message-queue

问题 A recent presentation I saw regarding RabbitMQ mentioned the use of something called an "idempotency barrier" for message de-duplication. Is this just a fancy name for a message conflator or is it something more specific. If so, what exactly is it? A google search yielded results which are mostly related to RabbitMQ, with little explanation of what it was. 回答1: Idempotency is the behavior of a function where performing the function on the function's output n times results in the same state as

问题 I am toying a bit with POSIX queues and I encountered a problem. When creating a new queue I can specify for example the size of the message and how many messages there can be in the queue. My normal limit is 10 as found in /proc/sys/fs/mqueue/msg_max is there an easy way to change it during program execution, apart from echo number > /proc/sys/fs/mqueue/msg_max maybe some system call for setting such things exists. 回答1: No. That limit is a system-wide limit; that's why it's in /proc/sys . If

问题 Can some one tell me how to check if there is any message in message queue. the message queue is implemented in C in linux based operating system. I just want to check if there is any message in the message queue at a particular time. 回答1: Just checking the amount (if any) of messages is done using the msgctl() function, and examining the msqid_ds structure on return, the msg_qnum in this structure is the amount of messages in the queue. Here is a link with an example: msgctl example, it does

问题 I'm writing a .NET Windows Forms application that will post a message to a Websphere MQ queue and then poll a different queue for a response. If a response is returned, the application will partially process the response in real time. But the response needs to stay in the queue so that a daily batch job, which also reads from the response queue, can do the rest of the processing. I've gotten as far as reading the message. What I haven't been able to figure out is how to read it without

问题 I have a small set of messages in an SQS queue, that are not deleted even though a deletion request sent to the AWS endpoint returns with a 200 response. The messages are processed by my application fine, and the deletion request is sent fine too. I'm using the Java AWS SDK 1.3.6. Has anyone else experienced this problem? 回答1: Whoops - the queue was accidentally set to defaultVisibilityTimeout=0 . Changing this to a positive value fixed the problem. This still raises a few questions though:

问题 I am spawning multiple worker threads from a main thread. Can I create message_queue for each thread from the main thread and send messages from the main thread. Am I asking this because message queues are meant for interprocess communication. Do I need to consider anything specific regarding this 回答1: As mentioned by Boost Message Queue not based on POSIX message queue? (and mentioned in the documentation). If you are talking about threads you have the same address space and do not need

问题 I am seeking Python 2.7 alternatives to ZeroMQ that are released under the BSD or MIT license. I am looking for something that supports request-reply and pub-sub messaging patterns. I can serialize the data myself if necessary. I found Twisted from Twisted Matrix Labs but it appears to require a blocking event loop, i.e. reactor.run(). I need a library that will run in the background and let my application check messages upon certain events. Are there any other alternatives? 回答1: Give nanomsg

问题 I have this in a class called "MessageQueueReceive". public MessageQueueTransaction BlockingReceive(out Message message) { MessageQueueTransaction tran = null; message = null; tran = new MessageQueueTransaction(); tran.Begin(); try { message = Queue.Receive(new TimeSpan(0, 0, 5), tran); } catch (MessageQueueException ex) { // If the exception was a timeout, then just continue // otherwise re-raise it. if (ex.MessageQueueErrorCode != MessageQueueErrorCode.IOTimeout) throw ex; } return tran; }

问题 Below is the desirable design of the queue with: P producer. The application that insert data X exchange. C1-C3 consumer. The applications that read from the queue Queue details: A. Is just like queue log, if there is no client binding then message will be discarded. B. This is a working queue. it will do something if there is criteria match. C. Also a working queue. it will transform the data A is optional, but B. C. will always in queue until some client process connect it. The problem is

问题 So basically we have a backend hosted in the cloud. This backend is composed of Web Servers (Django/Python), Databases (Postgresql), RabbitMQ, and Workers (Celery) We also have hardware components around the world. Those hardware components need to get things done from the backend. We were thinking of using RabbitMQ to store their jobs and using a polling mechanism from hardware components to get jobs to do. We saw that with Amazon SQS we can achieve this. They have a system allowing to get