Azure Functions Host Initializing over and over again

Question

Azure Functions Host Initializing over and over again

Tom Gutzler 21

I'm seeing multiple "Initializing Host" messages per hour in app insights. I wonder if this is to be expected.

My functions are mainly queue triggered and I've configured batchSize = 1 in my host.json so I don't expect parallel execution.
There is one timer triggered function that does nothing. It fires every 9 minutes.

Host initialization happens even when there is no activity on the queues.
I'm running functions v3

1 answer

Your answer

Answer 1

Pramod Valavala 20,656 Microsoft Employee Moderator

@Tom Gutzler While your batchSize is set to 1 and assuming you are running on the consumption tier, your function app could scale out to multiple instances causing the multiple logs. Also, when there is no activity, your function app would scale down to zero and a new message would trigger the function app to start up, again causing the log.

If you need to ensure your function app doesn't scale out beyond on a single instance, then you can limit the scale out as covered in the docs.

Tom Gutzler 21 Reputation points

2021-08-18T00:52:04.827+00:00

Thanks.
I thought that having the timer triggered function run every 9 minutes would prevent it from scaling in to zero.
I'll limit the scale out and keep an eye it.
Tom Gutzler 21 Reputation points

2021-08-19T02:22:27.51+00:00

@Pramod Valavala
To clear things up, I am on the consumption tier.
I have set the scale out limit to 1 3 hours ago and I've gotten two "Host Initialized" messages since.

I noticed that the "Initializing Host" message always follows a "Initializing Warmup Extension" message. The web tells me that this might happen during a scale out, which shouldn't happen. What's going on?

What concerns me is that I cannot find anything about hosts shutting down or dying anywhere. Surely loglevel = Information should be enough to bring those messages up.
Pramod Valavala 20,656 Reputation points Microsoft Employee Moderator

2021-08-23T14:55:05.667+00:00

@Tom Gutzler You could try setting up Scale Controller Logs that could shed more light on what's happening. For a deeper analysis, it would be best to open a support ticket to investigate this further.

Share via

Azure Functions Host Initializing over and over again

1 answer

Your answer