[tor-bugs] #28061 [Core Tor/sbws]: Check prioritisation, it should make 2 measurements that are 24 appart

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#28061: Check prioritisation, it should make 2 measurements that are 24 appart
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 Reporter:  juga           |          Owner:  (none)
     Type:  defect         |         Status:  new
 Priority:  Medium         |      Milestone:  sbws 1.0 (MVP nice)
Component:  Core Tor/sbws  |        Version:
 Severity:  Normal         |     Resolution:
 Keywords:                 |  Actual Points:
Parent ID:  #28042         |         Points:
 Reviewer:                 |        Sponsor:
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Comment (by pastly):

 Replying to [comment:13 juga]:
 > pastly, i suspect that the reason why the same relay gets measured twice
 within minutes, is because the threads are not sharing the same vision on
 the `best_priority` iterator. Would you mind to have a look to it?

 I don't think the measurement threads have different copies or ideas about
 the RelayPrioritizer because it is created in the main thread and never
 given to worker threads.
 [https://github.com/torproject/sbws/blob/ed1d61c98044e9ed081a7462d94ae31630b75705/sbws/core/scanner.py#L338
 See it defined here and never given to the workers].

 My untested theory is:

 A thread will grab one of the last relays in the RelayPrioritizer. While
 it is measuring that relay, the RelayPrioritizer is recalculating
 priority, finishes, and gives the same relay to another thread to also
 measure.

 This might be a good time to switch to using
 [https://docs.python.org/3.5/library/queue.html#queue.PriorityQueue
 Python's PriorityQueue] while figuring out the problem. I'll give it some
 thought this evening.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/28061#comment:14>
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