Benjamin Mahler created MESOS-7688:
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             Summary: Improve master failover performance by reducing 
unnecessary agent retries.
                 Key: MESOS-7688
                 URL: https://issues.apache.org/jira/browse/MESOS-7688
             Project: Mesos
          Issue Type: Improvement
          Components: agent, master
            Reporter: Benjamin Mahler


Currently, during a failover the agents will (re-)register with the master. 
While the master is recovering, the master may drop messages from the agents, 
and so the agents must retry registration using a backoff mechanism. For large 
clusters, there can be a lot of overhead in processing unnecessary retries from 
the agents, given that these messages must be deserialized and contain all of 
the task / executor information many times over.

In order to reduce this overhead, the idea is to avoid the need for agents to 
blindly retry (re-)registration with the master. Two approaches for this are:

(1) Update the MasterInfo in ZK when the master is recovered. This is a bit of 
an abuse of MasterInfo unfortunately, but the idea is for agents to only 
(re-)register when they see that the master reaches a recovered state. Once 
recovered, the master will not drop messages, and therefore agents only need to 
retry when the connection breaks.

(2) Have the master reply with a retry message when it's in the recovering 
state, so that agents get a clear signal that their messages were dropped. This 
one is less optimal, because the master may have to process a lot of messages 
and send retries, but once the master is recovered, the master will process 
only a single (re-)registration from each agent. Here, agents only retry when 
the connection breaks or they get a retry message.



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