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• ASP.NET inline code in a server control

  - by John

  Ok, we had a problem come up today at work. It is a strange one that I never would have even thought to try. <form id="form1" runat="server" method="post" action="Default.aspx?id=<%= ID %>" > Ok, it is very ugly and I wouldn't have ever tried it myself. It came up in some code that was written years ago but had been working up until this weekend after a bunch of updates were installed on a client's web server where the code is hosted. The actual result of this is the following html: <form name="form1" method="post" action="Default.aspx?id=&lt;%= ID %>" id="form1"> The url ends up like this: http://localhost:6735/Default.aspx?id=<%= ID %> Which as you can see, demonstrates that the "<" symbol is being encoded before ASP.NET actually processes the page. It seems strange to me as I thought that even though it is not pretty by any means, it should work. I'm confused. To make matters worse, the client insists that it is a bug in IE since it appears to work in Firefox. In fact, it is broken in Firefox as well, except for some reason Firefox treats it as a 0. Any ideas on why this happens and how to fix it easily? Everything I try to render within the server control ends up getting escaped. Edit Ok, I found a "fix" <form id="form1" runat="server" method="post" action='<%# String.Format("Default.aspx?id={0}", 5) %>' > But that requires me to call DataBind which is adding more of a hack to the original hack. Guess if nobody thinks of anything else I'll have to go with that.

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• high cpu in IIS

  - by Miki Watts

  Hi all. I'm developing a POS application that has a local database on each POS computer, and communicates with the server using WCF hosted in IIS. The application has been deployed in several customers for over a year now. About a week ago, we've started getting reports from one of our customers that the server that the IIS is hosted on is very slow. When I've checked the issue, I saw the application pool with my process rocket to almost 100% cpu on an 8 cpu server. I've checked the SQL Activity Monitor and network volume, and they showed no significant overload beyond what we usually see. When checking the threads in Process Explorer, I saw lots of threads repeatedly calling CreateApplicationContext. I've tried installing .Net 2.0 SP1, according to some posts I found on the net, but it didn't solve the problem and replaced the function calls with CLRCreateManagedInstance. I'm about to capture a dump using adplus and windbg of the IIS processes and try to figure out what's wrong. Has anyone encountered something like this or has an idea which directory I should check ? p.s. The same version of the application is deployed in another customer, and there it works just fine. I also tried rolling back versions (even very old versions) and it still behaves exactly the same. Edit: well, problem solved, turns out I've had an SQL query in there that didn't limit the result set, and when the customer went over a certain number of rows, it started bogging down the server. Took me two days to find it, because of all the surrounding noise in the logs, but I waited for the night and took a dump then, which immediately showed me the query.

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• Trap SIGPIPE when trying to write without reader

  - by Matt

  I am trying to implement a named-pipe communication solution in BASH between two processes. The first process runs a script which echo something in a named-pipe: send(){ echo 'something' > $NAMEDPIPE } And the second script is supposed to read the named-pipe via another script which contains: while true;do if read line < $NAMEDPIPE;do someCommands fi done Not that the named pipe has been previously created using the traditional command mkfifo $NAMEDPIPE My problem is that the reader script is not always running so that if the writer script try to write in the named-pipe it stay blocked until a reader connect the pipe. I want to avoid this behavior, and a solution would be to trap a SIGPIPE signal. Indeed, according to man 7 signal is supposed to be send when trying to write in a pipe with no reader. So I changed my red function by: read(){ trap 'echo "SIGPIPE received"' SIGPIPE echo 'something' > $NAMEDPIPE } But when I run the reader script, the script stay blocked, and not "SIGPIPE received" appears... Am I mistaking on the signal mechanism or is there any better solution to my problem ? Thank you for your help.

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• Is there a standard pattern for scanning a job table executing some actions?

  - by Howiecamp

  (I realize that my title is poor. If after reading the question you have an improvement in mind, please either edit it or tell me and I'll change it.) I have the relatively common scenario of a job table which has 1 row for some thing that needs to be done. For example, it could be a list of emails to be sent. The table looks something like this: ID Completed TimeCompleted anything else... ---- --------- ------------- ---------------- 1 No blabla 2 No blabla 3 Yes 01:04:22 ... I'm looking either for a standard practice/pattern (or code - C#/SQL Server preferred) for periodically "scanning" (I use the term "scanning" very loosely) this table, finding the not-completed items, doing the action and then marking them completed once done successfully. In addition to the basic process for accomplishing the above, I'm considering the following requirements: I'd like some means of "scaling linearly", e.g. running multiple "worker processes" simultaneously or threading or whatever. (Just a specific technical thought - I'm assuming that as a result of this requirement, I need some method of marking an item as "in progress" to avoid attempting the action multiple times.) Each item in the table should only be executed once. Some other thoughts: I'm not particularly concerned with the implementation being done in the database (e.g. in T-SQL or PL/SQL code) vs. some external program code (e.g. a standalone executable or some action triggered by a web page) which is executed against the database Whether the "doing the action" part is done synchronously or asynchronously is not something I'm considering as part of this question.

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• MSBuild / PowerShell: Copy SQL Server 2012 database to SQL Azure via BACPAC (for Continuous Integration)

  - by giveme5minutes

  I'm creating a continuous integration MSBuild script which copies a database in on-premise SQL Server 2012 to SQL Azure. Easy right? Methods After a fair bit of research I've come across the following methods: Use PowerShell to access the DAC library directly, then use the MSBuild PowerShell extension to wrap the script. This would require installing PowerShell 3 and working out how to make the MSBuild PowerShell extension work with it, as apparently MS moved the DAC API to a different namespace in the latest version of the library. PowerShell would give direct access to the API, but may require quite a bit of boilerplate. Use the sample DAC Framework Client Side Tools, which requires compiling them myself, as the downloads available from Codeplex only include the Hosted version. It would also require fixing them to use DAC 3.0 classes as they appear to currently use an earlier version of DAC. I could then call these tools from an <Exec Command="" /> in the MSBuild script. Less boilerplate and if I hit any bumps in the road I can just make changes to the source. Processes Using whichever method, the process could be either: Export from on-premise SQL Server 2012 to local BACPAC Upload BACPAC to blog storage Import BACPAC to SQL Azure via Hosted DAC Or: Export from on-premise SQL Server 2012 to local BACPAC Import BACPAC to SQL Azure via Client DAC Question All of the above seems to be quite a lot of effort for something that seems to be a standard feature... so before I start reinventing the wheel and documenting the results for all to see, is there something really obvious that I've missed here? Is there pre-written script that MS has released that I have not yet uncovered? There's an command in the GUI of SQL Server Management Studio 2012 that does EXACTLY what I'm trying to do (right click on local database, click "Tasks", click "Deploy Database to SQL Azure"). Surely if it's a few clicks in the GUI it must be a single command on the command line somewhere??

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• MUD (game) design concept question about timed events.

  - by mudder

  I'm trying my hand at building a MUD (multiplayer interactive-fiction game) I'm in the design/conceptualizing phase and I've run into a problem that I can't come up with a solution for. I'm hoping some more experienced programmers will have some advice. Here's the problem as best I can explain it. When the player decides to perform an action he sends a command to the server. the server then processes the command, determines whether or not the action can be performed, and either does it or responds with a reason as to why it could not be done. One reason that an action might fail is that the player is busy doing something else. For instance, if a player is mid-fight and has just swung a massive broadsword, it might take 3 seconds before he can repeat this action. If the player attempts to swing again to soon, the game will respond indicating that he must wait x seconds before doing that. Now, this I can probably design without much trouble. The problem I'm having is how I can replicate this behavior from AI creatures. All of the events that are being performed by the server ON ITS OWN, aka not as an immediate reaction to something a player has done, will have to be time sensitive. Some evil monster has cast a spell on you but must wait 30 seconds before doing it again... I think I'll probably be adding all these events to some kind of event queue, but how can I make that event queue time sensitive?

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• Determine if the current thread has low I/O priority

  - by Magnus Hoff

  I have a background thread that does some I/O-intensive background type work. To please the other threads and processes running, I set the thread priority to "background mode" using SetThreadPriority, like this: SetThreadPriority(GetCurrentThread(), THREAD_MODE_BACKGROUND_BEGIN); However, THREAD_MODE_BACKGROUND_BEGIN is only available in Windows Server 2008 or newer, as well as Windows Vista and newer, but the program needs to work well on Windows Server 2003 and XP as well. So the real code is more like this: if (!SetThreadPriority(GetCurrentThread(), THREAD_MODE_BACKGROUND_BEGIN)) { SetThreadPriority(GetCurrentThread(), THREAD_PRIORITY_LOWEST); } The problem with this is that on Windows XP it will totally disrupt the system by using too much I/O. I have a plan for a ugly and shameful way of mitigating this problem, but that depends on me being able to determine if the current thread has low I/O priority or not. Now, I know I can store which thread priority I ended up setting, but the control flow in the program is not really well suited for this. I would rather like to be able to test later whether or not the current thread has low I/O priority -- if it is in "background mode". GetThreadPriority does not seem to give me this information. Is there any way to determine if the current thread has low I/O priority?

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• Handling user interface in a multi-threaded application (or being forced to have a UI-only main thre

  - by Patrick

  In my application, I have a 'logging' window, which shows all the logging, warnings, errors of the application. Last year my application was still single-threaded so this worked [quite] good. Now I am introducing multithreading. I quickly noticed that it's not a good idea to update the logging window from different threads. Reading some articles on keeping the UI in the main thread, I made a communication buffer, in which the other threads are adding their logging messages, and from which the main thread takes the messages and shows them in the logging window (this is done in the message loop). Now, in a part of my application, the memory usage increases dramatically, because the separate threads are generating lots of logging messages, and the main thread cannot empty the communication buffer quickly enough. After the while the memory decreases again (if the other threads have finished their work and the main thread gradually empties the communication buffer). I solved this problem by having a maximum size on the communication buffer, but then I run into a problem in the following situation: the main thread has to perform a complex action the main thread takes some parts of the action and let's separate threads execute this while the seperate threads are executing their logic, the main thread processes the results from the other threads and continues with its work if the other threads are finished Problem is that in this situation, if the other threads perform logging, there is no UI-message loop, and so the communication buffer is filled, but not emptied. I see two solutions in solving this problem: require the main thread to do regular polling of the communication buffer only performing user interface logic in the main thread (no other logic) I think the second solution seems the best, but this may not that easy to introduce in a big application (in my case it performs mathematical simulations). Are there any other solutions or tips? Or is one of the two proposed the best, easiest, most-pragmatic solution? Thanks, Patrick

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• Request-local storage in ASP.NET (accessible to the code from IHttpModule implementation)

  - by IgorK

  I need to have some object hanging around between two events I'm interested in: PreRequestHandlerExecute (where I create an instance of my object and want to save it) and PostRequestHandlerExecute (where I want to get to the object). After the second event the object is not needed for my purposes and should be discarded either by storage or my explicit action. So the ideal context where my object should be stored is per request (with guaranteed no sharing issues when different threads are serving requests... or processes/servers :) ) Take into account that actual implementation I can do is being made from a HttpModule and is supposed to be a pluggable solution for already written web apps (so the option to provide some state using static/instance variables in Global.asax doesn't look good - I will have to modify Global.asax on every web application). Cache seems to be too broad for this use. I tried to see whether httpContext.Application (of type HttpApplicationState) is good for me or not, but cannot get whether it is exactly per HttpApplication instance or not (AFAIK you can have several instances of HttpApplications used on different threads and therefore serving several requests simultaneously - then using storage shared between threads will not work correctly; otherwise I would use it because one HttpApplication instance serves exactly one request at a time). Something could be done with storing state on the HttpModule instances if I know for sure that it's exactly bound 1-to-1 with every HttpApplication instance running (but again I need a proof that HttpApplication instance is 1-to-1 with my HttpModule's instance). Any valuable and reputable links on these topics are much appreciated... Would be great to find something particularly well-suited for per request situation (because otherwise I may end up with something ulgy... probably either some 'broader' scoped storage and some hacks to have different keys in the storage for different requests, OR using a thread-local thing and in this way commit to the theory that IIS/ASP.NET will not ever serve first event from one thread and the second event from the other thread and so on)

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• How to approach parallel processing of messages?

  - by Dan

  I am redesigning the messaging system for my app to use intel threading building blocks and am stumped trying to decide between two possible approaches. Basically, I have a sequence of message objects and for each message type, a sequence of handlers. For each message object, I apply each handler registered for that message objects type. The sequential version would be something like this (pseudocode): for each message in message_sequence <- SEQUENTIAL for each handler in (handler_table for message.type) apply handler to message <- SEQUENTIAL The first approach which I am considering processes the message objects in turn (sequentially) and applies the handlers concurrently. Pros: predictable ordering of messages (ie, we are guaranteed a FIFO processing order) (potentially) lower latency of processing each message Cons: more processing resources available than handlers for a single message type (bad parallelization) bad use of processor cache since message objects need to be copied for each handler to use large overhead for small handlers The pseudocode of this approach would be as follows: for each message in message_sequence <- SEQUENTIAL parallel_for each handler in (handler_table for message.type) apply handler to message <- PARALLEL The second approach is to process the messages in parallel and apply the handlers to each message sequentially. Pros: better use of processor cache (keeps the message object local to all handlers which will use it) small handlers don't impose as much overhead (as long as there are other handlers also to be run) more messages are expected than there are handlers, so the potential for parallelism is greater Cons: Unpredictable ordering - if message A is sent before message B, they may both be processed at the same time, or B may finish processing before all of A's handlers are finished (order is non-deterministic) The pseudocode is as follows: parallel_for each message in message_sequence <- PARALLEL for each handler in (handler_table for message.type) apply handler to message <- SEQUENTIAL The second approach has more advantages than the first, but non-deterministic ordering is a big disadvantage.. Which approach would you choose and why? Are there any other approaches I should consider (besides the obvious third approach: parallel messages and parallel handlers, which has the disadvantages of both and no real redeeming factors as far as I can tell)? Thanks!

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• C++ VB6 interfacing problem

  - by Roshan

  Hi, I'm tearing my hair out trying to solve this one, any insights will be much appreciated: I have a C++ exe which acquires data from some hardware in the main thread and processes it in another thread (thread 2). I use a c++ dll to supply some data processing functions which are called from thread 2. I have a requirement to make another set of data processing functions in VB6. I have thus created a VB6 dll, using the add-in vbAdvance to create a standard dll. When I call functions from within this VB6 dll from the main thread, everything works exactly as expected. When I call functions from this VB6 dll in thread 2, I get an access violation. I've traced the error to the CopyMemory command, it would seem that if this is used within the call from the main thread, it's fine but in a call from the process thread, it causes an exception. Why should this be so? As far as I understand, threads share the same address space. Here is the code from my VB dll Public Sub UserFunInterface(ByVal in1ptr As Long, ByVal out1ptr As Long, ByRef nsamples As Long) Dim myarray1() As Single Dim myarray2() As Single Dim i As Integer ReDim myarray1(0 To nsamples - 1) As Single ReDim myarray2(0 To nsamples - 1) As Single With tsa1din(0) ' defined as safearray1d in a global definitions module .cDims = 1 .cbElements = 4 .cElements = nsamples .pvData = in1ptr End With With tsa1dout .cDims = 1 .cbElements = 4 .cElements = nsamples .pvData = out1ptr End With CopyMemory ByVal VarPtrArray(myarray1), VarPtr(tsa1din(0)), 4 CopyMemory ByVal VarPtrArray(myarray2), VarPtr(tsa1dout), 4 For i = 0 To nsamples - 1 myarray2(i) = myarray1(i) * 2 Next i ZeroMemory ByVal VarPtrArray(myarray1), 4 ZeroMemory ByVal VarPtrArray(myarray2), 4 End Sub

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• C# - retrieve file path from config file - @ doesn't do it's magic

  - by Bart

  Hi guys, I'm currently working on a web service that retrieves an XML message, archives it and then processes it further. The archive folder is read from the Web.config. This is what the archive method looks like private void Archive(System.Xml.XmlDocument xmlDocument) { try { string directory = System.Configuration.ConfigurationManager.AppSettings.Get("ArchivePath"); ParseMessage(xmlDocument); directory = string.Format(@"{0}\{1}\{2}", @directory, _senderService, DateTime.Now.ToString("MMMyyyy")); System.IO.Directory.CreateDirectory(directory); string Id = _messageID; string senderService = _senderService; xmlDocument.Save(directory + @"\" + DateTime.Now.ToString("yyyyMMdd_") + Id + "_" + System.Guid.NewGuid().ToString().Substring(0, 13) + ".xml"); } The path structure I retrieve is C:\Program Files\Subfolder\Subfolder. In the development, QA, UAT and PRD environments everything works fine. But on another machine I now need to install the web service on (which I cannot debug, unfortunately), the directory string is 'C:Files'. Just to be sure I double checked the .NET version on the different machines (I thought perhaps the usage of @ before a string was version-dependent); all machines use 2.0.50727. Does anyone recognize this problem? Thanks in advance!

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• What constitutes a development environment, and how do you document it?

  - by Joel Coehoorn

  What items go into a software shop's development environment, how do you document it, and what processes do you follow to make changes? I thinking about this from the standpoint where I want to make it easier to bring new hires up to speed quickly by having all this on a checklist we follow when setting them up, and then while I'm at it making it easier for the new hires or existing team members to bring new powerful toolkits and ideas into the environment without disrupting things. I want to keep this platform agnostic, so even though I'm currently at a microsoft shop where Visual Studio would be assumed I'll go ahead and list compiler/IDE as one of the items: Here are some ideas for part 1: [edit]: I'm keeping this updated based on the better suggestions. Source Control access Issue/Bug/Project tracker System Documention, or references to find the system documentation in source control or in a wiki, including: build document/environment covered by this question design documents / technical notes Coding Style guidelines Deploy for review/testing/QA/staging/production procedures Licensing details for your tools and your product Team Calendar, including the project schedule(s), deadlines, vacation time, and support/on-call schedule (if required) compiler/IDE compiler/IDE extensions (things like source control plugins or visual studio add-ins) 3rd party SDKs/toolkits Database connection and tools Testing Frameworks Internal libraries communication tools (chat, wiki, etc) Static analysis tools (FxCop, FlawFinder, etc) Virtual machines (holding dev environment or for testing) Specialized editors (modeling, xml, etc) Other tools What else goes in this list, and how do you document it and vet changes?

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• Heavy Mysql operation & Time Constraints [closed]

  - by Rahul Jha

  There is a performance issue where that I have stuck with my application which is based on PHP & MySql. The application is for Data Migration where data has to be uploaded and after various processes (Cleaning from foreign characters, duplicate check, id generation) it has to be inserted into one central table and then to 5 different tables. There, an id is generated and that id has to be updated to central table. There are different sets of records and validation rules. The problem I am facing is that when I insert say(4K) rows file (containing 20 columns) it is working fine within 15 min it gets inserted everywhere. But, when I insert the same records again then at this time it is taking one hour to insert (ideally it should get inserted by marking earlier inserted data as duplicate). After going through the log file, I noticed is that there is a Mysql select statement where I am checking the duplicates and getting ID which are duplicates. Then I am calling a function inside for loop which is basically inserting records into 5 tables and updates id to central table. This Calling function is major time of whole process. P.S. The records has to be inserted record by record.. Kindly Suggest some solution.. //This is that sample code $query=mysql_query("SELECT DISTINCT p1.ID FROM table1 p1, table2 p2, table3 a WHERE p2.datatype =0 AND (p1.datatype =1 || p1.datatype=2) AND p2.ID =0 AND p1.ID = a.ID AND p1.coulmn1 = p2.column1 AND p1.coulmn2 = p2.coulmn2 AND a.coulmn3 = p2.column3"); $num=mysql_num_rows($query); for($i=0;$i<$num;$i++) { $f=mysql_result($query,$i,"ID"); //calling function RecordInsert($f); }

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• Unable to get data from a WCF client

  - by Scott

  I am developing a DLL that will provide sychronized time stamps to multiple applications running on the same machine. The timestamps are altered in a thread that uses a high performance timer and a scalar to provide the appearance of moving faster than real-time. For obvious reasons I want only 1 instance of this time library, and I thought I could use WCF for the other processes to connect to this and poll for timestamps whenever they want. When I connect however I never get a valid time stamp, just an empty DateTime. I should point out that the library does work. The original implementation was a single DLL that each application incorporated and each one was synced using windows messages. I'm fairly sure it has something to do with how I'm setting up the WCF stuff, to which I am still pretty new. Here are the contract definitions: public interface ITimerCallbacks { [OperationContract(IsOneWay = true)] void TimerElapsed(String id); } [ServiceContract(SessionMode = SessionMode.Required, CallbackContract = typeof(ITimerCallbacks))] public interface ISimTime { [OperationContract] DateTime GetTime(); } Here is my class definition: [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single)] public class SimTimeServer: ISimTime The host setup: // set up WCF interprocess comms host = new ServiceHost(typeof(SimTimeServer), new Uri[] { new Uri("net.pipe://localhost") }); host.AddServiceEndpoint(typeof(ISimTime), new NetNamedPipeBinding(), "SimTime"); host.Open(); and the implementation of the interface function server-side: public DateTime GetTime() { if (ThreadMutex.WaitOne(20)) { RetTime = CurrentTime; ThreadMutex.ReleaseMutex(); } return RetTime; } Lastly the client-side implementation: Callbacks myCallbacks = new Callbacks(); DuplexChannelFactory pipeFactory = new DuplexChannelFactory(myCallbacks, new NetNamedPipeBinding(), new EndpointAddress("net.pipe://localhost/SimTime")); ISimTime pipeProxy = pipeFactory.CreateChannel(); while (true) { string str = Console.ReadLine(); if (str.ToLower().Contains("get")) Console.WriteLine(pipeProxy.GetTime().ToString()); else if (str.ToLower().Contains("exit")) break; }

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• No Buffer Space available(maximum connection reached?) Form Postgres EDB Driver

  - by Listening.Platform

  We are facing an exception while connecting to database through our java application. The stack trace is as follows com.edb.util.PSQLException: The connection attempt failed. at com.edb.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:189) at com.edb.core.ConnectionFactory.openConnection(ConnectionFactory.java:64) at com.edb.jdbc2.AbstractJdbc2Connection.<init>(AbstractJdbc2Connection.java:161) at com.edb.jdbc3.AbstractJdbc3Connection.<init>(AbstractJdbc3Connection.java:30) at com.edb.jdbc3.Jdbc3Connection.<init>(Jdbc3Connection.java:24) at com.edb.Driver.makeConnection(Driver.java:391) at com.edb.Driver.connect(Driver.java:266) at java.sql.DriverManager.getConnection(Unknown Source) at java.sql.DriverManager.getConnection(Unknown Source) ... 12 more Caused by: java.net.SocketException: No buffer space available (maximum connections reached?): connect at java.net.PlainSocketImpl.socketConnect(Native Method) at java.net.PlainSocketImpl.doConnect(Unknown Source) at java.net.PlainSocketImpl.connectToAddress(Unknown Source) at java.net.PlainSocketImpl.connect(Unknown Source) at java.net.SocksSocketImpl.connect(Unknown Source) at java.net.Socket.connect(Unknown Source) at java.net.Socket.connect(Unknown Source) at java.net.Socket.<init>(Unknown Source) at java.net.Socket.<init>(Unknown Source) at com.edb.core.PGStream.<init>(PGStream.java:70) at com.edb.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:115) ... 20 more When the error occured we were not able to connect to internet and DB and had to reboot the system. But the error occured again after 3 days at same code i.e while connecting to DB. We checked TCP connections using netstat. But there were not many TCP connections i.e it has not reached the max limit. Our application has multiple long running Java processes that pools the DB connections (not more than 60) and keeps it alive for firing the next query (as it has to poll the DB every 2 seconds). Some of the queries in our application are joining large tables (10 million records) to get the related data. We are using following System and applications Windows 2003 server SP2 Java 1.6 Postgres Plus Advanced server 8.4 Database edb-jdbc14.jar driver for connection DB from Java We have used the default configuration of Postgres DB except increasing the connection to 120 from 100. Has anybody encountred the same error with postgres edb driver? Can anybody help us finding the solution?

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• PHP, MySQL prepared statements - can you use results of execute more than once by calling data_seek(

  - by Carvell Fenton

  Hello, I have a case where I want to use the results of a prepared statement more than once in a nested loop. The outer loop processes the results of another query, and the inner loop is the results of the prepared statement query. So the code would be something like this (just "pseudoish" to demonstrate the concept): // not showing the outer query, it is just a basic SELECT, not prepared statement // we'll call it $outer_query $obj_array = array(); // going to save objects in this $ids = array(18,19,20); // just example id numbers $query = "SELECT field1, field2 FROM table1 WHERE id=?"; $stmt = $db->prepare($query); foreach ($ids as $id) { $stmt->bind_param("i", $id); $stmt->execute(); $stmt->bind_result($var1, $var2); $stmt->store_result(); // I think I need this for data_seek while ($q1 = $outer_query->fetch_object()) { while ($stmt->fetch()) { if ($q1->field1 == $var1) { // looking for a match $obj = new stdClass(); $obj->var1 = $var1; $obj->var2 = $var2; $obj_array[] = $obj; $stmt->data_seek(0); // reset for outer loop break; // found match, so leave inner } } } } The problem I seem to be experiencing is that the values are not getting bound in the variables as I would expect after the first time I use fetch in the inner loop. Specifically, in one example I ran with 3 ids for the foreach, the first id was processed correctly, the second was processed incorrectly (matches were not found in the inner loop even though they existed), and then the third was processed correctly. Is there something wrong with the prepared statment function calls in the sequence I am doing above, or is this an invalid way to use the results of the prepared statement? Thanks.

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• What is the process involved in viewing a webservice in a browser from within visual studio?

  - by Sam Holder

  I have created a new VS2008 ASP.Net Web service project, with the default name WebService1. If I right click on the Service1.asmx file and select 'View in Browser' what are the processes that go on to make this happen? I am asking because I have a situation where when I run this from a visual studio project started in our development shell (which sets up a common build environment) I cannot get the web service to show up in the browser. It starts the asp.net development server and creates a single file: C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files\root\c43ddc22\268ae91b\hash\hash.web but when I start it from a stand alone project i get a whole slew of files in here: C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files\root\edad4eee\d198cf0e\App_Web_defaultwsdlhelpgenerator.aspx.cdcab7d2.vicgkf94.dll C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files\root\edad4eee\d198cf0e\service1.asmx.cdcab7d2.compiled etc etc I am trying to debug this but not really getting anywhere. i have inspected the output from VS but the only option I get is for the build output, which is basic and doesn't really contain any information that is useful. I have tried running both versions with DebugView running but no output there either. I would like to know if there are any log files I could look at, or if anyone has any suggestions on how I might be able to debug what is going wrong here? For completeness the output I get when it doesn't work is: Parser Error Description: An error occurred during the parsing of a resource required to service this request. Please review the following specific parse error details and modify your source file appropriately. Parser Error Message: Could not create type 'WebService1.Service1'. Source Error: Line 1: Source File: /Service1.asmx Line: 1 Version Information: Microsoft .NET Framework Version:2.0.50727.3603; ASP.NET Version:2.0.50727.3082

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• Spring Integration 1.0 RC2: Streaming file content?

  - by gdm

  I've been trying to find information on this, but due to the immaturity of the Spring Integration framework I haven't had much luck. Here is my desired work flow: New files are placed in an 'Incoming' directory Files are picked up using a file:inbound-channel-adapter The file content is streamed, N lines at a time, to a 'Stage 1' channel, which parses the line into an intermediary (shared) representation. This parsed line is routed to multiple 'Stage 2' channels. Each 'Stage 2' channel does its own processing on the N available lines to convert them to a final representation. This channel must have a queue which ensures no Stage 2 channel is overwhelmed in the event that one channel processes significantly slower than the others. The final representation of the N lines is written to a file. There will be as many output files as there were routing destinations in step 4. *'N' above stands for any reasonable number of lines to read at a time, from [1, whatever I can fit into memory reasonably], but is guaranteed to always be less than the number of lines in the full file. How can I accomplish streaming (steps 3, 4, 5) in Spring Integration? It's fairly easy to do without streaming the files, but my files are large enough that I cannot read the entire file into memory. As a side note, I have a working implementation of this work flow without Spring Integration, but since we're using Spring Integration in other places in our project, I'd like to try it here to see how it performs and how the resulting code compares for length and clarity.

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• ReaderWriterLockSlim and Pulse/Wait

  - by Jono

  Is there an equivalent of Monitor.Pulse and Monitor.Wait that I can use in conjunction with a ReaderWriterLockSlim? I have a class where I've encapsulated multi-threaded access to an underlying queue. To enqueue something, I acquire a lock that protects the underlying queue (and a couple of other objects) then add the item and Monitor.Pulse the locked object to signal that something was added to the queue. public void Enqueue(ITask task) { lock (mutex) { underlying.Enqueue(task); Monitor.Pulse(mutex); } } On the other end of the queue, I have a single background thread that continuously processes messages as they arrive on the queue. It uses Monitor.Wait when there are no items in the queue, to avoid unnecessary polling. (I consider this to be good design, but any flames (within reason) are welcome if they help me learn otherwise.) private void DequeueForProcessing(object state) { while (true) { ITask task; lock (mutex) { while (underlying.Count == 0) { Monitor.Wait(mutex); } task = underlying.Dequeue(); } Process(task); } } As more operations are added to this class (requiring read-only access to the lock protected underlying), someone suggested using ReaderWriterLockSlim. I've never used the class before, and assuming it can offer some performance benefit, I'm not against it, but only if I can keep the Pulse/Wait design.

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• C#. How to pass message from unsafe callback to managed code?

  - by maxima120

  Is there a simple example of how to pass messages from unsafe callback to managed code? I have a proprietary dll which receives some messages packed in structs and all is coming to a callback function. The example of usage is as follows but it calls unsafe code too. I want to pass the messages into my application which is all managed code. *P.S. I have no experience in interop or unsafe code. I used to develop in C++ 8 yrs ago but remember very little from that nightmarish times :) P.P.S. The application is loaded as hell, the original devs claim it processes 2mil messages per sec.. I need a most efficient solution.* static unsafe int OnCoreCallback(IntPtr pSys, IntPtr pMsg) { // Alias structure pointers to the pointers passed in. CoreSystem* pCoreSys = (CoreSystem*)pSys; CoreMessage* pCoreMsg = (CoreMessage*)pMsg; // message handler function. if (pCoreMsg->MessageType == Core.MSG_STATUS) OnCoreStatus(pCoreSys, pCoreMsg); // Continue running return (int)Core.CALLBACKRETURN_CONTINUE; } Thank you.

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• What could cause these Apache crash errors ?

  - by jacobanderssen

  Hello guys. I had a server crash several days ago. I use Cacti to keep stats: at the time when the server crashed, a huge spike from Load 1 to Load 200 occurred, with over 800 processes in the run queue ( from 300 average). Upon checking /var/log/httpd I notice this: * glibc detected /usr/sbin/httpd: double free or corruption (out): 0x00002b8f3142c2f0 ** Followed by alot of these: [Sat Mar 13 19:20:20 2010] [warn] child process 3090 still did not exit, sending a SIGTERM [Sat Mar 13 19:20:20 2010] [warn] child process 3091 still did not exit, sending a SIGTERM Followed by this: ======= Backtrace: ========= /lib64/libc.so.6[0x2b8f1463c2ef] /lib64/libc.so.6(cfree+0x4b)[0x2b8f1463c73b] /usr/lib64/libapr-1.so.0(apr_pool_destroy+0x131)[0x2b8f13f98821] /usr/sbin/httpd[0x2b8f126df47e] /usr/sbin/httpd[0x2b8f126df4ab] /lib64/libpthread.so.0[0x2b8f141b87c0] /etc/httpd/modules/mod_file_cache.so[0x2b8f1cdf00fb] ======= Memory map: ======== And finally a lot of these: [Sat Mar 13 19:20:27 2010] [error] could not make child process 733 exit, attempting to continue anyway [Sat Mar 13 19:20:27 2010] [error] could not make child process 24560 exit, attempting to continue anyway [Sat Mar 13 19:20:27 2010] [error] could not make child process 31384 exit, attempting to continue anyway I am also noticing one or two lines like this: [Mon Mar 15 01:17:26 2010] [notice] child pid 20765 exit signal Segmentation fault (11) Please help me shed some light on this. Thanks !

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• opening a new page and passing a parameter to it with Javascript

  - by recipriversexclusion

  I have a JS function that processes XML I GET from a server to dynamically create a table as below // Generate table of services by parsing the returned XML service list. function convertServiceXmlDataToTable(xml) { var tbodyElem = document.getElementById("myTbody"); var trElem, tdElem; var j = 0; $(xml).find("Service").each(function() { trElem = tbodyElem.insertRow(tbodyElem.rows.length); trElem.className = "tr" + (j % 2); // first column -> service ID var serviceID = $(this).attr("service__id"); tdElem = trElem.insertCell(trElem.cells.length); tdElem.className = "col0"; tdElem.innerHTML = serviceID; // second column -> service name tdElem = trElem.insertCell(trElem.cells.length); tdElem.className = "col1"; tdElem.innerHTML = "<a href=javascript:showServiceInfo(" + serviceID + ")>" + $(this).find("name").text() + "</a>"; j++; }); // each service } where showServiceInfo retrieves more detailed information about each service from the server based on the serviceID and displays it in the same page as the services table. So far so good. But, it turns out that I have to display the detailed service information in another page rather than the same page as the table. I have creates a generic service_info.html with an empty layout template, but I don't understand how to pass serviceID to this new page so that it gets customized with the detailed service info. How can I do this? Or, is there a better way to handle these situations? Thanks!

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• What about race condition in multithreaded reading?

  - by themoob

  Hi, According to an article on IBM.com, "a race condition is a situation in which two or more threads or processes are reading or writing some shared data, and the final result depends on the timing of how the threads are scheduled. Race conditions can lead to unpredictable results and subtle program bugs." . Although the article concerns Java, I have in general been taught the same definition. As far as I know, simple operation of reading from RAM is composed of setting the states of specific input lines (address, read etc.) and reading the states of output lines. This is an operation that obviously cannot be executed simultaneously by two devices and has to be serialized. Now let's suppose we have a situation when a couple of threads access an object in memory. In theory, this access should be serialized in order to prevent race conditions. But e.g. the readers/writers algorithm assumes that an arbitrary number of readers can use the shared memory at the same time. So, the question is: does one have to implement an exclusive lock for read when using multithreading (in WinAPI e.g.)? If not, why? Where is this control implemented - OS, hardware? Best regards, Kuba

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• How to write a flexible modular program with good interaction possibilities between modules?

  - by PeterK

  I went through answers on similar topics here on SO but could't find a satisfying answer. Since i know this is a rather large topic, i will try to be more specific. I want to write a program which processes files. The processing is nontrivial, so the best way is to split different phases into standalone modules which then would be used as necessary (since sometimes i will be only interested in the output of module A, sometimes i would need output of five other modules, etc). The thing is, that i need the modules to cooperate, because the output of one might be the input of another. And i need it to be FAST. Moreover i want to avoid doing certain processing more than once (if module A creates some data which then need to be processed by module B and C, i don't want to run module A twice to create the input for modules B,C ). The information the modules need to share would mostly be blocks of binary data and/or offsets into the processed files. The task of the main program would be quite simple - just parse arguments, run required modules (and perhaps give some output, or should this be the task of the modules?). I don't need the modules to be loaded at runtime. It's perfectly fine to have libs with a .h file and recompile the program every time there is a new module or some module is updated. The idea of modules is here mainly because of code readability, maintaining and to be able to have more people working on different modules without the need to have some predefined interface or whatever (on the other hand, some "guidelines" on how to write the modules would be probably required, i know that). We can assume that the file processing is a read-only operation, the original file is not changed. Could someone point me in a good direction on how to do this in C++ ? Any advice is wellcome (links, tutorials, pdf books...).

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