[
https://issues.apache.org/jira/browse/SOLR-5823?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13924138#comment-13924138
]
Hoss Man commented on SOLR-5823:
--------------------------------
miller & i talked a bit about this on IRC this morning, a few summary points...
* the reasons i'm looking for a general "am i the leader" type method, that can
be run as part of a scheduled executor -- instead of adding a new processing
thread to the Overseer class is two fold:
** i want the logic to be usable even if we aren't in cloud mode
** i'm trying to think about how other people who write plugins/components
would be able to do the same thing w/o needing to modify the overseer.
* Tim's patch goes the route of ensuring every node can ask "what is the name
of the overseer node" and then implements "am i the overseer node" by comparing
our name with the overser name
** in the case of "who is the shard leader" and "am i the shard leader" that
info is cached in the cluster state info, so calling those methods doesn't hit
ZK everytime
** we don't want to cache the overseer info in a similar way, because it's
risky and 99% of the time, nodes don't care "who is the overseer"
Which brought me to the key question where miller & i realized we had gotten
side tracked...
* i don't really care about the "what is the name of the overseer node" case --
and most people shouldn't -- i'm really just looking for the "am i currently
the overseer?" part of the equation
** this as a simple boolean should be a much easier question to answer
efficiently, because of how the overseer election works -- if a node is the
overseer, it's running hte overseer processing threads
** part of my confusion was the terminology: the idea of "Leader" is used a lot
in the overseer code, but that's not refering to "shard leader" in the solr
context, it's refering to the ZK jargon of "leader election", in many cases (in
the overseer classes) it refers to "who is the ("zk leader" in charge of being
the) overseer"
At this point, miller got disconnected from IRC ... but digging in a bit and
thinking about what he was telling me, it seems like we should be able to add
an efficient "ZkController.isOverseer()" method (that doesn't have to hit Zk
directly), by checking if the Overseer object is active or closed -- either
with a new state boolean, or maybe just by checking the threads it manages for
"null"
> Add utility function for internal code to know if it is currently the overseer
> ------------------------------------------------------------------------------
>
> Key: SOLR-5823
> URL: https://issues.apache.org/jira/browse/SOLR-5823
> Project: Solr
> Issue Type: Improvement
> Reporter: Hoss Man
> Attachments: SOLR-5823.patch
>
>
> It would be useful if there was some Overseer equivalent to
> CloudDescriptor.isLeader() that plugins running in solr could use to know "At
> this moment, am i the leader?"
--
This message was sent by Atlassian JIRA
(v6.2#6252)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
