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  • Help needed for SOAPUI

    - by Kangkan
    I am trying to test my webservice using SOAPUI (the free version). For testing concurrency, I wished to fire concurrent threads from SOAPUI onto the service. But with the options, the thred count increases gradually (even in the burst mode). The machine where SOAPUI is installed is a WinXP machine. Can I actually do the concurrency testing? If so how? Please guide me.

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  • What are all the concurrent things [data structure, algorithm, locking mechanism] missing in .Net 3.

    - by user49767
    First time I am bit disappointed in StackOverflow cause my http://stackoverflow.com/questions/2571727/c-concurrency-vs-java-concurrency-which-is-neatly-designed-which-is-better question was closed. My intension was just trying to gather knowledge from programming guru's who worked in both the programming technologies. Rather closing this question, please help me by discussing what is good, bad, and ugly in multi-threading part in both the platforms. It is also welcome, if someone would like to compare with .Net 4.0 with JDK 6 (or JDK 7)

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  • Threads, Sockets, and Designing Low-Latency, High Concurrency Servers

    - by lazyconfabulator
    I've been thinking a lot lately about low-latency, high concurrency servers. Specifically, http servers. http servers (fast ones, anyway) can serve thousands of users simultaneously, with very little latency. So how do they do it? As near as I can tell, they all use events. Cherokee and Lighttpd use libevent. Nginx uses it's own event library performing much the same function of libevent, that is, picking a platform optimal strategy for polling events (like kqueue on *bsd, epoll on linux, /dev/poll on Solaris, etc). They all also seem to employ a strategy of multiprocess or multithread once the connection is made - using worker threads to handle the more cpu intensive tasks while another thread continues to listen and handle connections (via events). This is the extent of my understanding and ability to grok the thousand line sources of these applications. What I really want are finer details about how this all works. In examples of using events I've seen (and written) the events are handling both input and output. To this end, do the workers employ some sort of input/output queue to the event handling thread? Or are these worker threads handling their own input and output? I imagine a fixed amount of worker threads are spawned, and connections are lined up and served on demand, but how does the event thread feed these connections to the workers? I've read about FIFO queues and circular buffers, but I've yet to see any implementations to work from. Are there any? Do any use compare-and-swap instructions to avoid locking or is locking less detrimental to event polling than I think? Or have I misread the design entirely? Ultimately, I'd like to take enough away to improve some of my own event-driven network services. Bonus points to anyone providing solid implementation details (especially for stuff like low-latency queues) in C, as that's the language my network services are written in.

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  • ado.net Concurrency violation

    - by Bicubic
    My first time using ADO.net. Trying to make database of Users. First I populate my DataSet: adapter.AcceptChangesDuringFill = true; adapter.AcceptChangesDuringUpdate = true; adapter.Fill(dataset); To create a user: User user = new User(); user.datarow = dataset.Users.NewUsersRow(); user.Name = username; user.PasswordHash = GetHash(password); user.Rights = UserRights.None; users.Add(user); dataset.Users.AddUsersRow(user.datarow); adapter.Update(dataset); When a user property is modified: adapter.Update(dataset); Creation by itself is fine. If I take an existing user and make multiple changes, fine. Multiple creations in a row, fine. Creation followed by a property change, I get this: "Concurrency violation: the UpdateCommand affected 0 of the expected 1 records." Any ideas?

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  • Hibernate 1:M relationship ,row order, constant values table and concurrency

    - by EugeneP
    table A and B need to have 1:M relationship a and b are added during application runtime, so A created, then say 4 B's created. Each B instance has to come in order, so that I could later extract them in the same order as I added them. The app will be a web-app running on Tomcat, so 10 instances may work simultaneously. So my question are: 1) How to preserve inserting order, so that I could extract B instances that A references in the same order as I persisted them. That's tricky, because we add to a Collection and then it gets saved (am I right?). So, it depends on how Hibernate saves it, what if it changes the order in what we added instances? I've seen something like LIST instead of SET when describing relationships, is that what I need? 2) How to add a 3-rd column to B so that I could differentiate the instances, something like SEX(M,F,U) in B table. Do I need a special table, or there's and easy way to describe constants in Hibernate. What do you recommend? 3) Talking about concurrency, what methods do you recommend to use? There should be no collisions in the db and as you see, there might easily be some if rows are not inserted (PK added) right where it is invoked without delays ?

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  • How to implement a virtual server running Ubuntu inside a fileserver in windows?

    - by user541445
    I work in a company that has some limitations regarding their budget. They need client/server aplication. I can code the aplication, I've made mini tests on primordial applications that work. The thing is that they only have fileservers, and the application they need must be concurrent compliant, so the database must be in their local network (Fileserver is the only choice). So far, I have explored almost any option available, starting with: Desktop databases. Access (We have a license)(But concurreny is just not effective, besides it's a windows software, yuck). Sqlite (Nice, but since the information they manage is a lot, I've performed some concurrency tests with INSERTs and doing SELECTS at the same time). It fails, somehow it just stops inserting. Open office Base (I dismember a base office only to see that it was a file mode HSQLDB). I've tried, not concurrent at all. Etc (You name the Open source Desktop Database manager, and yes, I've tried that one.) Server databases Call me a stubborn person, but reading some server databases documentation say that their databases will work in a file mode. I've tried a lot of products. Postgres, MySQL, FireBird, H2, Derby, Oracle Express, IBM DB2 Express, etc. So, I really need a hand here, I've been doing this install/delete/depression thing with a lot of databases for 3 weeks, until I got with a crazy idea and I just came here to express it. So, my question comes down to this: Installing a light virtual OS software like Virtual PC and then installing in there a Server OS like an Ubuntu server inside that virtual software will work? Will it work 24/7 or when I close the virtual pc software? Will this work in a fileserver? Any suggestion, answer, critic to the place I work, crazy new concurrent database that will work in fileserver will be most than welcome.

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  • Occasional InterruptedException when quitting a Swing application

    - by Joonas Pulakka
    I recently updated my computer to a more powerful one, with a quad-core hyperthreading processor (i7), thus plenty of real concurrency available. Now I'm occasionally getting the following error when quitting (System.exit(0)) an application (with a Swing GUI) that I'm developing: Exception while removing reference: java.lang.InterruptedException java.lang.InterruptedException at java.lang.Object.wait(Native Method) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:118) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:134) at sun.java2d.Disposer.run(Disposer.java:125) at java.lang.Thread.run(Thread.java:619) Well, given that it started to happen with a more concurrency-capable hardware, and it has to do with threads, and it happens occasionally, it's obviously some kind of timing thing. But the problem is that the stack trace is so short. All I have is the listing above. It doesn't include my own code at all, so it's somewhat hard to guess where the bug is. Has anyone experienced something like this before? Any ideas how to start solving it?

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  • iPhone UI addSubview causing concurrency exception

    - by Eli
    This is really odd... I run my app, and while it is opening and the views are constructing I get: Collection <CALayerArray: 0x124650> was mutated while being enumerated. The code trace goes through the following: main UIApplicationMain -[UIApplication _run] CFRunLoopRunInMode CFRunLoopRunSpecific _UIApplicationHandleEvent -[UIApplication sendEvent:] -[UIApplication handleEvent:withNewEvent:] -[UIApplication _runWithURL:sourceBundleID:] -[UIApplication _performInitilizationWithURL:sourceBundleID:] -[AppDelegate applicationDidFinishLaunching:] +[Controller initializeController] //This is my own function [window addSubview: pauseMenuController.view] //This is the last point of my code it goes through -[UIView(Hierarchy) addSubview:] -[UIView(Internal) _addSubview:positioned:relativeTo:] -[UIView(Hierarchy) _makeSubtreePerformSelector:withObject:] -[UIView(Hierarchy) _makeSubtreePerformSelector:withObject:withObject:copySublayers:] -[UIView(Hierarchy) _makeSubtreePerformSelector:withObject:withObject:copySublayers:] _NSFastEnumerationMutationHandler objc_exception_throw I've run the game lots and lots and lots of times and I've never seen this, then suddenly it popped up. The weird thing is that I'm not creating any other threads (that I know of) until after this code all gets called. It'll be easier for me to debug this if someone can give me some explanation of what might be getting modified while it's being accessed in a UIView. Does it have something to do with adding something to the view while it's already adding something, maybe? Any ideas?

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  • Concurrency Problem in Java ...

    - 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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  • Linq sql Attach, Update Check set to Never, but still Concurrency conflicts

    - by remdao
    In the dbml designer I've set Update Check to Never on all properties. But i still get an exception when doing Attach: "An attempt has been made to Attach or Add an entity that is not new, perhaps having been loaded from another DataContext. This is not supported." This approach seems to have worked for others on here, but there must be something I've missed. using(TheDataContext dc = new TheDataContext()) { test = dc.Members.FirstOrDefault(m => m.fltId == 1); } test.Name = "test2"; using(TheDataContext dc = new TheDataContext()) { dc.Members.Attach(test, true); dc.SubmitChanges(); }

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  • Controlling azure worker roles concurrency in multiple instance

    - by NER1808
    I have a simple work role in azure that does some data processing on an SQL azure database. The worker basically adds data from a 3rd party datasource to my database every 2 minutes. When I have two instances of the role, this obviously doubles up unnecessarily. I would like to have 2 instances for redundancy and the 99.95 uptime, but do not want them both processing at the same time as they will just duplicate the same job. Is there a standard pattern for this that I am missing? I know I could set flags in the database, but am hoping there is another easier or better way to manage this. Thanks

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  • handling Concurrency in SQL SERVER 2005

    - by sameer
    Hi, I have one question for you, if you can answer and refer resource it will be great help. I have a scenario where i need to create a appointment slot and a serial no for each slot memberwise. ex: Member Id |App Slot # 1|1 1|2 2|1 2|2 1|3 what im doing is take the Max slot number,increamenting it and insert it memberwise. but the problem is concurrent user can create a slot when i take the max slot after that if any other user insert the slot the value that im working with is no more valid, how to over come this problem Thanks & Regards, Sameer

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  • Can in-memory SQLite databases scale with concurrency?

    - by Kent Boogaart
    In order to prevent a SQLite in-memory database from being cleaned up, one must use the same connection to access the database. However, using the same connection causes SQLite to synchronize access to the database. Thus, if I have many threads performing reads against an in-memory database, it is slower on a multi-core machine than the exact same code running against a file-backed database. Is there any way to get the best of both worlds? That is, an in-memory database that permits multiple, concurrent calls to the database?

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  • ZeroMQ REQ/REP on ipc:// and concurrency

    - by Metiu
    I implemented a JSON-RPC server using a REQ/REP 0MQ ipc:// socket and I'm experiencing strange behavior which I suspect is due to the fact that the ipc:// underlying unix socket is not a real socket, but rather a single pipe. From the documentation, one has to enforce strict zmq_send()/zmq_recv() alternation, otherwise the out-of-order zmq_send() will return an error. However, I expected the enforcement to be per-client, not per-socket. Of course with a Unix socket there is just one pipeline from multiple clients to the server, so the server won't know who it is talking with. Two clients could zmq_send() simultaneously and the server would see this as an alternation violation. The sequence could be: ClientA: zmq_send() ClientB: zmq_send() : will it block until the other send/receive completes? will it return -1? (I suspect it will with ipc:// due to inherent low-level problems, but with TCP it could distinguish the two clients) ClientA: zmq_recv() ClientB: zmq_recv() so what about tcp:// sockets? Will it work concurrently? Should I use some other locking mechanism to work around this?

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  • Creating a WCF Restful service, concurrency issues

    - by pmillio
    Hi i am in the process of creating a restful service with WCF, the service is likely to be consumed by at least 500 people at any given time. What settings would i need to set in order to deal with this. Please give me any points and tips, thanks. Here is a sample of what i have so far; [ServiceBehavior(IncludeExceptionDetailInFaults = true, InstanceContextMode = InstanceContextMode.Single, ConcurrencyMode = ConcurrencyMode.Multiple)] And this is an example of a method being called; public UsersAPI getUserInfo(string UserID) { UsersAPI users = new UsersAPI(int.Parse(UserID)); return users; } [OperationContract] [WebGet(BodyStyle = WebMessageBodyStyle.Bare, ResponseFormat = WebMessageFormat.Json, UriTemplate = "User/{UserID}")] [WebHelp(Comment = "This returns a users info.")] UsersAPI getUserInfo(string UserID);

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  • Python sqlite3 and concurrency

    - by RexE
    I have a Python program that uses the "threading" module. Once every second, my program starts a new thread that fetches some data from the web, and stores this data to my hard drive. I would like to use sqlite3 to store these results, but I can't get it to work. The issue seems to be about the following line: conn = sqlite3.connect("mydatabase.db") If I put this line of code inside each thread, I get an OperationalError telling me that the database file is locked. I guess this means that another thread has mydatabase.db open through a sqlite3 connection and has locked it. If I put this line of code in the main program and pass the connection object (conn) to each thread, I get a ProgrammingError, saying that SQLite objects created in a thread can only be used in that same thread. Previously I was storing all my results in CSV files, and did not have any of these file-locking issues. Hopefully this will be possible with sqlite. Any ideas?

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  • Node.js or Erlang

    - by gotts
    I really like these tools when it comes to the concurrency level it can handle. Erlang looks like much more stable solution but requires much more learning and a lot of diving into functional language paradigm. And it looks like Erlang makes it much better when it comes to multi cores CPUs(fix me if I'm wrong). But which should I choose? Which one is better in the short/long term perspective?

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  • Embeddable database better than SQLite for java

    - by dexter
    I am creating a web application that is accessing a SQLite database in the server. I also have "clients" that updates this same database. As we know SQLite locks the entire database during INSERTs which are done by the clients and the web application is also trying to make some UPDATEs at the same time. So my problem now is about concurrency in database access. I would like to use an embeddable database like SQLite. Any suggestions.

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  • Having trouble doing an Update with a Linq to Sql object

    - by Pure.Krome
    Hi folks, i've got a simple linq to sql object. I grab it from the database and change a field then save. No rows have been updated. :( When I check the full Sql code that is sent over the wire, I notice that it does an update to the row, not via the primary key but on all the fields via the where clause. Is this normal? I would have thought that it would be easy to update the field(s) with the where clause linking on the Primary Key, instead of where'ing (is that a word :P) on each field. here's the code... using (MyDatabase db = new MyDatabase()) { var boardPost = (from bp in db.BoardPosts where bp.BoardPostId == boardPostId select bp).SingleOrDefault(); if (boardPost != null && boardPost.BoardPostId > 0) { boardPost.ListId = listId; // This changes the value from 0 to 'x' db.SubmitChanges(); } } and here's some sample sql.. exec sp_executesql N'UPDATE [dbo].[BoardPost] SET [ListId] = @p6 WHERE ([BoardPostId] = @p0) AND .... <snip the other fields>',N'@p0 int,@p1 int,@p2 nvarchar(9),@p3 nvarchar(10),@p4 int,@p5 datetime,@p6 int',@p0=1276,@p1=212787,@p2=N'ttreterte',@p3=N'ttreterte3',@p4=1,@p5='2009-09-25 12:32:12.7200000',@p6=72 Now, i know there's a datetime field in this update .. and when i checked the DB it's value was/is '2009-09-25 12:32:12.720' (less zero's, than above) .. so i'm not sure if that is messing up the where clause condition... but still! should it do a where clause on the PK's .. if anything .. for speed! Yes / no ? UPDATE After reading nitzmahone's reply, I then tried playing around with the optimistic concurrency on some values, and it still didn't work :( So then I started some new stuff ... with the optimistic concurrency happening, it includes a where clause on the field it's trying to update. When that happens, it doesn't work. so.. in the above sql, the where clause looks like this ... WHERE ([BoardPostId] = @p0) AND ([ListId] IS NULL) AND ... <rest snipped>) This doesn't sound right! the value in the DB is null, before i do the update. but when i add the ListId value to the where clause (or more to the point, when L2S add's it because of the optomistic concurrecy), it fails to find/match the row. wtf?

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  • Best (or appropriate) WSGI server for this Python script? - Python

    - by RadiantHex
    Hi folks, I'm having quite a problem deciding how to serve a few Python scripts. The problem is that the basic functionality could be generalized by this: do_something() time.sleep(3) do_something() I tried various WSGI servers, but they have all been giving me concurrency limitations, as in I have to specify how many threads to use and so on. I only wish that the resources on the server be used efficiently and liberally. Any ideas?

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  • Is there possible in clojure to make a deadlock (or anything bad case) using agents?

    - by hsestupin
    CLojure agents is powerful tool. So actions to the agents are asynchronously sent using functions "send" and "send-off". And in theory there couldn't appear something like deadlock. Is there possible to write some clojure code (for example invoking from some action another action to another agent) using agents in which we have some concurrency problem - it could be deadlock, race condition or anything else. (guys, i'm very sorry for my english)

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