EventGrid-triggered, Python Azure Function keeps triggering after successfully running?

Question

There are a couple other topics out there, but none with solutions or none pertaining to Python Functions.

Background:

• EventGrid-triggered, Python Azure Function
• EventGrid messages created only when a blob is uploaded to a given Storage Account
• Function receives message, downloads blob from message URL and does "stuff"
• Function can run for several seconds/minutes (up to 120 seconds for large blobs)

Example of issue:

• 4 files uploaded to blob container in correct Storage Account
• Function successfully triggered 4 times, by 4 separate EventGrid messages
• Function downloads blob from URL in each message, does "stuff"
• ~55 seconds later, 4 more EventGrid messages trigger the Function all over again (for the same 4 files!)
• Everything repeats

This happens multiple times resulting in 12 Function executions for 4 files:

• And corresponding output from the "stuff" the Function does!

It gets ridiculous when 2500 files are uploaded to the Storage Account!

Seems like I need to adjust the EventGrid retry timing. But I don't see a setting for this in the Portal:

How do I prevent this behavior?

EDIT 1: Then today... no issue with 16 files uploaded... why is this Function inconsistently being triggered by EventGrid?

EDIT 2: And again today... for no reason, ~an hour later... EventGrid fired off a bunch more triggers though NO MORE FILES have been uploaded to the storage account.

Here are the EventGrid stats for 16 files being uploaded to storage account.

• You can clearly see the numbers are all over the place with in some cases, ~1hour between retries.
• Looks quite arbitrary to me

EDIT 3: For anyone interested...

• What appears to be happening is: EventGrid is being triggered by TWO events within the Storage Account for a SINGLE file upload.
• This is generating two EventGrid schemas (one for a "Microsoft.Storage.BlobCreated event" and one for "Microsoft.Storage.BlobCreated event (Data Lake Storage Gen2)"
• Because the data.url parameter of the EventGrid message is different (xxx.blob.core.windows.net vs. xxx.dfs.core.windows.net), my Function is failing (as it uses BlobClient.from_blob_url
• More to come.

Answer 1

Based on the doc, the subscriber (such as your EventGridTrigger function) needs to send a response back to the AEG within the 30 seconds otherwise the message is queued for retry.

Note, that the event is removed from the retry queue when the AEG received within 3 minutes successful respond from the delivery destination endpoint (subscriber). If the deadlettering feature is on, the event is removed from the retry queue also when the respond failure code are 400 or 413.

Based on the above and your long running subscriber, the AEG sent a duplicate event within the 3 minutes.

I do recommend use a Push-Pull pattern in your solution such as delivery an event to the storage queue.