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From "FACORAT (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-10962) Cassandra should not create snapshot at restart for compactions_in_progress
Date Sun, 07 Feb 2016 14:44:39 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-10962?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15136275#comment-15136275
] 

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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