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https://issues.apache.org/jira/browse/CASSANDRA-10962?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15136275#comment-15136275
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FACORAT commented on CASSANDRA-10962:
-------------------------------------
OK, first to reproduce this you need to activate auto_snapshot in cassandra.yaml
http://docs.datastax.com/en/cassandra/2.2/cassandra/configuration/configCassandra_yaml.html?scroll=configCassandra_yaml__auto_snapshot
Then if you look at CassandraDaemon.java, you will note that at startup it will
discard compaction_in_progress:
https://github.com/apache/cassandra/blob/cassandra-2.2/src/java/org/apache/cassandra/service/CassandraDaemon.java#L220
SystemKeyspace.discardCompactionsInProgress() means truncating the
system.compactions_in_progress table:
https://github.com/apache/cassandra/blob/cassandra-2.2/src/java/org/apache/cassandra/db/SystemKeyspace.java#L402
So you end up with a snaphot in data_dir/system/compactions_in_progress/, but
you can't see it with "nodetool listsnaphots" which is filtering out system
keyspaces. However as this is temporary files, there's no need to snapshot
system.compactions_in_progress when doing a truncate on it IMHO.
Please note that CASSANDRA-7066 should fix this behavior in 3.0
> Cassandra should not create snapshot at restart for compactions_in_progress
> ---------------------------------------------------------------------------
>
> Key: CASSANDRA-10962
> URL: https://issues.apache.org/jira/browse/CASSANDRA-10962
> Project: Cassandra
> Issue Type: Bug
> Environment: Ubuntu 14.04.3 LTS
> Reporter: FACORAT
> Priority: Minor
>
> If auto_snapshot is set to true in cassandra.yaml, each time you restart
> Cassandra, a snapshot is created for system.compactions_in_progress as the
> table is truncated at cassandra start.
> However as datas in this table are temporary, Cassandra should not create
> snapshot for this table (or maybe even for system.* tables). This will be
> coherent with the fact that "nodetool listsnapshots" doesn't even list this
> table.
> Exemple:
> $ nodetool listsnapshots | grep compactions
> $ ls -lh
> system/compactions_in_progress-55080ab05d9c388690a4acb25fe1f77b/snapshots/
> total 16K
> drwxr-xr-x 2 cassandra cassandra 4.0K Nov 30 13:12
> 1448885530280-compactions_in_progress
> drwxr-xr-x 2 cassandra cassandra 4.0K Dec 7 15:36
> 1449498977181-compactions_in_progress
> drwxr-xr-x 2 cassandra cassandra 4.0K Dec 14 18:20
> 1450113621506-compactions_in_progress
> drwxr-xr-x 2 cassandra cassandra 4.0K Jan 4 12:53
> 1451908396364-compactions_in_progress
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