Seeking an understanding of ServiceStack.Redis: IRedisClient.PublishMessage vs IMessageQueueClient.Publish

问题

I am having a hard time separating the IRedisClient.PublishMessage and IMessageQueueClient.Publish and realize I must be mixing something up.

ServiceStack gives us the option to listen for pub/sub broadcasts like this:

    static IRedisSubscription _subscription;
    static IRedisClient redisClientSub;
    static int received = 0;
    static void ReadFromQueue()
    {
        redisClientSub = redisClientManager.GetClient();
        _subscription = redisClientSub.CreateSubscription();

        _subscription.OnMessage = (channel, msg) =>
        {
            try
            {
                received++;
            }
            catch (Exception ex)
            {
                    
            }
        };

        Task.Run(() => _subscription.SubscribeToChannels("Test"));
    }

Looks nice, straightforward. But what about the producer?

When looking at the classes available, I thought that one could either user the IRedisClient.PublishMessage(string toChannel, string message) or IMessageQueueClient.Publish(string queueName, IMessage message).

redisClient.PublishMessage("Test", json);
// or:     
myMessageQueueClient.Publish("Test", new Message<CoreEvent>(testReq));

In both cases, you specify the channel name yourself. This is the behaviour I am seeing:

• the subscriber above only receives the message if I use IRedisClient.PublishMessage(string toChannel, string message) and never if I use IMessageQueueClient.Publish(string queueName, IMessage message)
• If I publish using IRedisClient.PublishMessage, I expected the "Test" channel to be populated (if I view with a Redis browser), but it is not. I never see any trace of the queue (let's say I don't start the subscription, but producers adds messages)
• If I publish using IMessageQueueClient.Publish(string queueName, IMessage message), the channel "Test" is created and the messages are persisted there, but never popped/fetched-and-deleted.

I want to understand the difference between the two. I have looked at source code and read all I can about it, but I haven't found any documentation regarding IRedisClient.PublishMessage.

回答1:

Mythz answered this on ServiceStack forum, here.

He writes:

These clients should not be used interchangeably, you should only be using ServiceStack MQ clients to send MQ Messages or the Message MQ Message wrapper.

The redis subscription is low level API to create a Redis Pub/Sub subscription, a more useful higher level API is the Managed Pub/Sub Server which wraps the pub/sub subscription behind a managed thread.

Either way, MQ Server is only designed to process messages from MQ clients, if you’re going to implement your own messaging implementation use your own messages & redis clients not the MQ clients or MQ Message class.

and

No IRedisClient (& ServiceStack.Redis) APIs are for Redis Server, the PublishMessage API sends the redis PUBLISH command. IRedisSubscription creates a Redis Pub/Sub subscription, see Redis docs to learn how Redis Pub/Sub works. The ServiceStack.Redis library and all its APIs are just for Redis Server, it doesn’t contain any ServiceStack.Messaging MQ APIs.

So just use ServiceStack.Redis for your custom Redis Pub/Sub subscription implementation, i.e. don’t use any ServiceStack.Messaging APIs which is for ServiceStack MQ only.

来源：https://stackoverflow.com/questions/63441969/seeking-an-understanding-of-servicestack-redis-iredisclient-publishmessage-vs-i