How to calculate max requests per second of a Django app?

Question

I am about the deploy a Django app, and then it struck me that I couldn't find a way to anticipate how many requests per second my application can handle.

Is there a way of calculating how many requests per second can a Django application handle, without resorting to things like doing a test deployment and use an external tool such as locust?

I know there are several factors involved (such as number of database queries, etc.), but perhaps there is a convenient way of calculating, even estimating, how many visitors can a single Django app instance handle.

EDIT: Removed the mention to Gunicorn, since it only adds confusion to what I truly wanted to know.

Answer 1

Is there a way of calculating how many requests per second can a Django application handle, without resorting to things like doing a test deployment and use an external tool such as locust?

No and Yes. As mackarone pointed out, I don't think there's anyway you avoid measuring it. Consider the case where you did a local benchmark on your local dev server talking to a local DB instance, in order to generate a baseline for estimation. The issue with this is that the hardware, network (distance between services) all make a huge difference. So any numbers you generated locally would be relatively worthless for capacity planning.

In my experiences, local testing is great for relative changes. Consider the case where you wanted to see the performance impact of sql query planninng. Establishing a local baseline, making the change, than observing the effect locally is useful to gauge relative speedup.

How to generate these numbers?

I would recommend deploying the app to the hardware, and network you plan on testing on. This deploy should use your production configuration and component topology (ie if you're going to run gunicorn, make sure gunicorn is running instead of NGINX, or if you're going to have a proxy in front of gunicorn, make sure that is setup. I would run a single instance of your application using your production config.

Once this is running, I would launch a load test against the single instance using any of the popular load testing tools:

• Apache Benchmark
• Siege
• Vegeta
• K6
• etc

You can launch these load tests from your single machine and ramp up traffic until response times are no longer acceptable in order to get a feel for the # of concurrent connections, and throughput your application can accommodate.

Now you have some idea of what a single instance of your service is able to handle. Up until your db (or other shared resources) are saturated these numbers can be used to project how many instances of your service are necessary to handle some amount of traffic!