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azuremicroservicesazureservicebusazure-servicebus-queuesazure-servicebus-topics
Tom Vaidyan
Tom Vaidyan

Reputation: 400

Azure Service Bus Queues vs. Topics (Pub/Sub)

Need a bit of architectural guidance. I have a set of stateless services that do various functions. My architecture allows for multiple copies of each service to run at the same time (as they are stateless), allowing me to:

  1. scale up as needed for handling larger workloads
  2. have fault-tolerance (if one instance of a service fails, no problem as there will be others to take on that work).

However, I don't want duplication of work.

If Service A, Instance 1 has already taken Job ABC, I don't want Service A, Instance 2, to take on that same job. So, I could avoid this problem by using Azure Service Bus Queues. Only a single worker would get a particular item from the queue and would only be reassigned to another worker, if the worker didn't mark it as complete in a set time.

So what's an appropriate use-case for Topics (Pub/Sub)? It seems like if I ever have multiple copies of the same service, I must rely on Queues. Is that right?

Asked another way, is there a way to use Topics in Azure Service Bus or similar products/services but avoid duplication of work? Also, if there is a way to lock a message (for a short period of time) when using Topics, is it possible to lock that message to just one instance of Service A (so no other instances of Service A will have access to it) but the message will be broadcast to Service B, Service, C, etc.?

Upvotes: 0

Views: 1276

Answers (2)

Shahid Syed
Shahid Syed

Reputation: 639

Azure function triggers would provide all what you are looking for out of the box.

If you are not leveraging any advanced queuing features of service bus then I would recommend you look at storage queues to save some money.

If you need service bus then you can use service bus triggers.

Hope that helps.

Upvotes: 0

Gaurav Mantri
Gaurav Mantri

Reputation: 136346

is there a way to use Topics in Azure Service Bus or similar products/services but avoid duplication of work?

Yes, there is. Basically with that you would need to use each subscription as a queue. What you will need to do is define proper filters so that one kind of message is sent to a single subscription (that way it acts as a queue) and have multiple listeners (service instances in your case) listen to a specific subscription only.

Also, if there is a way to lock a message (for a short period of time) when using Topics, is it possible to lock that message to just one instance of Service A (so no other instances of Service A will have access to it) but the message will be broadcast to Service B, Service, C, etc.?

It is certainly possible to lock a message. For that you will need to fetch messages in Peek-Lock mode. However if multiple subscribers (services) are involved, then only one subscriber will be able to lock the message and access it. For other subscribers, the message will be invisible. You can't have a scenario where one service acquires the lock and other services still receive the message.

Upvotes: 2

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