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multi-threading based RabbitMQ consumer

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失恋的感觉
失恋的感觉 2021-02-07 15:01

We have a windows service which listen to single RabbitMQ queue and process the message.

We would like to extend same windows services so that it can listen to multiple

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  • 旧巷少年郎
    旧巷少年郎 (楼主)
    2021-02-07 15:34

    You may find this answer very helpful. I have a very basic understanding of how RabbitMQ works, but I'd probably go on with one subscriber per channel per thread, as suggested there.

    There is certainly more than one option to organize the threading model for this. The actual implementation will depend on how you need to process messages from multiple queues: either in parallel, or by aggregating them and serializing the processing. The following code is a console app which implements a simulation of the latter case. It uses the Task Parallel Library and the BlockingCollection class (which comes very handy for this kind of task). 

    using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace Console_21842880
{
    class Program
    {
        BlockingCollection _commonQueue;

        // process an individual queue
        void ProcessQueue(int id, BlockingCollection queue, CancellationToken token)
        {
            while (true)
            {
                // observe cancellation
                token.ThrowIfCancellationRequested();
                // get a message, this blocks and waits
                var message = queue.Take(token);

                // process this message
                // just place it to the common queue
                var wrapperMessage = "queue " + id + ", message: " + message;
                _commonQueue.Add(wrapperMessage);
            }
        }

        // process the common aggregated queue
        void ProcessCommonQeueue(CancellationToken token)
        {
            while (true)
            {
                // observe cancellation
                token.ThrowIfCancellationRequested();
                // this blocks and waits

                // get a message, this blocks and waits
                var message = _commonQueue.Take(token);

                // process this message
                Console.WriteLine(message.ToString());
            }
        }

        // run the whole process
        async Task RunAsync(CancellationToken token)
        {
            var queues = new List>();
            _commonQueue = new BlockingCollection();

            // start individual queue processors
            var tasks = Enumerable.Range(0, 4).Select((i) =>
            {
                var queue = new BlockingCollection();
                queues.Add(queue);

                return Task.Factory.StartNew(
                    () => ProcessQeueue(i, queue, token), 
                    TaskCreationOptions.LongRunning);
            }).ToList();

            // start the common queue processor
            tasks.Add(Task.Factory.StartNew(
                () => ProcessCommonQeueue(token),
                TaskCreationOptions.LongRunning));

            // start the simulators
            tasks.AddRange(Enumerable.Range(0, 4).Select((i) => 
                SimulateMessagesAsync(queues, token)));

            // wait for all started tasks to complete
            await Task.WhenAll(tasks);
        }

        // simulate a message source
        async Task SimulateMessagesAsync(List> queues, CancellationToken token)
        {
            var random = new Random(Environment.TickCount);
            while (true)
            {
                token.ThrowIfCancellationRequested();
                await Task.Delay(random.Next(100, 1000));
                var queue = queues[random.Next(0, queues.Count)];
                var message = Guid.NewGuid().ToString() + " " +  DateTime.Now.ToString();
                queue.Add(message);
            }
        }

        // entry point
        static void Main(string[] args)
        {
            Console.WriteLine("Ctrl+C to stop...");

            var cts = new CancellationTokenSource();
            Console.CancelKeyPress += (s, e) =>
            {
                // cancel upon Ctrl+C
                e.Cancel = true;
                cts.Cancel();
            };

            try
            {
                new Program().RunAsync(cts.Token).Wait();
            }
            catch (Exception ex)
            {
                if (ex is AggregateException)
                    ex = ex.InnerException;
                Console.WriteLine(ex.Message);
            }

            Console.WriteLine("Press Enter to exit");
            Console.ReadLine();
        }
    }
}



    Another idea may be to use Reactive Extensions (Rx). If you can think of the arriving messages as of events, and Rx can help aggregating them into single stream.
    
    
    
             
    
                                                        
    
            
            
    
              
                
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