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From Shai Erera <ser...@gmail.com>
Subject Re: Replica and node states
Date Wed, 25 Mar 2015 19:51:36 GMT
Thanks.

Does Solr ever clean up those states? I.e. does it ever remove "down"
replicas, or replicas belonging to non-live_nodes after some time? Or will
these remain in the cluster state forever (assuming they never come back
up)?

If they remain there, is there any penalty? E.g. Solr tries to send them
updates, maybe tries to route search requests to? I'm talking about
replicas that stay in ACTIVE state, but their nodes aren't under
/live_nodes.

Shai

On Wed, Mar 25, 2015 at 8:05 PM, Shalin Shekhar Mangar <
shalinmangar@gmail.com> wrote:

> Comments inline:
>
> On Wed, Mar 25, 2015 at 8:30 AM, Shai Erera <serera@gmail.com> wrote:
>
> > Hi
> >
> > Is it possible for a replica to be DOWN, while the node it resides on is
> > under /live_nodes? If so, what can lead to it, aside from someone
> unloading
> > a core.
> >
>
> Yes, aside from someone unloading the index, this can happen in two ways 1)
> during startup each core publishes it's state as 'down' before it enters
> recovery, and 2) the leader force-publishes a replica as 'down' if it is
> not able to forward updates to that replica (this mechanism is called
> Leader-Initiated-Recovery or LIR in short)
>
> The #2 above can happen when the replica is partitioned from leader but
> both are able to talk to ZooKeeper.
>
>
> >
> > I don't know if each SolrCore reports status to ZK independently, or it's
> > done by the Solr process as a whole.
> >
> >
> It is done on a per-core basis for now. But the 'live' node is maintained
> one per Solr instance (JVM).
>
>
> > Also, is it possible for a replica to report ACTIVE, while the node it
> > lives on is no longer under /live_nodes? Are there any ZK timings that
> can
> > cause that?
> >
>
> Yes, this can happen if the JVM crashed. A replica publishes itself as
> 'down' on shutdown so if the graceful shutdown step is skipped then the
> replica will continue to be 'active' in the cluster state. Even LIR doesn't
> apply here because there's no point in the leader marking a node as 'down'
> if it is not 'live' already.
>
>
> >
> > Shai
> >
>
>
>
> --
> Regards,
> Shalin Shekhar Mangar.
>

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