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

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

    [ https://issues.apache.org/jira/browse/CASSANDRA-5665?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13688331#comment-13688331 ] 

Jason Brown edited comment on CASSANDRA-5665 at 6/19/13 7:12 PM:
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I suspect it's just something we haven't noticed before. I found it when upgrading from 1.0 to 1.1, largely via the CASSANDRA-5660 debugging. It was exposed as an edge case of an edge case (using each_qourum, in ec2, during a major rev upgrade), however it probably applies to many upgrade scenarios.
                
      was (Author: jasobrown):
    I suspect it's just something we haven't noticed before. I found it when upgrading from 1.0 to 1.1, largely via the CASSANDRA-5660 debugging. It was exposed as an edge case of an edge case (using each_qourum, in ec2, during a major rev upgrade), however it probably applies to every upgrade scenario.
                  
> 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
>              Labels: gossip, upgrade
>             Fix For: 1.2.6, 2.0 beta 1
>
>         Attachments: 5665-v1.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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