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https://issues.apache.org/jira/browse/CASSANDRA-18111?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17856572#comment-17856572
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Stefan Miklosovic commented on CASSANDRA-18111:
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Yes, we only hold the paths to the snapshot directories themselves. Based on
your deployment, normally it is just 1 path, in case of multiple data dirs, 2
or more.
The next work, not in this patch, will be to enrich manifest.json with all
files a snapshot consists of. Then we might start to think about the snapshot
consistency verification as a switch to listsnapshots command. (we should also
introduce arguments for keyspace / table to narrow the output of listsnapshots
command). That way, we will detect which snapshots are "corrupted" and we might
consider their removal.
> 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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