Selenium node docker images NODE_MAX_SESSION and NODE_MAX_INSTANCES env variables

Question

I'm using docker compose file from selenium wiki.

For chrome and firefox nodes there are NODE_MAX_SESSION and NODE_MAX_INSTANCES env variables.

Is my understanding correct - there is no difference between configuring NODE_MAX_SESSION or NODE_MAX_INSTANCES for chrome or firefox image as for example chrome node can only start chrome browser and firefox node only firefox browser.

Why do then there are two of them ?

Answer 1

NODE_MAX_INSTANCES

NODE_MAX_SESSION

Both needs to be configured for ex :

NODE_MAX_INSTANCES=6 NODE_MAX_SESSION=3 runs a chrome node which can run 6 instances of chrome, and a max parallelization of 3

Hope that answers your question

Answer 2

As the official docs tell, we need both, if you plan sets the maximum amount of tests that can run at the same time in a node, so:

By default, each image will only allow one slot per container,...this can be configured via environment variables with the environment variable NODE_MAX_INSTANCES. Don't forget to combine this with the environment variable NODE_MAX_SESSION