how to limit parallel instances and multi-thread in Azure functions

Question

I have an azure function with a time trigger.

That time trigger grabs a batch of data and loop through it processing each record against an external API.

this API interacts with a very slow and sensitive system.

I've added this to host.json to limit parallelism

"extensions": {
"durableTask": {
"maxConcurrentActivityFunctions": 1,
"maxConcurrentOrchestratorFunctions": 1

},

How can I confirm it is working? is there a place in metrics that will display it is not popping parallel instances?

Regarding threads, the timer trigger invokes a normal foreach loop (not Parallel.ForEach). Would that be enough to guarantee each loop process one request at time?

Answer 1

@Joe White If you are using a normal for each loop, then it shouldn't be a problem since you are not fanning out and have only one orchestration running. You will have to check the frequency of the timer trigger though depending on your use case.

If you need only one orchestration (that the timer trigger starts) running at any time, then you might want to leverage the Singleton Orchestration Pattern. If you need to ensure an orchestration runs for each schedule, they might have to queue them up as well.

The settings that you have ensure that only one of each run at a time but your function app may scale out to multiple instances if each orchestration takes longer than the schedule between triggers.