How to increase concurrency on python function app hosted in app service plan?

There are multiple ways to increase the concurrency of python function app. I drew an architecture diagram, which can give us an overall understanding of the function app.

Based on the diagram, we can see we could increase function app concurrency by increasing instance count, python worker count and thread count. To better understand this, I build several labs to validate this. I will not demonstrate instance count as it is easy to understand. All these labs are having 4 concurrent incoming requests and each request takes 10 seconds to complete.

Lab1:

code:

sync

Configuration:

maxConcurrentRequests : 4

FUNCTIONS_WORKER_PROCESS_COUNT=1

PYTHON_THREADPOOL_THREAD_COUNT=1

Result:

It took 40 seconds to complete the 4 executions. We can see these 4 executions were triggered at the same time, this is because the function host level is using async. But actually these executions are executed one by one.

Lab2:

code: The same as Lab1.

Configuration:

maxConcurrentRequests : 4

FUNCTIONS_WORKER_PROCESS_COUNT=1

PYTHON_THREADPOOL_THREAD_COUNT=2

Result:

It took 20 seconds to complete the 4 executions.

Lab3:

code: The same as Lab1.

Configuration:

maxConcurrentRequests : 4

FUNCTIONS_WORKER_PROCESS_COUNT=2

PYTHON_THREADPOOL_THREAD_COUNT=2

Result:

It took 10 seconds to complete the 4 executions.

Lab4:

code:

async

Configuration:

maxConcurrentRequests : 4

FUNCTIONS_WORKER_PROCESS_COUNT=1

PYTHON_THREADPOOL_THREAD_COUNT=1

Result:

It took 10 seconds to complete the 4 executions.

Conclusion:

1.We can increase the concurrency by increasing FUNCTIONS_WORKER_PROCESS_COUNT and PYTHON_THREADPOOL_THREAD_COUNT. Just note that we can configure the concurrent setting in host.json file. This is the bottleneck of the concurrency.

2.It is more recommended to use async method instead of sync method as async has better performance than sync with the same configuration.

Reference link:

Azure Functions HTTP triggers and bindings | Microsoft Learn

Improve throughput performance of Python apps in Azure Functions | Microsoft Learn

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