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I am working on a project which gets change notifications through Event Hubs(https://learn.microsoft.com/en-us/graph/change-notifications-delivery).
My Azure Function(Event Receiver) receives the events in batches. After receiving each batch, it processes the data (does a bit of work). The second batch updates the value set by the first batch.
The Event Hub has 3 partitions.
The problem arises when multiples batches arrives at the same time. The second batch comes in before the first batch has updated the value.
Is there a way to receive only one batch at a time?
I am not bothered about the order of batches, but I want to get the next batch trigger only after the first batch is processed.
Thanks in advance.
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Are you trying to get something like FIFO (First In, First Out)?
Check this out: https://medium.com/@jeffhollan/in-order-event-processing-with-azure-functions-bb661eb55428
@Bruno Lucas Thanks for the reply.
I am not too bothered about the order of the messages.
I am already using EventData batches. But still if many changes happen at the same time, those can come in separate batches.
I want to process one batch at a time.
Is there a way to make the event hub trigger wait until the first batch is processed?
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Not Really. As soon you send the event and it hits the hub, the trigger function will pull that. There is also azure function parallelism that makes things more complicated.
Best I can think is to write a method like this: https://learn.microsoft.com/en-us/azure/event-hubs/event-hubs-dotnet-standard-getstarted-send#receive-events and use the Timer trigger to pull it every "X" minutes being X the average time it takes to process one whole batch (plus some extra time to make sure it clear it all).
I see that logic apps triggers for azure hub can pull a fixed number of events in one pull and wait:
https://learn.microsoft.com/en-us/azure/connectors/connectors-create-api-azure-event-hubs#trigger-polling-behavior
But I don't see anywhere a setting to wait for a batch to complete before starting another.
Maybe the MS staff may know something that I don't. They will stop to check this thread soon
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@Bruno Lucas has answered most part of the question. Thanks to you @Bruno Lucas
Additionally you can try to set the cardinality to one in the function.json and test it at your end.
@MughundhanRaveendran-MSFT thanks for confirming.
Would it be possible to achieve the sequential processing using a Durable Function?
@Newbie Dev , Yes it is possible with durable and normal azure functions as well by leveraging the above suggested methods. With durable functins, you can use functions chaining : https://learn.microsoft.com/en-us/azure/azure-functions/durable/durable-functions-overview?tabs=csharp#chaining
@MughundhanRaveendran-MSFT , but with function chaining if we have multiple instances of the function it will still fail?
@Newbie Dev , In durable functions, there is orchestrator and activity functions, if one of the activity function fails it will return error response to the orchestrator. The entire instance will not fail, you will be able to handle the exception