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From "Matt Byrd (JIRA)" <j...@apache.org>
Subject [jira] [Assigned] (CASSANDRA-14531) Only include data owned by the node in totals for repaired, un-repaired and pending repair.
Date Tue, 19 Jun 2018 23:45:00 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-14531?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Matt Byrd reassigned CASSANDRA-14531:
-------------------------------------

    Assignee: Matt Byrd

> Only include data owned by the node in totals for repaired, un-repaired and pending repair.
> -------------------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-14531
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-14531
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Metrics, Repair
>            Reporter: Matt Byrd
>            Assignee: Matt Byrd
>            Priority: Minor
>             Fix For: 4.x
>
>
> If there is data which is left over from a topology change and is not yet cleaned up,
it will be included in the total for BytesRepaired, BytesUnrepaired or BytesPendingRepair
metrics.
>  This can distort the total and lead to misleading metrics (albeit potentially short-lived).
>  As an operator if you wanted to keep track of percent repaired, you might not have an
accurate idea of the relevant percent repaired under such conditions.
> I propose we only include sstables owned by the node in the totals for BytesRepaired,
BytesUnrepaired, BytesPendingRepair and PercentRepaired. It feels more logical to only emit
metrics like repaired/un-repaired for data which can actually be repaired.
> When an SStable is partially owned by the node, we can compute the size which falls within
the token-range by binary searching the index for the uncompressed offsets.
>  We can finally also emit a metric which consists of all the data which is not owned
by the node.
>  This might also be helpful for operators to discover whether there is data which is
not owned by the node and hence the need to run cleanup.   
> On slight complication is that with a large number of sstables and a reasonable number
of vnodes, computing these values now becomes a bit expensive. There is probably a way of
keeping some of these metrics updated online rather than re-computing periodically, though
this might be a bit fiddly. Alternately using things like the interval tree or some other
data-structure might be enough to ensure it performs sufficiently and doesn't add undue
overhead.



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