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https://issues.apache.org/jira/browse/CASSANDRA-5665?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13693284#comment-13693284
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Jason Brown commented on CASSANDRA-5665:
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After discussion on IRC, decided to the brakes on this one as it seems like
we're getting into dangerous territory mucking with Endpoint's AppState like
that. I'll revisit this ticket again in the future to see if it's still a
problem.
> Gossiper.handleMajorStateChange can lose existing node ApplicationState
> -----------------------------------------------------------------------
>
> Key: CASSANDRA-5665
> URL: https://issues.apache.org/jira/browse/CASSANDRA-5665
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Affects Versions: 1.2.5
> Reporter: Jason Brown
> Assignee: Jason Brown
> Priority: Minor
> Labels: gossip, upgrade
> Attachments: 5665-v1.diff, 5665-v2.diff
>
>
> Dovetailing on CASSANDRA-5660, I discovered that further along during an
> upgrade, when more nodes are on the new major version, a node the previous
> version can get passed some incomplete Gossip info about another, already
> upgraded node, and the older node drops AppStat info about that node.
> I think what happens is that a 1.1 node (older rev) gets gossip info from a
> 1.2 node (A), which includes incomplete (lacking some AppState data) gossip
> info about another 1.2 node (B). The 1.1 node, which has marked incorrectly
> kicked node B out of gossip due to the bug described in #5660, then takes
> that incomplete node B info and wholesale replaces any previous known state
> about node B in Gossiper.handleMajorStateChanged. Thus, if we previously had
> DC/RACK info, it'll get dropped as part of the
> endpointStateMap.put(endpointstate). When the data being pased is incomplete,
> 1.1 will start referencing node B and gets into the NPE situation in #5498.
> Anecdotally, this bad state is short-lived, less than a few minutes, even as
> short as ten seconds, until gossip catches up and properly propagates the
> AppState data. Furthermore, when upgrading a two datacenter, 48 node cluster,
> it only occurred on two nodes for less than a minute each. Thus, the scope
> seems limited but can occur.
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