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From "Karl Mueller (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-6092) Leveled Compaction after ALTER TABLE creates pending but does not actually begin
Date Fri, 11 Oct 2013 06:40:43 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-6092?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13792400#comment-13792400
] 

Karl Mueller commented on CASSANDRA-6092:
-----------------------------------------

This doesn't make sense. You change a compaction strategy, it should start to take effect.
You shouldn't have to do anything else. This is a bug, plain and simple.

For one thing, the most likely users who want to use leveled compaction are people like me
who compact nightly to get rid of old update rows. We're the most likely ones to have a single
sstable.

This is not a bizarre corner case, but basic functionality!


> Leveled Compaction after ALTER TABLE creates pending but does not actually begin
> --------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-6092
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6092
>             Project: Cassandra
>          Issue Type: Bug
>         Environment: Cassandra 1.2.10
> Oracle Java 1.7.0_u40
> RHEL6.4
>            Reporter: Karl Mueller
>            Assignee: Daniel Meyer
>
> Running Cassandra 1.2.10.  N=5, RF=3
> On this Column Family (ProductGenomeDev/Node), it's been major compacted into a single,
large sstable.
> There's no activity on the table at the time of the ALTER command. I changed it to Leveled
Compaction with the command below.
> cqlsh:ProductGenomeDev> alter table "Node" with compaction = { 'class' : 'LeveledCompactionStrategy',
'sstable_size_in_mb' : 160 };
> Log entries confirm the change happened.
> [...]column_metadata={},compactionStrategyClass=class org.apache.cassandra.db.compaction.LeveledCompactionStrategy,compactionStrategyOptions={sstable_size_in_mb=160}
[...]
> nodetool compactionstats shows pending compactions, but there's no activity:
> pending tasks: 750
> 12 hours later, nothing has still happened, same number pending. The expectation would
be that compactions would proceed immediately to convert everything to Leveled Compaction
as soon as the ALTER TABLE command goes.
> I try a simple write into the CF, and then flush the nodes. This kicks off compaction
on 3 nodes. (RF=3)
> cqlsh:ProductGenomeDev> insert into "Node" (key, column1, value) values ('test123',
'test123', 'test123');
> cqlsh:ProductGenomeDev> select * from "Node" where key = 'test123';
>  key     | column1 | value
> ---------+---------+---------
>  test123 | test123 | test123
> cqlsh:ProductGenomeDev> delete from "Node" where key = 'test123';
> After a flush on every node, now I see:
> [cassandra@dev-cass00 ~]$ cas exec nt compactionstats
> *** dev-cass00 (0) ***
> pending tasks: 750
> Active compaction remaining time :        n/a
> *** dev-cass04 (0) ***
> pending tasks: 752
>           compaction type        keyspace   column family       completed           total
     unit  progress
>                CompactionProductGenomeDev            Node      3413333881    643290447928
    bytes     0.53%
> Active compaction remaining time :        n/a
> *** dev-cass01 (0) ***
> pending tasks: 750
> Active compaction remaining time :        n/a
> *** dev-cass02 (0) ***
> pending tasks: 751
>           compaction type        keyspace   column family       completed           total
     unit  progress
>                CompactionProductGenomeDev            Node      3374975141    642764512481
    bytes     0.53%
> Active compaction remaining time :        n/a
> *** dev-cass03 (0) ***
> pending tasks: 751
>           compaction type        keyspace   column family       completed           total
     unit  progress
>                CompactionProductGenomeDev            Node      3591320948    643017643573
    bytes     0.56%
> Active compaction remaining time :        n/a
> After inserting and deleting more columns, enough that all nodes have new data, and flushing,
now compactions are proceeding on all nodes.



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