Azure Functions warm-up trigger with Dedicated Plan

Question

Hello,

Is the warm-up trigger applicable to the Dedicated Plan?

We're seeing calls to admin/warmup every 5 minute with UserAgent: AlwaysOn which makes us believe that Azure Functions warm-up trigger is applicable to the Dedicated Plan as well.

We're asking because even if we have set AlwaysOn = true on the functions hosted on a Dedicated Plan, we're still seeing cold startup scenarios up to 10-40 seconds on our HTTP triggered function.

Thank you,
Cosmin

Answer 1

@Cosmin Stirbu It is recommended always on for dedicated plans. That said, always on and warm-up serve two separate purposes. Always on is to make sure existing instances don’t idle out if not used for 20 minutes.
Warm-up is to make sure, during and only during a scale-out operation, that everything is loaded(caches, outbound connections sessions, etc.) in the new instance(s) prior to them being added to the load balancer pool to handle requests.

So, if you have always on enabled but are seeing cold start times during a scale out operation then using a warmup trigger is what you need to do.

If you are experiencing cold start behavior without scaling out then that is something that will need to be looked from your function end as as that shouldn’t be occurring.

To troubleshoot it further I will suggest you to open a support ticket with us to assist you further. If you don't have support plan then please refer to my private comment so we can assist you further.