Inconsistent Data Upload and Processing on Azure

Question

I am experiencing inconsistent behavior while uploading and processing data on the Azure portal. I have two functions in one function app: one is an event-based trigger, and the other is a queue-based trigger.

I am uploading data from NAS to an Azure storage account. When a new blob is created, the event-based function is triggered, and it stores data in the queue. The queue-based function then processes one message at a time.

I initially thought that the issue was due to the consumption plan, which could cause timeout errors when uploading bulk data. However, I am seeing timeout errors even for single file uploads.

Why is there this inconsistency in file processing? I need help to resolve this issue.

Answer 1

Hello !

Thank you for posting on Microsoft Learn.

Are the Blob and Queue in the Same Storage Account? Because if you are mixing storage accounts, this can cause latency or permission issues.

So try to use the same storage account for blob and queue operations unless separation is required.

Don't forget that Azure Blob Storage events are not guaranteed for every write operation, especially for overwrite scenarios or if event grid subscription is misconfigured.

BlobTrigger is polling-based and has known consistency and latency issues under heavy load.

It is better to use Event Grid to subscribe to blob created events and push to a queue.

Timeout might happen in:

• Reading the blob (slow I/O).
• Processing logic (long-running tasks).

So you may need to check App Insights logs or queue message Dequeue Count, if it’s increasing, processing is failing or taking too long.