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• Daemon program that uses select() inside infinite loop uses significantly more CPU when ported from

  - by Jake

  I have a daemon app written in C and is currently running with no known issues on a Solaris 10 machine. I am in the process of porting it over to Linux. I have had to make minimal changes. During testing it passes all test cases. There are no issues with its functionality. However, when I view its CPU usage when 'idle' on my Solaris machine it is using around .03% CPU. On the Virtual Machine running Red Hat Enterprise Linux 4.8 that same process uses all available CPU (usually somewhere in the 90%+ range). My first thought was that something must be wrong with the event loop. The event loop is an infinite loop ( while(1) ) with a call to select(). The timeval is setup so that timeval.tv_sec = 0 and timeval.tv_usec = 1000. This seems reasonable enough for what the process is doing. As a test I bumped the timeval.tv_sec to 1. Even after doing that I saw the same issue. Is there something I am missing about how select works on Linux vs. Unix? Or does it work differently with and OS running on a Virtual Machine? Or maybe there is something else I am missing entirely? One more thing I am sure sure which version of vmware server is being used. It was just updated about a month ago though. Thanks.

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• Modify Executing Jar file

  - by pinkynobrain

  Hello Stack Overflow friends. I have a simple problem which i fear doesnt have a simple solution and i need advice as to how to proceed. I am developing a java application packaged as and executable JAR but it requires to modify some of its JAR file contents during execution. At this stage i hit a problem because some OS lock the file preventing writes to it. It is essential that the user sees an updated version of the jar file by the time the application exits allthough i can be pretty flexible as to how to achieve this. A clean and efficient solution is obviously prefereable but portability is the only hard requirement. The following are three approaches i can see to solving the problem, feel free to comment on them or suggest others. Tell Java to unlock the JAR file for writing(this doesnt seem possible but it would be the easyest solution) Copy the executable class files to a tempory file on application startup, use a class loader to load these files and unload the ones from the initial JAR file.(Not had much experience with the classloaders but hopefully the JVM would then be smart enough to realize that the original JAR is nolonger in use and so unlock it) Put a Second executable JAR File inside the First, on startup extract the inner jar to e temporaryfile, invoke a new java process and pass it the location of the Outer JAR, first process exits, second process modifys the Outer jar unincumbered.(This will work but im not sure there is a platform independant way of one java app invoking another) I know this is a weird question but any help would be appreciated.

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• Workflow UI Integration - is WF a good approach?

  - by AJ

  Somewhat similar to this question, except we haven't decided that we're going with WF yet. I'm working on designing a system that requires a series of decisions and activities on a "work object," so I naturally began to consider workflow, specifically WF. What I'm wondering is if WF is a good solution for a situation like the following (oversimplified for this question) case (please forgive bad ascii art): __________________ | Gather some info | | (web page) | |__________________| | | / \ / \ / \ / \ / cond \ \ 1 / \ / \ / \ / \ / | | ______________|_______________ | | | | | ______|______ ______|________ / do some / | Get more info | / process / | (web page) | /____________/ |_______________| | | / \ / \ / \ / cond. \ \ 2 / \ / \ / \ / | | |__________________ | | | | _____|_____ _____|_____ / some / / another / / process / / process / /__________/ /__________/ The part I'm struggling with is the get more info (web page) step and what happens subsequent, which would mean a halt in the execution of the workflow runtime. I'm aware that this is possible, but I'm not sure that WF is the best approach for this type of code, as the user interaction may be required at many different points through the entire workflow, and the workflow will drive what data entry screens are needed. We are using a WinForms/ASP.NET web forms package for UI, which is homegrown and difficult to push deployments on, so something like SharePoint integration is out of the question. Our back-end is DB2, and the workflow code (whether it's in WF or otherwise) will need to interact with that as well. I guess the bottom line is, should we look into using WF for this, or would we be better served just coding it ourselves? Can WF easily integrate data entry screens to capture information that can be used further on in the workflow?

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• Programmatically open an email from a POP3 and extract an attachment

  - by Josh

  We have a vendor that sends CSV files as email attachments. These CSV files contain statuses that are imported into our application. I'm trying to automate the process end-to-end, but it currently depends on someone opening an email, saving the attachment to a server share, so the application can use the file. Since I cannot convince the vendor to change their process, such as offering an FTP location or a Web Service, I'm stuck with trying to automate the existing process. Does anyone know of a way to programmatically open an email from a POP3 account and extract an attachment? The preferred solution would reside on a Windows 2003 server, be written VB.NET and secure. The application can reside on the same server as the POP3 server, for example, we could setup the free POP3 server that comes with Windows Server and pull against the mail file stored on the file system. BTW, we are willing to pay for an off-the-shelf solution, if one exists. Note: I did look at this question but the answer points to a CodeProject solution that doesn't deal with attachments.

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• Testing fault tolerant code

  - by Robert

  I’m currently working on a server application were we have agreed to try and maintain a certain level of service. The level of service we want to guaranty is: if a request is accepted by the server and the server sends on an acknowledgement to the client we want to guaranty that the request will happen, even if the server crashes. As requests can be long running and the acknowledgement time needs be short we implement this by persisting the request, then sending an acknowledgement to the client, then carrying out the various actions to fulfill the request. As actions are carried out they too are persisted, so the server knows the state of a request on start up, and there’s also various reconciliation mechanisms with external systems to check the accuracy of our logs. This all seems to work fairly well, but we have difficult saying this with any conviction as we find it very difficult to test our fault tolerant code. So far we’ve come up with two strategies but neither is entirely satisfactory: Have an external process watch the server code and then try and kill it off at what the external process thinks is an appropriate point in the test Add code the application that will cause it to crash a certain know critical points My problem with the first strategy is the external process cannot know the exact state of the application, so we cannot be sure we’re hitting the most problematic points in the code. My problem with the second strategy, although it gives more control over were the fault takes, is I do not like have code to inject faults within my application, even with optional compilation etc. I fear it would be too easy to over look a fault injection point and have it slip into a production environment.

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• Architecture Guidance Needed?

  - by vijay

  We are about to automate number of process for our reporting team. (The reports are like daily reports, weekly reports, monthly reports, etc..) Mostly the process is like pulling some data from the oracle and then fill them in particular excel template files. Each reports and so their templates are different from each other. Except the excel file manipulation, there are hardly any business logic behind these. Client wanted an integrated tool and all the automated processes are placed as menus/submenus. Right now roughly there are around 30 process waiting to be automated. And we are expecting more new reports in the next quarter. I am nowhere to near having any practical experience when comes to architecuring. Already i have been maintaining two or three systems(they are more than 4yrs old.) for this prestegious client.The possiblity of the above mentioned tool will be manintained for another 3 yrs is very likely. From my past experience i've been through the pain of implmenting change requests to the rigd & undocumented code base resulting in the break down of the system and then eventually myself. So My main and top most concern is the maintainablity. When i was searching for these i came across this link, Smart Clients Using CAB and SCSF is the above link appropriate for my requirement? Also Should i place each automated processes in separate forms under a single project, or place them in separate projects under a single solution.. Please correct me if have missed any other important information. Thx.

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• Eclipse CDT: cannot debug or terminate application

  - by Paul Lammertsma

  I have Eclipse set up fairly nicely to run the G++ compiler through Cygwin. Even the character encoding is set up correctly! There still seems to be something wrong with my configuration: I can't debug. The pause button in the debug view is simply disabled, and no threads appear in my application tree. It seems that gdb is simply not communicating with Eclipse. Presently, I have the debug settings as follows: Debugger: "Cygwin gdb Debugger" GDB debugger: gdb GDB command file: .gdbinit Protocol: Default I should mention here that I have no idea what .gdbinit does; in my project it is merely an empty file. What is wrong with my configuration? Debugging When attempting to terminate the application in debug mode, Eclipse displays the following error: Target request failed: failed to interrupt. I can't kill the process, either; I have to kill its parent gdb.exe, which in turn kills my application. Running When running it normally, a bunch of kill.exes are called, doing nothing, while Eclipse displays the following error: Terminate failed. I can kill FaceDetector.exe from the task manager. Process Explorer This is what it looks like in Process Explorer (debugging left, running right):

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• Problem consuming Exchange Web Service 2010 with jax-ws metro

  - by Johan Karlberg

  I am trying to consume the Exchange 2010 Web Service interface using JAX-WS. I'm using JAX-WS 2.2 RI (Metro 2.0). 2.1 exhibited the same problem. I am running into trouble with Exchange, which returns "HTTP/1.1 415 Cannot process the message because the content type 'text/xml;charset=utf-8' was not the expected type 'text/xml; charset=utf-8'." as a reponse (2.1 quoted the charset value, otherwise same response). Apparently I need to dictate the exact Content-type header for Exchange to be happy. Is there a way for me to do this without forcing me to manually rebuild the dependency? I currently rely on published maven artifacts, and would like to continue doing this if at all possible. The consuming process is a regular J2SE app, with no containers in sight. I have control of the application and can add pretty much anything required to the applications scope, but can not add out-of-process items like proxy servers. The client classes were generated from local WSDL, but the charset specification is derived from constants declared in the jaxws RI implementation, not the generated code. The resulting HTTP transport is thus handled by the standard http/https client from Sun JRE5 or JRE6.

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• Usage of static analysis tools - with Clear Case/Quest

  - by boyd4715

  We are in the process of defining our software development process and wanted to get some feed back from the group about this topic. Our team is spread out - US, Canada and India - and I would like to put into place some simple standard rules that all teams will apply to their code. We make use of Clear Case/Quest and RAD I have been looking at PMD, CPP, checkstyle and FindBugs as a start. My thought is to just put these into ANT and have the developers run these manually. I realize doing this you have to have some trust in that each developer will do this. The other thought is to add in some builders in to the IDE which would run a subset of the rules (keep the build process light) and then add another set (heavy) when they check in the code. Some other ideals is to make use of something like Cruse Control and have it set up to run these static analysis tools along with the unit test when ever Clear Case/Quest is idle. Wondering if others have done this and if it was successfully or can provide lessons learned.

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• Field specific errors for ETL

  - by AaronLS

  I am creating a ETL process in MS SQL Server and I would like to have errors specific to a particular column of a particular row. For example, the data is initially loaded from excel files into a table(we'll call the Initial table) where all columns are varchar(2000) and then I stage the data to another table(the DataTypedTable) that contains more specific data types (datetime,int, etc.) or more tightly constrained varchar lengths. I need to be able to create error messages for a specific field such as: "Jan. 13th" is not a valid date format for the submission date. Please use a format of MM/DD/YYYY These error messages would need to be stored in some way such that later in the process a automated process can create reports with the error messages such that each message references a specific row and field(someone will need to go back and correct the data in the source system and resubmit the excel file). So ideally it would be inserted into a Failures tables of some sort and contain the primary key of the failed row, the column name, and the error message. Question: So I am wondering if this can be accomplished with SSIS, or some open source tool like Talend, and if so, what would be your general approach? Or what hand coded approach you would take? Couple approaches I've thought of using SQL(up until no I have done ETL by hand in SQL procs, but I want to consider other approaches. Possible C# even.): Use a cursor to read through the Initial table, and for each row insert a blank record with only the primary key into the DataTyped table, then use a single update statement for each column, such that if that update fails I can insert a very specific error message specific to that column in the error messages table. Insert all the data as is into the DataTyped table, but have duplicate columns like SubmissionDate and SubmissionDateOld. After the initial insert the *Old columns have data, the rest are blank, and I have a single update for each column that sets the SubmissionDate based on the SubmissionDateOld. In addition to suggesting an approach, I'd like to know if you are using that approach or something similar already in the work you do.

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• Bind postback data from a strong type view of type List<T>

  - by Robert Koritnik

  I have a strong type view of type List<List<MyViewModelClass>> The outer list will always have two lists of List<MyViewModelClass>. For each of the two outer lists I want to display a group of checkboxes. Each set can have an arbitrary number of choices. My view model class looks similar to this: public class MyViewModelClass { public Area Area { get; set; } public bool IsGeneric { get; set; } public string Code { get; set; } public bool IsChecked { get; set; } } So the final view will look something like: Please select those that apply: First set of choices: x Option 1 x Option 2 x Option 3 etc. Second set of choices: x Second Option 1 x Second Option 2 x Second Option 3 x Second Option 4 etc. Checkboxes should display MyViewModelClass.Area.Name, and their value should be related to MyViewModelClass.Area.Id. Checked state is of course related to MyViewModel.IsChecked. Question I wonder how should I use Html.CheckBox() or Html.CheckBoxFor() helper to display my checkboxes? I have to get these values back to the server on a postback of course. I would like to have my controller action like one of these: public ActionResult ConsumeSelections(List<List<MyViewModelClass>> data) { // process data } public ActionResult ConsumeSelections(List<MyViewModelClass> first, List<MyViewModelClass> second) { // process data } If it makes things simpler, I could make a separate view model type like: public class Options { public List First { get; set; } public List Second { get; set; } } As well as changing my first version of controller action to: public ActionResult ConsumeSelections(Options data) { // process data }

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• Large number of soft page faults when assigning a TJpegImage to a TBitmap

  - by Robert Oschler

  I have a Delphi 6 Pro application that processes incoming jpeg frames from a streaming video server. The code works but I recently noticed that it generates a huge number of soft page faults over time. After doing some investigation, the page faults appear to be coming from one particular graphics operation. Note, the uncompressed bitmaps in question are 320 x 240 or about 300 KB in size so it's not due to the handling of large images. The number of page faults being generated isn't tolerable. Over an hour it can easily top 1000000 page faults. I created a stripped down test case that executes the code I have included below on a timer, 10 times a second. The page faults appear to happen when I try to assign the TJpegImage to a TBitmap in the GetBitmap() method. I know this because I commented out that line and the page faults do not occur. The assign() triggers a decompression operation on the part of TJpegImage as it pushes the decompressed bits into a newly created bitmap that GetBitmap() returns. When I run Microsoft's pfmon utility (page fault monitor), I get a huge number of soft page fault error lines concerning RtlFillMemoryUlong, so it appears to happen during a memory buffer fill operation. One puzzling note. The summary part of pfmon's report where it shows which DLL caused what page fault does not show any DLL names in the far left column. I tried this on another system and it happens there too. Can anyone suggest a fix or a workaround? Here's the code. Note, IReceiveBufferForClientSocket is a simple class object that holds bytes in an accumulating buffer. function GetBitmap(theJpegImage: TJpegImage): Graphics.TBitmap; begin Result := TBitmap.Create; Result.Assign(theJpegImage); end; // --------------------------------------------------------------- procedure processJpegFrame(intfReceiveBuffer: IReceiveBufferForClientSocket); var theBitmap: TBitmap; theJpegStream, theBitmapStream: TMemoryStream; theJpegImage: TJpegImage; begin theBitmap := nil; theJpegImage := TJPEGImage.Create; theJpegStream:= TMemoryStream.Create; theBitmapStream := TMemoryStream.Create; try // 2 // ************************ BEGIN JPEG FRAME PROCESSING // Load the JPEG image from the receive buffer. theJpegStream.Size := intfReceiveBuffer.numBytesInBuffer; Move(intfReceiveBuffer.bufPtr^, theJpegStream.Memory^, intfReceiveBuffer.numBytesInBuffer); theJpegImage.LoadFromStream(theJpegStream); // Convert to bitmap. theBitmap := GetBitmap(theJpegImage); finally // Free memory objects. if Assigned(theBitmap) then theBitmap.Free; if Assigned(theJpegImage) then theJpegImage.Free; if Assigned(theBitmapStream) then theBitmapStream.Free; if Assigned(theJpegStream) then theJpegStream.Free; end; // try() end; // --------------------------------------------------------------- procedure TForm1.Timer1Timer(Sender: TObject); begin processJpegFrame(FIntfReceiveBufferForClientSocket); end; // --------------------------------------------------------------- procedure TForm1.FormCreate(Sender: TObject); var S: string; begin FIntfReceiveBufferForClientSocket := TReceiveBufferForClientSocket.Create(1000000); S := loadStringFromFile('c:\test.jpg'); FIntfReceiveBufferForClientSocket.assign(S); end; // --------------------------------------------------------------- Thanks, Robert

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• using the window object for accessing global user defined objects and using text within html for cre

  - by timpone

  I don't do very much jquery / javascript but wanted to ask for some advice on the following piece. I have tried to cut out as much as possible. Most of this was semi-inherited code with catching a bunch of events just hardcoded in. I'd like to generalized them more by putting the object name in the html and accessing via jquery on processing (by_date, by_popularity). I retriev as string and access the object via window[current_obj]. Is this a good way to do this or am I missing something? Are there preferable ways to introduce specificity. thanks for any advice. <script> var by_date={}; by_date.current_page=1; by_date.per_page=4; var by_popularity={}; by_popularity.current_page=1; by_popularity.per_page=4; $(function(){ $('.previous.active').live('click',function(){ window[current_obj].current_page--; process(window[current_obj]); }); }); function process(game_obj){ //will process and output new items here } </script> <div class="otherContainer"> <a class='previous active'>Prev</a><div style="display:none;">by_date</div> | <a class='next'>Next</a><div style="display:none;">by_date</div> </div> <div class="topPrevNextContainer"> <a class='previous active'>Prev</a><div style="display:none;">by_popularity</div> | <a class='next'>Next</a><div style="display:none;">by_popularity</div> </div>

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• How to solve timing problems in automated UI tests with C# and Visual Studio?

  - by Lernkurve

  Question What is the standard approach to solve timing problems in automated UI tests? Concrete example I am using Visual Studio 2010 and Team Foundation Server 2010 to create automated UI tests and want to check whether my application has really stopped running: [TestMethod] public void MyTestMethod() { Assert.IsTrue(!IsMyAppRunning(), "App shouldn't be running, but is."); StartMyApp(); Assert.IsTrue(IsMyAppRunning(), "App should have been started and should be running now."); StopMyApp(); //Pause(500); Assert.IsTrue(!IsMyAppRunning(), "App was stopped and shouldn't be running anymore."); } private bool IsMyAppRunning() { foreach (Process runningProcesse in Process.GetProcesses()) { if (runningProcesse.ProcessName.Equals("Myapp")) { return true; } } return false; } private void Pause(int pauseTimeInMilliseconds) { System.Threading.Thread.Sleep(pauseTimeInMilliseconds); } StartMyApp() and StopMyApp() have been recorded with MS Test Manager 2010 and reside in UIMap.uitest. The last assert fails because the assertion is executed while my application is still in the process of shutting down. If I put a delay after StopApp() the test case passes. The above is just an example to explain my problem. What is the standard approach to solve these kinds of timing issues? One idea would be to wait with the assertion until I get some event notification that my app has been stopped.

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• Update a PDF to include an encrypted, hidden, unique identifier?

  - by Dave Jarvis

  Background The idea is this: Person provides contact information for online book purchase Book, as a PDF, is marked with a unique hash Person downloads book PDF passwords are annoying and extremely easy to circumvent. The ideal process would be something like: Generate hash based on contact information Store contact information and hash in database Acquire book lock Update an "include" file with hash text Generate book as PDF (using pdflatex) Apply hash to book Release book lock Send email with book download link Technologies The following technologies can be used (other programming languages are possible, but libraries will likely be limited to those supplied by the host): C, Java, PHP LaTeX files PDF files Linux Question What programming techniques (or open source software) should I investigate to: Embed a unique hash (or other mark) to a PDF Create a collusion-attack resistant mark Develop a non-fragile (e.g., PDF -> EPS -> PDF still contains the mark) solution Research I have looked at the following possibilities: Steganography Natural Language Processing (NLP) Convert blank pages in PDF to images; mark those images; reassemble PDF LaTeX watermark package ImageMagick Steganograhy requires keeping a master copy of the images, and I'm not sure if the watermark would survive PDF -> EPS -> PDF, or other types of conversion. LaTeX creates an image cache, so any steganographic process would have to intercept that process somehow. NLP introduces grammatical errors. Inserting blank pages as images is immediately suspect; it is easy to replace suspicious blank pages. The LaTeX watermark package draws visible marks. ImageMagick draws visible marks. What other solutions are possible? Related Links http://www.tcpdf.org/ invisible watermarks in images Thank you!

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• Utilizing Windows Handles without a forum.

  - by Scott Chamberlain

  I have a program that needs to sit in the background and when a user connects to a RDP session it will do some stuff then launch a program. when the program is closed it will do some housekeeping and logoff the session. The current way I am doing it is like this I have the terminal server launch this application. I have it set as a windows forms application and my code is this public static void Main() { //Do some setup work Process proc = new Process(); //setup the process proc.Start(); proc.WaitForExit(); //Do some housecleaning NativeMethods.ExitWindowsEx(0, 0); } I really like this because there is no item in the taskbar and there is nothing showing up in alt-tab. However to do this I gave up access to functions like void WndProc(ref Message m) So Now I can't listen to windows messages (Like WTS_REMOTE_DISCONNECT or WTS_SESSION_LOGOFF) and do not have a handle to use for for bool WTSRegisterSessionNotification(IntPtr hWnd, int dwFlags); I would like my code to be more robust so it will do the housecleaning if the user logs off or disconnects from the session before he closes the program. Any reccomendations on how I can have my cake and eat it too?

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• struts datagrid problem - can't solve this problem

  - by shien-angel

  i am creating datagrid using the struts-layout. and i encountered this problem javax.servlet.ServletException: DispatchMapping[/monitor/datagridBL]???????????????????? at org.apache.struts.actions.DispatchAction.getParameter(DispatchAction.java:325) at org.apache.struts.actions.DispatchAction.execute(DispatchAction.java:170) at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431) at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236) at jp.terasoluna.fw.web.struts.action.RequestProcessorEx.process(RequestProcessorEx.java:149) at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196) at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414) at javax.servlet.http.HttpServlet.service(HttpServlet.java:707) at javax.servlet.http.HttpServlet.service(HttpServlet.java:820) at weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:227) at weblogic.servlet.internal.StubSecurityHelper.invokeServlet(StubSecurityHelper.java:125) at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:292) at weblogic.servlet.internal.TailFilter.doFilter(TailFilter.java:26) at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:56) at jp.co.anicom.fw.web.common.controller.RequestEncodeFilter.doFilter(RequestEncodeFilter.java:42) at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:56) at jp.co.anicom.fw.web.common.controller.SessionExpirationFilter.doFilter(SessionExpirationFilter.java:89) at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:56) at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.run(WebAppServletContext.java:3588) at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:321) at weblogic.security.service.SecurityManager.runAs(SecurityManager.java:121) at weblogic.servlet.internal.WebAppServletContext.securedExecute(WebAppServletContext.java:2200) at weblogic.servlet.internal.WebAppServletContext.execute(WebAppServletContext.java:2106) at weblogic.servlet.internal.ServletRequestImpl.run(ServletRequestImpl.java:1428) at weblogic.work.ExecuteThread.execute(ExecuteThread.java:201) at weblogic.work.ExecuteThread.run(ExecuteThread.java:173) i have been looking for ways on how to solve this. would somebody help me please...

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• Any HTTP proxies with explicit, configurable support for request/response buffering and delayed conn

  - by Carlos Carrasco

  When dealing with mobile clients it is very common to have multisecond delays during the transmission of HTTP requests. If you are serving pages or services out of a prefork Apache the child processes will be tied up for seconds serving a single mobile client, even if your app server logic is done in 5ms. I am looking for a HTTP server, balancer or proxy server that supports the following: A request arrives to the proxy. The proxy starts buffering in RAM or in disk the request, including headers and POST/PUT bodies. The proxy DOES NOT open a connection to the backend server. This is probably the most important part. The proxy server stops buffering the request when: A size limit has been reached (say, 4KB), or The request has been received completely, headers and body Only now, with (part of) the request in memory, a connection is opened to the backend and the request is relayed. The backend sends back the response. Again the proxy server starts buffering it immediately (up to a more generous size, say 64KB.) Since the proxy has a big enough buffer the backend response is stored completely in the proxy server in a matter of miliseconds, and the backend process/thread is free to process more requests. The backend connection is immediately closed. The proxy sends back the response to the mobile client, as fast or as slow as it is capable of, without having a connection to the backend tying up resources. I am fairly sure you can do 4-6 with Squid, and nginx appears to support 1-3 (and looks like fairly unique in this respect). My question is: is there any proxy server that empathizes these buffering and not-opening-connections-until-ready capabilities? Maybe there is just a bit of Apache config-fu that makes this buffering behaviour trivial? Any of them that it is not a dinosaur like Squid and that supports a lean single-process, asynchronous, event-based execution model? (Siderant: I would be using nginx but it doesn't support chunked POST bodies, making it useless for serving stuff to mobile clients. Yes cheap 50$ handsets love chunked POSTs... sigh)

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• Which Code Should Go Where in MVC Structure

  - by Oguz

  My problem is in somewhere between model and controller.Everything works perfect for me when I use MVC just for crud (create, read, update, delete).I have separate models for each database table .I access these models from controller , to crud them . For example , in contacts application,I have actions (create, read, update, delete) in controller(contact) to use model's (contact) methods (create, read, update, delete). The problem starts when I try to do something more complicated. There are some complex processes which I do not know where should I put them. For example , in registering user process. I can not just finish this process in user model because , I have to use other models too (sending mails , creating other records for user via other models) and do lots of complex validations via other models. For example , in some complex searching processes , I have to access lots of models (articles, videos, images etc.) Or, sometimes , I have to use apis to decide what I will do next or which database model I will use to record data So where is the place to do this complicated processes. I do not want to do them in controllers , Because sometimes I should use these processes in other controllers too. And I do not want to put these process in models because , I use models as database access layers .May be I am wrong,I want to know . Thank you for your answer .

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• DotNetOpenAuth occasionally throws a NotImplementedException

  - by Chris Moschini

  I have DotNetOpenAuth running on a background thread making calls to Google authorized with OAuth on a regular basis. About once a day, which is about one in 10,000 calls, I get the following Exception: An unhandled exception occurred and the process was terminated. Application ID: DefaultDomain Process ID: 3316 Exception: System.NotImplementedException Message: The method or operation is not implemented. StackTrace: at DotNetOpenAuth.Messaging.ProtocolException.GetObjectData(SerializationInfo info, StreamingContext context) in c:\Users\andarno\git\dotnetopenid\src\DotNetOpenAuth\Messaging\ProtocolException.cs:line 90 at System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo.InitSerialize(Object obj, ISurrogateSelector surrogateSelector, StreamingContext context, SerObjectInfoInit serObjectInfoInit, IFormatterConverter converter, ObjectWriter objectWriter, SerializationBinder binder) at System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo.Serialize(Object obj, ISurrogateSelector surrogateSelector, StreamingContext context, SerObjectInfoInit serObjectInfoInit, IFormatterConverter converter, ObjectWriter objectWriter, SerializationBinder binder) at System.Runtime.Serialization.Formatters.Binary.ObjectWriter.Serialize(Object graph, Header[] inHeaders, __BinaryWriter serWriter, Boolean fCheck) at System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Serialize(Stream serializationStream, Object graph, Header[] headers, Boolean fCheck) at System.Runtime.Remoting.Channels.CrossAppDomainSerializer.SerializeObject(Object obj, MemoryStream stm) at System.AppDomain.Serialize(Object o) at System.AppDomain.MarshalObject(Object o) If it was thrown and caught once a day I'd be fine, but this is a big one - I'm getting this in the Application Error log on the server, and it's crashing the process entirely - the site goes down and restarts. Has anyone else run into this? Something I'm clearly doing wrong?

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• Problem with fork exec kill when redirecting output in perl

  - by Edu

  I created a script in perl to run programs with a timeout. If the program being executed takes longer then the timeout than the script kills this program and returns the message "TIMEOUT". The script worked quite well until I decided to redirect the output of the executed program. When the stdout and stderr are being redirected, the program executed by the script is not being killed because it has a pid different than the one I got from fork. It seems perl executes a shell that executes my program in the case of redirection. I would like to have the output redirection but still be able to kill the program in the case of a timeout. Any ideas on how I could do that? A simplified code of my script is: #!/usr/bin/perl use strict; use warnings; use POSIX ":sys_wait_h"; my $timeout = 5; my $cmd = "very_long_program 1>&2 > out.txt"; my $pid = fork(); if( $pid == 0 ) { exec($cmd) or print STDERR "Couldn't exec '$cmd': $!"; exit(2); } my $time = 0; my $kid = waitpid($pid, WNOHANG); while ( $kid == 0 ) { sleep(1); $time ++; $kid = waitpid($pid, WNOHANG); print "Waited $time sec, result $kid\n"; if ($timeout > 0 && $time > $timeout) { print "TIMEOUT!\n"; #Kill process kill 9, $pid; exit(3); } } if ( $kid == -1) { print "Process did not exist\n"; exit(4); } print "Process exited with return code $?\n"; exit($?); Thanks for any help.

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• C# Serialization lock out

  - by Greycrow

  When I try to Serialize a class to an xml file I get the exception: The process cannot access the file 'C:\settings.xml' because it is being used by another process. Settings currentSettings = new Settings(); public void LoadSettings() { //Load Settings from XML file try { Stream stream = File.Open("settings.xml", FileMode.Open); XmlSerializer s = new XmlSerializer(typeof(Settings)); currentSettings = (Settings)s.Deserialize(stream); stream.Close(); } catch //Can't read XML - use default settings { currentSettings.Name = GameSelect.Items[0].ToString(); currentSettings.City = MapSelect.Items[0].ToString(); currentSettings.Country = RaceSelect.Items[0].ToString(); } } public void SaveSettings() { //Save Settings to XML file try { Stream stream = File.Open("settings.xml", FileMode.Create); XmlSerializer x = new XmlSerializer(typeof(Settings)); x.Serialize(stream, currentSettings); stream.Close(); } catch { MessageBox.Show("Unable to open XML File - File in use by other process"); } It appears that when I Deserialize it locks the file for writing back, even if I closed the stream. Thanks in advance.

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• Cassandra hot keyspace structure change

  - by Pierre

  Hello. I'm currently running a 12-node Cassandra cluster storing 4TB of data, with a replication factor set to 3. For the needs of an application update, we need to change the configuration of our keyspace, and we'd like to avoid any downtime if possible. I read on a mailing list that the best way to do it is to: Kill cassandra process on one server of the cluster Start it again, wait for the commit log to be written on the disk, and kill it again Make the modifications in the storage.xml file Rename or delete the files in the data directories according to the changes we made Start cassandra Goto 1 with next server on the list My questions would be: Did I understand the process well? Is there any risk of data corruption? During the process, there will be servers with different versions of the storage.xml file in the same cluser, same keyspace. Is it a problem? Same question as above if we not only add, rename and remove ColumnFamilies, but if we change the CompareWith parameter / transform an existing column family into a super one. Or do we need to change the name? Thank you for your answers. It's the first time I'll do this, and I'm a little bit scared.

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• Perl cron job stays running

  - by Dylan

  I'm currently using a cron job to have a Perl script that tells my Arduino to cycle my aquaponics system and all is well, except the Perl script doesn't die as intended. Here is my cron job: */15 * * * * /home/dburke/scripts/hal/bin/main.pl cycle And below is my Perl script: #!/usr/bin/perl -w # Sample Perl script to transmit number # to Arduino then listen for the Arduino # to echo it back use strict; use Device::SerialPort; use Switch; use Time::HiRes qw ( alarm ); $|++; # Set up the serial port # 19200, 81N on the USB ftdi driver my $device = '/dev/arduino0'; # Tomoc has to use a different tty for testing #$device = '/dev/ttyS0'; my $port = new Device::SerialPort ($device) or die('Unable to open connection to device');; $port->databits(8); $port->baudrate(19200); $port->parity("none"); $port->stopbits(1); my $lastChoice = ' '; my $pid = fork(); my $signalOut; my $args = shift(@ARGV); # Parent must wait for child to exit before exiting itself on CTRL+C $SIG{'INT'} = sub { waitpid($pid,0) if $pid != 0; exit(0); }; # What child process should do if($pid == 0) { # Poll to see if any data is coming in print "\nListening...\n\n"; while (1) { my $incmsg = $port->lookfor(9); # If we get data, then print it if ($incmsg) { print "\nFrom arduino: " . $incmsg . "\n\n"; } } } # What parent process should do else { if ($args eq "cycle") { my $stop = 0; sleep(1); $SIG{ALRM} = sub { print "Expecting plant bed to be full; please check.\n"; $signalOut = $port->write('2'); # Signal to set pin 3 low print "Sent cmd: 2\n"; $stop = 1; }; $signalOut = $port->write('1'); # Signal to arduino to set pin 3 High print "Sent cmd: 1\n"; print "Waiting for plant bed to fill...\n"; alarm (420); while ($stop == 0) { sleep(2); } die "Done."; } else { sleep(1); my $choice = ' '; print "Please pick an option you'd like to use:\n"; while(1) { print " [1] Cycle [2] Relay OFF [3] Relay ON [4] Config [$lastChoice]: "; chomp($choice = <STDIN>); switch ($choice) { case /1/ { $SIG{ALRM} = sub { print "Expecting plant bed to be full; please check.\n"; $signalOut = $port->write('2'); # Signal to set pin 3 low print "Sent cmd: 2\n"; }; $signalOut = $port->write('1'); # Signal to arduino to set pin 3 High print "Sent cmd: 1\n"; print "Waiting for plant bed to fill...\n"; alarm (420); $lastChoice = $choice; } case /2/ { $signalOut = $port->write('2'); # Signal to set pin 3 low print "Sent cmd: 2"; $lastChoice = $choice; } case /3/ { $signalOut = $port->write('1'); # Signal to arduino to set pin 3 High print "Sent cmd: 1"; $lastChoice = $choice; } case /4/ { print "There is no configuration available yet. Please stab the developer."; } else { print "Please select a valid option.\n\n"; } } } } } Why wouldn't it die from the statement die "Done.";? It runs fine from the command line and also interprets the 'cycle' argument fine. When it runs in cron it runs fine, however, the process never dies and while each process doesn't continue to cycle the system it does seem to be looping in some way due to the fact that it ups my system load very quickly. If you'd like more information, just ask. EDIT: I have changed to code to: #!/usr/bin/perl -w # Sample Perl script to transmit number # to Arduino then listen for the Arduino # to echo it back use strict; use Device::SerialPort; use Switch; use Time::HiRes qw ( alarm ); $|++; # Set up the serial port # 19200, 81N on the USB ftdi driver my $device = '/dev/arduino0'; # Tomoc has to use a different tty for testing #$device = '/dev/ttyS0'; my $port = new Device::SerialPort ($device) or die('Unable to open connection to device');; $port->databits(8); $port->baudrate(19200); $port->parity("none"); $port->stopbits(1); my $lastChoice = ' '; my $signalOut; my $args = shift(@ARGV); # Parent must wait for child to exit before exiting itself on CTRL+C if ($args eq "cycle") { open (LOG, '>>log.txt'); print LOG "Cycle started.\n"; my $stop = 0; sleep(2); $SIG{ALRM} = sub { print "Expecting plant bed to be full; please check.\n"; $signalOut = $port->write('2'); # Signal to set pin 3 low print "Sent cmd: 2\n"; $stop = 1; }; $signalOut = $port->write('1'); # Signal to arduino to set pin 3 High print "Sent cmd: 1\n"; print "Waiting for plant bed to fill...\n"; print LOG "Alarm is being set.\n"; alarm (420); print LOG "Alarm is set.\n"; while ($stop == 0) { print LOG "In while-sleep loop.\n"; sleep(2); } print LOG "The loop has been escaped.\n"; die "Done."; print LOG "No one should ever see this."; } else { my $pid = fork(); $SIG{'INT'} = sub { waitpid($pid,0) if $pid != 0; exit(0); }; # What child process should do if($pid == 0) { # Poll to see if any data is coming in print "\nListening...\n\n"; while (1) { my $incmsg = $port->lookfor(9); # If we get data, then print it if ($incmsg) { print "\nFrom arduino: " . $incmsg . "\n\n"; } } } # What parent process should do else { sleep(1); my $choice = ' '; print "Please pick an option you'd like to use:\n"; while(1) { print " [1] Cycle [2] Relay OFF [3] Relay ON [4] Config [$lastChoice]: "; chomp($choice = <STDIN>); switch ($choice) { case /1/ { $SIG{ALRM} = sub { print "Expecting plant bed to be full; please check.\n"; $signalOut = $port->write('2'); # Signal to set pin 3 low print "Sent cmd: 2\n"; }; $signalOut = $port->write('1'); # Signal to arduino to set pin 3 High print "Sent cmd: 1\n"; print "Waiting for plant bed to fill...\n"; alarm (420); $lastChoice = $choice; } case /2/ { $signalOut = $port->write('2'); # Signal to set pin 3 low print "Sent cmd: 2"; $lastChoice = $choice; } case /3/ { $signalOut = $port->write('1'); # Signal to arduino to set pin 3 High print "Sent cmd: 1"; $lastChoice = $choice; } case /4/ { print "There is no configuration available yet. Please stab the developer."; } else { print "Please select a valid option.\n\n"; } } } } }

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• How can I automatically release resources RAII-style in Perl?

  - by Philip Potter

  Say I have a resource (e.g. a filehandle or network socket) which has to be freed: open my $fh, "<", "filename" or die "Couldn't open filename: $!"; process($fh); close $fh or die "Couldn't close filename: $!"; Suppose that process might die. Then the code block exits early, and $fh doesn't get closed. I could explicitly check for errors: open my $fh, "<", "filename" or die "Couldn't open filename: $!"; eval {process($fh)}; my $saved_error = $@; close $fh or die "Couldn't close filename: $!"; die $saved_error if $saved_error; but this kind of code is notoriously difficult to get right, and only gets more complicated when you add more resources. In C++ I would use RAII to create an object which owns the resource, and whose destructor would free it. That way, I don't have to remember to free the resource, and resource cleanup happens correctly as soon as the RAII object goes out of scope - even if an exception is thrown. Unfortunately in Perl a DESTROY method is unsuitable for this purpose as there are no guarantees for when it will be called. Is there a Perlish way to ensure resources are automatically freed like this even in the presence of exceptions? Or is explicit error checking the only option?

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