Blob Trigger is no longer firing in Azure Function

Question

Blob Trigger is no longer firing in Azure Function

David Campos 5

My Azure Function suddenly stopped processing new blobs. The Blob Trigger is no longer firing when a new file is uploaded to the storage container.

To verify whether the application was the issue, I manually sent a message using Microsoft Azure Storage Explorer, and the function processed it successfully. This indicates that the function itself is working correctly, but the Blob Trigger is not being invoked automatically.

No application code changes were made before the issue started.

Has anyone experienced this issue before? Are there any Azure configuration, storage account, or runtime settings that I should check?

Any suggestions or guidance would be greatly appreciated. Thank you in advance for your help!

Harshavardhan Sriramula 0 Reputation points Microsoft External Staff Moderator

2026-07-28T00:28:35.0133333+00:00
Hello **David Campos,

**Based on what you described (the Function app works when you manually send/trigger, but the Blob trigger stops invoking on new uploads), the most common causes to check are: Function host/runtime startup/invocation errors, and Blob-trigger polling/latency behavior (especially on Consumption).

Here are the key things to validate and what to try:

1) Confirm the Function host is actually starting (or not crashing)

If the Functions runtime host isn’t starting due to an exception, Blob triggers won’t fire.

If Application Insights is enabled, you can query for startup exceptions like:

SQL :
exceptions| where customDimensions.Category == "Host.Startup"

If you’re using an App Service cluster with Log Analytics, the document suggests querying App Service console logs for startup errors.

2) If the host starts, check whether invocations are failing

Sometimes the trigger is invoked, but then the function fails during execution due to an exception.

Application Insights example:

YAML :
exceptions| where customDimensions.prop__functionName =~ "MyFunctionName"

Log Analytics example is also provided in the documentation (FunctionAppLogs / Error-level “FunctionCompleted” related entries).

3) Check if the issue is “host idle” / polling latency (classic Blob trigger behavior)

Azure Functions’ Blob trigger (classic polling-based behavior) can introduce delay:

Blobs are scanned in batches of 10,000 with a continuation token between intervals.

If your Function App is on the Consumption plan, there can be up to ~10 minutes delay when the app has gone idle.

If you uploaded blobs and didn’t see any trigger activity right away, waiting a bit longer after inactivity is worth testing.

4) Ensure you’re not expecting events that were “already processed” (blob receipts)

The runtime tracks processed blob versions using blob receipts to ensure the same blob version isn’t called more than once.

If you’re uploading a blob version you believe “should re-trigger,” it may be that the runtime has already recorded it.

Per the doc:

Blob receipts are stored in a container named azure-webjobs-hosts in the storage account for your function app (this is defined by the AzureWebJobsStorage app setting).

To force reprocessing, you can delete the blob receipt for that blob.

You can also update the scaninfo blob in azure-webjobs-hosts/blobscaninfo to force scanning based on LatestScan.

5) Confirm no other Function App is competing for the same queue/messages

The provided doc notes that if multiple Function Apps are pulling from the same queue, one can look idle. This is more relevant for certain trigger/queue designs, but it’s still a check worth making if you’ve got multiple apps configured similarly.

Follow-up questions (so we can narrow it down quickly)

What hosting plan is your Function App on (Consumption, Premium, Dedicated/App Service)?

Is Application Insights enabled for this Function App? If yes, do you see any exceptions related to Host.Startup around the time it stopped firing?

In the storage account, are uploads happening with the same blob name/version behavior you’ve used before (or are you overwriting blobs)?

Are there any other Function Apps (or deployments/slots) using the same AzureWebJobsStorage and monitoring the same container/path?

When it “stops,” do you see any function logs at all (errors or otherwise) corresponding to the expected trigger time? References (Relevant Documentation) :

Azure Functions troubleshooting: Function failed to trigger (recommended steps + Application Insights / Log Analytics queries) https://learn.microsoft.com/azure/azure-functions/

Azure Functions Blob trigger: Polling and latency + blob receipts https://learn.microsoft.com/azure/azure-functions/functions-bindings-storage-blob-trigger

Q&A (blob trigger not firing after deployment / things to check) https://learn.microsoft.com/answers/a/12261735

Q&A (blob trigger not working reliably/randomly) https://learn.microsoft.com/answers/a/8265854

(Additional) Blob trigger binding overview (if you need it for context) https://learn.microsoft.com/azure/azure-functions/functions-bindings-storage-blob
Harshavardhan Sriramula 0 Reputation points Microsoft External Staff Moderator

2026-07-29T21:31:49.0233333+00:00

Hello @David Campos ,

Following up to see if you had a chance to check the above response and if it was helpful. Please let me know if you have any questions.
If these answer your question, click "Upvote" which may be beneficial to other community members reading this thread.
Harshavardhan Sriramula 0 Reputation points Microsoft External Staff Moderator

2026-07-30T23:08:10.84+00:00

Hello @David Campos ,

Following up to see if you had a chance to check the above response and if it was helpful. Please let me know if you have any questions. If these answer your question, click "Upvote" which may be beneficial to other community members reading this thread.
Pomes Silvestro 0 Reputation points

2026-09-07T11:15:46.8566667+00:00

I have the same issue, or similar, and it happens to be related to this GitHub issue: there's a regression in
Microsoft.Azure.WebJobs.Extensions.Storage.Blobs 5.3.8
https://github.com/Azure/azure-sdk-for-net/issues/61660
Harshavardhan Sriramula 0 Reputation points Microsoft External Staff Moderator

2026-09-10T23:17:04.25+00:00

Hello @Pomes Silvestro ,

This behavior is with Microsoft.Azure.WebJobs.Extensions.Storage.Blobs** version **5.3.8. The issue has been identified as a regression in the Blob Trigger polling mechanism, which may prevent newly uploaded blobs from being detected under certain conditions. The issue is documented in the public GitHub thread: Azure SDK Issue #61660. [github.com]

As a resolution, upgrade the Storage Blobs extension to a newer version (for example, 5.3.9 or later) where the issue is addressed and validated. After upgrading, restart the Function App/WebJob and verify that Blob Trigger processing resumes as expected. Newer package versions are available through the official package releases. [Azure WebJ...soft Learn | Learn.Microsoft.com], [nuget.org]

1 answer

Your answer

Harshavardhan Sriramula 0 Reputation points Microsoft External Staff Moderator

2026-07-29T21:31:49.0233333+00:00

Hello @David Campos ,

Following up to see if you had a chance to check the above response and if it was helpful. Please let me know if you have any questions.
If these answer your question, click "Upvote" which may be beneficial to other community members reading this thread.
Harshavardhan Sriramula 0 Reputation points Microsoft External Staff Moderator

2026-07-30T23:08:10.84+00:00

Hello @David Campos ,

Following up to see if you had a chance to check the above response and if it was helpful. Please let me know if you have any questions. If these answer your question, click "Upvote" which may be beneficial to other community members reading this thread.
Pomes Silvestro 0 Reputation points

2026-09-07T11:15:46.8566667+00:00

I have the same issue, or similar, and it happens to be related to this GitHub issue: there's a regression in
Microsoft.Azure.WebJobs.Extensions.Storage.Blobs 5.3.8
https://github.com/Azure/azure-sdk-for-net/issues/61660
Harshavardhan Sriramula 0 Reputation points Microsoft External Staff Moderator

2026-09-10T23:17:04.25+00:00

Hello @Pomes Silvestro ,

This behavior is with Microsoft.Azure.WebJobs.Extensions.Storage.Blobs** version **5.3.8. The issue has been identified as a regression in the Blob Trigger polling mechanism, which may prevent newly uploaded blobs from being detected under certain conditions. The issue is documented in the public GitHub thread: Azure SDK Issue #61660. [github.com]

As a resolution, upgrade the Storage Blobs extension to a newer version (for example, 5.3.9 or later) where the issue is addressed and validated. After upgrading, restart the Function App/WebJob and verify that Blob Trigger processing resumes as expected. Newer package versions are available through the official package releases. [Azure WebJ...soft Learn | Learn.Microsoft.com], [nuget.org]

Answer 1

Yes. A common cause is blob-trigger polling behavior rather than an application defect.

Checks that match this symptom:

Check whether the Function App is on the Consumption plan.
- Blob trigger polling can be delayed by up to 10 minutes if the app has gone idle.
- This often looks like the trigger has stopped, even though the function still works when invoked through its internal queue path.
Check whether the app is going cold/idle.
- If faster or more reliable blob processing is required, use an App Service plan with Always On enabled.
- A similar reported case was resolved by keeping the function warm or enabling Always On.
Check the storage account used by AzureWebJobsStorage.
- Blob trigger state is stored in the azure-webjobs-hosts container in that storage account.
- Azure Functions keeps blob receipts there so the same blob version is not processed more than once.
Check for stale blob receipts.
- If a blob version was already marked as processed, the trigger will not run again for that same version.
- To force reprocessing, delete the blob receipt for that blob from azure-webjobs-hosts.
- To trigger rescanning sooner, update the scaninfo blob in azure-webjobs-hosts/blobscaninfo. Any blobs with a last modified time after the LatestScan property are scanned again.
- Warning: deleting receipts or changing scan info can cause blobs to be processed again.
Check for poison blob handling.
- If processing failed repeatedly, Azure Functions retries five times by default.
- After that, it writes a message to the webjobs-blobtrigger-poison queue.
- If new blobs are ending up there, the trigger is firing but processing is failing.
Check logs with polling limitations in mind.
- Blob polling relies partly on storage logs, and those logs are created on a best-effort basis. Some events can be missed.
- If more reliable triggering is needed, consider a trigger option other than the classic polling blob trigger.
Verify deployed configuration matches local settings.
- Confirm the blob path and connection settings in the Function App configuration match the working local configuration.
- Also confirm blobs are being uploaded to the exact container the function is listening to.

A practical troubleshooting path is:

Confirm hosting plan and whether the app is idling.
Inspect AzureWebJobsStorage and the azure-webjobs-hosts container.
Check for blob receipts for the affected blobs.
Check the webjobs-blobtrigger-poison queue.
If the issue is intermittent or happens after idle periods, move to a plan with Always On or keep the app warm.

References: