Blob triggered Azure Function not executed when Blob is uploaded by certain user. The Blob Created Event is matched and delivered as expected.

Nico Kestel 0

I have set up an Azure Function that is triggered by Blob Create Events via an Event Subscription.

When I upload a file to the container, the Blob Creation Event is published, matched and delivered, also the Function is invoked and the file gets processed as expected.

When a colleague uploads a file to the container, the Blob Creation Event is also published, matched and delivered but the Function is not invoked.

I have already checked that the Blob types of both of our blobs are the same (Block Blob) and I have already tested different upload methods such as uploading via the Azure Portal and SFTP. I can not replicate the behaviour my colleague experiences.

1 answer

Pinaki Ghatak 5,575 Reputation points Microsoft Employee

2025-01-13T10:20:02.3066667+00:00
Hello @Nico Kestel

There are two things to check:

The function app is not tied to a user account, but using a Managed Identity to get the file from Storage account.

The function is running on the context of Azure cloud, and not locally (as in VS Code or Visual Studio debug mode).

See that the file uploaded by your colleague is actually there, by using the Azure storage explorer.
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Nico Kestel 0 Reputation points

2025-01-15T08:04:40.52+00:00

Hello Pinaki,

thank you for the suggestions! In the meantime I was able to get more information regarding the upload procedures.

As can be seen in the Event Grid Monitoring, my colleague uploads the files via SFTP and uses an SFTP user that is setup for the storage account to do so. SFTP itself is also enabled for the storage account. Now, I was trying to replicate the behaviour by setting up another SFTP user with the exact same permissions, i.e. Read, Create, Write, List, Delete. Both SFTP users have the permission to access the specific Blob Container and both users can upload files to that Blob Container successfully.

The difference now is that the files that I upload via the new SFTP user trigger the Events (published, matched, delivered) that invoke the Azure Function. The files that my colleague uploads via the original SFTP user also trigger the exact same Events (published, matched, delivered) but they do not invoke the Azure Function at all.

Public network access of the storage account is set to "Enabled from all networks". The public network access of the Function App is set to "Enabled with no access restrictions (using default behaviour)".

The Azure Function is not granted access to the storage account as a managed identity. Nevertheless, the Function is invoked if either I upload the files via the new SFTP user or my personal Azure Account, e.g. in the Azure Portal. So I would expect the Azure Function itself to not be tied to a specific user because it is supposed to be triggered by the Event Subscription either way.

Also the Function does not run locally in my development environment but is deployed to the actual Function App in the Azure Cloud.

I hope this further clarifies the problem we are facing.

best,

Nico
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Blob triggered Azure Function not executed when Blob is uploaded by certain user. The Blob Created Event is matched and delivered as expected.

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