Queuing for web api methods

Question

I have one web api method :-

[POST]
public void SaveData()
{
}

I want to implement in such a way that , if code inside SaveData() method is already getting executed , then SaveData method will not accept any other call.

i.e. I want to keep calls to the savedata method in a queue. When one call will finish , other call will occure.

Note:- Calling SaveData() method is not within my scope. I can not decide to call this api method synchronously or asynchronously.

Only thing within my scope is writing code for SaveData Method. It will be called thorough external system.

Answer 1

I strongly suggest that you use a message queuing system in your application. mjwills provided two great message-broker software solutions in the comments section:

• RabbitMQ: is open-source lightweight and easy to deploy on premises and in the cloud
• Amazon Simple Queue Service (SQS): is a fully managed cloud based solution provided by AWS

There's an integration effort before you can use any of these solutions in your app, but afterwards it will be as simple as:

[POST]
public void SaveData()
{
    var msg = new SaveDataMessage();
    /* populate msg object... */

    this.queueClient.Publish(msg);
}

This pseudo-code publishes a message to the queue. On the other end a queue subscriber will be receiving and processing theses messages sequentially, for instance:

public void OnMessage(SaveDataMessage msg)
{
    /* process message... */
}

Additional benefits are i) the subscriber can run in an independent process, which means your API request can return immediately, and a background worker will take care of processing messages ii) this architecture will be compatible with load balanced APIs, as your app scales up.

It's definitely worth the effort of building this structure early on into your app. It will give you more flexibility and productivity in the long run.

I have written an article about this subject which contains more detailed, complementary information to this answer: Using queues to offload Web API