[jira] [Commented] (CASSANDRA-14190) Non-disruptive seed node list reload

["Jason Brown (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-14190?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16339230#comment-16339230 ] 

Jason Brown commented on CASSANDRA-14190:
-----------------------------------------

[~SFink] On the whole, this looks pretty good. On {{getseeds}} output, it might be good to indicate that this listing excludes the local node itself if it is in the seeds list (as provided by {{SeedProvider}}. Otherwise, call {{DatabaseDescriptor#getSeeds }}as that's an unfiltered list.

I've added a unit test for safety, and is here:

||14190||
|[branch|https://github.com/jasobrown/cassandra/tree/14190]|
|[utests|https://circleci.com/gh/jasobrown/workflows/cassandra/tree/14190]|

> Non-disruptive seed node list reload
> ------------------------------------
>
>                 Key: CASSANDRA-14190
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-14190
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Configuration, Lifecycle
>            Reporter: Samuel Fink
>            Assignee: Samuel Fink
>            Priority: Minor
>             Fix For: 4.x
>
>         Attachments: 14190-trunk.patch
>
>
> Add a mechanism for reloading the Gossiper in-memory seed node IP list without requiring a service restart.
> The Gossiper keeps an in-memory copy of the seed node IP list and uses it during a gossip round to determine if the random node that was gossiped to is a seed node and for picking a seed node to gossip to in maybeGossipToSeed.
> Currently the Gossiper seed node list is only updated when an endpoint is removed, at the start of a shadow round, and on startup. Those scenarios don’t handle the case of seed nodes changing IP addresses (eg. DHCP lease changes) or additional seed nodes being added to the cluster.
> As described in CASSANDRA-3829 the current way to ensure that all nodes in the cluster have the same seed node list when there has been a change is to do a rolling restart of every node in the cluster. In large clusters rolling restarts can be very complicated to manage and can have performance impacts because the caches get flushed.



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