There is a more direct way: ThreadPoolExecutor executor = new ThreadPoolExecutor( 1, 1, 0L, TimeUnit.MILLISECONDS, new LinkedBlockingQueue<Runnable>() ); // add jobs // … int size = executor.getQueue().size(); This is directly copied from Executors.newSingleThreadExecutor in JDK 1.6. The LinkedBlockingQueue that is passed to the constructor is actually the very object that you will get back from … Read more
I use postgres for a FIFO queue as well. I originally used ACCESS EXCLUSIVE, which yields correct results in high concurrency, but has the unfortunate effect of being mutually exclusive with pg_dump, which acquires a ACCESS SHARE lock during its execution. This causes my next() function to lock for a very long time (the duration … Read more
Assuming you mean Queue<T> you could just use: if (queue.Count != 0) But why bother? Just iterate over it anyway, and if it’s empty you’ll never get into the body: Queue<string> queue = new Queue<string>(); // It’s fine to use foreach… foreach (string x in queue) { // We just won’t get in here… }
Edit: I googled to check my answer: “Processing Data Queues in SQL Server with READPAST and UPDLOCK”. It’s been years since I read about and played with this solution. Original: If you use the READPAST hint, then locked rows are skipped. You’ve used ROWLOCK so you should avoid lock escalation. You also need UPDLOCK, as … Read more
You can loop over a copy of the underlying data store: for elem in list(q.queue) Eventhough this bypasses the locks for Queue objects, the list copy is an atomic operation and it should work out fine. If you want to keep the locks, why not pull all the tasks out of the queue, make your … Read more
Queue can be generally thought as horizontal in structure i.e, breadth/width can be attributed to it – BFS, whereas Stack is visualized as a vertical structure and hence has depth – DFS.
Good question, I will begin by how laravel docs explains it Events : Laravel’s events provides a simple observer implementation, allowing you to subscribe and listen for various events that occur in your application. Events serve as a great way to decouple various aspects of your application, since a single event can have multiple listeners … Read more
Queue.task_done is not there for the workers’ benefit. It is there to support Queue.join. If I give you a box of work assignments, do I care about when you’ve taken everything out of the box? No. I care about when the work is done. Looking at an empty box doesn’t tell me that. You and … Read more
I found this extremely useful when developing my applications. As it gives you an alternative to simply re-queuing your messages. This can easily reduce the complexity of your code, and is one of many powerful hidden features in RabbitMQ. Steps First we need to set up two basic channels, one for the main queue, and … Read more
I don’t know of a lock-free solution, but you can take a look at the new Dataflow library, part of the Async CTP. A simple BufferBlock<T> should suffice, e.g.: BufferBlock<int> buffer = new BufferBlock<int>(); Production and consumption are most easily done via extension methods on the dataflow block types. Production is as simple as: buffer.Post(13); … Read more