[jira] [Created] (MESOS-1517) Maintain a queue of messages that arrive before the master recovers.

["Benjamin Mahler (JIRA)" <ji...@apache.org>]

Benjamin Mahler created MESOS-1517:
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             Summary: Maintain a queue of messages that arrive before the master recovers.
                 Key: MESOS-1517
                 URL: https://issues.apache.org/jira/browse/MESOS-1517
             Project: Mesos
          Issue Type: Improvement
          Components: master
            Reporter: Benjamin Mahler
             Fix For: 0.19.0


Currently when the master is recovering, we drop all incoming messages. If slaves and frameworks knew about the leading master only once it has recovered, then we would only expect to see messages after we've recovered.

We previously considered enqueuing all messages through the recovery future, but this has the downside of forcing all messages to go through the master's queue twice:

{code}
  // TODO(bmahler): Consider instead re-enqueing *all* messages
  // through recover(). What are the performance implications of
  // the additional queueing delay and the accumulated backlog
  // of messages post-recovery?
  if (!recovered.get().isReady()) {
    VLOG(1) << "Dropping '" << event.message->name << "' message since "
            << "not recovered yet";
    ++metrics.dropped_messages;
    return;
  }
{code}

However, an easy solution to this problem is to maintain an explicit queue of incoming messages that gets flushed once we finish recovery. This ensures that all messages post-recovery are processed normally.



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