Fix race conditions in Faraday::Utils::Headers

[leocassarani]

Faraday::Utils::Headers uses a shared KeyMap hash to cache symbol -> string mappings of HTTP header names. When multiple threads are writing to the cache, race conditions may occur, as the Hash class is not thread-safe in Ruby.

This commit adds a mutex to synchronize writes to the KeyMap hash. This was enough to remove the race conditions I was seeing in my multi-threaded app running on Rubinius.

[mislav]

Good catch. Two things:

1. There's no reason to assign the mutex to a constant. It can simply be a local variable declared above the hash block; it will be accessible inside the block just fine.
2. Mutex is not guaranteed to be defined before you require 'thread'. Utils file should do the require

[coveralls]

Coverage decreased (-0.16%) when pulling 9719f8d on leocassarani:keymap-mutex into ca8c169 on lostisland:master.

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[leocassarani]

Hey @mislav, thanks for the feedback.

1. You're absolutely right. I was quite conflicted as to what I should assign the mutex to. My main reason for assigning it to a constant was that it seemed a bit more readable and I could declare it after KeyMap itself. But I'm very happy to move it to a local variable and define it above it so the closure can "capture" it.
2. Very good point (and one I always forget). I'll amend the commit.

[coveralls]

Coverage increased (+0.08%) when pulling 69096c0 on leocassarani:keymap-mutex into ca8c169 on lostisland:master.

View Details