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  • SQLAlchemy - SQLite for testing and Postgresql for devlopment - How to port?

    - by StackUnderflow
    I want to use sqlite memory database for all my testing and Postgresql for my development/production server. But the SQL syntax is not same in both dbs. for ex: SQLite has autoincrement, and Postgresql has serial Is it easy to port the SQL script from sqlite to postgresql... what are your solutions? If you want me to use standard SQL, how should I go about generating primary key in both the databases?

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  • How to implement blocking request-reply using Java concurrency primitives?

    - by Uri
    My system consists of a "proxy" class that receives "request" packets, marshals them and sends them over the network to a server, which unmarshals them, processes, and returns some "response packet". My "submit" method on the proxy side should block until a reply is received to the request (packets have ids for identification and referencing purposes) or until a timeout is reached. If I was building this in early versions of Java, I would likely implement in my proxy a collection of "pending messages ids", where I would submit a message, and wait() on the corresponding id (with a timeout). When a reply was received, the handling thread would notify() on the corresponding id. Is there a better way to achieve this using an existing library class, perhaps in java.util.concurrency? If I went with the solution described above, what is the correct way to deal with the potential race condition where a reply arrives before wait() is invoked?

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  • How to get SimpleRpcClient.Call() to be a blocking call to achieve synchronous communication with RabbitMQ?

    - by Nick Josevski
    In the .NET version (2.4.1) of RabbitMQ the RabbitMQ.Client.MessagePatterns.SimpleRpcClient has a Call() method with these signatures: public virtual object[] Call(params object[] args); public virtual byte[] Call(byte[] body); public virtual byte[] Call(IBasicProperties requestProperties, byte[] body, out IBasicProperties replyProperties); The problem: With various attempts, the method still continues to not block where I expect it to, so it's unable ever handle the response. The Question: Am I missing something obvious in the setup of the SimpleRpcClient, or earlier with the IModel, IConnection, or even PublicationAddress? More Info: I've also tried various paramater configurations of the QueueDeclare() method too with no luck. string QueueDeclare(string queue, bool durable, bool exclusive, bool autoDelete, IDictionary arguments); Some more reference code of my setup of these: IConnection conn = new ConnectionFactory{Address = "127.0.0.1"}.CreateConnection()); using (IModel ch = conn.CreateModel()) { var client = new SimpleRpcClient(ch, queueName); var queueName = ch.QueueDeclare("t.qid", true, true, true, null); ch.QueueBind(queueName, "exch", "", null); //HERE: does not block? var replyMessageBytes = client.Call(prop, msgToSend, out replyProp); } Looking elsewhere: Or is it likely there's an issue in my "server side" code? With and without the use of BasicAck() it appears the client has already continued execution.

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  • Can WCF TCP and HTTP endpoints have the same port?

    - by dlanod
    I'm interested in one WCF server exposing both HTTP and TCP interfaces. It'll be used with Silverlight clients, so the thinking is that the HTTP interface will be for secure communications while TCP will be used the rest of the time. Is it possible for these two interfaces to use the same port in their endpoints, e.g. http://localhost:9000/ and net.tcp://localhost:9000/?

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  • How can two threads access a common array of buffers with minimal blocking ? (c#)

    - by Jelly Amma
    Hello, I'm working on an image processing application where I have two threads on top of my main thread: 1 - CameraThread that captures images from the webcam and writes them into a buffer 2 - ImageProcessingThread that takes the latest image from that buffer for filtering. The reason why this is multithreaded is because speed is critical and I need to have CameraThread to keep grabbing pictures and making the latest capture ready to pick up by ImageProcessingThread while it's still processing the previous image. My problem is about finding a fast and thread-safe way to access that common buffer and I've figured that, ideally, it should be a triple buffer (image[3]) so that if ImageProcessingThread is slow, then CameraThread can keep on writing on the two other images and vice versa. What sort of locking mechanism would be the most appropriate for this to be thread-safe ? I looked at the lock statement but it seems like it would make a thread block-waiting for another one to be finished and that would be against the point of triple buffering. Thanks in advance for any idea or advice. J.

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  • How do I change the curosr during a jQuery synchronous browser blocking POST?

    - by Tommy
    $.ajax({ url: "/cgi-bin/stats.exe", method: "post", async: false, data: { refresh: "a41" } }); Using ajax post synchronously - "async: false". While it blocks the browser during the active request, what is the most efficient way to change the cursor to the hourglass or display a wait .gif? Perhaps set the cursor as it enters this function then change it back in the success or complete function? Any advice is appreciated. Thank You.

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  • Capturing stdout from an imported module in wxpython and sending it to a textctrl, without blocking the GUI

    - by splafe
    There are alot of very similar questions to this but I can't find one that applies specifically to what I'm trying to do. I have a simulation (written in SimPy) that I'm writing a GUI for, the main output of the simulation is text - to the console from 'print' statements. Now, I thought the simplest way would be to create a seperate module GUI.py, and import my simulation program into it: import osi_model I want all the print statements to be captured by the GUI and appear inside a Textctrl, which there's countless examples of on here, along these lines: class MyFrame(wx.Frame): def __init__(self, *args, **kwds): <general frame initialisation stuff..> redir=RedirectText(self.txtCtrl_1) sys.stdout=redir class RedirectText: def __init__(self,aWxTextCtrl): self.out=aWxTextCtrl def write(self,string): self.out.WriteText(string) I am also starting my simulation from a 'Go' button: def go_btn_click(self, event): print 'GO' self.RT = threading.Thread(target=osi_model.RunThis()) self.RT.start() This all works fine, and the output from the simulation module is captured by the TextCtrl, except the GUI locks up and becomes unresponsive - I still need it to be accessible (at the very minimum to have a 'Stop' button). I'm not sure if this is a botched attempt at creating a new thread that I've done here, but I assume a new thread will be needed at some stage in this process. People suggest using wx.CallAfter, but I'm not sure how to go about this considering the imported module doesn't know about wx, and also I can't realistically go through the entire simulation architecture and change all the print statements to wx.CallAfter, and any attempt to capture the shell from inside the imported simulation program leads to the program crashing. Does anybody have any ideas about how I can best achieve this? So all I really need is for all console text to be captured by a TextCtrl while the GUI remains responsive, and all text is solely coming from an imported module. (Also, secondary question regarding a Stop button - is it bad form to just kill the simulation thread?). Thanks, Duncan

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  • How to efficiently implement a blocking call with Rails, while letting the client wait for the reply

    - by Kyle Heironimus
    We have a web service written in Rails. The API is published and we cannot change it. Our app communicates with a remote web service that sometimes hangs or takes several seconds to reply. Client -> Our Web Service -> Remote Web Service Currently, if the remote web service hangs for 5 seconds, one of our rails processes on our web service also hangs with it, which is what we need to avoid. I've seen things such as mod-x-sendfile, modporter, and delayed jobs, but the best I can tell, they all assume the client is not waiting for an answer. Since the API is already established, we cannot tell the client "I'm attempting to do what you want, check back later for the answer." The best option we have come up with so far is to add a second, non-rails web server running eventmachine to process these particular calls. Is there a better way?

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  • Trying to packetize TCP with non-blocking IO is hard! Am I doing something wrong?

    - by Ricket
    Oh how I wish TCP was packet-based like UDP is! But alas, that's not the case, so I'm trying to implement my own packet layer. Here's the chain of events so far (ignoring writing packets) Oh, and my Packets are very simply structured: two unsigned bytes for length, and then byte[length] data. (I can't imagine if they were any more complex, I'd be up to my ears in if statements!) Server is in an infinite loop, accepting connections and adding them to a list of Connections. PacketGatherer (another thread) uses a Selector to figure out which Connection.SocketChannels are ready for reading. It loops over the results and tells each Connection to read(). Each Connection has a partial IncomingPacket and a list of Packets which have been fully read and are waiting to be processed. On read(): Tell the partial IncomingPacket to read more data. (IncomingPacket.readData below) If it's done reading (IncomingPacket.complete()), make a Packet from it and stick the Packet into the list waiting to be processed and then replace it with a new IncomingPacket. There are a couple problems with this. First, only one packet is being read at a time. If the IncomingPacket needs only one more byte, then only one byte is read this pass. This can of course be fixed with a loop but it starts to get sorta complicated and I wonder if there is a better overall way. Second, the logic in IncomingPacket is a little bit crazy, to be able to read the two bytes for the length and then read the actual data. Here is the code, boiled down for quick & easy reading: int readBytes; // number of total bytes read so far byte length1, length2; // each byte in an unsigned short int (see getLength()) public int getLength() { // will be inaccurate if readBytes < 2 return (int)(length1 << 8 | length2); } public void readData(SocketChannel c) { if (readBytes < 2) { // we don't yet know the length of the actual data ByteBuffer lengthBuffer = ByteBuffer.allocate(2 - readBytes); numBytesRead = c.read(lengthBuffer); if(readBytes == 0) { if(numBytesRead >= 1) length1 = lengthBuffer.get(); if(numBytesRead == 2) length2 = lengthBuffer.get(); } else if(readBytes == 1) { if(numBytesRead == 1) length2 = lengthBuffer.get(); } readBytes += numBytesRead; } if(readBytes >= 2) { // then we know we have the entire length variable // lazily-instantiate data buffers based on getLength() // read into data buffers, increment readBytes // (does not read more than the amount of this packet, so it does not // need to handle overflow into the next packet's data) } } public boolean complete() { return (readBytes > 2 && readBytes == getLength()+2); } Basically I need feedback on my code. Please suggest any improvements. Even overhauling my entire system would be okay, if you have suggestions for how better to implement the whole thing. Book recommendations are welcome too; I love books. I just get the feeling that something isn't quite right.

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  • How to modify TaskDialog's Show() call to be blocking and return a value when closed?

    - by JustABill
    I'm using the WindowsAPICodePack's TaskDialog implementation, but it bugs me that I have to listen to click handlers on its buttons for even the more basic implementations. I'd like to convert/wrap it so that like the old MessageBox it blocks until closed and then returns a value based on what was done. Is there anything I can read for the basics on how to do this? I just have no idea where to even start, as I am admittedly not that familiar with the Win32 underpinnings.

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  • How to avoid concurrent execution of a time-consuming task without blocking?

    - by Diego V
    I want to efficiently avoid concurrent execution of a time-consuming task in a heavily multi-threaded environment without making threads wait for a lock when another thread is already running the task. Instead, in that scenario, I want them to gracefully fail (i.e. skip its attempt to execute the task) as fast as possible. To illustrate the idea considerer this unsafe (has race condition!) code: private static boolean running = false; public void launchExpensiveTask() { if (running) return; // Do nothing running = true; try { runExpensiveTask(); } finally { running = false; } } I though about using a variation of Double-Checked Locking (consider that running is a primitive 32-bit field, hence atomic, it could work fine even for Java below 5 without the need of volatile). It could look like this: private static boolean running = false; public void launchExpensiveTask() { if (running) return; // Do nothing synchronized (ThisClass.class) { if (running) return; running = true; try { runExpensiveTask(); } finally { running = false; } } } Maybe I should also use a local copy of the field as well (not sure now, please tell me). But then I realized that anyway I will end with an inner synchronization block, that still could hold a thread with the right timing at monitor entrance until the original executor leaves the critical section (I know the odds usually are minimal but in this case we are thinking in several threads competing for this long-running resource). So, could you think in a better approach?

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  • What is the minimum number of socket port(s) required for a TCP server?

    - by Gwilym
    Hey SO Doing a some practice questions for exam tomorrow can't figure out this one What is the minimum number of socket port(s) required for a TCP server to connect a TCP client for communication? Surely its just two right? one for the server one for the client, but this seems to obvious. My mates thinks TCP uses two ports at the server end for for data in and one for data out. thanks in advance

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  • A version of the Windows "FILE:" port which does not prompt for the file name but autogenerates one.

    - by Thorbjørn Ravn Andersen
    Hi. I have a process where one of the things to do is to capture the output from a print into a file for further processing. For this I have configured a "FILE:" printer port which works very nicely but asks everytime for the file name to use. Unfortunately "FILE" is not a very descriptive word when trying to use a search engine :( Is there a small driver somewhere which does exactly the same as the FILE: driver, but can automatically generate a filename (perhaps based on a pattern) and just print to that?

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  • Stop MSVC++ debug errors from blocking the current process?

    - by Mike Arthur
    Any failed ASSERT statements on Windows cause the below debug message to appear and freeze the applications execution. I realise this is expected behaviour but it is running periodically on a headless machine so prevent the unit tests from failing, instead waiting on user input indefinitely. Is there s a registry key or compiler flag I can use to prevent this message box from requesting user input whilst still allowing the test to fail under ASSERT? Basically, I want to do this without modifying any code, just changing compiler or Windows options. Thanks!

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  • Captcha in my Joomla site it not blocking spam robots.

    - by jax
    In my joomla install I have removed the email registration and instead added a Captcha field to the PHP code using the recaptcha.net method. For some reason I am still getting what I think are spam users (robots) but I don't know how they would get around the Captcha field. Anything I should check?

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  • How to port real time video service by FMS from PC to mobile phone(symbian,android,iphone)?

    - by wamp
    Now I've set up the flash application to work in to stage: the uploading stage: uploading the stream from pc A's camera to FMS play stage: watch the real time stream from PC B's browser I want to make stage 2 work on mobile phones too. But currently it's using flash(actionscript) to connect and play the stream, which is not supported out of the box. How to port this kind of application to mobile phones?

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  • Why is this one div container blocking the other from floating right?

    - by user2824289
    I know the answer is very simple, it's probably one little CSS property, but I've tried to find the solution without asking it here, no luck.. There are two div containers within a div container, and they aren't playing nice. The one is positioned to float right in the upper righthand corner of the parent div, and it won't let any other container float to the right of it. I tried display:inline and display:inline-block but no luck... Here's the code, though something tells me the answer is so easy you won't need it!: The parent div, the upper righthand corner div, and the poor div trying to float right: #um-home-section4 { width:100%; height:300px; background-color: green; } #um-title-right { float:right; width:500px; height:50px; margin-right:20px; margin-top:20px; background-color: fuchsia; } #take-me-there { float:right; margin-top:240px; margin-right:0px; height:50px; width:100px; background-color: gray; } <div id="um-home-section4"> <div id="um-title-right"></div> <div id="take-me-there"></div> </div>

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