Config web concurrency

[mathemancer]

Fixes #4831

This adds a WEB_CONCURRENCY environment variable to the docker compose setup. Appropriate settings are documented in the same file.

TODO

• Document the variable for from scratch installs.
• Document the variable for 1-click deployments.

Technical details

This variable is used by Gunicorn to set the number of workers, and is the only variable supported for changing concurrency settings, other than the variable to set all command-line arguments. The default I chose is "3", which is reasonable as long as Mathesar is running with at least 1 logical core available. This will improve the situation, but only a bit. Basically, with the sync worker type, we need one worker per concurrent request. So, this takes us from 1 to 3 🎊 .

Long-term, we should try to use the gevent worker type, since that enables async I/O, and Mathesar is extremely I/O, rather than CPU, bound. However, that doesn't work (easily) in Psycopg2, which means it doesn't affect Explorations. It does improve (fix, really) performance in the non-exploration part of the codebase, but I didn't want to make the change in the current limited-QA situation. If we decide we are not going to try to squeeze this PR into 0.6.0, then I think we should make that change as well, to get the benefits in the parts of the codebase where we're using psycopg3.

This is yet another spot where our failure to deal with Explorations and the deprecated SQLAlchemy part of the codebase is biting us.

To test this, you can just load big tables in multiple browsers manually, or follow the instructions in #4841 .

Checklist

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  visible errors.

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[mathemancer]

@zackkrida This is mergable, and doesn't harm the 1-click deployments, but I think it would make sense to document setting this variables for those scenarios as well. I'm not sure how the users should determine the number of vCPUs on various platforms, which is a prerequisite to setting this variable correctly.

[Anish9901]

Is this change necessary, I rememeber making a conscious decision to not expose the postgres port to the host.

[zackkrida]

@mathemancer was this for testing purposes or some other reason?

[mathemancer]

Oops! Great eye, @Anish9901 . That was for testing.

[mathemancer]

Okay, reverted in 1682771

[pavish]

@mathemancer @zackkrida This commit cb2504f adds a default value for WEB_CONCURRENCY env variable for the from-scratch script based installation.