[ruby-core:114766] [Ruby master Bug#9115] Logger traps all exceptions; breaks Timeout

Issue #9115 has been updated by shyouhei (Shyouhei Urabe).


Eregon (Benoit Daloze) wrote in #note-12:
> mame (Yusuke Endoh) wrote in #note-11:
> > As a better-than-nothing mitigation, it is proposed to enclose the entire `Logger::LogDevice#write` in `Thread.handle_interrupt(:never) { ... }`.
> > It could be a problem if the method takes a very long time because `Timeout.timeout` cannot interrupt the execution, but such a case will be rare (hopefully).
> 
> This sounds problematic, especially since that is doing IO, possibly even network IO (e.g. NFS, or logging over some API).

Right.  It's never an ultimate fix.  However considering the way a log destination is designed generally, I think it's rare for that blocking IO to block indefinitely.  Sure, with `handle_interrupt` a timeout can delay for seconds.  That's better than never, and "never" is the way it is now.

> I believe all libraries should only catch specific errors they want to rescue and if that's hard to determine than StandardError at most, never Exception.
> Rescuing Exception without re-raise is always a bug (e.g. NoMemoryError/SystemStackError can be silent and that can cause pretty serious inconsistencies and indirectly what looks like memory corruption).

The Logger author seems hesitating to interface with its callers at any cost (understandable).  It is unfortunate that we currently have no idiomatic ways to achieve their goals.

----------------------------------------
Bug #9115: Logger traps all exceptions; breaks Timeout
https://bugs.ruby-lang.org/issues/9115#change-104603

* Author: cphoenix (Chris Phoenix)
* Status: Assigned
* Priority: Normal
* Assignee: sonots (Naotoshi Seo)
* ruby -v: ruby 2.0.0p247 (2013-06-27) [i386-mingw32]
----------------------------------------
Line 577-579 of logger.rb

      rescue Exception => ignored
        warn("log writing failed. #{ignored}")
      end

Thus, when the system times out in the middle of writing a log message, it warns "log writing failed. execution expired" and just keeps right on running.

This is true in 1.9.3 as well. I haven't looked at older versions.

Pardon me while I go grep "rescue Exception" in the entire Ruby codebase, and see whether I can reliably use Timeout at all...

OK, you might check out C:\Ruby200\lib\ruby\gems\2.0.0\gems\activerecord-3.2.13\lib\active_record\railties\databases.rake

All the other "rescue Exception" seem to re-raise it, except maybe C:\Ruby200\lib\ruby\2.0.0\xmlrpc\server.rb and C:\Ruby200\lib\ruby\gems\2.0.0\gems\activesupport-3.2.13\lib\active_support\callbacks.rb





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