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• Fast single thread comet server, possible?

  - by Pepijn

  I recently encountered a few cases where a server would distribute an event stream that contains the exact same data for all listeners, such as a 'recent activity' box. It occurred to me that it is quite strange and inefficient to have a server like Apache run a thread processing and querying the database for every single comet stream containing the same data. What I would do for those global(not per user) streams is run a single thread that continuously emits data, and a new (green)thread for every new request that outputs the headers and then 'merges' into the main thread. Is it possible for one thread to serve multiple sockets, or for multiple clients to listen to the same socket? An example o = event # threads received | a b # 3 o / / # 3 - |/_/ | # 1 o c # 2 a, b | / o/ # 2 a, b o # 1 a, b, c | # connection b closed o # 1 a, c Does something like this exist? Would it work? Is it possible to do? Disclaimer: I'm not a server expert.

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• Converting raw bytes into audio sound

  - by Afro Genius

  In my application I inherit a javastreamingaudio class from the freeTTS package then bypass the write method which sends an array of bytes to the SourceDataLine for audio processing. Instead of writing to the data line, I write this and subsequent byte arrays into a buffer which I then bring into my class and try to process into sound. My application processes sound as arrays of floats so I convert to float and try to process but always get static sound back. I am sure this is the way to go but am missing something along the way. I know that sound is processed as frames and each frame is a group of bytes so in my application I have to process the bytes into frames somehow. Am I looking at this the right way? Thanx in advance for any help.

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• Log4Net GetLogger creates rolling files even for the unreferenced files

  - by ybastiand

  Hi, I have a C# solution that contains three executables. I have each of these three executables sharing the same log4net configuration file. At startup of each of the executable, they retrieve a logger (one logger per executable, as per configuration file further below). When one of the executable performs Log.GetLogger(), it creates all the rolling files instead of only the one rolling file that is referred to as appender-ref in the executable's logger configuration. For instance, when I startup my sending daemon executable, it performs Log.GetLogger("SendingDaemonLogger") which creates 3 files Log/RuleScheduler.txt, Log/NotificationGenerator.txt and Log/NotificationSender.txt instead of only the desired Log/NotificationSender.txt. Then when I startup another of the executables, for instance the rule scheduler daemon, this other process cannot write in Log/RuleScheduler.txt because it has been created and locked by the sending daemon process. I am guessing that there may be three different solutions to my problem: The GetLogger should only create the rolling file appenders that are referenced in the config I should have one config file per executable, this way each config file could list only one rolling file appender and starting each of the executable would not create the rolling files of the other daemons. I am however reluctant to do this because some of the configuration (SMTP appender, console appender) is shared between the daemons and I don't want to have duplicate copies to maintain. Unless there is a way to have a config file including another one? Maybe there is a way to configure the rolling file so that concurrent access across processes is allowed? This solution still isn't perfect in my opinion because any of the daemons should not be creating the rolling files of some other daemons. Thanks in advance for your help! I have difficulties for posting the config file properly here (this website interprets as HTML). Please go to the following link for seeing my log4net configuration file: log4Net configuration file

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• Process XML in C# using external entity file

  - by Ryan Berger

  I am processing an XML file (which does not contain any dtd or ent declarations) in C# that contains entities such as &eacute; and &agrave;. I receive the following exception when attempting to load an XML file... XmlDocument xmlDoc = new XmlDocument(); xmlDoc.LoadXml(record); Reference to undeclared entity 'eacute'. I was able to track down the proper ent file here. How do I tell XmlDocument to use this ent file when loading my XML file?

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• how to commit 'commit log' itself in same svn version?

  - by understack

  It might sound unnecessary, but let me explain my problem first. Probably then it would make sense. Few artists keep updating images based on clients' change requests. An artist makes changes accordingly and commits with proper 'commit messages'. Just before actual commit, I want to create a text file with image properties like size and all the 'commit messages'. And then this file would be committed itself. So basically some sort of pre-commit processing is required. Even though most of the artists are not very comfortable with svn, they can always see what changes were made last time to the image via simple text file. So artists only do update and commit with svn. How this could be done? Are there any better alternatives?

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• Multiple Socket Connections

  - by BSchlinker

  I need to write a server which accepts connections from multiple client machines, maintains track of connected clients and sends individual clients data as necessary. Sometimes, all clients may be contacted at once with the same message, other times, it may be one individual client or a group of clients. Since I need confirmation that the clients received the information and don't want to build an ACK structure for a UDP connection, I decided to use a TCP streaming method. However, I've been struggling to understand how to maintain multiple connections and keep them idle. I seem to have three options. Use a fork for each incoming connection to create a separate child process, use pthread_create to create an entire new thread for each process, or use select() to wait on all open socket IDs for a connection. Recommendations as to how to attack this? I've begun working with pthreads but since performance will likely not be an issue, multicore processing is not necessary and perhaps there is a simpler way.

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• How to properly use Gearman with my PHP application?

  - by luckytaxi

  For now I just want to use Gearman for background processing. For example, I need to email a recipient that they have a private message waiting for them once the sender submits their message into the DB. I assume I can run the worker/client and server on my primary server but I have no problems offloading some of the tasks to a different web server. Anyways, my question is how do I handle multiple "functions?" Let's say I need a job that handles the email portion and a job to handle image manipulation. Can I have multiple functions in the worker? I've followed a couple of examples I found online but each example only shows one function being initialized. Do I have to start up multiple "workers" to handle multiple functions?

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• PostgreSQL insert on primary key failing with contention, even at serializable level

  - by Steven Schlansker

  I'm trying to insert or update data in a PostgreSQL db. The simplest case is a key-value pairing (the actual data is more complicated, but this is the smallest clear example) When you set a value, I'd like it to insert if the key is not there, otherwise update. Sadly Postgres does not have an insert or update statement, so I have to emulate it myself. I've been working with the idea of basically SELECTing whether the key exists, and then running the appropriate INSERT or UPDATE. Now clearly this needs to be be in a transaction or all manner of bad things could happen. However, this is not working exactly how I'd like it to - I understand that there are limitations to serializable transactions, but I'm not sure how to work around this one. Here's the situation - ab: => set transaction isolation level serializable; a: => select count(1) from table where id=1; --> 0 b: => select count(1) from table where id=1; --> 0 a: => insert into table values(1); --> 1 b: => insert into table values(1); --> ERROR: duplicate key value violates unique constraint "serial_test_pkey" Now I would expect it to throw the usual "couldn't commit due to concurrent update" but I'm guessing since the inserts are different "rows" this does not happen. Is there an easy way to work around this?

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• Java Memory Management

  - by Tara Singh

  I am designing a client-server chat application in Java. This is a secure application where the messages are exchanged using cryptographic algorithms. I have one server and it can support many clients. My problem is that when one client logs on the server it works fine, but when another user logs into the system, the server starts giving me bad padding exceptions for the encrypted text. I am not able to figure out the problem, according to my logic, when new connection request to server is made, the server creates a thread for listening to the client. Is it possible that once the instance of thread class is created, it does all the processing correctly for the first client, but not for the second client because the variables in server listener thread class already have some previous value, and thus the encrypted text is not decrypted properly? Please advise how I can make this process more robust so that the number of clients does not affect how well the server functions.

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• Design Decision - Scaling out web based application's architecture

  - by Vadi

  This question is about design decision. I am currently working on a web project that will have 40K users to start with and in couple of month expected to grow 50M users (not concurrent users though). I would like to have a architecture that can be scaled out easily without much effort. In order to explain, I would like to use a trivial scenario. Lets say, User entities and services such as CreateUser, AuthenticateUser etc., are a simple method calls for the Page Controllers. But once the traffic increases, for example, authenticating user (or such services related to user entities) has to be moved out to a different internal server to spread the load. But at the same time using RPC calls over the network when the user count is 40K would become overkill. My proposal was to use IPC initially and when we need to scale out we can interally switch to TCP based RPC calls so that it can easily scale out. For example, I am referring to System.IO.Pipes.NamedPipeStreamServer to start with and move on to a TcpListener later on. If we have proper design that can encapsulate above said approach, it would easy for us to scale out services into multiple network servers but at the same time avoid network calls when the user count is small. Is this is a best approach? Any suggestions would be great .. Note: The database scaling is definetly the second phase optimization so we have already made architectural design in place to easily partition data when traffic increases. The primary bottleneck would be application servers over the time period.

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• Using Windows media foundation

  - by Martin Beckett

  Ok so my new gig is high performance video (think Google streetview but movies) - the hard work is all embedded capture and image processing but: I was looking at the new MS video offerings to display content = Windows Media Foundation. Is anyone actually using this ? There are no books on the topic. The only documentation is a developer team blog with a single entry 9 months old. I thought we had got past having to learn an MS api by spying on the com control messages! Is it just another wrapper around the same old activeX control?

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• Object tree navigation language in Java

  - by lewap

  In the system which I'm currently developing I often have to navigate an object tree and based on its state and values take actions. In normal Java this results in tedious for loops, if statements etc... Are there alternative ways to achieve tree navigation, similar to XPath for XML? I know there is JXPath and OGNL, but do you know any other libraries for such purpose? Do you know any libraries which generate bytecodes for specific tree navigation expressions to make the processing as fast as Java native fors and ifs?

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• Using HTTP Vary header to decide on a strategy to process a request

  - by Jacques René Mesrine

  I have a specific REST endpoint that creates a topic in a forum; but I want to apply different strategies when processing the request. e.g. If client A makes the call, perform moderation. if client B makes the call, do something else. The easiest would be to add a query param for differentiation: POST /resource?from=xyz Another brilliant idea is to use the Vary HTTP header. POST /resource Vary: xyz Any problems with this approach ?

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• Will pool the connection help threading in sqlite (and how)?

  - by mamcx

  I currently use a singleton to acces my database (see related question) but now when try to add some background processing everything fall apart. I read the sqlite docs and found that sqlite could work thread-safe, but each thread must have their own db connection. I try using egodatabase that promise a sqlite wrapper with thread safety but is very buggy, so I return to my old FMDB library I start to see how use it in multi-thread way. Because I have all code with the idea of singleton, change everything will be expensive (and a lot of open/close connections could become slow), so I wonder if, as the sqlite docs hint, build a pooling for each connection will help. If is the case, how make it? How know wich connection get from the pool (because 2 threads can't share the connection)? I wonder if somebody already use sqlite in multu-threading with NSOperation or similar stuff, my searching only return "yeah, its possible" but let the details to my imagination...

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• javascript ajax variable question..

  - by Kelso

  Hey there, new to AJAX, JS.. Im trying to add to a Javascript/Ajax search script that I've put together. Previously, it had a single search field, called search_word, I added one called search_date. $(".search_button").click(function() { var search_word = $("#search_box").val(); var search_date = $("#datepicker").val(); var dataString = 'search_word='+ search_word; if(search_word=='') { } else { $.ajax({ type: "GET", url: "searchdata.php", data: dataString, In the Ajax, it appears to pass data of dataString, to my processing script. How do I add search date to the dataString so that I can use that var in my searchdata.php? In searchdata, I can do this $search_word=$_GET['search_word']; and use that var, but so far every time i attempt to alter the dataString, it breaks all the other functionality. Thanks!

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• BackgroundWorker vs background Thread

  - by freddy smith

  I have a stylistic question about the choice of background thread implementation I should use on a windows form app. Currently I have a BackgroundWorker on a form that has an infinite (while(true)) loop. In this loop I use WaitHandle.WaitAny to keep the thread snoozing until something of interest happens. One of the event handles I wait on is a "stopthread" event so that I can break out of the loop. This event is signaled when from my overridden Form.Dispose(). I read somewhere that BackgroundWorker is really intended for operations that you dont want to tie up the UI with and have an finite end - like downloading a file, or processing a sequence of items. In this case the "end" is unknown and only when the window is closed. Therefore would it be more appropriate for me to use a background Thread instead of BackgroundWorker for this purpose?

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• Change a localized InfoPlist.strings using an Xcode target

  - by nevan

  Here's an obscure problem. I'm using an InfoPlist.strings to localize my app name. It's only got one value: CFBundleDisplayName = "Mon App". The strings file is localized (putting it in a directory for that localization). I've just made an extra target, where I change things like the non-localized app name (different Info.plists), and the icon. I'm also changing the Default.png using a run script build phase (copying different files depending on the app type I'm building). I've tried using the script to copy different versions of my InfoPlist.strings, but I couldn't make it work. Here's what I used: if($TARGET_NAME == "MonApp")then cp fr.lproj/MonApp_InfoPlist.strings fr.lproj/InfoPlist.strings endif I've seen a post suggesting wincent strings util for processing strings, but wanted to see if there's an easy way to do this. Any help greatly appreciated.

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• GWT RPC - Does it do enough to protect against CSRF ?

  - by sri

  GWT's RPC mechanism does the following things on every HTTP Request - Sets two custom request headers - X-GWT-Permutation and X-GWT-Module-Base Sets the content-type as text/x-gwt-rpc; charset=utf-8 The HTTP request is always a POST, and on server side GET methods throw an exception (method not supported). Also, if these headers are not set or have the wrong value, the server fails processing with an exception "possibly CSRF?" or something to that effect. Question is : Is this sufficient to prevent CSRF? Is there a way to set custom headers and change content type in a pure cross-site request forgery method?

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• What Python based Dashboard options exist?

  - by stuartcw

  I want to create a Dashboard on each server to show it's health and the results of some daily processing. I plan to hook up shell scripts and Python programs to collect the data. Instead of writing a web-based interface, I thought it would be good to use a python based web dashboard that could render the results in various business user and manager friendly formats. What are my options to do this? I am primarily interested in Python RedHat Linux, but other platforms are interesting too. I'm also open to Perl and Ruby based solutions especially if the plugins can be language neutral.

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• Performance logging tips

  - by Germstorm

  I am developing large data collecting ASP.Net/Windows service application-pair that uses Microsoft SQL Server 2005 through LINQ2Sql. Performance is always the issue. Currently the application is divided into multiple larger processing parts, each logging the duration of their work. This is not detailed and does not help us with anything. It would be nice to have some database tables that contain statistics that the application itself collected from its own behavior. What logging tips and data structures do you recommend to spot the parts that cause performance problems?

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• A linked list with multiple heads in Java

  - by Emile

  Hi, I have a list in which I'd like to keep several head pointers. I've tried to create multiple ListIterators on the same list but this forbid me to add new elements in my list... (see Concurrent Modification exception). I could create my own class but I'd rather use a built-in implementation ;) To be more specific, here is an inefficient implementation of two basic operations and the one wich doesn't work : class MyList <E { private int[] _heads; private List<E _l; public MyList ( int nbHeads ) { _heads = new int[nbHeads]; _l = new LinkedList<E(); } public void add ( E e ) { _l.add(e); } public E next ( int head ) { return _l.get(_heads[head++]); // ugly } } class MyList <E { private Vector<ListIterator<E _iters; private List<E _l; public MyList ( int nbHeads ) { _iters = new Vector<ListIterator<E(nbHeads); _l = new LinkedList<E(); for( ListIterator<E iter : _iters ) iter = _l.listIterator(); } public void add ( E e ) { _l.add(e); } public E next ( int head ) { // ConcurrentModificationException because of the add() return _iters.get(head).next(); } } Emile

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• Starting with versioning mysql schemata without overkill. Good solutions?

  - by tharkun

  I've arrived at the point where I realise that I must start versioning my database schemata and changes. I consequently read the existing posts on SO about that topic but I'm not sure how to proceed. I'm basically a one man company and not long ago I didn't even use version control for my code. I'm on a windows environment, using Aptana (IDE) and SVN (with Tortoise). I work on PHP/mysql projects. What's a efficient and sufficient (no overkill) way to version my database schemata? I do have a freelancer or two in some projects but I don't expect a lot of branching and merging going on. So basically I would like to keep track of concurrent schemata to my code revisions. [edit] Momentary solution: for the moment I decided I will just make a schema dump plus one with the necessary initial data whenever I'm going to commit a tag (stable version). That seems to be just enough for me at the current stage.[/edit] [edit2]plus I'm now also using a third file called increments.sql where I put all the changes with dates, etc. to make it easy to trace the change history in one file. from time to time I integrate the changes into the two other files and empty the increments.sql[/edit]

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• Django model field value preprocessing before returning

  - by Satoru.Logic

  Hi, all. I have a Note model class like this: class Note(models.Model): author = models.ForeignKey(User, related_name='notes') content = NoteContentField(max_length=256) NoteContentField is a custom sub-class of CharField that override the to_python method in purpose of doing some twitter-text-conversion processing. class NoteContentField(models.CharField): __metaclass__ = models.SubfieldBase def to_python(self, value): value = super(NoteContentField, self).to_python(value) from ..utils import linkify return mark_safe(linkify(value)) However, this doesn't work. When I save a Note object like this: note = Note(author=request.use, content=form.cleaned_data['content']) The conversed value is saved into the database, which is not what I wanna see. Would you please tell me what's wrong with this? Thanks in advance.

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• Garbage collecting at ColdFusion CFC

  - by Sergii

  Hello. I have a CFC as singletone object in Application scope. One of the methods is used for massive data processing and periodically causes the "Java heap space" errors. EDIT All variables inside the method are VAR-scoped, so they should not be kept in the object scope when invokation ended. It can be a bit dumb question for Java people, but I'd like to know how Java garbage collector cleans up the CFC methods memory: only when whole request ends, or maybe right after each method/function invokation? Second option is interesting because it can allow me to split my large method into the few, as one of the possible optimizations.

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• advancedDatagrid multipleSelection: Was a row already selected?

  - by Werner

  Hi, after multiple Selection in a advanced datagrid, I want to check if the clicked row, was already selected. Anyway my idea below (in the nested if clause I want to check if the newly clicked item's processing data is already in the added Array Collection) is not working, but I assume there must be a better way to differiante if an click was made on a already selected row. Probably I was not as clear in my description as needed, please ask your questions! Thank you very much, already in advance, Werner model.processingData = out; if (model.selectedIndices.length > 1){ //check if item already added var tempInt:int = model.multipleProcessingData.getItemIndex(model.processingData); if (tempInt == -1){ model.multipleProcessingData.addItem(model.processingData); } } else{ model.multipleProcessingData.removeAll(); model.multipleProcessingData.addItem(model.processingData); }

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