[jira] [Commented] (KUDU-2962) Fix kudu::itest::FindTabletFollowers() test utility function

["Bankim Bhavsar (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KUDU-2962?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16956555#comment-16956555 ] 

Bankim Bhavsar commented on KUDU-2962:
--------------------------------------

I think there are 2 high-level approaches here:
 # In {{FindTabletFollowers}} go through each supplied tablet servers and sanitize that the tablet server hosts the supplied tablet id . Then use the reduced/filtered list below in the existing implementation. This can be accomplished using helper methods like {{GetConsensusState()}} from {{cluster_itest_util.cc}}.
 # Alternative is to query the master for tablet servers for specified tablet id. This can be accomplished using helper method {{GetTabletLocations}} and filtering out leader tablet. In this case, the caller to FindTabletFollowers() need not even supply the tablet server map but instead needs the master proxy.

Method #2 looks better to me unless there is a reason not to go through the master and instead rely/verify state of the tablet servers directly.

[~aserbin] what do you think?

> Fix kudu::itest::FindTabletFollowers() test utility function
> ------------------------------------------------------------
>
>                 Key: KUDU-2962
>                 URL: https://issues.apache.org/jira/browse/KUDU-2962
>             Project: Kudu
>          Issue Type: Improvement
>          Components: test
>            Reporter: Alexey Serbin
>            Assignee: Bankim Bhavsar
>            Priority: Minor
>              Labels: newbie
>
> The {{kudu::itest::FindTabletFollowers()}} function is unsafe: it uses {{kudu::itest::FindTabletLeader()}} to generate the result as a complement to tablet servers hosting the leader replica, but it doesn't sanitize the set of tablet servers to make sure it contains only tablet servers hosting replicas of the specified tablet.
> For example, if you have a cluster with 10 tablet servers, and a tablet with 3 tablet replicas, passing the map for all tablet servers in the 10-node cluster would result in {{FindTabletFollowers()}} reporting 9 followers.  Whoops!
> It's necessary to either fix the implementation of this utility function to sanitize its first argument, or simply get rid of it.



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