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Gunicorn Best Practice

Prefix

Gunicorn is a Python WSGI HTTP Server that usually lives between a reverse proxy (e.g., Nginx) or load balancer (e.g., AWS ELB) and a web application such as Django or Flask.

Gunicorn Improve Performance

To improve performance when using Gunicorn we have to keep in mind 3 means of concurrency.

1. workers.

Basic fundamental for handling concurrency process using by workers. The suggested number of workers is (2*CPU)+1.

If we are using a dual-core(2 CPU) machine, 5 is the suggested workers value.

gunicorn --workers=5 main:app

2. threads on workers.

Each workers allow have multiple threads when python application running. If we implement threads to workers, by default worker class set is to gthread.

The suggested maximum concurrent requests when using workers and threads is still(2*CPU)+1.

If we are using a dual-core(2 CPU) machine and we want to use a mix of workers and threads, we could use 5 workers and 1 threads, to get 5 maximum concurrent requests.

gunicorn --workers=5 --threads=1 main:app

it same as :

gunicorn --workers=5 --threads=1 --worker-class=gthread main:app

3. pseudo-threads.

There are some Python libraries such as gevent and Asyncio that enable concurrency in Python by using pseudo-threads implemented with coroutines.

Gunicorn allows for the usage of these asynchronous Python libraries by setting their corresponding worker class.

Here the settings that would work for a single core machine that we want to run using gevent:

gunicorn --worker-class=gevent --worker-connections=1000 --workers=3 main:app

Info

worker-connections is a specific setting for the gevent worker class. See also worker class on https://docs.gunicorn.org/en/stable/settings.html#worker-class

(2*CPU)+1 is still the suggested workers since we only have 1 core, we’ll be using 3 workers.

In this case, the maximum number of concurrent requests is 3000 (3 workers * 1000 connections per worker)

Credits

https://medium.com/building-the-system/gunicorn-3-means-of-concurrency-efbb547674b7 https://docs.gunicorn.org/en/stable/settings.html#worker-processes