Azure Function with Timer trigger not always firing on set time. When browsing the function in Azure Portal, it suddenly fires like it "forgot to".

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Azure Function with Timer trigger not always firing on set time. When browsing the function in Azure Portal, it suddenly fires like it "forgot to".

Karl 21

Hi,

I have an Azure Function which is set to run 9AM every tuesday with the help of a Timer Trigger. This usually works just fine, however, today a customer reached out and said the files they were expecting had not been delivered.

So I went to check on the function in the Azure Portal, and the function decided to run immediately when I was checking the monitor logs, just like I caught it sleeping.

I have noticed similar behaviour when working with Blob triggers, after uploading an Azure Function using blob trigger to the cloud, it won't boot up or trigger as expected until I at least choose to view the function in the Portal. Afterwards it works as expected.

Anyone know how and why these issues exists and is there a way to solve them?

Thanks in advance.

EDIT: I forgot to mention, these functions are set up in consumtion plan.

Mike 6 Reputation points

2022-03-18T16:32:54.85+00:00

We're seeing this very same behavior and it seems to have started in the last couple months (Jan/Feb/March) after working flawlessly for several months prior.

We're using full NCRONTAB (6 digit) schedules, none of them are attributed with RunOnStartup.

We've also been adding more and more Functions to the Function App so it would have less chance to go idle if that were the issue, there's mroe things running more frequently.

Literally the second that we notice that all the Functions have stopped running and we look at the Function in the portal via a web browser, all the functions run with a reason code of past due.

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Mike 6 Reputation points

2022-03-18T16:32:54.85+00:00

We're seeing this very same behavior and it seems to have started in the last couple months (Jan/Feb/March) after working flawlessly for several months prior.

We're using full NCRONTAB (6 digit) schedules, none of them are attributed with RunOnStartup.

We've also been adding more and more Functions to the Function App so it would have less chance to go idle if that were the issue, there's mroe things running more frequently.

Literally the second that we notice that all the Functions have stopped running and we look at the Function in the portal via a web browser, all the functions run with a reason code of past due.

Answer 1

JayaC-MSFT 5,606

<<Posting the private comment>>

@Karl
Please confirm that the CRON expression used is not modified and correct which should be something like :

You can verify the expression : https://arminreiter.com/2017/02/azure-functions-time-trigger-cron-cheat-sheet/

Also , please check runOnStartup and make sure that is set to false

https://learn.microsoft.com/en-us/azure/azure-functions/functions-bindings-timer?tabs=python#configuration

Please let me know if this helps.

Karl 21 Reputation points

2021-02-02T08:35:10+00:00

Hey JayaC.

Thank you very much for your reply. The issue was indeed that some of our timer triggers were configured with 5 digits instead of 6. We changed these to look similar as the documentation you linked and it seems to have done the trick.

Why our functions would run fairly correct using the other format is unkown. But it seems stable now and I hope it will continue without any issues.

I'm not sure where we got the 5 digits configurations from, probably another site explaining CRON expressions.

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Azure Function with Timer trigger not always firing on set time. When browsing the function in Azure Portal, it suddenly fires like it "forgot to".

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