[jira] [Commented] (CASSANDRA-6092) Leveled Compaction after ALTER TABLE creates pending but does not actually begin

["Tomas Salfischberger (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-6092?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13791974#comment-13791974 ] 

Tomas Salfischberger commented on CASSANDRA-6092:
-------------------------------------------------

I have accidentally reproduced this on a test-cluster, N=3 and RF=3 with 1.2.10. The CF I was testing with started out as LCS with sstable_size of 5mb (original default in 1.0) which created 30.000+ files. I switched it to SizeTieredCompactionStrategy, which made it compact everything to a single sstable.

My initial goal was to use sstablesplit on this, but then I realized I could just try to switch back to LCS and see what it would do. This exhibited exactly the behavior described in this issue. It created a set of pending tasks and never tried to execute them.

Then I ran "nodetool compact" on the CF and that started the compaction process (visible in both the logs and nodetool compactionstats). After a few hours the compact-command returned, all pending tasks were cleared and the sstables were nicely split in the configured sizes. Checking the json metadata for LCS shows the files all ended up in L1.

So to summarize: 1. I've reprocuded the issue and 2. running "nodetool compact" seems a good workaround.

> 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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