Catch exceptions in hooks defined by users

[andrykonchin]

Description

Suppress exceptions in user defined hooks (like on_worker_boot). We have just to rescue and log them.

Example of logged message:

WARNING hook on_restart failed with exception (RuntimeError) Error from hook
% Traceback (most recent call last):
	14: from /Users/andrykonchin/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/minitest-5.14.0/lib/minitest/parallel.rb:33:in `block (2 levels) in start'
	13: from /Users/andrykonchin/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/minitest-5.14.0/lib/minitest.rb:1026:in `run_one_method'
	12: from /Users/andrykonchin/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/minitest-5.14.0/lib/minitest/test.rb:93:in `run'
	11: from /Users/andrykonchin/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/minitest-5.14.0/lib/minitest/test.rb:211:in `with_info_handler'
	10: from /Users/andrykonchin/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/minitest-5.14.0/lib/minitest.rb:365:in `on_signal'
	 9: from /Users/andrykonchin/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/minitest-5.14.0/lib/minitest/test.rb:94:in `block in run'
	 8: from /Users/andrykonchin/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/minitest-5.14.0/lib/minitest.rb:270:in `time_it'
	 7: from /Users/andrykonchin/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/minitest-5.14.0/lib/minitest/test.rb:95:in `block (2 levels) in run'
	 6: from /Users/andrykonchin/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/minitest-5.14.0/lib/minitest/test.rb:195:in `capture_exceptions'
	 5: from /Users/andrykonchin/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/minitest-5.14.0/lib/minitest/test.rb:98:in `block (3 levels) in run'
	 4: from /Users/andrykonchin/projects/puma/test/test_config.rb:226:in `test_run_hooks_and_exception'
	 3: from /Users/andrykonchin/projects/puma/lib/puma/configuration.rb:279:in `run_hooks'
	 2: from /Users/andrykonchin/projects/puma/lib/puma/configuration.rb:279:in `each'
	 1: from /Users/andrykonchin/projects/puma/lib/puma/configuration.rb:281:in `block in run_hooks'
/Users/andrykonchin/projects/puma/test/test_config.rb:220:in `block (2 levels) in test_run_hooks_and_exception': Error from hook (RuntimeError)

Closes #1551

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[nateberkopec]

Makes sense and LGTM.

[andrykonchin]

@nateberkopec

There is only one issue with logging. I looked through the project and found out there are two options

• to directly write into STDERR
• to use Events (which could write either to STDOUT/STDERR or to strings).

I prefer the second one because it's easier to check in tests and Events provides more flexible interface - we can optionally print exception stack trace as debug message.

Please let me know if you prefer the first option.

[nateberkopec]

Thanks for your contribution @andrykonchin!