[tor-bugs] #28663 [Core Tor/sbws]: sbws stops accumulating, silently

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#28663: sbws stops accumulating, silently
---------------------------+-----------------------------------
 Reporter:  stefani        |          Owner:  juga
     Type:  defect         |         Status:  assigned
 Priority:  Medium         |      Milestone:  sbws: 1.0.x-final
Component:  Core Tor/sbws  |        Version:  sbws: 1.0.2
 Severity:  Major          |     Resolution:
 Keywords:                 |  Actual Points:
Parent ID:  #28639         |         Points:
 Reviewer:                 |        Sponsor:
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Comment (by teor):

 Replying to [comment:13 juga]:
 > The instantiated locks without acquire and release use the context
 manager, so that might not be a failure.
 > The point where sbws is stalled is in this loop:
 https://github.com/torproject/sbws/blob/ee64d76df54ceb3a3c9e1e2a797fd70d68bb0035/sbws/core/scanner.py#L362,
 which was added in #28061 in order to stop measuring the same relay by two
 threads when a new loop starts.

 This code can block forever at a few point. I will open a new child ticket
 for every location that can block.

 > Turned out that there's 1 thread that is not measuring relays, it's the
 one storing the results, so that could be solved just changing "> 0" to ">
 1", i'll try that.

 pending_results is a list of AsyncResults, not threads:
 https://docs.python.org/2/library/multiprocessing.html#multiprocessing.pool.AsyncResult

 So this change doesn't do what you say it does.

 > However, there's still the mistery about why commenting the lines in
 relaprioritizer solves the problem too.

 It might solve the problem by changing where the code blocks.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/28663#comment:14>
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