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https://issues.apache.org/jira/browse/CASSANDRA-18111?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17856570#comment-17856570
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Francisco Guerrero commented on CASSANDRA-18111:
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Looking more closely at what we are keeping in memory for snapshots, this won't
be an issue unless you have a really large number of snapshots (thanks Stefan
for doing the work above). For low thousands of snapshots, this won't take up
that much memory, so I don't have concerns there. My original concern came from
keeping, in addition to the metadata, each snapshot file path in memory, which
is not the case for what SnapshotManager is holding in memory.
> Centralize all snapshot operations to SnapshotManager and cache snapshots
> -------------------------------------------------------------------------
>
> Key: CASSANDRA-18111
> URL: https://issues.apache.org/jira/browse/CASSANDRA-18111
> Project: Cassandra
> Issue Type: Improvement
> Components: Local/Snapshots
> Reporter: Paulo Motta
> Assignee: Stefan Miklosovic
> Priority: Normal
> Fix For: 5.x
>
> Time Spent: 1h 10m
> Remaining Estimate: 0h
>
> Everytime {{nodetool listsnapshots}} is called, all data directories are
> scanned to find snapshots, what is inefficient.
> For example, fetching the
> {{org.apache.cassandra.metrics:type=ColumnFamily,name=SnapshotsSize}} metric
> can take half a second (CASSANDRA-13338).
> This improvement will also allow snapshots to be efficiently queried via
> virtual tables (CASSANDRA-18102).
> In order to do this, we should:
> a) load all snapshots from disk during initialization
> b) keep a collection of snapshots on {{SnapshotManager}}
> c) update the snapshots collection anytime a new snapshot is taken or cleared
> d) detect when a snapshot is manually removed from disk.
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