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  • priority_queue with dynamic priorities

    - by Layne
    Hey, I have a server application which accepts incomming queries and executes them. If there are too many queries they should be queued and if some of the other queries got executed the queued queries should be executed as well. Since I want to pass queries with different priorities I think using a priority_queue would be the best choice. e.g. The amout of the axcepting queries (a) hit the limt and new queries will be stored in the queue. All queries have a priority of 1 (lowest) if some of the queries from (a) get executed the programm will pick the query with the highest priority out of the queue and execute it. Still no problem. Now someone is sending a query with a priority of 5 which gets added to the queue. Since this is the query with the highest priority the application will execute this query as soon as the running queries no longer hit the limit. There might be the worst case that 500 queries with a priority of 1 are queued but wont be executed since someone is always sending queries with a priority of 5 hence these 500 queries will be queued for a looooong time. In order to prevent that I want to increase the prioritiy of all queries which have a lower priority than the query with the higher priority, in this example which have a priority lower than 5. So if the query with a priority of 5 gets pulled out of the queue all other queries with a priority < 5 should be increased by 0.2. This way queries with a low priority wont be queued for ever even if there might be 100 queries with a higher priority. I really hope can help me to solve the problem with the priorities: Since my queries consist of an object I thought something like this might work: class Query { public: Query( std::string p_stQuery ) : stQuery( p_stQuery ) {}; std::string getQuery() const {return stQuery;}; void increasePriority( const float fIncrease ) {fPriority += fIncrease;}; friend bool operator < ( const Query& PriorityFirst, const Query& PriorityNext ) { if( PriorityFirst.fPriority < PriorityNext.fPriority ) { if( PriorityFirst.fStartPriority < PriorityNext.fStartPriority ) { Query qTemp = PriorityFirst; qTemp.increasePriority( INCREASE_RATE ); } return true; } else { return false; } }; private: static const float INCREASE_RATE = 0.2; float fPriority; // current priority float fStartPriority; // initialised priority std::string stQuery; };

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  • easiest and best way to make a server queue java

    - by houlahan
    i have a server at the moment which makes a new thread for every user connected but after about 6 people are on the server for more than 15 mins it tends to flop and give me java heap out of memory error i have 1 thread that checks with a mysql database every 30 seconds to see if any of the users currently logged on have any new messages. what would be the easiest way to implement a server queue? this is the my main method for my server: public class Server { public static int MaxUsers = 1000; //public static PrintStream[] sessions = new PrintStream[MaxUsers]; public static ObjectOutputStream[] sessions = new ObjectOutputStream[MaxUsers]; public static ObjectInputStream[] ois = new ObjectInputStream[MaxUsers]; private static int port = 6283; public static Connection conn; static Toolkit toolkit; static Timer timer; public static void main(String[] args) { try { conn = (Connection) Mysql.getConnection(); } catch (Exception ex) { Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex); } System.out.println("****************************************************"); System.out.println("* *"); System.out.println("* Cloud Server *"); System.out.println("* ©2010 *"); System.out.println("* *"); System.out.println("* Luke Houlahan *"); System.out.println("* *"); System.out.println("* Server Online *"); System.out.println("* Listening On Port " + port + " *"); System.out.println("* *"); System.out.println("****************************************************"); System.out.println(""); mailChecker(); try { int i; ServerSocket s = new ServerSocket(port); for (i = 0; i < MaxUsers; ++i) { sessions[i] = null; } while (true) { try { Socket incoming = s.accept(); boolean found = false; int numusers = 0; int usernum = -1; synchronized (sessions) { for (i = 0; i < MaxUsers; ++i) { if (sessions[i] == null) { if (!found) { sessions[i] = new ObjectOutputStream(incoming.getOutputStream()); ois[i]= new ObjectInputStream(incoming.getInputStream()); new SocketHandler(incoming, i).start(); found = true; usernum = i; } } else { numusers++; } } if (!found) { ObjectOutputStream temp = new ObjectOutputStream(incoming.getOutputStream()); Person tempperson = new Person(); tempperson.setFlagField(100); temp.writeObject(tempperson); temp.flush(); temp = null; tempperson = null; incoming.close(); } else { } } } catch (IOException ex) { System.out.println(1); Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex); } } } catch (IOException ex) { System.out.println(2); Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex); } } public static void mailChecker() { toolkit = Toolkit.getDefaultToolkit(); timer = new Timer(); timer.schedule(new mailCheck(), 0, 10 * 1000); } }

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  • BizTalk and IBM WebSphere MQ Errors

    - by Christopher House
    The project I'm currently working on is going to make heavy use of IBM WebShere MQ to send messages from BizTalk to the client's iSeries box.  I'd never previously worked with WebSphere MQ, so I didn't really have any idea what it would take to get this to work.  I was pleasantly surprised that it wasn't too difficult to configure a send port and pass messages through it to a queue.  Or so I thought... A couple of weeks ago, the client gave me the name of a host, queue manager and queue that I'd been using for my development.  Everything was going great, I was able to put messages onto the queue, I was happy, the client was happy.  Life was good.  Then the client tells me that the host I've been connecting to is actually a Solaris box and that in prod, we'll actually be sending to an iSeries.  We both agree that it would behoove us to start pointing my dev environment to their dev iSeries box in order to flush out any weirdness there might be.  As it turns out, it was a good thing we made the change.  As soon as I reconfigured my BRE policy that sets endpoint information to point to the iSeries queue, we started seeing failures in the event log.  An example from the event log: Event Type: Error Event Source: BizTalk Server 2009 Event Category: BizTalk Server 2009 Event ID: 5754 Date:  6/9/2010 Time:  10:16:41 AM User:  N/A Computer: WINDOWS2003 Description: A message sent to adapter "MQSC" on send port "<my dynamic sendport name>" with URI "mqsc://client/tcp/<hostname>(1414)/<queue manager name>/<queue name>" is suspended.  Error details: Failure encountered while attempting to open queue. queue = <queue name> queueManager = <queue manager name>, reasonCode = 6124  MessageId:  {76825C7C-611A-4A56-8A6F-35E1124BDB5C}  InstanceID: {BA389103-DF9B-493F-8C61-44574822AAD6} The key piece of information in the event entry is the reasonCode, 6124.  A quick Google search shows that reasonCode 6124 is the code for MQRC_NOT_CONNECTED.  According to IBM's docs, this means that you've tried to send a message without first opening a connection to the queue manager.  Obviously, in the context of BizTalk, this is an unexpected error, since this sort of thing should be managed entirely by the send adapter. Perusing IBM's documentation a bit more, I came across some info on how to turn on tracing for MQ.  With tracing enabled, I tried sending a message again, then went and reviewed the trace files.  The bulk of the information in the trace files didn't mean a thing to me, but at the end of one of the files, I did notice this: 00006257 15:40:20.327795   3500.4      RSESS:000009 ------{  reqReleaseConn 00006258 15:40:20.328714   3500.4      RSESS:000009 ------}  reqReleaseConn (rc=OK) 00006259 15:40:20.328727   3500.4      RSESS:000009 ------{  xcsClearTraceIdent 0000625A 15:40:20.328739   3500.4           :       ------}  xcsClearTraceIdent (rc=OK) 0000625B 15:40:20.328752   3500.4           :       -----}! trmzstMQCONNX (rc=MQRC_NOT_AUTHORIZED) 0000625C 15:40:20.328765   3500.4           :       ----}! MQCONNX (rc=MQRC_NOT_AUTHORIZED) 0000625D 15:40:20.328766   3500.4           :       ---}! ImqQueueManager::connect (rc=MQRC_NOT_AUTHORIZED) 0000625E 15:40:20.328767   3500.4           :       --}! ImqObject::open (rc=MQRC_NOT_CONNECTED) 0000625F 15:40:20.328768   3500.4           :       --{  ImqQueue::lock 00006260 15:40:20.328769   3500.4           :       --}! ImqQueue::lock (rc=Unknown(1)) 00006261 15:40:20.328769   3500.4           :       --{  ImqQueue::unlock 00006262 15:40:20.328769   3500.4           :       --}! ImqQueue::unlock (rc=Unknown(1)) It seemed like the MQRC_NOT_CONNECTED error was being caused by a security related issue (MQRC_NOT_AUTHORIZED).  I did notice something earlier in the log where it appeared that MQ was passing a field named UID with a value equal to the account name that my BizTalk service was running under.  I ended up creating a new local account on the BizTalk server that had the same name as a user which had access to the queue manager on the iSeries.  I then created a new host instance that ran under this new account, created a send handler for the MQSC adapter on this new host instance and reconfigured my orchestration to run on the new host instance.  After bouncing all my host instances, I was now able to send messages to the iSeries. It's still not clear to me why we were able to connect to the Solaris server.  I ended up contacting IBM's support and they did confirm that the process sending to MQ does in fact pass the identity to the queue manager it's connecting to.

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  • C#/.NET Little Wonders: The Concurrent Collections (1 of 3)

    - by James Michael Hare
    Once again we consider some of the lesser known classes and keywords of C#.  In the next few weeks, we will discuss the concurrent collections and how they have changed the face of concurrent programming. This week’s post will begin with a general introduction and discuss the ConcurrentStack<T> and ConcurrentQueue<T>.  Then in the following post we’ll discuss the ConcurrentDictionary<T> and ConcurrentBag<T>.  Finally, we shall close on the third post with a discussion of the BlockingCollection<T>. For more of the "Little Wonders" posts, see the index here. A brief history of collections In the beginning was the .NET 1.0 Framework.  And out of this framework emerged the System.Collections namespace, and it was good.  It contained all the basic things a growing programming language needs like the ArrayList and Hashtable collections.  The main problem, of course, with these original collections is that they held items of type object which means you had to be disciplined enough to use them correctly or you could end up with runtime errors if you got an object of a type you weren't expecting. Then came .NET 2.0 and generics and our world changed forever!  With generics the C# language finally got an equivalent of the very powerful C++ templates.  As such, the System.Collections.Generic was born and we got type-safe versions of all are favorite collections.  The List<T> succeeded the ArrayList and the Dictionary<TKey,TValue> succeeded the Hashtable and so on.  The new versions of the library were not only safer because they checked types at compile-time, in many cases they were more performant as well.  So much so that it's Microsoft's recommendation that the System.Collections original collections only be used for backwards compatibility. So we as developers came to know and love the generic collections and took them into our hearts and embraced them.  The problem is, thread safety in both the original collections and the generic collections can be problematic, for very different reasons. Now, if you are only doing single-threaded development you may not care – after all, no locking is required.  Even if you do have multiple threads, if a collection is “load-once, read-many” you don’t need to do anything to protect that container from multi-threaded access, as illustrated below: 1: public static class OrderTypeTranslator 2: { 3: // because this dictionary is loaded once before it is ever accessed, we don't need to synchronize 4: // multi-threaded read access 5: private static readonly Dictionary<string, char> _translator = new Dictionary<string, char> 6: { 7: {"New", 'N'}, 8: {"Update", 'U'}, 9: {"Cancel", 'X'} 10: }; 11:  12: // the only public interface into the dictionary is for reading, so inherently thread-safe 13: public static char? Translate(string orderType) 14: { 15: char charValue; 16: if (_translator.TryGetValue(orderType, out charValue)) 17: { 18: return charValue; 19: } 20:  21: return null; 22: } 23: } Unfortunately, most of our computer science problems cannot get by with just single-threaded applications or with multi-threading in a load-once manner.  Looking at  today's trends, it's clear to see that computers are not so much getting faster because of faster processor speeds -- we've nearly reached the limits we can push through with today's technologies -- but more because we're adding more cores to the boxes.  With this new hardware paradigm, it is even more important to use multi-threaded applications to take full advantage of parallel processing to achieve higher application speeds. So let's look at how to use collections in a thread-safe manner. Using historical collections in a concurrent fashion The early .NET collections (System.Collections) had a Synchronized() static method that could be used to wrap the early collections to make them completely thread-safe.  This paradigm was dropped in the generic collections (System.Collections.Generic) because having a synchronized wrapper resulted in atomic locks for all operations, which could prove overkill in many multithreading situations.  Thus the paradigm shifted to having the user of the collection specify their own locking, usually with an external object: 1: public class OrderAggregator 2: { 3: private static readonly Dictionary<string, List<Order>> _orders = new Dictionary<string, List<Order>>(); 4: private static readonly _orderLock = new object(); 5:  6: public void Add(string accountNumber, Order newOrder) 7: { 8: List<Order> ordersForAccount; 9:  10: // a complex operation like this should all be protected 11: lock (_orderLock) 12: { 13: if (!_orders.TryGetValue(accountNumber, out ordersForAccount)) 14: { 15: _orders.Add(accountNumber, ordersForAccount = new List<Order>()); 16: } 17:  18: ordersForAccount.Add(newOrder); 19: } 20: } 21: } Notice how we’re performing several operations on the dictionary under one lock.  With the Synchronized() static methods of the early collections, you wouldn’t be able to specify this level of locking (a more macro-level).  So in the generic collections, it was decided that if a user needed synchronization, they could implement their own locking scheme instead so that they could provide synchronization as needed. The need for better concurrent access to collections Here’s the problem: it’s relatively easy to write a collection that locks itself down completely for access, but anything more complex than that can be difficult and error-prone to write, and much less to make it perform efficiently!  For example, what if you have a Dictionary that has frequent reads but in-frequent updates?  Do you want to lock down the entire Dictionary for every access?  This would be overkill and would prevent concurrent reads.  In such cases you could use something like a ReaderWriterLockSlim which allows for multiple readers in a lock, and then once a writer grabs the lock it blocks all further readers until the writer is done (in a nutshell).  This is all very complex stuff to consider. Fortunately, this is where the Concurrent Collections come in.  The Parallel Computing Platform team at Microsoft went through great pains to determine how to make a set of concurrent collections that would have the best performance characteristics for general case multi-threaded use. Now, as in all things involving threading, you should always make sure you evaluate all your container options based on the particular usage scenario and the degree of parallelism you wish to acheive. This article should not be taken to understand that these collections are always supperior to the generic collections. Each fills a particular need for a particular situation. Understanding what each container is optimized for is key to the success of your application whether it be single-threaded or multi-threaded. General points to consider with the concurrent collections The MSDN points out that the concurrent collections all support the ICollection interface. However, since the collections are already synchronized, the IsSynchronized property always returns false, and SyncRoot always returns null.  Thus you should not attempt to use these properties for synchronization purposes. Note that since the concurrent collections also may have different operations than the traditional data structures you may be used to.  Now you may ask why they did this, but it was done out of necessity to keep operations safe and atomic.  For example, in order to do a Pop() on a stack you have to know the stack is non-empty, but between the time you check the stack’s IsEmpty property and then do the Pop() another thread may have come in and made the stack empty!  This is why some of the traditional operations have been changed to make them safe for concurrent use. In addition, some properties and methods in the concurrent collections achieve concurrency by creating a snapshot of the collection, which means that some operations that were traditionally O(1) may now be O(n) in the concurrent models.  I’ll try to point these out as we talk about each collection so you can be aware of any potential performance impacts.  Finally, all the concurrent containers are safe for enumeration even while being modified, but some of the containers support this in different ways (snapshot vs. dirty iteration).  Once again I’ll highlight how thread-safe enumeration works for each collection. ConcurrentStack<T>: The thread-safe LIFO container The ConcurrentStack<T> is the thread-safe counterpart to the System.Collections.Generic.Stack<T>, which as you may remember is your standard last-in-first-out container.  If you think of algorithms that favor stack usage (for example, depth-first searches of graphs and trees) then you can see how using a thread-safe stack would be of benefit. The ConcurrentStack<T> achieves thread-safe access by using System.Threading.Interlocked operations.  This means that the multi-threaded access to the stack requires no traditional locking and is very, very fast! For the most part, the ConcurrentStack<T> behaves like it’s Stack<T> counterpart with a few differences: Pop() was removed in favor of TryPop() Returns true if an item existed and was popped and false if empty. PushRange() and TryPopRange() were added Allows you to push multiple items and pop multiple items atomically. Count takes a snapshot of the stack and then counts the items. This means it is a O(n) operation, if you just want to check for an empty stack, call IsEmpty instead which is O(1). ToArray() and GetEnumerator() both also take snapshots. This means that iteration over a stack will give you a static view at the time of the call and will not reflect updates. Pushing on a ConcurrentStack<T> works just like you’d expect except for the aforementioned PushRange() method that was added to allow you to push a range of items concurrently. 1: var stack = new ConcurrentStack<string>(); 2:  3: // adding to stack is much the same as before 4: stack.Push("First"); 5:  6: // but you can also push multiple items in one atomic operation (no interleaves) 7: stack.PushRange(new [] { "Second", "Third", "Fourth" }); For looking at the top item of the stack (without removing it) the Peek() method has been removed in favor of a TryPeek().  This is because in order to do a peek the stack must be non-empty, but between the time you check for empty and the time you execute the peek the stack contents may have changed.  Thus the TryPeek() was created to be an atomic check for empty, and then peek if not empty: 1: // to look at top item of stack without removing it, can use TryPeek. 2: // Note that there is no Peek(), this is because you need to check for empty first. TryPeek does. 3: string item; 4: if (stack.TryPeek(out item)) 5: { 6: Console.WriteLine("Top item was " + item); 7: } 8: else 9: { 10: Console.WriteLine("Stack was empty."); 11: } Finally, to remove items from the stack, we have the TryPop() for single, and TryPopRange() for multiple items.  Just like the TryPeek(), these operations replace Pop() since we need to ensure atomically that the stack is non-empty before we pop from it: 1: // to remove items, use TryPop or TryPopRange to get multiple items atomically (no interleaves) 2: if (stack.TryPop(out item)) 3: { 4: Console.WriteLine("Popped " + item); 5: } 6:  7: // TryPopRange will only pop up to the number of spaces in the array, the actual number popped is returned. 8: var poppedItems = new string[2]; 9: int numPopped = stack.TryPopRange(poppedItems); 10:  11: foreach (var theItem in poppedItems.Take(numPopped)) 12: { 13: Console.WriteLine("Popped " + theItem); 14: } Finally, note that as stated before, GetEnumerator() and ToArray() gets a snapshot of the data at the time of the call.  That means if you are enumerating the stack you will get a snapshot of the stack at the time of the call.  This is illustrated below: 1: var stack = new ConcurrentStack<string>(); 2:  3: // adding to stack is much the same as before 4: stack.Push("First"); 5:  6: var results = stack.GetEnumerator(); 7:  8: // but you can also push multiple items in one atomic operation (no interleaves) 9: stack.PushRange(new [] { "Second", "Third", "Fourth" }); 10:  11: while(results.MoveNext()) 12: { 13: Console.WriteLine("Stack only has: " + results.Current); 14: } The only item that will be printed out in the above code is "First" because the snapshot was taken before the other items were added. This may sound like an issue, but it’s really for safety and is more correct.  You don’t want to enumerate a stack and have half a view of the stack before an update and half a view of the stack after an update, after all.  In addition, note that this is still thread-safe, whereas iterating through a non-concurrent collection while updating it in the old collections would cause an exception. ConcurrentQueue<T>: The thread-safe FIFO container The ConcurrentQueue<T> is the thread-safe counterpart of the System.Collections.Generic.Queue<T> class.  The concurrent queue uses an underlying list of small arrays and lock-free System.Threading.Interlocked operations on the head and tail arrays.  Once again, this allows us to do thread-safe operations without the need for heavy locks! The ConcurrentQueue<T> (like the ConcurrentStack<T>) has some departures from the non-concurrent counterpart.  Most notably: Dequeue() was removed in favor of TryDequeue(). Returns true if an item existed and was dequeued and false if empty. Count does not take a snapshot It subtracts the head and tail index to get the count.  This results overall in a O(1) complexity which is quite good.  It’s still recommended, however, that for empty checks you call IsEmpty instead of comparing Count to zero. ToArray() and GetEnumerator() both take snapshots. This means that iteration over a queue will give you a static view at the time of the call and will not reflect updates. The Enqueue() method on the ConcurrentQueue<T> works much the same as the generic Queue<T>: 1: var queue = new ConcurrentQueue<string>(); 2:  3: // adding to queue is much the same as before 4: queue.Enqueue("First"); 5: queue.Enqueue("Second"); 6: queue.Enqueue("Third"); For front item access, the TryPeek() method must be used to attempt to see the first item if the queue.  There is no Peek() method since, as you’ll remember, we can only peek on a non-empty queue, so we must have an atomic TryPeek() that checks for empty and then returns the first item if the queue is non-empty. 1: // to look at first item in queue without removing it, can use TryPeek. 2: // Note that there is no Peek(), this is because you need to check for empty first. TryPeek does. 3: string item; 4: if (queue.TryPeek(out item)) 5: { 6: Console.WriteLine("First item was " + item); 7: } 8: else 9: { 10: Console.WriteLine("Queue was empty."); 11: } Then, to remove items you use TryDequeue().  Once again this is for the same reason we have TryPeek() and not Peek(): 1: // to remove items, use TryDequeue. If queue is empty returns false. 2: if (queue.TryDequeue(out item)) 3: { 4: Console.WriteLine("Dequeued first item " + item); 5: } Just like the concurrent stack, the ConcurrentQueue<T> takes a snapshot when you call ToArray() or GetEnumerator() which means that subsequent updates to the queue will not be seen when you iterate over the results.  Thus once again the code below will only show the first item, since the other items were added after the snapshot. 1: var queue = new ConcurrentQueue<string>(); 2:  3: // adding to queue is much the same as before 4: queue.Enqueue("First"); 5:  6: var iterator = queue.GetEnumerator(); 7:  8: queue.Enqueue("Second"); 9: queue.Enqueue("Third"); 10:  11: // only shows First 12: while (iterator.MoveNext()) 13: { 14: Console.WriteLine("Dequeued item " + iterator.Current); 15: } Using collections concurrently You’ll notice in the examples above I stuck to using single-threaded examples so as to make them deterministic and the results obvious.  Of course, if we used these collections in a truly multi-threaded way the results would be less deterministic, but would still be thread-safe and with no locking on your part required! For example, say you have an order processor that takes an IEnumerable<Order> and handles each other in a multi-threaded fashion, then groups the responses together in a concurrent collection for aggregation.  This can be done easily with the TPL’s Parallel.ForEach(): 1: public static IEnumerable<OrderResult> ProcessOrders(IEnumerable<Order> orderList) 2: { 3: var proxy = new OrderProxy(); 4: var results = new ConcurrentQueue<OrderResult>(); 5:  6: // notice that we can process all these in parallel and put the results 7: // into our concurrent collection without needing any external locking! 8: Parallel.ForEach(orderList, 9: order => 10: { 11: var result = proxy.PlaceOrder(order); 12:  13: results.Enqueue(result); 14: }); 15:  16: return results; 17: } Summary Obviously, if you do not need multi-threaded safety, you don’t need to use these collections, but when you do need multi-threaded collections these are just the ticket! The plethora of features (I always think of the movie The Three Amigos when I say plethora) built into these containers and the amazing way they acheive thread-safe access in an efficient manner is wonderful to behold. Stay tuned next week where we’ll continue our discussion with the ConcurrentBag<T> and the ConcurrentDictionary<TKey,TValue>. For some excellent information on the performance of the concurrent collections and how they perform compared to a traditional brute-force locking strategy, see this wonderful whitepaper by the Microsoft Parallel Computing Platform team here.   Tweet Technorati Tags: C#,.NET,Concurrent Collections,Collections,Multi-Threading,Little Wonders,BlackRabbitCoder,James Michael Hare

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  • Oracle 10.2.0.1 --> 10.2.0.4 patchset errors on Advanced Queuing tables. Serious or not?

    - by hurfdurf
    We're running Oracle on RHEL 5.4 64-bit. We recently did an upgrade from 10.2.0.1 to 10.2.0.4. Many errors were generated during the upgrade (sample listed below from trace.log) but during application testing afterward everything seemed fine (clean EXP, inserts, updates, deletes, etc.). The errors look like they are all related to Advanced Queuing tables and views. We are not using replication at all, this is a simple single instance db. ORA-24002: QUEUE_TABLE SYS.AQ_EVENT_TABLE does not exist ORA-24032: object AQ$_AQ_SRVNTFN_TABLE_T exists, index could not be created ORA-24032: object AQ$_ALERT_QT_S exists, index could not be created for queue ORA-06512: at "SYS.DBMS_AQADM_SYSCALLS", line 117 ORA-06512: at "SYS.DBMS_AQADM_SYS", line 5116 Is this worth worrying about, and if so, how do I go about cleaning up/recreating the corrupted and/or missing objects?

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  • How do I use qmqtool to list emails from a specific envelope sender?

    - by jimp
    Occassionally a user's email password will become compromised and the spammer will flood the Qmail queue with 10,000+ emails sent through a specific user's account. I know how to use qmqtool to remove messages that match a specific string: qmqtool -d -f "[email protected]" However the -f argument matches anywhere in the message. -f 'STRING' display comma separated list of message number(s) containing STRING. That means messages to, from, and even mentioning that email address will all be deleted. Does qmqtool (or another qmail tool) have a command for matching messages from a specific envelope sender? Note: I only want to match the authenticated sender, not the "From:" which is always forged in this case anyway.

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  • How to manage SOAP requests to a pool of VM each listening on a HTTP port with a priority value in these requests?

    - by sputnick
    I have a front SOAP web-server under Linux. It will have to communicate with Windows Servers VM listening each on a HTTP port, for a HTTP POST request. The chosen VM should return a report of the task to the SOAP client. In the SOAP requests, there's a special variable : the priority of the request (kind of SLA), and my question is coming right now : I think of using a ha software (nginx, HAProxy, HeartBeat...) that can manage priority in this point of view. Is it relevant or do you think I need to implement a queue by myself with some specific developments? Ex: I have a SOAP requests with low priority in the pipe : the weight priority for these VM should be decreased if I have high priority SOAP requests at the same time. Any clue will be really appreciated.

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  • Java performance problem with LinkedBlockingQueue

    - by lofthouses
    Hello, this is my first post on stackoverflow...i hope someone can help me i have a big performance regression with Java 6 LinkedBlockingQueue. In the first thread i generate some objects which i push in to the queue In the second thread i pull these objects out. The performance regression occurs when the take() method of the LinkedBlockingQueue is called frequently. I monitored the whole program and the take() method claimed the most time overall. And the throughput goes from ~58Mb/s to 0.9Mb/s... the queue pop and take methods ar called with a static method from this class public class C_myMessageQueue { private static final LinkedBlockingQueue<C_myMessageObject> x_queue = new LinkedBlockingQueue<C_myMessageObject>( 50000 ); /** * @param message * @throws InterruptedException * @throws NullPointerException */ public static void addMyMessage( C_myMessageObject message ) throws InterruptedException, NullPointerException { x_queue.put( message ); } /** * @return Die erste message der MesseageQueue * @throws InterruptedException */ public static C_myMessageObject getMyMessage() throws InterruptedException { return x_queue.take(); } } how can i tune the take() method to accomplish at least 25Mb/s, or is there a other class i can use which will block when the "queue" is full or empty. kind regards Bart P.S.: sorry for my bad english, i'm from germany ;)

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  • Using jQuery delay() with separate elements

    - by boomturn
    I want to fake a simple animation on page load by sequentially revealing several pngs, each appearing instantly but with unique, precisely timed delay before the next one. Using the latest version of jQuery (1.4.2 at writing), which provides a delay method. My first (braindead) impulse was: $('#image1').show('fast').delay(800); $('#image2').show('fast').delay(1200); $('#image3').show('fast'); Of course all come up simultaneously. jQuery doc examples refer to a single item being chained, not handling multiple items. OK... try again using nested callbacks from show(): $('#image1').show('fast', function() { $('#image2').show('fast', function() { $('#image3').show('fast', function() { }); }); }); Looks ugly (imagine doing 10, also wonder what processor hit would be) but hey, it works sequentially! Without delay though. So... chain delay() after show() using a callback function from it (not even sure if it supports one): $('#image1').show('fast').delay(800, function() { $('#image2').show('fast').delay(1200, function() { $('#image3').show('fast'); }); }); Hm. Opposite result of what I thought might happen: the callback works, but still no delay. So... should I be using some combination of queue and delay instead of nested callbacks? jQuery doc examples for queue again only use one element for example. Guessing this would involve using a custom queue, but am uncertain how to implement this. Or maybe I'm missing a simple way? (For a simple problem!)

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  • Tree-like queues

    - by Rehno Lindeque
    I'm implementing a interpreter-like project for which I need a strange little scheduling queue. Since I'd like to try and avoid wheel-reinvention I was hoping someone could give me references to a similar structure or existing work. I know I can simply instantiate multiple queues as I go along, I'm just looking for some perspective by other people who might have better ideas than me ;) I envision that it might work something like this: The structure is a tree with a single root. You get a kind of "insert_iterator" to the root and then push elements onto it (e.g. a and b in the example below). However, at any point you can also split the iterator into multiple iterators, effectively creating branches. The branches cannot merge into a single queue again, but you can start popping elements from the front of the queue (again, using a kind of "visitor_iterator") until empty branches can be discarded (at your discretion). x -> y -> z a -> b -> { g -> h -> i -> j } f -> b Any ideas? Seems like a relatively simple structure to implement myself using a pool of circular buffers but I'm following the "think first, code later" strategy :) Thanks

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  • Message Driven Bean with Java Message Queue down

    - by Rafa de Castro
    I have the following problem deploying my application. It uses JMS and a remote openMQ for communication between servers. The problem is that the connection is not fully reliable so it can be up or down. For reconnecting I set the jms reconnect glassfish property so it reconnects if at some moment the connection gets lost. The problem arises when i try to deploy the application and there is no connection. It looks like it keeps retrying the connection but the application does not finish deployment until connection is available. Is it possible to configure it in any way that the deployment continues even if there is no connection and keeps retrying until there is connection available? Thanks a lot.

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  • jquery delay() doesn't delay attr() in the queue

    - by luca
    hi, what is wrong in this code? I'm trying to get this effect: fadeOut(500) and attr('class','myClass') delayed by 600 millisecs.. then delay(600) again, and fadeIn(500). The delays happen correctly but the attr() is not being delayed, it fires when #myDiv is still fading! :'( $('#myDiv').fadeOut(500).delay(600).attr('class','myClass').delay(600).fadeIn(500); many thanks in advance for any suggestions! Luca

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  • jquery issue, disable on mouseenter queue

    - by jason
    When you mouseenter .li_group class it does a slide down effect on 1 single <li> tag, everything goes smoothly, but during the delay if you take your mouse off and on .li_group it "queues" the effect and slides the li down, delay, slides it down again etc etc... I have tried every way i can think of, even stop(); but it still does it... the reason i use mouseenter instead of hover, is because it works better for ul / li list $(".li_group").live('mouseenter',function(){ var id = "#ec1"; $(id).slideDown(); }).live('mouseleave',function(){ if (jQuery.support.cssFloat==true || getInternetExplorerVersion() > 7) { //ie < 8 endless up/down on close var id = "#ec1"; $(id).delay(5000).slideUp('fast'); } });

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  • Is Oracle AQ/Streams of any use in my situation?

    - by RenderIn
    I'm writing a workflow system that is driven entirely at each step by explicit human interaction. That is, a task is assigned to a person, that person selects from a few limited options {approve, reject, forward}, and then it is either sent along to the next person or terminated. Just curious of Oracle Streams/AQ has anything to offer over flat tables managed by regular web application code. The amount of processing after each action is fairly limited and the volume is not terribly high, so there's not really a need to throttle things by throwing them into a queue. What are some of the benefits of introducing a queue structure, or is it overkill for my situation?

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  • jQuery: Counter, Tricky problem with effects for brainy people.

    - by Marius
    Hello there! I made this counter that I think is cool because it only makes visible changes to the numbers being changed between each time it is triggered. This is the code // counter $('a').click(function(){ var u = ''; var newStr = ''; $('.counter').each(function(){ var len = $(this).children('span').length; $(this).children('span').each(function(){ u = u + $(this).text(); }); v = parseInt(u) + 1; v = v + ''; for (i=v.length - 1; i >= 0; i--) { if (v.charAt(i) == u.charAt(i)) { break; } } slce = len - (v.length - (i + 1)) updates = $(this).children('span').slice(slce); $(updates).fadeTo(100,0).delay(100).each(function(index){ f = i + 1 + index; $(this).text(v.charAt(f)); }).fadeTo(100,1); }); }); Markup: <span class="counter"> <span></span><span></span><span></span><span></span><span></span><span></span><span style="margin-right:4px;">9</span><span>9</span><span>9</span><span>9</span> </span> <a href="">Add + 1</a> The problem is that I previously used queue() function to delay() $(this).text(v.charAt(f)); by 100ms, (without queue the text()-function would not be delayed because it isnt in the fx catergory) so that the text would be updated before the object had faded to opacity = 0. That would look stupid. When adding multiple counters, only one of the counters would count. When removing the queue function, both counters would work, but as you can imagine, the delay of the text() would be gone (as it isnt fx-category). It is probably a bit tricky to make out how I can have multiple counters, and still delay the text()-function by 100ms, but I was hoping there is somebody here with spare brain capacity for these things ;) You can see a (NSFW) problem demo here: Just look underneath the sharing icons and you will notice that the text changes WHILE the objects fade out. Looking for some help to sove this problem. I would like to call the text() function once the text has faded to opacity 0, then fade in once the text() has executed. Thank you for your time.

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  • C# Thread Queue Synchronize

    - by ikurtz
    Greetings, I am trying to play some audio files without holding up the GUI. Below is a sample of the code: if (audio) { if (ThreadPool.QueueUserWorkItem(new WaitCallback(CoordinateProc), fireResult)) { } else { MessageBox.Show("false"); } } if (audio) { if (ThreadPool.QueueUserWorkItem(new WaitCallback(FireProc), fireResult)) { } else { MessageBox.Show("false"); } } if (audio) { if (ThreadPool.QueueUserWorkItem(new WaitCallback(HitProc), fireResult)) { } else { MessageBox.Show("false"); } } The situation is the samples are not being played in order. some play before the other and I need to fix this so the samples are played one after another in order. How do I implement this please? Thank you.

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  • Queue-like data structure with fast search and insertion

    - by Max
    I need a datastructure with the following properties: It contains integer numbers, no duplicates. After it reaches the maximal size the first element is removed. So if the capacity is 3, then this is how it would look when putting in it sequential numbers: {}, {1}, {1, 2}, {1, 2, 3}, {2, 3, 4}, {3, 4, 5} etc. Only two operations are needed: inserting a number into this container (INSERT) and checking if the number is already in the container (EXISTS). The number of EXISTS operations is expected to be approximately 2 * number of INSERT operations. I need these operations to be as fast as possible. What would be the fastest data structure or combination of data structures for this scenario?

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  • SQL Agent Job - to execute as queue

    - by BINEESHTHOMAS
    I have a job which is calling 10 other jobs using sp_start_job. The job is having 10 steps, each step calling each sub jobs, When i execute the main job, i can see it started with step 1 and in a few secods it shows 'finished successfully' But the jobs take long time time, and when i see the log mechanism i have put inside , it shows the all the 10 steps are running simultaniously at the back, till it finishes after few hours. My requirement is, it should finish step 1 first and then only step2 should start. aNY HELP PLS ?

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  • Whats the best method for queuing time-sensitive messages with PHP/MySQL?

    - by Mike Diena
    I'm building an SMS call and response system in a new app that receives a message via an aggregator gateway, checks it for functional keywords (run, stop, ask, etc), then processes it appropriately (save to the database, return an answer, or execute a task based on the users authorization). It's running fine at the moment as there are only a few users, but I figure its going to have more issues as we scale it up. We're currently running it on a single DV machine (mediatemple base dv). My question is this: does it make more sense to set something up like Memcached to run a queue, or a simple database with a daemon running to process each message one by one? I don't have much experience with either, so any advice would be helpful. Since the messaging is somewhat time-sensitive, what would be the fastest and most reliable way to handle this? Also, since we're sending responses, I'll probably need to set up and outbound message queue as well. Would it make sense to use the same concept for both?

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  • Current tasks count at Appengine Task Queue

    - by splix
    Are there any ways to get count of current unfinished tasks at Google Appengine development server? I need it for making my integration test. I found a way to get this when running it local (just in mem), as described at appengine docs. But when i'm running it as a standalone server, from maven, this doesn't work. Just because library appengine-testing conflicts with Appengine SDK classes, and i can't use those classes together, when running sdk dev server.

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  • Messaging strategies to connect different systems

    - by n002213f
    I have a system to handle Applications online and a different system to send SMS/Email notifications to applicants on completion using web services. I can't guarantee the availability of the SMS/Email gateway. Option 1 After an application is complete, place a message on a JMS queue. A Message Driven bean receives the message and make a call for the web service, if it fails leave the message on the queue. I suspect (please correct if incorrect) that if the gate way is offline the continuosly try to send the message which might use up valuable resources. Can the above option be refined are are there any other messaging strategies that can be used?

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  • Process xml-like log file queue

    - by Zsolt Botykai
    Hi all, first of all: I'm not a programmer, never was, although had learn a lot during my professional carreer as a support consultant. Now my task is to process - and create some statistics about a constantly written and rapidly growing XML like log file. It's not valid XML, because it does not have a proper <root> element, e.g. the log looks like this: <log itemdate="somedate"> <field id="0" /> ... </log> <log itemdate="somedate+1"> <field id="0" /> ... </log> <log itemdate="somedate+n"> <field id="0" /> ... </log> E.g. I have to count all the items with field id=0. But most of the solutions I had found (e.g. using XPath) reports an error about the garbage after the first closing </log>. Most probably I can use python (2.6, although I can compile 3.x as well), or some really old perl version (5.6.x), and recently compiled xmlstarlet which really looks promising - I was able to create the statistics for a certain period after copying the file, and pre- & appending the opening and closing root element. But this is a huge file and copying takes time as well. Isn't there a better solution? Thanks in advance!

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