Azure Durable Function getting slower and slower over time

Question

My Azure Durable Function(Runtime V3) getting an average of 3M events per day. When it runs for two or three weeks it is getting slower and slower. When I remove two table storages(History & Instances) used by Durable Function Framework, it is getting better and works as expected. I hosted my function app in the consumption plan. And also inside my function app, I'm used Durabel Entities as well. In my code, I'm using sub orchestrators as well for the Fan-Out mechanism.

Is this problem possible when it comes to heavy workload? Do I need to clear those table storages from time to time or do I need to Delete the state of completed entities inside my Durable Entity Function?

Someone, please help me

Answer 1

Yes, you should perform periodic clean-ups yourself by calling the PurgeInstanceHistoryAsync method. See a similar post on how to do this: https://stackoverflow.com/a/60894392

Answer 2

Also review any loops or Monitor patterns that you may have in your code. Any looping logic, (like foreach, for or while loops) will replay from the initial startup state. Whilst the Durable Function replay architecture is very efficient at doing this, the code we write may not be optimised for repetitive iterations.

Durable Monitor Pattern is almost an Anti-Pattern. The concept is OK but it is easily misinterpreted and is open to abuse. It is designed for a low-frequency loop that polls an endpoint either for a set number of iterations or up until a finite time, or of course when the state of the endpoint being monitoried has changed. That state change will be the trigger to perform the rest of the operation.

It is NOT an example of how to use general or high frequency looping structures in Durable functions

It is NOT and example of how to implement a traditional HTTP endpoint reporting monitor in an infinite loop (while(true)) style, perhaps to record changes into a data store over time.

If your durable function logic has an iterator that may involve many iterations, consider migrating the iteration step to a sub-orchestration that uses the Eternal Orchestration pattern