Fix race condition starting CacheCleanupThread #586
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This fixes two race conditions 1. Thread execution may start before `CacheCleanupThread.new` returns the class instance. In this case `t` is not yet defined inside the thread block and results in a "undefined method `sleepy_run' for nil:NilClass" error. 2. Thread execution may start before member variables `@store`, `@interval`, etc are initialized in `CacheCleanupThread#initialize` This results in "undefined method '*' for nil:NilClass" in should_cleanup? (this error only occurs after the first race condition is fixed) More detail: A subclassed thread is scheduled for execution as soon as `super` is called. The code block of the thread may start to execute before the class is fully instantiated. See https://www.ruby-forum.com/t/thread-super-should-be-first-line-or-last-line/150617
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Amazing work. There's not way I would have ever figured out point #2 especially... great job! |
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Thanks @nateberkopec 🙌 This was a particularly fun one. I had a hunch about points #1 and #2. But I applied them separately at first, which made it appear that neither one made a difference. It took a while to figure out they both needed to be applied. |
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This fixes two race conditions
Thread execution may start before
CacheCleanupThread.newreturns the class instance. In this casetis not yet defined inside the thread block and results in a "undefined method `sleepy_run' for nil:NilClass" error.Thread execution may start before member variables
@store,@interval, etc are initialized inCacheCleanupThread#initializeThis results in "undefined method '*' for nil:NilClass" in should_cleanup? (this error only occurs after the first race condition is fixed)More detail: A subclassed thread is scheduled for execution as soon as
superis called. The code block of the thread may start to execute before the class is fully instantiated. See https://www.ruby-forum.com/t/thread-super-should-be-first-line-or-last-line/150617Fixes #566