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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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• Cache consistency & spawning a thread

  - by Dave Keck

  Background I've been reading through various books and articles to learn about processor caches, cache consistency, and memory barriers in the context of concurrent execution. So far though, I have been unable to determine whether a common coding practice of mine is safe in the strictest sense. Assumptions The following pseudo-code is executed on a two-processor machine: int sharedVar = 0; myThread() { print(sharedVar); } main() { sharedVar = 1; spawnThread(myThread); sleep(-1); } main() executes on processor 1 (P1), while myThread() executes on P2. Initially, sharedVar exists in the caches of both P1 and P2 with the initial value of 0 (due to some "warm-up code" that isn't shown above.) Question Strictly speaking – preferably without assuming any particular CPU – is myThread() guaranteed to print 1? With my newfound knowledge of processor caches, it seems entirely possible that at the time of the print() statement, P2 may not have received the invalidation request for sharedVar caused by P1's assignment in main(). Therefore, it seems possible that myThread() could print 0. References These are the related articles and books I've been reading. (It wouldn't allow me to format these as links because I'm a new user - sorry.) Shared Memory Consistency Models: A Tutorial hpl.hp.com/techreports/Compaq-DEC/WRL-95-7.pdf Memory Barriers: a Hardware View for Software Hackers rdrop.com/users/paulmck/scalability/paper/whymb.2009.04.05a.pdf Linux Kernel Memory Barriers kernel.org/doc/Documentation/memory-barriers.txt Computer Architecture: A Quantitative Approach amazon.com/Computer-Architecture-Quantitative-Approach-4th/dp/0123704901/ref=dp_ob_title_bk

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• Can a large transaction log cause cpu hikes to occur

  - by Simon Rigby

  Hello all, I have a client with a very large database on Sql Server 2005. The total space allocated to the db is 15Gb with roughly 5Gb to the db and 10 Gb to the transaction log. Just recently a web application that is connecting to that db is timing out. I have traced the actions on the web page and examined the queries that execute whilst these web operation are performed. There is nothing untoward in the execution plan. The query itself used multiple joins but completes very quickly. However, the db server's CPU hikes to 100% for a few seconds. The issue occurs when several simultaneous users are working on the system (when I say multiple .. read about 5). Under this timeouts start to occur. I suppose my question is, can a large transaction log cause issues with CPU performance? There is about 12Gb of free space on the disk currently. The configuration is a little out of my hands but the db and log are both on the same physical disk. I appreciate that the log file is massive and needs attending to, but I'm just looking for a heads up as to whether this may cause CPU spikes (ie trying to find the correlation). The timeouts are a recent thing and this app has been responsive for a few years (ie its a recent manifestation). Many Thanks,

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• Scheduling of tasks to a single resource using Prolog

  - by Reed Debaets

  I searched through here as best I could and though I found some relevant questions, I don't think they covered the question at hand: Assume a single resource and a known list of requests to schedule a task. Each request includes a start_after, start_by, expected_duration, and action. The goal is to schedule the tasks for execution as soon as possible while keeping each task scheduled between start_after and start_by. I coded up a simple prolog example that I "thought" should work but I've been unfortunately getting errors during run time: "=/2: Arguments are not sufficiently instantiated". Any help or advice would be greatly appreciated startAfter(1,0). startAfter(2,0). startAfter(3,0). startBy(1,100). startBy(2,500). startBy(3,300). duration(1,199). duration(2,199). duration(3,199). action(1,'noop1'). action(2,'noop2'). action(3,'noop3'). can_run(R,T) :- startAfter(R,TA),startBy(R,TB),T>=TA,T=<TB. conflicts(T,R1,T1) :- duration(R1,D1),T=<D1+T1,T>T1. schedule(R1,T1,R2,T2,R3,T3) :- can_run(R1,T1),\+conflicts(T1,R2,T2),\+conflicts(T1,R3,T3), can_run(R2,T2),\+conflicts(T2,R1,T1),\+conflicts(T2,R3,T3), can_run(R3,T3),\+conflicts(T3,R1,T1),\+conflicts(T3,R2,T2). % when traced I *should* see T1=0, T2=400, T3=200 Edit: conflicts goal wasn't quite right: needed extra TT1 clause. Edit: Apparently my schedule goal works if I supply valid Request,Time pairs ... but I'm stucking trying to force prolog to find valid values for T1..3 when given R1..3?

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• Function returning dictionary, not seen by calling function

  - by twiga

  Hi There, I have an interesting problem, which is a function that returns a Dictionary<String,HashSet<String>>. The function converts some primitive structs to a Dictionary Class. The function is called as follows: Dictionary<String, HashSet<String>> Myset = new Dictionary<String,HashSet<String>>(); Myset = CacheConverter.MakeDictionary(_myList); Upon execution of the two lines above, Myset is non-existent to the debugger. Adding a watch results in: "The name 'Myset' does not exist in the current context" public Dictionary<String, HashSet<String>> MakeDictionary(LightWeightFetchListCollection _FetchList) { Dictionary<String, HashSet<String>> _temp = new Dictionary<String, HashSet<String>>(); // populate the Dictionary // return return _temp; } The Dictionary _temp is correctly populated by the called function and _temp contains all the expected values. The problem seems to be with the dictionary not being returned at all. Examples I could find on the web of functions returning primitive Dictionary<string,string> work as expected.

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• Code bacteria: evolving mathematical behavior

  - by Stefano Borini

  It would not be my intention to put a link on my blog, but I don't have any other method to clarify what I really mean. The article is quite long, and it's in three parts (1,2,3), but if you are curious, it's worth the reading. A long time ago (5 years, at least) I programmed a python program which generated "mathematical bacteria". These bacteria are python objects with a simple opcode-based genetic code. You can feed them with a number and they return a number, according to the execution of their code. I generate their genetic codes at random, and apply an environmental selection to those objects producing a result similar to a predefined expected value. Then I let them duplicate, introduce mutations, and evolve them. The result is quite interesting, as their genetic code basically learns how to solve simple equations, even for values different for the training dataset. Now, this thing is just a toy. I had time to waste and I wanted to satisfy my curiosity. however, I assume that something, in terms of research, has been made... I am reinventing the wheel here, I hope. Are you aware of more serious attempts at creating in-silico bacteria like the one I programmed? Please note that this is not really "genetic algorithms". Genetic algorithms is when you use evolution/selection to improve a vector of parameters against a given scoring function. This is kind of different. I optimize the code, not the parameters, against a given scoring function.

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• DataTable won't DataBind with a DataTable.NewRow()

  - by David

  Is DataRow.NewRow() insufficient as the only row in a DataTable? I would expect this to work, but it doesn't. It's near the end of my Page_Load inside my If(!Postback) block. gridCPCP is GridView DataTable dt = new DataTable(); dt.Columns.Add("ID", int.MinValue.GetType()); dt.Columns.Add("Code", string.Empty.GetType()); dt.Columns.Add("Date", DateTime.MinValue.GetType()); dt.Columns.Add("Date2", DateTime.MinValue.GetType()); dt.Columns.Add("Filename", string.Empty.GetType()); //code to add rows if (dt.Rows.Count > 0) { gridCPCP.DataSource = dt; gridCPCP.DataBind(); } else { dt.Rows.Add(dt.NewRow()); gridCPCP.DataSource = dt; gridCPCP.DataBind(); //EXCEPTION int TotalColumns = gridCPCP.Rows[0].Cells.Count; gridCPCP.Rows[0].Cells.Clear(); gridCPCP.Rows[0].Cells.Add(new TableCell()); gridCPCP.Rows[0].Cells[0].ColumnSpan = TotalColumns; gridCPCP.Rows[0].Cells[0].Text = "No Record Found"; } The exception throws on gridCPCP.DataBind() and only when execution reaches the else block. If there were rows added above via dt.Rows.Add(new object[] { ... } binding works. System.ArgumentOutOfRangeException: Length cannot be less than zero. Parameter name: length

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• BackgroundWorker might be causing my application to hang

  - by alexD

  I have a Form that uses a BackgroundWorker to execute a series of tests. I use the ProgressChanged event to send messages to the main thread, which then does all of the updates on the UI. I've combed through my code to make sure I'm not doing anything to the UI in the background worker. There are no while loops in my code and the BackgroundWorker has a finite execution time (measured in seconds or minutes). However, for some reason when I lock my computer, often times the application will be hung when I log back in. The thing is, the BackgroundWorker isn't even running when this happens. The reason I believe it is related to the BackgroundWorker though is because the form only hangs when the BackgroundWorker has been executed since the application was loaded (it only runs when given a certain user input). I pass this thread a List of TreeNodes from a TreeView in my UI through the RunWorkerAsync method, but I only read those nodes in the worker thread..any modifications I make to them is done in the UI thread through the progressChanged event. I do use Thread.Sleep in my worker thread to execute tests at timed intervals (which involves sending messages over a TCP socket, which was not created in the worker thread). I am completely perplexed as to why my application might be hanging. I'm sure I'm doing something 'illegal' somewhere, I just don't know what.

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• Java performance issue

  - by Colby77

  Hi, I've got a question related to java performance and method execution. In my app there are a lot of place where I have to validate some parameter, so I've written a Validator class and put all the validation methods into it. Here is an example: public class NumberValidator { public static short shortValidator(String s) throws ValidationException{ try{ short sh = Short.parseShort(s); if(sh < 1){ throw new ValidationException(); } return sh; }catch (Exception e) { throw new ValidationException("The parameter is wrong!"); } } ... But I'm thinking about that. Is this OK? It's OO and modularized, but - considering performance - is it a good idea? What if I had awful lot of invocation at the same time? The snippet above is short and fast, but there are some methods that take more time. What happens when there are a lot of calling to a static method or an instance method in the same class and the method is not synchronized? All the calling methods have to fall in line and the JVM executes them sequentially? Is it a good idea to have some class that are identical to the above-mentioned and randomly call their identical methods? I think it is not, because "Don't repeat yourself " and "Duplication is Evil" etc. But what about performance? Thanks is advance.

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• Error handling in PHP

  - by Industrial

  Hi guys, We're building a PHP app based on Good old MVC (codeigniter framework) and have run into trouble with a massive chained action that consists of multiple model calls, that together is a part of a big transaction to the database. We want to be able to do a list of actions and get a status report of each one back from the function, whatever the outcome is. Our first initial idea was to utilize the exceptions of PHP5, but since we want to also need status messages that doesnt break the execution of the script, this was our solution that we came up with. It goes a little something like this: $sku = $this->addSku( $name ); if ($sku === false) { $status[] = 'Something gone terrible wrong'; $this->db->trans_rollback(); return $status; } $image= $this->addImage( $filename); if ($image=== false) { $error[] = 'Image could not be uploaded, check filesize'; $this->db->trans_rollback(); return $status; } Our controller looks like this: $var = $this->products->addProductGroup($array); if (is_array($var)) { foreach ($var as $error) { echo $error . '<br />'; } } It appears to be a very fragile solution to do what we need, but it's neither scalable, neither effective when compared to pure PHP exceptions for instance. Is this really the way that this kind of stuff generally is handled in MVC based apps? Thanks!

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• DBD::CSV: Problem with file-name-extensions

  - by sid_com

  In this script I have problems with file-name-extensions: if I use /home/mm/test_x it works, with file named /home/mm/test_x.csv it doesn't: #!/usr/bin/env perl use warnings; use strict; use 5.012; use DBI; my $table_1 = '/home/mm/test_1.csv'; my $table_2 = '/home/mm/test_2.csv'; #$table_1 = '/home/mm/test_1'; #$table_2 = '/home/mm/test_2'; my $dbh = DBI->connect( "DBI:CSV:" ); $dbh->{RaiseError} = 1; $table_1 = $dbh->quote_identifier( $table_1 ); $table_2 = $dbh->quote_identifier( $table_2 ); my $sth = $dbh->prepare( "SELECT a.id, a.name, b.city FROM $table_1 AS a NATURAL JOIN $table_2 AS b" ); $sth->execute; $sth->dump_results; $dbh->disconnect; Output with file-name-extention: DBD::CSV::st execute failed: Execution ERROR: No such column '"/home/mm/test_1.csv".id' called from /usr/local/lib/perl5/site_perl/5.12.0/x86_64-linux/DBD/File.pm at 570. Output without file-name-extension: '1', 'Brown', 'Laramie' '2', 'Smith', 'Watertown' 2 rows Is this a bug?

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• Total Order between !different! volatile variables?

  - by andreas

  Hi all, Consider the following Java code: volatile boolean v1 = false; volatile boolean v2 = false; //Thread A v1 = true; if (v2) System.out.println("v2 was true"); //Thread B v2 = true; if (v1) System.out.println("v1 was true"); If there was a globally visible total order for volatile accesses then at least one println would always be reached. Is that actually guaranteed by the Java Standard? Or is an execution like this possible: A: v1 = true; B: v2 = true; A: read v2 = false; B: read v1 = false; A: v2 = true becomes visible (after the if) B: v1 = true becomes visible (after the if) I could only find statements about accesses to the same volatile variable in the Standard (but I might be missing something). "A write to a volatile variable (§8.3.1.4) v synchronizes-with all subsequent reads of v by any thread (where subsequent is defined according to the synchronization order)." http://java.sun.com/docs/books/jls/third_edition/html/memory.html#17.4.4 Thanks!

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• Whats wrong with this piece of code?

  - by cambr

  vector<int>& mergesort(vector<int> &a) { if (a.size() == 1) return a; int middle = a.size() / 2; vector<int>::const_iterator first = a.begin(); vector<int>::const_iterator mid = a.begin() + (middle - 1); vector<int>::const_iterator last = a.end(); vector<int> ll(first, mid); vector<int> rr(mid, last); vector<int> l = mergesort(ll); vector<int> r = mergesort(rr); vector<int> result; result.reserve(a.size()); int dp = 0, lp = 0, rp = 0; while (dp < a.size()) { if (lp == l.size()) { result[dp] = (r[rp]); rp++; } else if (rp == r.size()) { result[dp] = (l[lp]); lp++; } else if (l[lp] < r[rp]) { result[dp] = (l[lp]); lp++; } else { result[dp] = (r[rp]); rp++; } dp++; } a = result; return a; } It compiles coorectly but while execution, I am getting: This application has requested the runtime to end it in an unusual way. This is a weird error. Is there something that is fundamentally wrong with the code?

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• Best intro to C++ static metaprogramming?

  - by jwfearn

  Static metaprogramming (aka "template metaprogramming") is a great C++ technique that allows the execution of programs at compile-time. A light bulb went off in my head as soon as I read this canonical metaprogramming example: #include <iostream> using namespace std; template< int n > struct factorial { enum { ret = factorial< n - 1 >::ret * n }; }; template<> struct factorial< 0 > { enum { ret = 1 }; }; int main() { cout << "7! = " << factorial< 7 >::ret << endl; // 5040 return 0; } If one wants to learn more about C++ static metaprogramming, what are the best sources (books, websites, on-line courseware, whatever)?

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• TypeError: Error #1009 - (Null reference error) With Flash.

  - by Wind Chimez

  I am not an expert in flash, but i do work with AS and tweak Flash projects , though not having deep expertise in it. Currently i need to revamp a flash website done by one another guy, and the code base given to me, upon execution is throwing the following error. "--- TypeError: Error #1009: Cannot access a property or method of a null object reference. at NewSite_fla::MainTimeline/__setProp_ContactOutP1_ContactOut_Contents_0() at NewSite_fla::MainTimeline/frame1() --" The structure of the project is like, it has the different sections split into different movie clips. There is no single main timeline, but click actions on different areas of seperate movie clips will take them between one another. All the AS logic of event handling are written inline in FLA , no seperate Document class exists. Preloader Movie clip is the first one getting loaded. As i understood the error is getting thrown initially itself, and it is not happening due to any Action script logic written inline, because it is throwing error even before hitting the first inline AS code. I am not able to figure Out what exactly it causing the problem, or where to resolve it. I really got stuck at this point. Any help will be great.I had not seen the particular solution i am looking for anywhere yet, though Error #1009 is common. I uploaded the fla, here ( http://tinyurl.com/249e95p ), for reference.It may not be working , since the included/refered video files and all are not there, but reviwing the action code/movie clips will be possible. Please let me know if somebody will be able to trace the issue exactly.

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• Index Tuning for SSIS tasks

  - by Raj More

  I am loading tables in my warehouse using SSIS. Since my SSIS is slow, it seemed like a great idea to build indexes on the tables. There are no primary keys (and therefore, foreign keys), indexes (clustered or otherwise), constraints, on this warehouse. In other words, it is 100% efficiency free. We are going to put indexes based on usage - by analyzing new queries and current query performance. So, instead of doing it our old fashioned sweat and grunt way of actually reading the SQL statements and execution plans, I thought I'd put the shiny new Database Engine Tuning Advisor to use. I turned SQL logging off in my SSIS package and ran a "Tuning" trace, saved it to a table and analyzed the output in the Tuning Advisor. Most of the lookups are done as: exec sp_executesql N'SELECT [Active], [CompanyID], [CompanyName], [CompanyShortName], [CompanyTypeID], [HierarchyNodeID] FROM [dbo].[Company] WHERE ([CompanyID]=@P1) AND ([StartDateTime] IS NOT NULL AND [EndDateTime] IS NULL)',N'@P1 int',1 exec sp_executesql N'SELECT [Active], [CompanyID], [CompanyName], [CompanyShortName], [CompanyTypeID], [HierarchyNodeID] FROM [dbo].[Company] WHERE ([CompanyID]=@P1) AND ([StartDateTime] IS NOT NULL AND [EndDateTime] IS NULL)',N'@P1 int',2 exec sp_executesql N'SELECT [Active], [CompanyID], [CompanyName], [CompanyShortName], [CompanyTypeID], [HierarchyNodeID] FROM [dbo].[Company] WHERE ([CompanyID]=@P1) AND ([StartDateTime] IS NOT NULL AND [EndDateTime] IS NULL)',N'@P1 int',3 exec sp_executesql N'SELECT [Active], [CompanyID], [CompanyName], [CompanyShortName], [CompanyTypeID], [HierarchyNodeID] FROM [dbo].[Company] WHERE ([CompanyID]=@P1) AND ([StartDateTime] IS NOT NULL AND [EndDateTime] IS NULL)',N'@P1 int',4 and when analyzed, these statements have the reason "Event does not reference any tables". Huh? Does it not see the FROM dbo.Company??!! What is going on here? So, I have multiple questions: How do I get it to capture the actual statement executing in my trace, not what was submitted in a batch? Are there any best practices to follow for tuning performance related to SSIS packages running against SQL Server 2008?

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• Using the Apple Scripting bridge with Mail to send an attachment causes the message background to go

  - by Naym

  Hello, When I use the Apple Scripting Bridge to send a message with an attachment the background of the message is set to black which is a problem because the text is also black. The code in question is: MailApplication *mail = [SBApplication applicationWithBundleIdentifier:@"com.apple.Mail"]; /* create a new outgoing message object */ MailOutgoingMessage *emailMessage = [[[mail classForScriptingClass:@"outgoing message"] alloc] initWithProperties: [NSDictionary dictionaryWithObjectsAndKeys: emailSubject, @"subject", [self composeEmailBody], @"content", nil]]; /* add the object to the mail app */ [[mail outgoingMessages] addObject: emailMessage]; /* set the sender, show the message */ emailMessage.sender = [NSString stringWithFormat:@"%@ <%@>",[[[mail accounts] objectAtIndex:playerOptions.mailAccount] fullName],[[[[mail accounts] objectAtIndex:playerOptions.mailAccount] emailAddresses] objectAtIndex:0]]; emailMessage.visible = YES; /* create a new recipient and add it to the recipients list */ MailToRecipient *theRecipient = [[[mail classForScriptingClass:@"to recipient"] alloc] initWithProperties: [NSDictionary dictionaryWithObjectsAndKeys: opponentEmail, @"address", nil]]; [emailMessage.toRecipients addObject: theRecipient]; /* add an attachment, if one was specified */ if ( [playerInfo.gameFile length] > 0 ) { /* create an attachment object */ MailAttachment *theAttachment = [[[mail classForScriptingClass:@"attachment"] alloc] initWithProperties: [NSDictionary dictionaryWithObjectsAndKeys: playerInfo.gameFile, @"fileName", nil]]; /* add it to the list of attachments */ [[emailMessage.content attachments] addObject: theAttachment]; } /* send the message */ [emailMessage send]; The actual change to the background colour occurs on the second last line, which is: [[emailMessage.content attachments] addObject: theAttachment]; The code sections above are essentially lifted from the SBSendMail example code from Apple. At this stage I've really only made the changes necessary to integrate with the data from my application. If I build and run the SBSendMail example after freshly downloading it from Apple the message background is also changed to black with execution of the same line. It does not appear to matter which type of file is attached, where it is located, or on which computer or operating system is used. This could be a bug in Apple's scripting bridge but has anyone come across this problem and found a solution? ALternatively does anyone know if the background colour of a MailOutgoingMessage instance can be changed with the scripting bridge? Thanks for any assistance with this, Naym.

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• Qt - QWebView Problem

  - by user547057

  Hi, I have a PyQt gui script which consists of a QWebView widget. I'm trying to send a GET request, i.e go to a page, fill a form and hit click using the code at the bottom of this question. Since i'm dealing with the documentElement(a QWebElement) of the webview, I need to place all DOM actions in a separate function(which I have named fillForm) and connect the loadFinished() signal into the function. Without connecting the signal, the document will not have loaded and I won't be able to get the elements I want. I'm able to submit the form correctly and get the proper response from the webpage. The problem i'm having is that, the above leads to a sort of infinite loop. This is because the webpage gets reloaded each time a new page is loaded, so the form gets filled each and every single time without stopping. I'd like to know if there's some way of finding out whether the WebView's page has loaded fully, non-asynchronously or maybe pause execution of the script(without freezing the gui) until the whole document has loaded. I'm unable to come up with a satisfactory solution(my idea consisted of keeping a global variable to track clicks) to this problem. I would appreciate it if someone could help me out with a better way to tackle this. Thanks! Here's the code i'm using import sys from PyQt4.QtCore import * from PyQt4.QtGui import * from PyQt4.QtWebKit import * from PyQt4 import QtCore app = QApplication(sys.argv) web = QWebView() web.load(QUrl("http://mywebsite.com")) def fillForm(): doc = web.page().mainFrame().documentElement() searchform = doc.findFirst("input[type=text]") searchform.setAttribute("value", "hello") button = doc.findFirst("input[type=submit]") button.evaluateJavaScript("click()") QtCore.QObject.connect(web, QtCore.SIGNAL("loadFinished"), fillForm) web.show() sys.exit(app.exec_())

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• .Net Entity objectcontext thread error

  - by Chris Klepeis

  I have an n-layered asp.net application which returns an object from my DAL to the BAL like so: public IEnumerable<SourceKey> Get(SourceKey sk) { var query = from SourceKey in _dataContext.SourceKeys select SourceKey; if (sk.sourceKey1 != null) { query = from SourceKey in query where SourceKey.sourceKey1 == sk.sourceKey1 select SourceKey; } return query.AsEnumerable(); } This result passes through my business layer and hits the UI layer to display to the end users. I do not lazy load to prevent query execution in other layers of my application. I created another function in my DAL to delete objects: public void Delete(SourceKey sk) { try { _dataContext.DeleteObject(sk); _dataContext.SaveChanges(); } catch (Exception ex) { Debug.WriteLine(ex.Message + " " + ex.StackTrace + " " + ex.InnerException); } } When I try to call "Delete" after calling the "Get" function, I receive this error: New transaction is not allowed because there are other threads running in the session This is an ASP.Net app. My DAL contains an entity data model. The class in which I have the above functions share the same _dataContext, which is instantiated in my constructor. My guess is that the reader is still open from the "Get" function and was not closed. How can I close it?

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• Multiple threads modifying a collection in Java??

  - by posdef

  Hi, The project I am working on requires a whole bunch of queries towards a database. In principle there are two types of queries I am using: read from excel file, check for a couple of parameters and do a query for hits in the database. These hits are then registered as a series of custom classes. Any hit may (and most likely will) occur more than once so this part of the code checks and updates the occurrence in a custom list implementation that extends ArrayList. for each hit found, do a detail query and parse the output, so that the classes created in (I) get detailed info. I figured I would use multiple threads to optimize time-wise. However I can't really come up with a good way to solve the problem that occurs with the collection these items are stored in. To elaborate a little bit; throughout the execution objects are supposed to be modified by both (I) and (II). I deliberately didn't c/p any code, as it would be big chunks of code to make any sense.. I hope it make some sense with the description above. Thanks,

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• Conditional macro expansion

  - by Dave DeLong

  Heads up: This is a weird question. I've got some really useful macros that I like to use to simplify some logging. For example I can do Log(@"My message with arguments: %@, %@, %@", @"arg1", @"arg2", @"arg3"), and that will get expanded into a more complex method invocation that includes things like self, _cmd, __FILE__, __LINE__, etc, so that I can easily track where things are getting logged. This works great. Now I'd like to expand my macros to not only work with Objective-C methods, but general C functions. The problem is the self and _cmd portions that are in the macro expansion. These two parameters don't exist in C functions. Ideally, I'd like to be able to use this same set of macros within C functions, but I'm running into problems. When I use (for example) my Log() macro, I get compiler warnings about self and _cmd being undeclared (which makes total sense). My first thought was to do something like the following (in my macro): if (thisFunctionIsACFunction) { DoLogging(nil, nil, format, ##__VA_ARGS__); } else { DoLogging(self, _cmd, format, ##__VA_ARGS__); } This still produces compiler warnings, since the entire if() statement is substituted in place of the macro, resulting in errors with the self and _cmd keywords (even though they will never be executed during function execution). My next thought was to do something like this (in my macro): if (thisFunctionIsACFunction) { #define SELF nil #define CMD nil } else { #define SELF self #define CMD _cmd } DoLogging(SELF, CMD, format, ##__VA_ARGS__); That doesn't work, unfortunately. I get "error: '#' is not followed by a macro parameter" on my first #define. My other thought was to create a second set of macros, specifically for use in C functions. This reeks of a bad code smell, and I really don't want to do this. Is there some way I can use the same set of macros from within both Objective-C methods and C functions, and only reference self and _cmd if the macro is in an Objective-C method?

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• standard way to perform a clean shutdown with Boost.Asio

  - by Timothy003

  I'm writing a cross-platform server program in C++ using Boost.Asio. Following the HTTP Server example on this page, I'd like to handle a user termination request without using implementation-specific APIs. I've initially attempted to use the standard C signal library, but have been unable to find a design pattern suitable for Asio. The Windows example's design seems to resemble the signal library closest, but there's a race condition where the console ctrl handler could be called after the server object has been destroyed. I'm trying to avoid race conditions that cause undefined behavior as specified by the C++ standard. Is there a standard (correct) way to stop the server? So far: #include <csignal> #include <functional> #include <boost/asio.hpp> using std::signal; using boost::asio::io_service; extern "C" { static void handle_signal(int); } namespace { std::function<void ()> sighandler; } void handle_signal(int) { sighandler(); } int main() { io_service s; sighandler = std::bind(&io_service::stop, &s); auto res = signal(SIGINT, &handle_signal); // race condition? SIGINT raised before I could set ignore back if (res == SIG_IGN) signal(SIGINT, SIG_IGN); res = signal(SIGTERM, &handle_signal); // race condition? SIGTERM raised before I could set ignore back if (res == SIG_IGN) signal(SIGTERM, SIG_IGN); s.run(); // reset signals signal(SIGTERM, SIG_DFL); signal(SIGINT, SIG_DFL); // is it defined whether handle_signal can still be in execution at this // point? sighandler = nullptr; }

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• Flex/Flash 4 ExternalInterface.call - trying to get a string from HTML to Actionscript.

  - by Setori

  Dear all, I need to obtain a string from HTML and put it into Actionscript. the actionscript: import flash.external.ExternalInterface; protected function getUserName():void{ var isAvailable:Boolean = ExternalInterface.available; var findUserName:String = "findUserName"; if(isAvailable){ var foundUserName:String = ExternalInterface.call(findUserName); Alert.show(foundUserName);}} the javascript: function findUserName() { var label = document.getElementById("username-label"); if(label.value != ""){ alert("the name in the box is: " + label.value); return label.value;} else return "nothing in the textbox";}} the JSP: <%IUserSession userSession = SessionManager.getSession();%> <logic:notEmpty name="userSession"> <logic:notEqual value="anonymous" name="userSession" property="userLoginId"> <td align="right" width="10%" > <input id="username-label" type="text" value="<bean:write name="userSession" property="userLoginId"/>" /> </td> </logic:notEqual> </logic:notEmpty> the rendered HTML: <td align="right" width="10%"> <input id="username-label" type="text" value="a-valid-username" /> </td> when the javascript execution hits var label = document.getElementById("username-label"); a null is returned and crashes, no alert shows no error message is shown. firfox 3.5 windows, container is Tomcat. Please advise, and thank you in advance.

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• How to parameterize a path in ANT?

  - by strelokstrelok

  I have the following defined in a file called build-dependencies.xml <?xml version="1.0" encoding="UTF-8"?> <project name="build-dependencies"> ... <path id="common-jars"> <fileset file="artifacts/project-1/jar/some*.jar" /> <fileset file="artifacts/project-2/jar/someother*.jar" /> </path> ... </project> I include it at the top of my build.xml file. Now I need to make the artifacts folder a parameter so it can be changed during execution of different targets. Having this... <?xml version="1.0" encoding="UTF-8"?> <project name="build-dependencies"> ... <path id="common-jars"> <fileset file="${artifacts}/project-1/jar/some*.jar" /> <fileset file="${artifacts}/project-2/jar/someother*.jar" /> </path> ... </project> ...and defining an "artifacts" property (and changing it) in the target does not work because it seems that the property substitution happens when the path is defined in build-dependencies.xml How can I solve this? One way I was thinking was to have a parameterized macro and call that before the path is actually used, but that seems not elegant. Something like this: <macrodef name="create-common-jars"> <attribute name="artifacts"/> <sequential> <path id="common-jars"> <fileset file="@{artifacts}/project-1/jar/some*.jar" /> <fileset file="@{artifacts}/project-2/jar/someother*.jar" /> </path> </sequential> </macrodef>

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• Writing a JavaScript zip code validation function

  - by mkoryak

  I would like to write a JavaScript function that validates a zip code, by checking if the zip code actually exists. Here is a list of all zip codes: http://www.census.gov/tiger/tms/gazetteer/zips.txt (I only care about the 2nd column) This is really a compression problem. I would like to do this for fun. OK, now that's out of the way, here is a list of optimizations over a straight hashtable that I can think of, feel free to add anything I have not thought of: Break zipcode into 2 parts, first 2 digits and last 3 digits. Make a giant if-else statement first checking the first 2 digits, then checking ranges within the last 3 digits. Or, covert the zips into hex, and see if I can do the same thing using smaller groups. Find out if within the range of all valid zip codes there are more valid zip codes vs invalid zip codes. Write the above code targeting the smaller group. Break up the hash into separate files, and load them via Ajax as user types in the zipcode. So perhaps break into 2 parts, first for first 2 digits, second for last 3. Lastly, I plan to generate the JavaScript files using another program, not by hand. Edit: performance matters here. I do want to use this, if it doesn't suck. Performance of the JavaScript code execution + download time. Edit 2: JavaScript only solutions please. I don't have access to the application server, plus, that would make this into a whole other problem =)

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