Weird runtime behavior when sending many HTTP requests at the same time (limit of 256)

[sean-kuzco]

What version of Bun is running?

1.1.8+89d25807f

What platform is your computer?

Darwin 23.5.0 arm64 arm

What steps can reproduce the bug?

Try to send many network requests (e.g. 1,000+) in a script run with Bun.

What is the expected behavior?

All requests would be sent to the server (the behavior if the script is run with NodeJS).

What do you see instead?

Requests are apparently sent with a limit of 256.

Additional information

We have a minimal reproduction of this behavior with more information here: https://github.com/context-labs/kuzco-bun-bug-reproduction

[sean-kuzco]

We discovered this is because of a default concurrency limit of 256 for Bun's HTTP implementation, which can be configured with the BUN_CONFIG_MAX_HTTP_REQUESTS environment variable.

This PR changes the default to be consistent with NodeJS: #12221