 23 13:44:14 xeon sensord: Core 3: 37.0 C Aug 23 13:44:24 xeon hddtemp[1411]: /dev/sdc: WDC WD15NPVT-00Z2TT0: 34 C Aug 23 13:44:24 xeon hddtemp[1411]: /dev/sdd: WDC WD15NPVT-00Z2TT0: 34 C Aug 23 13:47:01 xeon kernel: imklog 5.8.6, log source = /proc/kmsg started. Aug 23 13:47:01 xeon rsyslogd: [origin software="rsyslogd" swVersion="5.8.6" x-pid="582" x-info="http://www.rsyslog.com"] start Aug 23 13:47:01 xeon rsyslogd: rsyslogd's groupid changed to 103 Aug 23 13:47:01 xeon rsyslogd: rsyslogd's userid changed to 101 Aug 23 13:47:00 xeon rsyslogd-2039: Could not open output pipe '/dev/xconsole' [try http://www.rsyslog.com/e/2039 ] Aug 23 13:47:01 xeon kernel: [ 0.000000] Initializing cgroup subsys cpuset Aug 23 13:47:01 xeon kernel: [ 0.000000] Initializing cgroup subsys cpu Aug 23 13:47:01 xeon kernel: [ 0.000000] Initializing cgroup subsys cpuacct Aug 23 13:47:01 xeon kernel: [ 0.000000] Linux version 3.11.0-26-generic (buildd@komainu) (gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5) ) #45~precise1-Ubuntu SMP Tue Jul 15 04:02:35 UTC 2014 (Ubuntu 3.11.0-26.45~precise1-generic 3.11.10.12) Aug 23 13:47:01 xeon kernel: [ 0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-3.11.0-26-generic root=UUID=0daa7f53-6c74-47d2-873e-ebd339cd39b0 ro splash quiet vt.handoff=7 Aug 23 13:47:01 xeon kernel: [ 0.000000] KERNEL supported cpus: Aug 23 13:47:01 xeon kernel: [ 0.000000] Intel GenuineIntel Aug 23 13:47:01 xeon kernel: [ 0.000000] AMD AuthenticAMD Aug 23 13:47:01 xeon kernel: [ 0.000000] Centaur CentaurHauls Aug 23 13:47:01 xeon kernel: [ 0.000000] e820: BIOS-provided physical RAM map: Aug 23 13:47:01 xeon kernel: [ 0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009bbff] usable Aug 23 13:47:01 xeon kernel: [ 0.000000] BIOS-e820: [mem 0x000000000009bc00-0x000000000009ffff] reserved Dmseg - nothing strange.

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  • Prevent your Silverlight XAP file from caching in your browser.

    - by mbcrump
    If you work with Silverlight daily then you have run into this problem. Your XAP file has been cached in your browser and you have to empty your browser cache to resolve it. If your using Google Chrome then you typically do the following: Go to Options –> Clear Browsing History –> Empty the Cache and finally click Clear Browsing data. As you can see, this is a lot of unnecessary steps. It is even worse when you have a customer that says, “I can’t see the new features you just implemented!” and you realize it’s a cached xap problem.  I have been struggling with a way to prevent my XAP file from caching inside of a browser for a while now and decided to implement the following solution. If the Visual Studio Debugger is attached then add a unique query string to the source param to force the XAP file to be refreshed. If the Visual Studio Debugger is not attached then add the source param as Visual Studio generates it. This is also in case I forget to remove the above code in my production environment. I want the ASP.NET code to be inline with my .ASPX page. (I do not want a separate code behind .cs page or .vb page attached to the .aspx page.) Below is an example of the hosting code generated when you create a new Silverlight project. As a quick refresher, the hard coded param name = “source” specifies the location of your XAP file.  <form id="form1" runat="server" style="height:100%"> <div id="silverlightControlHost"> <object data="data:application/x-silverlight-2," type="application/x-silverlight-2" width="100%" height="100%"> <param name="source" value="ClientBin/SilverlightApplication2.xap"/> <param name="onError" value="onSilverlightError" /> <param name="background" value="white" /> <param name="minRuntimeVersion" value="4.0.50826.0" /> <param name="autoUpgrade" value="true" /> <a href="http://go.microsoft.com/fwlink/?LinkID=149156&v=4.0.50826.0" style="text-decoration:none"> <img src="http://go.microsoft.com/fwlink/?LinkId=161376" alt="Get Microsoft Silverlight" style="border-style:none"/> </a> </object><iframe id="_sl_historyFrame" style="visibility:hidden;height:0px;width:0px;border:0px"></iframe></div> </form> We are going to use a little bit of inline ASP.NET to generate the param name = source dynamically to prevent the XAP file from caching. Lets look at the completed solution: <form id="form1" runat="server" style="height:100%"> <div id="silverlightControlHost"> <object data="data:application/x-silverlight-2," type="application/x-silverlight-2" width="100%" height="100%"> <% string strSourceFile = @"ClientBin/SilverlightApplication2.xap"; string param; if (System.Diagnostics.Debugger.IsAttached) //Debugger Attached - Refresh the XAP file. param = "<param name=\"source\" value=\"" + strSourceFile + "?" + DateTime.Now.Ticks + "\" />"; else { //Production Mode param = "<param name=\"source\" value=\"" + strSourceFile + "\" />"; } Response.Write(param); %> <param name="onError" value="onSilverlightError" /> <param name="background" value="white" /> <param name="minRuntimeVersion" value="4.0.50826.0" /> <param name="autoUpgrade" value="true" /> <a href="http://go.microsoft.com/fwlink/?LinkID=149156&v=4.0.50826.0" style="text-decoration:none"> <img src="http://go.microsoft.com/fwlink/?LinkId=161376" alt="Get Microsoft Silverlight" style="border-style:none"/> </a> </object><iframe id="_sl_historyFrame" style="visibility:hidden;height:0px;width:0px;border:0px"></iframe></div> </form> We add the location to our XAP file to strSourceFile and if the debugger is attached then it will append DateTime.Now.Ticks to the XAP file source and force the browser to download the .XAP. If you view the page source of your Silverlight Application then you can verify it worked properly by looking at the param name = “source” tag as shown below. <param name="source" value="ClientBin/SilverlightApplication2.xap?634299001187160148" /> If the debugger is not attached then it will use the standard source tag as shown below. <param name="source" value="ClientBin/SilverlightApplication2.xap"/> At this point you may be asking, How do I prevent my XAP file from being cached on my production app? Well, you have two easy options: 1) I really don’t recommend this approach but you can force the XAP to be refreshed everytime with the following code snippet.  <param name="source" value="ClientBin/SilverlightApplication2.xap?<%=Guid.NewGuid().ToString() %>"/> NOTE: You could also substitute the “Guid.NewGuid().ToString() for anything that create a random field. (I used DateTime.Now.Ticks earlier). 2) Another solution that I like even better involves checking the XAP Creation Date and appending it to the param name = source. This method was described by Lars Holm Jenson. <% string strSourceFile = @"ClientBin/SilverlightApplication2.xap"; string param; if (System.Diagnostics.Debugger.IsAttached) param = "<param name=\"source\" value=\"" + strSourceFile + "\" />"; else { string xappath = HttpContext.Current.Server.MapPath(@"") + @"\" + strSourceFile; DateTime xapCreationDate = System.IO.File.GetLastWriteTime(xappath); param = "<param name=\"source\" value=\"" + strSourceFile + "?ignore=" + xapCreationDate.ToString() + "\" />"; } Response.Write(param); %> As you can see, this problem has been solved. It will work with all web browsers and stubborn proxy servers that are caching your .XAP. If you enjoyed this article then check out my blog for others like this. You may also want to subscribe to my blog or follow me on Twitter.   Subscribe to my feed

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  • Using Entity Framework Entity splitting customisations in an ASP.Net application

    - by nikolaosk
    I have been teaching in the past few weeks many people on how to use Entity Framework. I have decided to provide some of the samples I am using in my classes. First let’s try to define what EF is and why it is going to help us to create easily data-centric applications.Entity Framework is an object-relational mapping (ORM) framework for the .NET Framework.EF addresses the problem of Object-relational impedance mismatch . I will not be talking about that mismatch because it is well documented in many...(read more)

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  • Some problems with the keyboard layout

    - by user203053
    When I press some keys, sometimes some letters are replaced by others. For example e is replaced with "0we" and c with "x9a". Also other keys are changed. My keyboard layout is actually German. But whenever this problem occurs, it changes to English and I cannot change it back. Occasionally everything works fine. How do I find out whether the keyboard is damaged or just some settings are not right?

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  • Talend vs. SSIS: A Simple Performance Comparison

    With all of the ETL tools in the marketplace, which one is best? Jeff Singleton brings us simple performance comparison pitting SSIS against open source powerhouse Talend. Optimize SQL Server performance“With SQL Monitor, we can be proactive in our optimization process, instead of waiting until a customer reports a problem,” John Trumbul, Sr. Software Engineer. Optimize your servers with a free trial.

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  • Good approach for hundreds of comsumers and big files

    - by ????? ???????
    I have several files (nearly 1GB each) with data. Data is a string line. I need to process each of these files with several hundreds of consumers. Each of these consumers does some processing that differs from others. Consumers do not write anywhere concurrently. They only need input string. After processing they update their local buffers. Consumers can easily be executed in parallel. Important: With one specific file each consumer has to process all lines (without skipping) in correct order (as they appear in file). The order of processing different files doesn't matter. Processing of a single line by one consumer is comparably fast. I expect less than 50 microseconds on Corei5. So now I'm looking for the good approach to this problem. This is going to be be a part of a .NET project, so please let's stick with .NET only (C# is preferable). I know about TPL and DataFlow. I guess that the most relevant would be BroadcastBlock. But i think that the problem here is that with each line I'll have to wait for all consumers to finish in order to post the new one. I guess that it would be not very efficient. I think that ideally situation would be something like this: One thread reads from file and writes to the buffer. Each consumer, when it is ready, reads the line from the buffer concurrently and processes it. The entry from the buffer shouldn't be deleted as one consumer reads it. It can be deleted only when all consumers have processed it. TPL schedules consumer threads itself. If one consumer outperforms the others, it shouldn't wait and can read more recent entries from the buffer. Am i right with this kind of approach? Whether yes or not, how can i implement the good solution? A bit was already discussed on StackOverflow: link

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  • Timestep schemes for physics simulations

    - by ktodisco
    The operations used for stepping a physics simulation are most commonly: Integrate velocity and position Collision detection and resolution Contact resolution (in advanced cases) A while ago I came across this paper from Stanford that proposed an alternative scheme, which is as follows: Collision detection and resolution Integrate velocity Contact resolution Integrate position It's intriguing because it allows for robust solutions to the stacking problem. So it got me wondering... What, if any, alternative schemes are available, either simple or complex? What are their benefits, drawbacks, and performance considerations?

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  • Lubuntu: neither shut-down nor restart works

    - by Rantanplan
    aI have a freshly installed Lubuntu 14.04.1 (installed with forcepae option on a laptop with Pentium M processor). The only problem that I have found so far is that I cannot shut-down or restart the laptop. It always continues showing "Lubuntu" and some dots. Pressing Esc it says wait-for-state stop/waiting * Stopping rsync daemon rsync [OK] * Asking all remaining processes to terminate… [OK] * Killing all remaining processes… [fail] ModemManager [597] : <info> Caught signal, shutting down… ModemManager [597] : <info> ModemManager is shut down nm-dispatcher.action: Could not get the system bus. Make sure the message bus daemon is running! Message: Did not receive a reply. Possible causes: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken. * Deactivating swap… [OK] * Will now halt The cursor remains blinking but the only way to switch it off is to hold the power-off key pressed for some seconds. I tried sudo shutdown -h now, sudo halt and sudo poweroff resulting in the same problem. I also tried to add acpi=force in GRUB_CMDLINE_LINUX_DEFAULT="quiet splash" in /etc/default/grub and run sudo update-grub; then, using the taskbar's shot-down button lead to a direct stop of the laptop equal to holding the power-off key pressed for some seconds. Next I followed the answer http://askubuntu.com/a/202481/288322. Now, I directly receive some messages during shut-down starting wait-for-state stop/waiting * Stopping rsync daemon rsync [OK] * Asking all remaining processes to terminate… [OK] [ 240.944277] INFO: task kworker/0:2:24: block for more than 120 seconds. [ 240.944461] Tainted: G S 3.13.0-34-generic #60-Ubuntu [ 240.944623] "echo 0 > /proc/sys/kernel/hung_tasks_timeout_secs" disables this message. followed by some more similar lines and then: * Killing all remaining processes… [fail] ModemManager [576] : <info> Caught signal, shutting down… nm-dispatcher.action: Caught signal 15, shutting down... ModemManager [576] : <info> ModemManager is shut down * Deactivating swap… [OK] * Will now halt [ 600.944276] INFO: task kworker/0:2:24: block for more than 120 seconds. [ 600.944458] Tainted: G S 3.13.0-34-generic #60-Ubuntu [ 600.944619] "echo 0 > /proc/sys/kernel/hung_tasks_timeout_secs" disables this message. Then, nothing more was coming during the next 5 minutes. If you know where can I find relevant error information, I will be happy to search for them.

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  • Website speed issue

    - by Jose David Garcia Llanos
    I've exhausted all my options. The website that I am developing had a load speed of 1.12 seconds and for some unknown reason it is now taking 2 seconds to connect then load. I've tried deactivating loads of plugins but is not the plugins or javascript or images. http://tools.pingdom.com/fpt/#!/ONC4QfFJt/n1bar.com I've tried re-configuring the cache and the .htacess file but still taking long for the first connection. Can someone help me find the problem...

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  • Scrum and Google Docs burndown chart

    - by Michal Minicki
    There is a tutorial on how to create a burndown chart for Scrum in the Google Docs application: http://www.scrumology.net/2011/05/03/how-to-create-a-burndown-chart-in-google-docs/ The problem I see with it though is, it has only a place to update progress once per sprint but the burndown is supposed to be updated with daily progress, right? How can one modify this chart to be able to put daily progress on it?

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  • Courier Maildrop error user unknown. Command output: Invalid user specified

    - by cad
    Hello I have a problem with maildrop. I have read dozens of webs/howto/emails but couldnt solve it. My objective is moving automatically spam messages to a spam folder. My email server is working perfectly. It marks spam in subject and headers using spamassasin. My box has: Ubuntu 9.04 Web: Apache2 + Php5 + MySQL MTA: Postfix 2.5.5 + SpamAssasin + virtual users using mysql IMAP: Courier 0.61.2 + Courier AuthLib WebMail: SquirrelMail I have read that I could use Squirrelmail directly (not a good idea), procmail or maildrop. As I already have maildrop in the box (from courier) I have configured the server to use maildrop (added an entry in transport table for a virtual domain). I found this error in email: This is the mail system at host foo.net I'm sorry to have to inform you that your message could not be delivered to one or more recipients. It's attached below. For further assistance, please send mail to postmaster. If you do so, please include this problem report. You can delete your own text from the attached returned message. The mail system <[email protected]>: user unknown. Command output: Invalid user specified. Final-Recipient: rfc822; [email protected] Action: failed Status: 5.1.1 Diagnostic-Code: x-unix; Invalid user specified. ---------- Forwarded message ---------- From: test <[email protected]> To: [email protected] Date: Sat, 1 May 2010 19:49:57 +0100 Subject: fail fail An this in the logs May 1 18:50:18 foo.net postfix/smtpd[14638]: connect from mail-bw0-f212.google.com[209.85.218.212] May 1 18:50:19 foo.net postfix/smtpd[14638]: 8A9E9DC23F: client=mail-bw0-f212.google.com[209.85.218.212] May 1 18:50:19 foo.net postfix/cleanup[14643]: 8A9E9DC23F: message-id=<[email protected]> May 1 18:50:19 foo.net postfix/qmgr[14628]: 8A9E9DC23F: from=<[email protected]>, size=1858, nrcpt=1 (queue active) May 1 18:50:23 foo.net postfix/pickup[14627]: 1D4B4DC2AA: uid=5002 from=<[email protected]> May 1 18:50:23 foo.net postfix/cleanup[14643]: 1D4B4DC2AA: message-id=<[email protected]> May 1 18:50:23 foo.net postfix/pipe[14644]: 8A9E9DC23F: to=<[email protected]>, relay=spamassassin, delay=3.8, delays=0.55/0.02/0/3.2, dsn=2.0.0, status=sent (delivered via spamassassin service) May 1 18:50:23 foo.net postfix/qmgr[14628]: 8A9E9DC23F: removed May 1 18:50:23 foo.net postfix/qmgr[14628]: 1D4B4DC2AA: from=<[email protected]>, size=2173, nrcpt=1 (queue active) **May 1 18:50:23 foo.netpostfix/pipe[14648]: 1D4B4DC2AA: to=<[email protected]>, relay=maildrop, delay=0.22, delays=0.06/0.01/0/0.15, dsn=5.1.1, status=bounced (user unknown. Command output: Invalid user specified. )** May 1 18:50:23 foo.net postfix/cleanup[14643]: 4C2BFDC240: message-id=<[email protected]> May 1 18:50:23 foo.net postfix/qmgr[14628]: 4C2BFDC240: from=<>, size=3822, nrcpt=1 (queue active) May 1 18:50:23 foo.net postfix/bounce[14651]: 1D4B4DC2AA: sender non-delivery notification: 4C2BFDC240 May 1 18:50:23 foo.net postfix/qmgr[14628]: 1D4B4DC2AA: removed May 1 18:50:24 foo.net postfix/smtp[14653]: 4C2BFDC240: to=<[email protected]>, relay=gmail-smtp-in.l.google.com[209.85.211.97]:25, delay=0.91, delays=0.02/0.03/0.12/0.74, dsn=2.0.0, status=sent (250 2.0.0 OK 1272739824 37si5422420ywh.59) May 1 18:50:24 foo.net postfix/qmgr[14628]: 4C2BFDC240: removed My config files: http://lar3d.net/main.cf (/etc/postfix) http://lar3d.net/master.c (/etc/postfix) http://lar3d.net/local.cf (/etc/spamassasin) http://lar3d.net/maildroprc (maildroprc) If I change master.cf line (as suggested here) maildrop unix - n n - - pipe flags=DRhu user=vmail argv=/usr/lib/courier/bin/maildrop -d ${recipient} with maildrop unix - n n - - pipe flags=DRhu user=vmail argv=/usr/lib/courier/bin/maildrop -d vmail ${recipient} I get the email in /home/vmail/MailDir instead of the correct dir (/home/vmail/foo.net/info/.SPAM ) After reading a lot I have some guess but not sure. - Maybe I have to install userdb? - Maybe is something related with mysql, but everything is working ok - If I try with procmail I will face same problem... - What are flags DRhu for? Couldnt find doc about them - In some places I found maildrop line with more parameters flags=DRhu user=vmail argv=/usr/lib/courier/bin/maildrop -d $ ${recipient} ${extension} ${recipient} ${user} ${nexthop} ${sender} I am really lost. Dont know how to continue. If you have any idea or need another config file please let me know. Thanks!!!

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  • Best partition Scheme for Ubuntu Server

    - by K.K Patel
    I am going to deploy Ubuntu server having Following servers on it Bind server, dhcp server, LAMP Server, Openssh Server, Ldap server, Monodb database, FTP server,mail server, Samba server, NFS server , in future I want to set Openstack for PAAS. Currently I have Raid 5 with 10TB. How should I make my Partition Scheme So never get problem in future and easily expand Storage size. Suggest me such a partition Scheme with giving specific percentage of Storage to partitions like /, /boot, /var, /etc. Thanks In advance

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  • index.html in subdirectory will not open

    - by Dušan
    I want to have a website structure like this example.com/ - homepage example.com/solutions/ - this will be the solution parent page example.com/solutions/solution-one - child solution page example.com/solutions/solution-two- child solution page i have setup the example.com/solutions/index.html file so it can be opened as a parent page, but is shows me an error You don't have permission to access /solutions/.html on this server. What is the problem to this, how can i open parent, directory page? I na just using regular html pages, no cms or anything...

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  • I am not able to install wine

    - by Jose Ramon
    I can't install wine in Ubuntu 12.10. The report is: Los siguientes paquetes tienen dependencias incumplidas: (The following packages have unmet dependencies) wine1.4: PreDepends: dpkg (>= 1.15.7.2~) pero 1.16.7ubuntu6 no está instalado Depends: libc6 (>= 2.14) pero 2.15-0ubuntu20 no está instalado Depends: wine1.4-amd64 (= 1.4.1-0ubuntu1) pero 1.4.1-0ubuntu1 no está instalado Depends: wine1.4-i386 (= 1.4.1-0ubuntu1) pero no va a ser instalado I would like that you help me in this problem. Thanks for everything.

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  • Favorite moments of JavaOne

    - by Tori Wieldt
    There are so many events and sessions to attend at JavaOne, it's unfair to ask people to choose just one thing they liked, but here are some favorite moments: I loved meeting many open source contributors and friends I have not met in person before and seeing that projects like e.g. Hudson are alive and kicking and have a great future ahead of them. -Manfred Moser My "The Problem with Women" session. It had LOADS of interactivity from the audience, who really helped to make that session.  I came out if it with a real sense of optimism - we love our jobs, we love what we do, and we should be proud of telling everyone about it to attract different talent into the industry. (Read her blog JavaOne: The Problem With Women - A Technical Approach for details.) -Trish Gee My kudos to Oracle for making the presentation materials quickly available to the public. Some of them were already available during JavaOne. Lots of slide decks are already there, and in some cases you may even find the video recordings too. Go to http://www.oracle.com/javaone and select JavaOne Technical Sessions.  -Yakov Fain I loved that not only was James Gosling present at the Community Keynote (which felt more like the keynotes of old times [big space, big screens, fun and tech]) but he was also found wandering the halls of the Hilton the day prior. Bring back James! Add back the toys section in the Community Keynote. Let the t-shirt tossing begin anew. These are "small" things that really fire up the community. -Andres Almiray Seeing James Gosling at JavaOne was a real shot in the arm for Java.  He needs to be there every year. -Frank Greco +42 on having James and the T-shirt tossing. -Stephan Janssen The session "Integrate Java with Robots, Home Automation, Musical Instruments, and Kinect." Fabiane Nardon explained connecting Jenkins to jHome to a truck horn placed in their sysadmin's bedroom. She dubbed it "extreme feedback."  -Tori Wieldt The User Group Forum [on Sunday] was a success! Congratulations Bruno Souza and John Yeary and everybody that were involved. I believe it really helps to increase community participation! There were lots of interesting talks, and great discussion with JUG leaders and members. Thank you Oracle for supporting that! -Yara Senger What was your favorite moment? Please comment! 

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  • How one decision can turn web services to hell

    - by DigiMortal
    In this posting I will show you how one stupid decision may turn developers life to hell. There is a project where bunch of complex applications exchange data frequently and it is very hard to change something without additional expenses. Well, one analyst thought that string is silver bullet of web services. Read what happened. Bad bad mistake In the early stages of integration project there was analyst who also established architecture and technical design for web services. There was one very bad mistake this analyst made: All data must be converted to strings before exchange! Yes, that’s correct, this was the requirement. All integers, decimals and dates are coming in and going out as strings. There was also explanation for this requirement: This way we can avoid data type conversion errors! Well, this guy works somewhere else already and I hope he works in some burger restaurant – far away from computers. Consequences If you first look at this requirement it may seem like little annoying piece of crap you can easily survive. But let’s see the real consequences one stupid decision can cause: hell load of data conversions are done by receiving applications and SSIS packages, SSIS packages are not error prone and they depend heavily on strings they get from different services, there are more than one format per type that is used in different services, for larger amounts of data all these conversion tasks slow down the work of integration packages, practically all developers have been in hurry with some SSIS import tasks and some fields that are not used in different calculations in SSAS cube are imported without data conversions (by example, some prices are strings in format “1.021 $”). The most painful problem for developers is the part of data conversions because they don’t expect that there is such a stupid requirement stated and therefore they are not able to estimate the time their tasks take on these web services. Also developers must be prepared for cases when suddenly some service sends data that is not in acceptable format and they must solve the problems ASAP. This puts unexpected load on developers and they are not very happy with it because they can’t understand why they have to live with this horror if it is possible to fix. What to do if you see something like this? Well, explain the problem to customer and demand special tasks to project schedule to get this mess solved before going on with new developments. It is cheaper to solve the problems now that later.

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