Commits on Sep 27, 2024

1. Refactor PeerProvider & hashring interaction …

   As the result:
    - hashring never misses updated (no "channel is full" situation possible)
    - subscribers of MultiringResolver (history, matching) will always get
      sane ChangedEvent which reflects the REAL changes (see details below)
   
   Previously there were problems:
    - hashring subscribed to PeerProvider (ringpop/uns) with non-buffered channel
      which led to failures to write every time `ring` was doing something
      else than reading the channel (happened 60% of times based on error-logs).
      Switched to calling handlers instead which are implementing
      schedule-update with channel with cap=1 approach (see `signalSelf`).
      This approach never skips updates.
    - PeerProvider supplies ChangedEvent to `ring`, but in reality, we do
      not use it - we refresh everything from scratch. This makes very
      misleading to even rely on the ChangedEvent. Basically, we might be
      triggered by some event (host "c" appeared), but during refresh() we
      realise there are more changes (host "a" removed, host "c" added as
      well, etc.), and we notify our Subscribers with an absolutely
      irrelevant data.
    - Same misleading took place in other methods like
      `emitHashIdentifier`. It retrieved list of members from PeerProvider
      **independantly**, which could lead to emitting hash of a different
      state than members we just retrieved in refresh().
    - Some tests were working "by mistake": like
      `TestFailedLookupWillAskProvider` and
      `TestRefreshUpdatesRingOnlyWhenRingHasChanged`.
   
   All in all, not methods are more synchronised, called more expectedly
   (`compareMembers` should not make a new map), and notifiying subscribers
   is **inseparable** from ring::refresh() like it should be.

   

   dkrotx committed Sep 27, 2024
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2. Adding more tests to ringpop provider …

   Also fixed race-condition: we were waiting for ring to stop, but in
   order to read stop-channel it sometimes had to finish notifying
   subscribers which took the same lock. We need to be careful with
   lock-scope.

   

   dkrotx committed Sep 27, 2024
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