Limit Azure Function to execute only once

Question

I have an Azure Function triggered by an EventGrid when a blob is created.
Based on the size of the blob (this is a pdf file), my Azure Function can take any where between 2 seconds to 600 seconds (10 minutes) to execute.

As per Azure documentation, the ExentGrid retries to deliver the event again if it does not receive a response from the end point (in this case, the end point is my Azure function) with in 30 seconds.

• 10 seconds
• 30 seconds
• 1 minute
• 5 minutes
• 10 minutes
• 30 minutes
• 1 hour
• 3 hours
• 6 hours
• Every 12 hours up to 24 hours

I don't see any issues for the smaller files that I upload to the storage, My azure function executes and hopefully the EventGrid receives the response under 30 senconds, hence my function is execute only once.

Issue: For larger files, My azure function is triggered by the eventgrid (as expected) and the execution starts, however due to the large file size, my function executes for well over 30 seconds, Since the eventgrid did not receive any success response from end point (as the function is still executing), it sends another event and my function initiates another instance for the same file, this way the function executes several times for time same file.

How can I handle this situation, Can I change the retry mechanism for the eventgrid only for this function, or is there a better way to handle this problem.

Any help would be greatly appreciated.

Answer 1

Azure looks for timely response(<30s) from Azure Function or webhook event handlers, there seems to be no setting to increase this time limit. On receiving an event, instead of doing the actual long running work, you must push a message to a Azure queue, and let your function pick up messages from that queue. This allows you to just enqueue the work and quickly return response to Azure Event grid within 30seconds, and also scales up your event handling[even if more blobs are uploaded as a burst, your application can handle it].