[
https://issues.apache.org/jira/browse/CASSANDRA-13327?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15944229#comment-15944229
]
Ariel Weisberg commented on CASSANDRA-13327:
--------------------------------------------
It seems to me that for host replacement there is simply no pending state at
all. My reading says that the host replacement can only occur when the host
being replacement is not alive although I imagine at some nodes it might be
considered alive.
So why can't the replacing node transition directly to a state where it is no
longer joining, but has replaced it's target node, and in that situation it is
simply a node that is badly behind and in need of repair. Bootstrap can then
run on the replacing node to provide missing data while it serves both writes
and reads?
Is that an issue for CL.ONE which already has weak guarantees?
> Pending endpoints size check for CAS doesn't play nicely with
> writes-on-replacement
> -----------------------------------------------------------------------------------
>
> Key: CASSANDRA-13327
> URL: https://issues.apache.org/jira/browse/CASSANDRA-13327
> Project: Cassandra
> Issue Type: Bug
> Components: Coordination
> Reporter: Ariel Weisberg
> Assignee: Ariel Weisberg
>
> Consider this ring:
> 127.0.0.1 MR UP JOINING -7301836195843364181
> 127.0.0.2 MR UP NORMAL -7263405479023135948
> 127.0.0.3 MR UP NORMAL -7205759403792793599
> 127.0.0.4 MR DOWN NORMAL -7148113328562451251
> where 127.0.0.1 was bootstrapping for cluster expansion. Note that, due to
> the failure of 127.0.0.4, 127.0.0.1 was stuck trying to stream from it and
> making no progress.
> Then the down node was replaced so we had:
> 127.0.0.1 MR UP JOINING -7301836195843364181
> 127.0.0.2 MR UP NORMAL -7263405479023135948
> 127.0.0.3 MR UP NORMAL -7205759403792793599
> 127.0.0.5 MR UP JOINING -7148113328562451251
> It’s confusing in the ring - the first JOINING is a genuine bootstrap, the
> second is a replacement. We now had CAS unavailables (but no non-CAS
> unvailables). I think it’s because the pending endpoints check thinks that
> 127.0.0.5 is gaining a range when it’s just replacing.
> The workaround is to kill the stuck JOINING node, but Cassandra shouldn’t
> unnecessarily fail these requests.
> It also appears like required participants is bumped by 1 during a host
> replacement so if the replacing host fails you will get unavailables and
> timeouts.
> This is related to the check added in CASSANDRA-8346
--
This message was sent by Atlassian JIRA
(v6.3.15#6346)
