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• Java Process "The pipe has been ended" problem

  - by Amit Kumar

  I am using Java Process API to write a class that receives binary input from the network (say via TCP port A), processes it and writes binary output to the network (say via TCP port B). I am using Windows XP. The code looks like this. There are two functions called run() and receive(): run is called once at the start, while receive is called whenever there is a new input received via the network. Run and receive are called from different threads. The run process starts an exe and receives the input and output stream of the exe. Run also starts a new thread to write output from the exe on to the port B. public void run() { try { Process prc = // some exe is `start`ed using ProcessBuilder OutputStream procStdIn = new BufferedOutputStream(prc.getOutputStream()); InputStream procStdOut = new BufferedInputStream(prc.getInputStream()); Thread t = new Thread(new ProcStdOutputToPort(procStdOut)); t.start(); prc.waitFor(); t.join(); procStdIn.close(); procStdOut.close(); } catch (Exception e) { e.printStackTrace(); printError("Error : " + e.getMessage()); } } The receive forwards the received input from the port A to the exe. public void receive(byte[] b) throws Exception { procStdIn.write(b); } class ProcStdOutputToPort implements Runnable { private BufferedInputStream bis; public ProcStdOutputToPort(BufferedInputStream bis) { this.bis = bis; } public void run() { try { int bytesRead; int bufLen = 1024; byte[] buffer = new byte[bufLen]; while ((bytesRead = bis.read(buffer)) != -1) { // write output to the network } } catch (IOException ex) { Logger.getLogger().log(Level.SEVERE, null, ex); } } } The problem is that I am getting the following stack inside receive() and the prc.waitfor() returns immediately afterwards. The line number shows that the stack is while writing to the exe. The pipe has been ended java.io.IOException: The pipe has been ended at java.io.FileOutputStream.writeBytes(Native Method) at java.io.FileOutputStream.write(FileOutputStream.java:260) at java.io.BufferedOutputStream.write(BufferedOutputStream.java:105) at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:65) at java.io.BufferedOutputStream.write(BufferedOutputStream.java:109) at java.io.FilterOutputStream.write(FilterOutputStream.java:80) at xxx.receive(xxx.java:86) Any advice about this will be appreciated.

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• TFS and shared projects in multiple solutions

  - by David Stratton

  Our .NET team works on projects for our company that fall into distinct categories. Some are internal web apps, some are external (publicly facing) web apps, we also have internal Windows applications for our corporate office users, and Windows Forms apps for our retail locations (stores). Of course, because we hate code reuse, we have a ton of code that is shared among the different applications. Currently we're using SVN as our source control, and we've got our repository laid out like this: - = folder, | = Visual Studio Solution -SVN - Internet | Ourcompany.com | Oursecondcompany.com - Intranet | UniformOrdering website | MessageCenter website - Shared | ErrorLoggingModule | RegularExpressionGenerator | Anti-Xss | OrgChartModule etc... So.. The OurCompany.com solution in the Internet folder would have a website project, and it would also include the ErrorLoggingModule, RegularExpressionGenerator, and Anti-Xss projects from the shared directory. Similarly, our UniformOrdering website solution would have each of these projects included in the solution as well. We prefer to have a project reference to a .dll reference because, first of all, if we need to add or fix a function in the ErrorLoggingModule while working on the OurCompany.com website, it's right there. Also, this allows us to build each solution and see if changes to shared code break any other applications. This should work well on a build server as well if I'm correct. In SVN, there is no problem with this. SVN and Visual Studio aren't tied together in the way TFS's source control is. We never figured out how to work this type of structure in TFS when we were using it, because in TFS, the TFS project was always tied to a Visual Studio Solution. The Source Code repository was a child of the TFS Project, so if we wanted to do this, we had to duplicate the Shared code in each TFS project's source code repository. As my co-worker put it, this "breaks every known best practice about code reuse and simplicity". It was enough of a deal breaker for us that we switched to SVN. Now, however, we're faced with truly fixing our development processes, and the Application Lifecycle Management of TFS is pretty close to exactly what we want, and how we want to work. Our one sticking point is the shared code issue. We're evaluating other commercial and open source solutions, but since we're already paying for TFS with our MSDN Subscriptions, and TFS is pretty much exactly what we want, we'd REALLY like to find a way around this issue. Has anybody else faced this and come up with a solution? If you've seen an article or posting on this that you can share with me, that would help as well. As always, I'm open to answers like "You're looking at it all wrong, bonehead, HERE'S the way it SHOULD be done.

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• IIS7 MVC deploy - 404 not found on actions that accept "id" parameter.

  - by majkinetor

  Hello. Once deployed parts of my web-application stop working. Index-es on each controller do work, and one form posting via Ajax, Login works too. Other then that yields 404. I understand that nothing particular should be done in integrated mode. I don't know how to proceed with troubleshooting. Some info: App is using default app pool set to integrated mode. WebApp is done in net framework 3.5. I use default routing model. Along web.config in root there is web.config in /View folder referencing HttpNotFoundHandler. OS is Windows Server 2008. Admins issued aspnet_regiis.exe -i IIS 7 Any help is appreciated. Thx. EDIT: I determined that only actions that accept ID parameter don't work. On the contrary, when I add dummy id method in Home controller of default MVC app it works. My Views/Web.config <?xml version="1.0"?> <configuration> <system.web> <httpHandlers> <add path="*" verb="*" type="System.Web.HttpNotFoundHandler"/> </httpHandlers> <!-- Enabling request validation in view pages would cause validation to occur after the input has already been processed by the controller. By default MVC performs request validation before a controller processes the input. To change this behavior apply the ValidateInputAttribute to a controller or action. --> <pages validateRequest="false" pageParserFilterType="System.Web.Mvc.ViewTypeParserFilter, System.Web.Mvc, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" pageBaseType="System.Web.Mvc.ViewPage, System.Web.Mvc, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" userControlBaseType="System.Web.Mvc.ViewUserControl, System.Web.Mvc, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"> <controls> <add assembly="System.Web.Mvc, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" namespace="System.Web.Mvc" tagPrefix="mvc" /> </controls> </pages> </system.web> <system.webServer> <validation validateIntegratedModeConfiguration="false"/> <handlers> <remove name="BlockViewHandler"/> <add name="BlockViewHandler" path="*" verb="*" preCondition="integratedMode" type="System.Web.HttpNotFoundHandler"/> </handlers> </system.webServer> </configuration>

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• Eventlet or gevent or Stackless + Twisted, Pylons, Django and SQL Alchemy

  - by Khorkrak

  We're using Twisted extensively for apps requiring a great deal of asynchronous io. There are some cases where stuff is cpu bound instead and for that we spawn a pool of processes to do the work and have a system for managing these across multiple servers as well - all done in Twisted. Works great. The problem is that it's hard to bring new team members up to speed. Writing asynchronous code in Twisted requires a near vertical learning curve. It's as if humans just don't think that way naturally. We're considering a mixed approach perhaps. Maybe do the xmlrpc server part and process management in Twisted still but the other stuff in code that at least looks synchronous while not being as such. Then again I like explicit over implicit so hmmm. Anyway onto greenlets - how well does that stuff work? So there's Stackless and as you can see from my Gallentean avatar I'm well aware of the tremendous success in it's use for CCP's flagship EVE Online game first hand. What about Eventlet or gevent? Well for now only Eventlet works with Twisted. However gevent claims to be faster since it's not a pure python implementation it instead uses libevent. It also has fewer idiosyncrasies and defects supposedly. The documentation there is minimal in comparison to Eventlet and it's maintained by 1 guy as far as I can tell. This makes me leery but all great projects start this way so... Then there's PyPy - I haven't even finished reading about that one yet - just saw it in this thread: Drawbacks of Stackless. So confusing - I'm wondering what the heck to do - sounds like Eventlet is probably the best bet but is it really stable enough? Anyone out there have any experience with it? Should we go with Stackless instead as it's been around and is proven technology - just like Twisted is as well - and they do work together nicely. But still I hate having to have a separate version of Python to do this. what to do.... This somewhat obnoxious blog entry hit the nail on the head for me though: Asynchronous IO for Grownups We're stuck using MySQL as well - I never knew how great PostgreSQL was until having had to work on a production OLTP system in MySQL instead - but that's another story. But if that monkey patch thing really works then wow. Just wow.

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• Unable to retrieve information form HP-UX pst_status object

  - by bogertron

  I am attempting to get process information by using the HP-UX C/C++ library. After scouring the internet, I have discovered that HP-UX has the pstat.h header file which allows programmers to retrieve the process information. After attempting to understand code from the internet hp website, I attempted to create a little test sample to comprehend what the code does. I attempted to use example 3, however, I ran into several issues. The first issue came when I attempted to execute the following line of code: (void)printf("pid is %d, command is %s\n", pst[i].pst_pid, pst[i].pst_ucomm); When I attempted to print the string, I hit a memory fault. So I decided to attempt to see what the string is and came up with the following: #include <sys/param.h> #include <sys/pstat.h> #include <sys/unistd.h> #include <string.h> int main(int argc, char** argv) { #define BURST ((size_t)10) struct pst_status pst[BURST]; int i, count; int idx = 0; /* index within the context */ int index = 0; /* loop until count == 0, will occur all have been returned */ while ((count=pstat_getproc(pst, sizeof(pst[0]),BURST,idx))>0) { index = 0; printf("index: %d", index); /* got count (max of BURST) this time. process them */ while (pst[i].pst_ucomm[index] != '\0') { printf("%c", pst[i].pst_ucomm[index]); index++; } printf("\n"); for (i = 0; i < count; i++) { printf("pid is %d, command is \n", pst[i].pst_pid); } /* * now go back and do it again, using the next index after * the current 'burst' */ idx = pst[count-1].pst_idx + 1; } if (count == -1) perror("pstat_getproc()"); #undef BURST } Unfortunately, what happens is that I get the first process printed, then pid is 2, command is pid is 2, command is pid is 2, command is... I know that I must be doing something foolish since my C/C++ skills are not that great, but I cannot figure out what the issue is since the code is largely copied from the hp website. So here's the question(s) for clarity: 1. Why can't printf("%s", pst[i].pst_ucomm); handle strings? 2. Why can't I iterate over the processes in the system? Any help is greatly appreciated.

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• Properly clean up excel interop objects revisited: Wrapper objects

  - by chiccodoro

  Hi all, Excel 2007 Hangs When Closing via .NET How to properly clean up Excel interop objects in C# How to properly clean up interop objects in C# All of these struggle with the problem that C# does not release the Excel COM objects properly after using them. There are mainly two directions of working around this issue: Kill the Excel process when Excel is not used anymore. Take care to assign each COM object used explicitly to a variable and to Marshal.ReleaseComObject all of these. Some have stated that 2 is too tedious and there is always some uncertainty whether you forget to stick to this rule at some places in the code. Still 1 seems dirty and dangerous to me, also I could imagine that in an environment with restricted access killing processes is not allowed. So I've been thinking about solving 2 by creating another proxy object model which mimics the Excel object model (for me, it would suffice to implement the objects I actually need). The principle would look as follows: Each Excel Interop class has its proxy which wraps an object of that class. The proxy releases the COM object in its destructor. The proxy mimics the interface of the Interop class (maybe by inheriting it). Any methods that usually return another COM object return a proxy instead. The other methods simply delegate the implementation to the inner COM object. This is a rough sketch of the code: public class Application : Microsoft.Office.Interop.Excel.Application { private Microsoft.Office.Interop.Excel.Application innerApplication = new Microsoft.Office.Interop.Excel.Application innerApplication(); ~Application() { Marshal.ReleaseCOMObject(innerApplication); } public Workbooks Workbooks { get { return new Workbooks(innerApplication.Workbooks); } } } public class Workbooks { private Microsoft.Office.Interop.Excel.Workbooks innerWorkbooks; Workbooks(Microsoft.Office.Interop.Excel.Workbooks innerWorkbooks) { this.innerWorkbooks = innerWorkbooks; } ~Workbooks() { Marshal.ReleaseCOMObject(innerWorkbooks); } } My questions to you are in particular: Who finds this a bad idea and why? Who finds this a gread idea? If so, why hasn't anybody implemented/published such a model yet? Just due to the effort, or am I missing a killing problem with that idea? Is it impossible/bad/dangerous to do the ReleaseCOMObject in the destructor? (I've only seen proposals to put it in a Dispose() rather than in a destructor - why?) If the approach makes sense, any suggestions to improve it?

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• Hooking DirectX EndScene from an injected DLL

  - by Etan

  I want to detour EndScene from an arbitrary DirectX 9 application to create a small overlay. As an example, you could take the frame counter overlay of FRAPS, which is shown in games when activated. I know the following methods to do this: Creating a new d3d9.dll, which is then copied to the games path. Since the current folder is searched first, before going to system32 etc., my modified DLL gets loaded, executing my additional code. Downside: You have to put it there before you start the game. Same as the first method, but replacing the DLL in system32 directly. Downside: You cannot add game specific code. You cannot exclude applications where you don't want your DLL to be loaded. Getting the EndScene offset directly from the DLL using tools like IDA Pro 4.9 Free. Since the DLL gets loaded as is, you can just add this offset to the DLL starting address, when it is mapped to the game, to get the actual offset, and then hook it. Downside: The offset is not the same on every system. Hooking Direct3DCreate9 to get the D3D9, then hooking D3D9-CreateDevice to get the device pointer, and then hooking Device-EndScene through the virtual table. Downside: The DLL cannot be injected, when the process is already running. You have to start the process with the CREATE_SUSPENDED flag to hook the initial Direct3DCreate9. Creating a new Device in a new window, as soon as the DLL gets injected. Then, getting the EndScene offset from this device and hooking it, resulting in a hook for the device which is used by the game. Downside: as of some information I have read, creating a second device may interfere with the existing device, and it may bug with windowed vs. fullscreen mode etc. Same as the third method. However, you'll do a pattern scan to get EndScene. Downside: doesn't look that reliable. How can I hook EndScene from an injected DLL, which may be loaded when the game is already running, without having to deal with different d3d9.dll's on other systems, and with a method which is reliable? How does FRAPS for example perform it's DirectX hooks? The DLL should not apply to all games, just to specific processes where I inject it via CreateRemoteThread.

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• How to override PHP configuration when running in CGI mode

  - by Fitrah M

  There are some tutorials out there telling me how to override PHP configuration when it is running in CGI mode. But I'm still confused because lots of them assume that the server is running on Linux. While I need to do that also in Windows. My hosting is indeed using Linux but my local development computer is using Windows XP with Xampp 1.7.3. So I need to do that in my local computer first, then I want to change the configuration on hosting server. The PHP in my hosting server is already run as CGI while in my local computer still run as Apache module. At this point, the processes that I understand are: Change PHP to work in CGI mode. I did this by commenting these two line in "httpd-xampp.conf": # LoadFile "C:/xampp/php/php5ts.dll" # LoadModule php5_module modules/php5apache2_2.dll Create "cgi-bin" directory in DocumentRoot. My DocumentRoot is in "D:\www\" (I'm using apache with virtual host). So it is now "D:\www\cgi-bin". Change the default "cgi-bin" directory settings from "C:/xampp/cgi-bin/" to "D:\www\cgi-bin": ScriptAlias /cgi-bin/ "D:/www/cgi-bin/" <Directory "D:\www\cgi-bin"> Options MultiViews Indexes SymLinksIfOwnerMatch Includes ExecCGI AllowOverride All Allow from All </Directory> At this point, my PHP is now running as CGI. I checked this with phpinfo(). It tells me that Server API is now CGI/FastCGI. Now I want to override php configuration. I copied 'php.ini' file to "D:\www\cgi-bin" and modify upload_max_filesize setting from 128M to 10M. Create 'php.cgi' file in "D:\www\cgi-bin" and put these code inside the file: #!/bin/sh /usr/local/cpanel/cgi-sys/php5 -c /home/user/public_html/cgi-bin/ That's it. I'm stuck at this point. All of tutorials tell me to create 'php.cgi' file and put shell code inside the file. How to do the 6th step on Windows? I know the next step is to create handler in .htaccess file to load that 'php.cgi'. And also, because I will also need to change PHP configuration on my hosting server (Linux), is the 6th step above right? Some tutorial tells to insert these line instead of above: #!/bin/sh export PHPRC=/site/ini/1 exec /cgi-bin/php5.cgi I'm sorry if my question is not clear. I'm a new member and this is my first question in this site. Thank you.

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• kill -9 doesn't work

  - by Daniel

  I have a server with 3 oracle instances on it, and the file system is nfs with netapp. After shutdown the databases, one process for each database doesn't quit for a long time. Each kill -i doesn't work. I tried to truss, pfile it, the command through error. And iostat shows there are lots of IO to the netapp server. So someone said the process was busy writing data to remote netapp server, and before the write complete, it won't quit. So what need to be done was just wait until all the IO was done. After wait for longer time (about 1.5 hours), the processes exit. So my question is: how can a process ignore the kill signal? As far as I know, if we kill -9, it will stop immediately. Do you encounter such situation kill -i doesn't kill the process right away? TEST7-stdby-phxdbnfs11$ ps -ef|grep dbw0 oracle 1469 25053 0 22:36:53 pts/1 0:00 grep dbw0 oracle 26795 1 0 21:55:23 ? 0:00 ora_dbw0_TEST7 oracle 1051 1 0 Apr 08 ? 3958:51 ora_dbw0_TEST2 oracle 471 1 0 Apr 08 ? 6391:43 ora_dbw0_TEST1 TEST7-stdby-phxdbnfs11$ kill -9 1051 TEST7-stdby-phxdbnfs11$ ps -ef|grep dbw0 oracle 1493 25053 0 22:37:07 pts/1 0:00 grep dbw0 oracle 26795 1 0 21:55:23 ? 0:00 ora_dbw0_TEST7 oracle 1051 1 0 Apr 08 ? 3958:51 ora_dbw0_TEST2 oracle 471 1 0 Apr 08 ? 6391:43 ora_dbw0_TEST1 TEST7-stdby-phxdbnfs11$ kill -9 471 TEST7-stdby-phxdbnfs11$ ps -ef|grep dbw0 oracle 26795 1 0 21:55:23 ? 0:00 ora_dbw0_TEST7 oracle 1051 1 0 Apr 08 ? 3958:51 ora_dbw0_TEST2 oracle 471 1 0 Apr 08 ? 6391:43 ora_dbw0_TEST1 oracle 1495 25053 0 22:37:22 pts/1 0:00 grep dbw0 TEST7-stdby-phxdbnfs11$ ps -ef|grep smon oracle 1524 25053 0 22:38:02 pts/1 0:00 grep smon TEST7-stdby-phxdbnfs11$ ps -ef|grep dbw0 oracle 1526 25053 0 22:38:06 pts/1 0:00 grep dbw0 oracle 26795 1 0 21:55:23 ? 0:00 ora_dbw0_TEST7 oracle 1051 1 0 Apr 08 ? 3958:51 ora_dbw0_TEST2 oracle 471 1 0 Apr 08 ? 6391:43 ora_dbw0_TEST1 TEST7-stdby-phxdbnfs11$ kill -9 1051 471 26795 TEST7-stdby-phxdbnfs11$ ps -ef|grep dbw0 oracle 1528 25053 0 22:38:19 pts/1 0:00 grep dbw0 oracle 26795 1 0 21:55:23 ? 0:00 ora_dbw0_TEST7 oracle 1051 1 0 Apr 08 ? 3958:51 ora_dbw0_TEST2 oracle 471 1 0 Apr 08 ? 6391:43 ora_dbw0_TEST1 TEST7-stdby-phxdbnfs11$ truss -p 26795 truss: unanticipated system error: 26795 TEST7-stdby-phxdbnfs11$ pfiles 26795 pfiles: unanticipated system error: 26795

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• PHP: Can pcntl_alarm() and socket_select() peacefully exist in the same thread?

  - by DWilliams

  I have a PHP CLI script mostly written that functions as a chat server for chat clients to connect to (don't ask me why I'm doing it in PHP, thats another story haha). My script utilizes the socket_select() function to hang execution until something happens on a socket, at which point it wakes up, processes the event, and waits until the next event. Now, there are some routine tasks that I need performed every 30 seconds or so (check of tempbanned users should be unbanned, save user databases, other assorted things). From what I can tell, PHP doesn't have very great multi-threading support at all. My first thought was to compare a timestamp every time the socket generates an event and gets the program flowing again, but this is very inconsistent since the server could very well sit idle for hours and not have any of my cleanup routines executed. I came across the PHP pcntl extensions, and it lets me use assign a time interval for SIGALRM to get sent and a function get executed every time it's sent. This seems like the ideal solution to my problem, however pcntl_alarm() and socket_select() clash with each other pretty bad. Every time SIGALRM is triggered, all sorts of crazy things happen to my socket control code. My program is fairly lengthy so I can't post it all here, but it shouldn't matter since I don't believe I'm doing anything wrong code-wise. My question is: Is there any way for a SIGALRM to be handled in the same thread as a waiting socket_select()? If so, how? If not, what are my alternatives here? Here's some output from my program. My alarm function simply outputs "Tick!" whenever it's called to make it easy to tell when stuff is happening. This is the output (including errors) after allowing it to tick 4 times (there were no actual attempts at connecting to the server despite what it says): [05-28-10 @ 20:01:05] Chat server started on 192.168.1.28 port 4050 [05-28-10 @ 20:01:05] Loaded 2 users from file PHP Notice: Undefined offset: 0 in /home/danny/projects/PHPChatServ/ChatServ.php on line 112 PHP Warning: socket_select(): unable to select [4]: Interrupted system call in /home/danny/projects/PHPChatServ/ChatServ.php on line 116 [05-28-10 @ 20:01:15] Tick! PHP Warning: socket_accept(): unable to accept incoming connection [4]: Interrupted system call in /home/danny/projects/PHPChatServ/ChatServ.php on line 126 [05-28-10 @ 20:01:25] Tick! PHP Warning: socket_getpeername() expects parameter 1 to be resource, boolean given in /home/danny/projects/PHPChatServ/ChatServ.php on line 129 [05-28-10 @ 20:01:25] Accepting socket connection from PHP Notice: Undefined offset: 1 in /home/danny/projects/PHPChatServ/ChatServ.php on line 112 PHP Warning: socket_select(): unable to select [4]: Interrupted system call in /home/danny/projects/PHPChatServ/ChatServ.php on line 116 [05-28-10 @ 20:01:35] Tick! PHP Warning: socket_accept(): unable to accept incoming connection [4]: Interrupted system call in /home/danny/projects/PHPChatServ/ChatServ.php on line 126 [05-28-10 @ 20:01:45] Tick! PHP Warning: socket_getpeername() expects parameter 1 to be resource, boolean given in /home/danny/projects/PHPChatServ/ChatServ.php on line 129 [05-28-10 @ 20:01:45] Accepting socket connection from PHP Notice: Undefined offset: 2 in /home/danny/projects/PHPChatServ/ChatServ.php on line 112

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• Does oneway declaration in Android .aidl guarantee that method will be called in a separate thread?

  - by Dan Menes

  I am designing a framework for a client/server application for Android phones. I am fairly new to both Java and Android (but not new to programming in general, or threaded programming in particular). Sometimes my server and client will be in the same process, and sometimes they will be in different processes, depending on the exact use case. The client and server interfaces look something like the following: IServer.aidl: package com.my.application; interface IServer { /** * Register client callback object */ void registerCallback( in IClient callbackObject ); /** * Do something and report back */ void doSomething( in String what ); . . . } IClient.aidl: package com.my.application; oneway interface IClient { /** * Receive an answer */ void reportBack( in String answer ); . . . } Now here is where it gets interesting. I can foresee use cases where the client calls IServer.doSomething(), which in turn calls IClient.reportBack(), and on the basis of what is reported back, IClient.reportBack() needs to issue another call to IClient.doSomething(). The issue here is that IServer.doSomething() will not, in general, be reentrant. That's OK, as long as IClient.reportBack() is always invoked in a new thread. In that case, I can make sure that the implementation of IServer.doSomething() is always synchronized appropriately so that the call from the new thread blocks until the first call returns. If everything works the way I think it does, then by declaring the IClient interface as oneway, I guarantee this to be the case. At least, I can't think of any way that the call from IServer.doSomething() to IClient.reportBack() can return immediately (what oneway is supposed to ensure), yet IClient.reportBack still be able to reinvoke IServer.doSomething recursively in the same thread. Either a new thread in IServer must be started, or else the old IServer thread can be re-used for the inner call to IServer.doSomething(), but only after the outer call to IServer.doSomething() has returned. So my question is, does everything work the way I think it does? The Android documentation hardly mentions oneway interfaces.

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• Problems doing asynch operations in C# using Mutex.

  - by firoso

  I've tried this MANY ways, here is the current iteration. I think I've just implemented this all wrong. What I'm trying to accomplish is to treat this Asynch result in such a way that until it returns AND I finish with my add-thumbnail call, I will not request another call to imageProvider.BeginGetImage. To Clarify, my question is two-fold. Why does what I'm doing never seem to halt at my Mutex.WaitOne() call, and what is the proper way to handle this scenario? /// <summary> /// re-creates a list of thumbnails from a list of TreeElementViewModels (directories) /// </summary> /// <param name="list">the list of TreeElementViewModels to process</param> public void BeginLayout(List<AiTreeElementViewModel> list) { // *removed code for canceling and cleanup from previous calls* // Starts the processing of all folders in parallel. Task.Factory.StartNew(() => { thumbnailRequests = Parallel.ForEach<AiTreeElementViewModel>(list, options, ProcessFolder); }); } /// <summary> /// Processes a folder for all of it's image paths and loads them from disk. /// </summary> /// <param name="element">the tree element to process</param> private void ProcessFolder(AiTreeElementViewModel element) { try { var images = ImageCrawler.GetImagePaths(element.Path); AsyncCallback callback = AddThumbnail; foreach (var image in images) { Console.WriteLine("Attempting Enter"); synchMutex.WaitOne(); Console.WriteLine("Entered"); var result = imageProvider.BeginGetImage(callback, image); } } catch (Exception exc) { Console.WriteLine(exc.ToString()); // TODO: Do Something here. } } /// <summary> /// Adds a thumbnail to the Browser /// </summary> /// <param name="result">an async result used for retrieving state data from the load task.</param> private void AddThumbnail(IAsyncResult result) { lock (Thumbnails) { try { Stream image = imageProvider.EndGetImage(result); string filename = imageProvider.GetImageName(result); string imagePath = imageProvider.GetImagePath(result); var imageviewmodel = new AiImageThumbnailViewModel(image, filename, imagePath); thumbnailHash[imagePath] = imageviewmodel; HostInvoke(() => Thumbnails.Add(imageviewmodel)); UpdateChildZoom(); //synchMutex.ReleaseMutex(); Console.WriteLine("Exited"); } catch (Exception exc) { Console.WriteLine(exc.ToString()); // TODO: Do Something here. } } }

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• Asynchronous subprocess on Windows

  - by Stigma

  First of all, the overall problem I am solving is a bit more complicated than I am showing here, so please do not tell me 'use threads with blocking' as it would not solve my actual situation without a fair, FAIR bit of rewriting and refactoring. I have several applications which are not mine to modify, which take data from stdin and poop it out on stdout after doing their magic. My task is to chain several of these programs. Problem is, sometimes they choke, and as such I need to track their progress which is outputted on STDERR. pA = subprocess.Popen(CommandA, shell=False, stdout=subprocess.PIPE, stderr=subprocess.PIPE) # ... some more processes make up the chain, but that is irrelevant to the problem pB = subprocess.Popen(CommandB, shell=False, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=pA.stdout ) Now, reading directly through pA.stdout.readline() and pB.stdout.readline(), or the plain read() functions, is a blocking matter. Since different applications output in different paces and different formats, blocking is not an option. (And as I wrote above, threading is not an option unless at a last, last resort.) pA.communicate() is deadlock safe, but since I need the information live, that is not an option either. Thus google brought me to this asynchronous subprocess snippet on ActiveState. All good at first, until I implement it. Comparing the cmd.exe output of pA.exe | pB.exe, ignoring the fact both output to the same window making for a mess, I see very instantaneous updates. However, I implement the same thing using the above snippet and the read_some() function declared there, and it takes over 10 seconds to notify updates of a single pipe. But when it does, it has updates leading all the way upto 40% progress, for example. Thus I do some more research, and see numerous subjects concerning PeekNamedPipe, anonymous handles, and returning 0 bytes available even though there is information available in the pipe. As the subject has proven quite a bit beyond my expertise to fix or code around, I come to Stack Overflow to look for guidance. :) My platform is W7 64-bit with Python 2.6, the applications are 32-bit in case it matters, and compatibility with Unix is not a concern. I can even deal with a full ctypes or pywin32 solution that subverts subprocess entirely if it is the only solution, as long as I can read from every stderr pipe asynchronously with immediate performance and no deadlocks. :)

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• LINQ InsertOnSubmit Required Fields needed for debugging

  - by Derek Hunziker

  Hi All, I've been using the ADO.NET Strogly-Typed DataSet model for about 2 years now for handling CRUD and stored procedure executions. This past year I built my first MVC app and I really enjoyed the ease and flexibility of LINQ. Perhaps the biggest selling point for me was that with LINQ I didn't have to create "Insert" stored procedures that would return the SCOPE_IDENTITY anymore (The auto-generated insert statements in the DataSet model were not capable of this without modification). Currently, I'm using LINQ with ASP.NET 3.5 WebForms. My inserts are looking like this: ProductsDataContext dc = new ProductsDataContext(); product p = new product { Title = "New Product", Price = 59.99, Archived = false }; dc.products.InsertOnSubmit(p); dc.SubmitChanges(); int productId = p.Id; So, this product example is pretty basic, right, and in the future, I'll probably be adding more fields to the database such as "InStock", "Quantity", etc... The way I understand it, I will need to add those fields to the database table and then delete and re-add the tables to the LINQ to SQL Class design view in order to refresh the DataContext. Does that sound right? The problem is that any new fields that are non-null are NOT caught by the ASP.NET build processes. For example, if I added a non-null field of "Quantity" to the database, the code above would still build. In the DataSet model, the stored procedure method would accept a certain amount of parameters and would warn me that my Insert would fail if I didn't include a quantity value. The same goes for LINQ stored procedure methods, however, to my knowledge, LINQ doesn't offer a way to auto generate the insert statements and that means I'm back to where I started. The bottom line is if I used insert statements like the one above and I add a non-null field to my database, it would break my app in about 10-20 places and there would be no way for me to detect it. Is my only option to do a solution-side search for the keyword "products.InsertOnSubmit" and make sure the new field is getting assigned? Is there a better way? Thanks!

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• Techniques for modeling a dynamic dataflow with Java concurrency API

  - by Maian

  Is there an elegant way to model a dynamic dataflow in Java? By dataflow, I mean there are various types of tasks, and these tasks can be "connected" arbitrarily, such that when a task finishes, successor tasks are executed in parallel using the finished tasks output as input, or when multiple tasks finish, their output is aggregated in a successor task (see flow-based programming). By dynamic, I mean that the type and number of successors tasks when a task finishes depends on the output of that finished task, so for example, task A may spawn task B if it has a certain output, but may spawn task C if has a different output. Another way of putting it is that each task (or set of tasks) is responsible for determining what the next tasks are. Sample dataflow for rendering a webpage: I have as task types: file downloader, HTML/CSS renderer, HTML parser/DOM builder, image renderer, JavaScript parser, JavaScript interpreter. File downloader task for HTML file HTML parser/DOM builder task File downloader task for each embedded file/link If image, image renderer If external JavaScript, JavaScript parser JavaScript interpreter Otherwise, just store in some var/field in HTML parser task JavaScript parser for each embedded script JavaScript interpreter Wait for above tasks to finish, then HTML/CSS renderer (obviously not optimal or perfectly correct, but this is simple) I'm not saying the solution needs to be some comprehensive framework (in fact, the closer to the JDK API, the better), and I absolutely don't want something as heavyweight is say Spring Web Flow or some declarative markup or other DSL. To be more specific, I'm trying to think of a good way to model this in Java with Callables, Executors, ExecutorCompletionServices, and perhaps various synchronizer classes (like Semaphore or CountDownLatch). There are a couple use cases and requirements: Don't make any assumptions on what executor(s) the tasks will run on. In fact, to simplify, just assume there's only one executor. It can be a fixed thread pool executor, so a naive implementation can result in deadlocks (e.g. imagine a task that submits another task and then blocks until that subtask is finished, and now imagine several of these tasks using up all the threads). To simplify, assume that the data is not streamed between tasks (task output-succeeding task input) - the finishing task and succeeding task won't exist together, so the input data to the succeeding task will not be changed by the preceeding task (since it's already done). There are only a couple operations that the dataflow "engine" should be able to handle: A mechanism where a task can queue more tasks A mechanism whereby a successor task is not queued until all the required input tasks are finished A mechanism whereby the main thread (or other threads not managed by the executor) blocks until the flow is finished A mechanism whereby the main thread (or other threads not managed by the executor) blocks until certain tasks have finished Since the dataflow is dynamic (depends on input/state of the task), the activation of these mechanisms should occur within the task code, e.g. the code in a Callable is itself responsible for queueing more Callables. The dataflow "internals" should not be exposed to the tasks (Callables) themselves - only the operations listed above should be available to the task. Note that the type of the data is not necessarily the same for all tasks, e.g. a file download task may accept a File as input but will output a String. If a task throws an uncaught exception (indicating some fatal error requiring all dataflow processing to stop), it must propagate up to the thread that initiated the dataflow as quickly as possible and cancel all tasks (or something fancier like a fatal error handler). Tasks should be launched as soon as possible. This along with the previous requirement should preclude simple Future polling + Thread.sleep(). As a bonus, I would like to dataflow engine itself to perform some action (like logging) every time task is finished or when no has finished in X time since last task has finished. Something like: ExecutorCompletionService<T> ecs; while (hasTasks()) { Future<T> future = ecs.poll(1 minute); some_action_like_logging(); if (future != null) { future.get() ... } ... } Are there straightforward ways to do all this with Java concurrency API? Or if it's going to complex no matter what with what's available in the JDK, is there a lightweight library that satisfies the requirements? I already have a partial solution that fits my particular use case (it cheats in a way, since I'm using two executors, and just so you know, it's not related at all to the web browser example I gave above), but I'd like to see a more general purpose and elegant solution.

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• Keeping files or database records? Java and Python

  - by danpalmer

  My website will use a Neural Network to predict thing based on user data. The user can select the data to be used in training the network and then use their trained network to predict things. I am using a framework to create, train and query the networks. This uses Java. The framework has persistence for saving a network to an XML file. What is the best way to store these files? I can see several potential ideas, but I need help on choosing which is best: Save each network to a separate XML file with a name that is stored in the database. Load this each time. Save all the networks to the same XML file with each network having a different name that is stored in the database. Somehow pass what would normally be written to an XML file to the Django site for writing to the database. This would need to be returned to the Java code when a prediction needs to be made. I am able to do 1 or 2, but I think their performance will be quite limited and I am on shared hosting at the moment, so I don't know how pleased they would be with thousands of files. Also, after adding a few thousand records to one XML file, I was noticing a massive performance hit on saving to it. If I were able to implement version 3 somehow I think it would be best. No issues with separate processes accessing the database and I think performance would be better. Not to mention having no files lying around. However, the stuff in the neural network framework I am using (Encog) for saving to a file needs access to a Java file object, not a string that could be saved to a database. Unless there is some Java magic I can do here (I know very little Java), the only way I can see of doing this would be with a temporary files but I don't know if this is the correct way to do it. I would appreciate any ideas on the best way to implement any of the above 3 ideas or any alternatives. Thanks!

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• Why does one loop take longer to detect a shared memory update than another loop?

  - by Joseph Garvin

  I've written a 'server' program that writes to shared memory, and a client program that reads from the memory. The server has different 'channels' that it can be writing to, which are just different linked lists that it's appending items too. The client is interested in some of the linked lists, and wants to read every node that's added to those lists as it comes in, with the minimum latency possible. I have 2 approaches for the client: For each linked list, the client keeps a 'bookmark' pointer to keep its place within the linked list. It round robins the linked lists, iterating through all of them over and over (it loops forever), moving each bookmark one node forward each time if it can. Whether it can is determined by the value of a 'next' member of the node. If it's non-null, then jumping to the next node is safe (the server switches it from null to non-null atomically). This approach works OK, but if there are a lot of lists to iterate over, and only a few of them are receiving updates, the latency gets bad. The server gives each list a unique ID. Each time the server appends an item to a list, it also appends the ID number of the list to a master 'update list'. The client only keeps one bookmark, a bookmark into the update list. It endlessly checks if the bookmark's next pointer is non-null ( while(node->next_ == NULL) {} ), if so moves ahead, reads the ID given, and then processes the new node on the linked list that has that ID. This, in theory, should handle large numbers of lists much better, because the client doesn't have to iterate over all of them each time. When I benchmarked the latency of both approaches (using gettimeofday), to my surprise #2 was terrible. The first approach, for a small number of linked lists, would often be under 20us of latency. The second approach would have small spats of low latencies but often be between 4,000-7,000us! Through inserting gettimeofday's here and there, I've determined that all of the added latency in approach #2 is spent in the loop repeatedly checking if the next pointer is non-null. This is puzzling to me; it's as if the change in one process is taking longer to 'publish' to the second process with the second approach. I assume there's some sort of cache interaction going on I don't understand. What's going on?

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• crash in calloc

  - by mmd

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

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• A simple Python deployment problem - a whole world of pain

  - by Evgeny

  We have several Python 2.6 applications running on Linux. Some of them are Pylons web applications, others are simply long-running processes that we run from the command line using nohup. We're also using virtualenv, both in development and in production. What is the best way to deploy these applications to a production server? In development we simply get the source tree into any directory, set up a virtualenv and run - easy enough. We could do the same in production and perhaps that really is the most practical solution, but it just feels a bit wrong to run svn update in production. We've also tried fab, but it just never works first time. For every application something else goes wrong. It strikes me that the whole process is just too hard, given that what we're trying to achieve is fundamentally very simple. Here's what we want from a deployment process. We should be able to run one simple command to deploy an updated version of an application. (If the initial deployment involves a bit of extra complexity that's fine.) When we run this command it should copy certain files, either out of a Subversion repository or out of a local working copy, to a specified "environment" on the server, which probably means a different virtualenv. We have both staging and production version of the applications on the same server, so they need to somehow be kept separate. If it installs into site-packages, that's fine too, as long as it works. We have some configuration files on the server that should be preserved (ie. not overwritten or deleted by the deployment process). Some of these applications import modules from other applications, so they need to be able to reference each other as packages somehow. This is the part we've had the most trouble with! I don't care whether it works via relative imports, site-packages or whatever, as long as it works reliably in both development and production. Ideally the deployment process should automatically install external packages that our applications depend on (eg. psycopg2). That's really it! How hard can it be?

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• What to do when you need more verbs in REST

  - by Richard Levasseur

  There is another similar question to mine, but the discussion veered away from the problem I'm encounting. Say I have a system that deals with expense reports (ER). You can create and edit them, add attachments, and approve/reject them. An expense report might look like this: GET /er/1 => {"title": "Trip to NY", "totalcost": "400 USD", "comments": [ "john: Please add the total cost", "mike: done, can you approve it now?" ], "approvals": [ {"john": "Pending"}, {"finance-group": "Pending"}] } That looks fine, right? Thats what an expense report document looks like. If you want to update it, you can do this: POST /er/1 {"title": "Trip to NY 2010"} If you want to approve it, you can do this: POST /er/1/approval {"approved": true} But, what if you want to update the report and approve it at the same time? How do we do that? If you only wanted to approve, then doing a POST to something like /er/1/approval makes sense. We could put a flag in the URL, POST /er/1?approve=1, and send the data changes as the body, but that flag doesn't seem RESTful. We could put special field to be submitted, too, but that seems a bit hacky, too. If we did that, then why not send up data with attributes like set_title or add_to_cost? We could create a new resource for updating and approving, but (1) I can't think of how to name it without verbs, and (2) it doesn't seem right to name a resource based on what actions can be done to it (what happens if we add more actions?) We could have an X-Approve: True|False header, but headers seem like the wrong tool for the job. It'd also be difficult to get set headers without using javascript in a browser. We could use a custom media-type, application/approve+yes, but that seems no better than creating a new resource. We could create a temporary "batch operations" url, /er/1/batch/A. The client then sends multiple requests, perhaps POST /er/1/batch/A to update, then POST /er/1/batch/A/approval to approve, then POST /er/1/batch/A/status to end the batch. On the backend, the server queues up all the batch requests somewhere, then processes them in the same backend-transaction when it receives the "end batch processing" request. The downside with this is, obviously, that it introduces a lot of complexity. So, what is a good, general way to solve the problem of performing multiple actions in a single request? General because its easy to imagine additional actions that might be done in the same request: Suppress or send notifications (to email, chat, another system, whatever) Override some validation (maximum cost, names of dinner attendees) Trigger backend workflow that doesn't have a representation in the document.

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• How to design this ?

  - by Akku

  how can i make this entire process as 1 single event??? http://code.google.com/apis/visualization/documentation/dev/dsl_get_started.html and draw the chart on single click? I am new to servlets please guide me When a user clicks the "go " button with some input. The data goes to the servlet say "Test3". The servlet processes the data by the user and generates/feeds the data table dynamically Then I call the html page to draw the chart as shown in the tutorial link above. The problem is when I call the servlet it gives me a long json string in the browser as given in the tutorials "google.visualization.Query.setResponse({version:'0.6',status:'ok',sig:'1333639331',table:{cols:[{............................" Then when i manually call the html page to draw the chart i am see the chart. But when I call html page directly using the request dispatcher via the servlet I dont get the result. This is my code and o/p...... I need sugession as to how should be my approach to call the chart public class Test3 extends HttpServlet implements DataTableGenerator { protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { DataSourceHelper.executeDataSourceServletFlow(request, response, this , isRestrictedAccessMode() ); RequestDispatcher rd; rd = request.getRequestDispatcher("new.html");// it call's the html page which draws the chart as per the data added by the servlet..... rd.include(request, response);//forward(request, response); @Override public Capabilities getCapabilities() { return Capabilities.NONE; } protected boolean isRestrictedAccessMode() { return false; } @Override public DataTable generateDataTable(Query query, HttpServletRequest request) { // Create a data table. DataTable data = new DataTable(); ArrayList<ColumnDescription> cd = new ArrayList<ColumnDescription>(); cd.add(new ColumnDescription("name", ValueType.TEXT, "Animal name")); cd.add......... I get the following result along with unprocessed html page google.visualization.Query.setResponse({version:'0.6',statu..... <html> <head> <title>Getting Started Example</title> .... Entire html page as it is on the Browser. What I need is when a user clicks the go button the servlet should process the data and call the html page to draw the chart....Without the json string appearing on the browser.(all in one user click) What should be my approach or how should i design this.... there are no error in the code. since when i run the servlet i get the json string on the browser and then when i run the html page manually i get the chart drawn. So how can I do (servlet processing + html page drawing chart as final result) at one go without the long json string appearing on the browser. There is no problem with the html code....

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• Scala actors: receive vs react

  - by jqno

  Let me first say that I have quite a lot of Java experience, but have only recently become interested in functional languages. Recently I've started looking at Scala, which seems like a very nice language. However, I've been reading about Scala's Actor framework in Programming in Scala, and there's one thing I don't understand. In chapter 30.4 it says that using react instead of receive makes it possible to re-use threads, which is good for performance, since threads are expensive in the JVM. Does this mean that, as long as I remember to call react instead of receive, I can start as many Actors as I like? Before discovering Scala, I've been playing with Erlang, and the author of Programming Erlang boasts about spawning over 200,000 processes without breaking a sweat. I'd hate to do that with Java threads. What kind of limits am I looking at in Scala as compared to Erlang (and Java)? Also, how does this thread re-use work in Scala? Let's assume, for simplicity, that I have only one thread. Will all the actors that I start run sequentially in this thread, or will some sort of task-switching take place? For example, if I start two actors that ping-pong messages to each other, will I risk deadlock if they're started in the same thread? According to Programming in Scala, writing actors to use react is more difficult than with receive. This sounds plausible, since react doesn't return. However, the book goes on to show how you can put a react inside a loop using Actor.loop. As a result, you get loop { react { ... } } which, to me, seems pretty similar to while (true) { receive { ... } } which is used earlier in the book. Still, the book says that "in practice, programs will need at least a few receive's". So what am I missing here? What can receive do that react cannot, besides return? And why do I care? Finally, coming to the core of what I don't understand: the book keeps mentioning how using react makes it possible to discard the call stack to re-use the thread. How does that work? Why is it necessary to discard the call stack? And why can the call stack be discarded when a function terminates by throwing an exception (react), but not when it terminates by returning (receive)? I have the impression that Programming in Scala has been glossing over some of the key issues here, which is a shame, because otherwise it's a truly excellent book.

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• What happens when several Java servlet apps running on the same port ?

  - by Frank

  Something strange happened to my servlets and I think I've figured out why, yet I'm more confused. I used Netbean6.7 to develop a Paypal IPN (Instant Payment Notification) message servlet, it listens on port 8080 by default for Paypal IPN messages. I used some sample Java code from it's web site, but when it ran, only about 1 in 10 messages came through, and they looked correct, but why 1 in 10 ? Not 100% or none ? So I asked some questions here and got some advices, one in particular points me to Google's App Engine, so I downloaded it and ran the demo guestbook while my IPN servlet is still running on Netbeans, the strange thing happened, after I entered "appengine-java-sdk-1.3.2\bin\dev_appserver.cmd appengine-java-sdk-1.3.2\demos\guestbook\war" from the command prompt, I went to the following url on my browser "http://localhost:8080/", I thought I would see the Google demo guestbook page, NO, what I saw was another servlet I developed 2 years ago : "Web Academy", online course registration app. How can that happen ? I never started it, and I haven't touch that project for years. I guess because it's also listening on port 8080, so now I understand why the IPN messages only came through 1 in 10 times, because another servlet was also listening on that port and could have got the messages intended for IPN, or some how those two servlets' processes mixed up and therefore couldn't respond to Paypal properly, and failed. In order to verify some of my guesses, I turn off Netbeans, and ran the Google guestbook again at the prompt, this time on my browser http://localhost:8080/ points to the demo guestbook page. My Urls look like this : [A] Paypal IPN : http://localhost:8080/PayPal_App/PayPal_Servlet [B] Web Academy : http://localhost:8080/ So now, my questions are : <1> Why the "Web Academy" servlet was auto started when I ran the Paypal servlet ? <2> If I change the IPN listening port to 8083, would that mean I can run both of them on my PC at the same time without affecting each other ? <3> But I still don't understand, [A] and [B] look different, if a page for [A] is refreshed, it should show the Paypal content, and another page looking at [B] should show the Web Academy content, and that's exactly what happens when I started Netbeans to run the Paypal servlet, both pages show their respective content correctly side by side without interfering with each other, how come the IPN messages couldn't get through 100% of the time ? <4> In Netbeans how to assign 8080 to servlet [A] and assign port 8083 to servlet [B] ? <5> How to turn off auto start of Web Academy by Netbeans ?

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• Adobe Reader process fails when starting second instance

  - by Reddog

  In our C# WinForms application, we generate PDF files and launch Adobe Reader (or whatever the default system .pdf handler is) via the Process class. Since our PDF files can be large (approx 200K), we handle the Exited event to then clean up the temp file afterwards. The system works as required when a file is opened and then closed again. However, when a second file is opened (before closing Adobe Reader) the second process immediately exits (since Reader is now using it's MDI powers) and in our Exited handler our File.Delete call should fail because it's locked by the now joined Adobe process. However, in Reader we instead get: There was an error opening this document. This file cannot be found. The unusual thing is that if I put a debugger breakpoint before the file deletion and allow it to attempt (and fail) the deletion, then the system behaves as expected! I'm positive that the file exists and fairly positive that all handles/file streams to the file are closed before starting the process. We are launching with the following code: // Open the file for viewing/printing (if the default program supports it) var pdfProcess = new Process(); pdfProcess.StartInfo.FileName = tempFileName; if (pdfProcess.StartInfo.Verbs.Contains("open", StringComparer.InvariantCultureIgnoreCase)) { var verb = pdfProcess.StartInfo.Verbs.First(v => v.Equals("open", StringComparison.InvariantCultureIgnoreCase)); pdfProcess.StartInfo.Verb = verb; } pdfProcess.StartInfo.Arguments = "/N"; // Specifies a new window will be used! (But not definitely...) pdfProcess.SynchronizingObject = this; pdfProcess.EnableRaisingEvents = true; pdfProcess.Exited += new EventHandler(pdfProcess_Exited); _pdfProcessDictionary.Add(pdfProcess, tempFileName); pdfProcess.Start(); Note: We are using the _pdfProcessDictionary to store references to the Process objects so that they stay in scope so that Exited event can successfully be raised. Our cleanup/exited event is: void pdfProcess_Exited(object sender, EventArgs e) { Debug.Assert(!InvokeRequired); var p = sender as Process; try { if (_pdfProcessDictionary.ContainsKey(p)) { var tempFileName = _pdfProcessDictionary[p]; if (File.Exists(tempFileName)) // How else can I check if I can delete it!!?? { // NOTE: Will fail if the Adobe Reader application instance has been re-used! File.Delete(tempFileName); _pdfProcessDictionary.Remove(p); } CleanOtherFiles(); // This function will clean up files for any other previously exited processes in our dictionary } } catch (IOException ex) { // Just swallow it up, we will deal with trying to delete it at another point } } Possible solutions: Detect that the file is still open in another process Detect that the second process hasn't really been fully exited and that the file is opened in the first process instead

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• nhibernate fatal error

  - by Afif Lamloumi

  i have an error ( System.InvalidCastException: Unable to cast object of type 'AccountProxy' to type 'System.String'.) when i did this code i mapped the tables( Account,AccountString,EventData,...) of the the database opengts ( open source) i have this error when i called a function from EventData.cs IQuery query = session.CreateQuery("FROM Eventdata"); IList pets = query.List(); return pets; the Stack Trace: [InvalidCastException: Impossible d'effectuer un cast d'un objet de type 'AccountProxy' en type 'System.String'.] (Object , Object[] , SetterCallback ) +431 NHibernate.Bytecode.Lightweight.AccessOptimizer.SetPropertyValues(Object target, Object[] values) +20 NHibernate.Tuple.Component.PocoComponentTuplizer.SetPropertyValues(Object component, Object[] values) +49 NHibernate.Type.ComponentType.SetPropertyValues(Object component, Object[] values, EntityMode entityMode) +34 NHibernate.Type.ComponentType.ResolveIdentifier(Object value, ISessionImplementor session, Object owner) +150 NHibernate.Type.ComponentType.NullSafeGet(IDataReader rs, String[] names, ISessionImplementor session, Object owner) +42 NHibernate.Loader.Loader.GetKeyFromResultSet(Int32 i, IEntityPersister persister, Object id, IDataReader rs, ISessionImplementor session) +93 NHibernate.Loader.Loader.GetRowFromResultSet(IDataReader resultSet, ISessionImplementor session, QueryParameters queryParameters, LockMode[] lockModeArray, EntityKey optionalObjectKey, IList hydratedObjects, EntityKey[] keys, Boolean returnProxies) +92 NHibernate.Loader.Loader.DoQuery(ISessionImplementor session, QueryParameters queryParameters, Boolean returnProxies) +675 NHibernate.Loader.Loader.DoQueryAndInitializeNonLazyCollections(ISessionImplementor session, QueryParameters queryParameters, Boolean returnProxies) +129 NHibernate.Loader.Loader.DoList(ISessionImplementor session, QueryParameters queryParameters) +116 [GenericADOException: could not execute query [ select eventdata0_.deviceID as deviceID5_, eventdata0_.timestamp as timestamp5_, eventdata0_.statusCode as statusCode5_, eventdata0_.accountID as accountID5_, eventdata0_.latitude as latitude5_, eventdata0_.longitude as longitude5_, eventdata0_.gpsAge as gpsAge5_, eventdata0_.speedKPH as speedKPH5_, eventdata0_.heading as heading5_, eventdata0_.altitude as altitude5_, eventdata0_.transportID as transpo11_5_, eventdata0_.inputMask as inputMask5_, eventdata0_.outputMask as outputMask5_, eventdata0_.address as address5_, eventdata0_.DataSource as DataSource5_, eventdata0_.rawdata as rawdata5_, eventdata0_.distanceKM as distanceKM5_, eventdata0_.odometerKM as odometerKM5_, eventdata0_.geozoneIndex as geozone19_5_, eventdata0_.geozoneID as geozoneID5_, eventdata0_.creationTime as creatio21_5_ from eventdata eventdata0_ ] [SQL: select eventdata0_.deviceID as deviceID5_, eventdata0_.timestamp as timestamp5_, eventdata0_.statusCode as statusCode5_, eventdata0_.accountID as accountID5_, eventdata0_.latitude as latitude5_, eventdata0_.longitude as longitude5_, eventdata0_.gpsAge as gpsAge5_, eventdata0_.speedKPH as speedKPH5_, eventdata0_.heading as heading5_, eventdata0_.altitude as altitude5_, eventdata0_.transportID as transpo11_5_, eventdata0_.inputMask as inputMask5_, eventdata0_.outputMask as outputMask5_, eventdata0_.address as address5_, eventdata0_.DataSource as DataSource5_, eventdata0_.rawdata as rawdata5_, eventdata0_.distanceKM as distanceKM5_, eventdata0_.odometerKM as odometerKM5_, eventdata0_.geozoneIndex as geozone19_5_, eventdata0_.geozoneID as geozoneID5_, eventdata0_.creationTime as creatio21_5_ from eventdata eventdata0_]] NHibernate.Loader.Loader.DoList(ISessionImplementor session, QueryParameters queryParameters) +213 NHibernate.Loader.Loader.ListIgnoreQueryCache(ISessionImplementor session, QueryParameters queryParameters) +18 NHibernate.Loader.Loader.List(ISessionImplementor session, QueryParameters queryParameters, ISet`1 querySpaces, IType[] resultTypes) +79 NHibernate.Hql.Ast.ANTLR.Loader.QueryLoader.List(ISessionImplementor session, QueryParameters queryParameters) +51 NHibernate.Hql.Ast.ANTLR.QueryTranslatorImpl.List(ISessionImplementor session, QueryParameters queryParameters) +231 NHibernate.Engine.Query.HQLQueryPlan.PerformList(QueryParameters queryParameters, ISessionImplementor session, IList results) +369 NHibernate.Impl.SessionImpl.List(String query, QueryParameters queryParameters, IList results) +317 NHibernate.Impl.SessionImpl.List(String query, QueryParameters parameters) +282 NHibernate.Impl.QueryImpl.List() +163 DATA1.EventdataExtensions.GetEventdata() in C:\Users\HP\Desktop\our_project\DATA1\Queries\Eventdata.cs:33 MvcApplication7.Controllers.HistoriqueController.Index() in C:\Users\HP\Desktop\our_project\MvcApplication7\Controllers\HistoriqueController.cs:17 lambda_method(Closure , ControllerBase , Object[] ) +62 System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters) +17 System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters) +208 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +27 System.Web.Mvc.<>c__DisplayClass15.<InvokeActionMethodWithFilters>b__12() +55 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation) +263 System.Web.Mvc.<>c__DisplayClass17.<InvokeActionMethodWithFilters>b__14() +19 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodWithFilters(ControllerContext controllerContext, IList`1 filters, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +191 System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) +343 System.Web.Mvc.Controller.ExecuteCore() +116 System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext) +97 System.Web.Mvc.ControllerBase.System.Web.Mvc.IController.Execute(RequestContext requestContext) +10 System.Web.Mvc.<>c__DisplayClassb.<BeginProcessRequest>b__5() +37 System.Web.Mvc.Async.<>c__DisplayClass1.<MakeVoidDelegate>b__0() +21 System.Web.Mvc.Async.<>c__DisplayClass8`1.<BeginSynchronous>b__7(IAsyncResult _) +12 System.Web.Mvc.Async.WrappedAsyncResult`1.End() +62 System.Web.Mvc.<>c__DisplayClasse.<EndProcessRequest>b__d() +50 System.Web.Mvc.SecurityUtil.<GetCallInAppTrustThunk>b__0(Action f) +7 System.Web.Mvc.SecurityUtil.ProcessInApplicationTrust(Action action) +22 System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +60 System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +9 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +8841105 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +184 Any suggestions? how can correct this error Data entity class (outtake from comment): public class MyClass { public virtual string DeviceID { get; set; } public virtual int Timestamp { get; set; } public virtual string Account { get; set; } public virtual int StatusCode { get; set; } public virtual double Latitude { get; set; } public virtual double Longitude { get; set; } public virtual int GpsAge { get; set; } public virtual double SpeedKPH { get; set; } public virtual double Heading { get; set; } public override bool Equals(object obj) { return true; } public override int GetHashCode() { return 0; } }

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