Downloader does not fail fast on an offline localhost server.

Description of the bug:

In a situation where the downloader config has a rewrite to a local address (127.3.3.3:8000 for example), it will not fail fast in a situation where it cannot connect, and seems to outright hang up trying to connect.

Which category does this issue belong to?

Core

What's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

Use a downloader config with the following:

rewrite https://(bcr.bazel.build)/(.*) http://127.3.3.3:8000/$2

Do not host any server or mirror at that address and port, just let it try.

This should reproduce upon trying to download a module, but other URL rewrites to the same thing (a dead end localhost address) should work.

Which operating system are you running Bazel on?

Linux, Ubuntu 24.04

What is the output of bazel info release?

release 9.2.0

If bazel info release returns development version or (@non-git), tell us how you built Bazel.

No response

What's the output of git remote get-url origin; git rev-parse HEAD ?

If this is a regression, please try to identify the Bazel commit where the bug was introduced with bazelisk --bisect.

No response

Have you found anything relevant by searching the web?

No response

Any other information, logs, or outputs that you want to share?

I was unable to get any logs out of the downloader, not sure how to do so and would appreciate pointers.