[jira] [Created] (CASSANDRA-5665) Gossiper.handleMajorStateChange can lose existing node ApplicationState

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

Jason Brown created CASSANDRA-5665:
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             Summary: 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
            Priority: Minor
             Fix For: 1.2.6, 2.0 beta 1


Dovetailing on #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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