Redirect STDERR to /dev/null during eager_preload

[mvz]

This is a rebased version of #618.

This is a patch by @markiz.

Fixes #396.

[mvz]

I've included the patch from #602 to have a non-failing base build.

[mvz]

It looks like the tests are green on modern Rubies and Railses ... If #617 is accepted I can rebase and all should be fine ...

[mvz]

I rebased and now the build is green.

[rafaelfranca]

Thank you for the pull request. I believe #655 fix the same problem. Can you confirm?

[mvz]

I'm not sure how to trigger this problem reliably anymore, but I think I was just hit by #396 again with the new spring version 3.1.1 (on Ruby 2.7.4).

[mvz]

@markiz since this is your patch, perhaps you can chime in on whether #655 fixes the problem for you?

[markiz]

@mvz Hey, apologies about the delay, just looking at the changeset, I imagine it's good.

The context there so far as I remember was that we had a ton of warnings (40+ lines) emitted upon rails startup from some other library, and the stderr buffer was not large enough to fit it all, and since it was not drained anywhere, it got immediately overflown, silently freezing spring.

Unfortunately, I don't have the access to that code anymore, so I can't verify.

[chrisblatchley]

hey @mvz i was having the same issue and found this PR. I was investigating this issue myself and arrived on a similar solution then found this PR already open. I tested these changes on our application and it worked great! I ended up making a similar fix that would write to spring_env.log_file instead of /dev/null but either works. would love to see this get merged!

[mvz]

@rafaelfranca thanks for merging this!