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From "Davide (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-8140) Compaction has no effects
Date Mon, 20 Oct 2014 18:15:34 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-8140?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14177231#comment-14177231
] 

Davide commented on CASSANDRA-8140:
-----------------------------------

Check here: https://gist.github.com/DAddYE/158f6b98253331dc2845
Unfortunately we had to reduce the verbosity due to very large logs.

I hope it helps

> Compaction has no effects
> -------------------------
>
>                 Key: CASSANDRA-8140
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8140
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>            Reporter: Davide
>            Assignee: Marcus Eriksson
>
> Hi there,
> I'm on cassandra 2.1 since then I figured out that in some circumstances (I can't find
a way to reproduce them constantly) minor compactions and full compactions had no effects.
> We are on a cluster composed of 5 nodes with around 500gb of data, no deletions around
1.5k updates/s and same on reads.
> After a repair I saw that a couple of nodes were `slow`, I investigate further and I
found that on these two nodes the number of sstable were around 20.000+ ! We use STC.
> So with node tool I triggered a full compaction, It took less than I minute (with nothing
in the logs) and of course the number of sstable didn't go down.
> Then I drained the node, and I ran again with `nodetool compact`, at that point the number
of sstables went down to less than 10.
> I tough was a strange spot problem. However after a week I noticed that one node had
~100 sstabels where others just 8-10.
> I ran again the compaction (It last less than a minute with nothing in logs) and didn't
change anything. I drained it and restarted then compacted and took several hours to get it
back close to 2/3 sstables.
> What could be? We never incurred this behavior before.
> Here informations about the table:
> {code}
> CREATE TABLE xyz (
>     ppk text PRIMARY KEY,
>    .. ten more columns...
> ) WITH bloom_filter_fp_chance = 0.01
>     AND caching = '{"keys":"ALL", "rows_per_partition":"NONE"}'
>     AND comment = ''
>     AND compaction = {'min_threshold': '4', 'cold_reads_to_omit': '0.0', 'class': 'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy',
'max_threshold': '32'}
>     AND compression = {'sstable_compression': 'org.apache.cassandra.io.compress.SnappyCompressor'}
>     AND dclocal_read_repair_chance = 0.0
>     AND default_time_to_live = 0
>     AND gc_grace_seconds = 864000
>     AND max_index_interval = 2048
>     AND memtable_flush_period_in_ms = 0
>     AND min_index_interval = 128
>     AND read_repair_chance = 0.0
>     AND speculative_retry = '99.0PERCENTILE';
> {code}
> Here the current cf stats:
> {code}
> 		SSTable count: 11
> 		Space used (live), bytes: 118007220865
> 		Space used (total), bytes: 118007220865
> 		Space used by snapshots (total), bytes: 170591332257
> 		SSTable Compression Ratio: 0.3643916626015517
> 		Memtable cell count: 920306
> 		Memtable data size, bytes: 70034097
> 		Memtable switch count: 25
> 		Local read count: 5358772
> 		Local read latency: 54.621 ms
> 		Local write count: 4715106
> 		Local write latency: 0.069 ms
> 		Pending flushes: 0
> 		Bloom filter false positives: 53757
> 		Bloom filter false ratio: 0.04103
> 		Bloom filter space used, bytes: 220634056
> 		Compacted partition minimum bytes: 18
> 		Compacted partition maximum bytes: 61214
> 		Compacted partition mean bytes: 1935
> 		Average live cells per slice (last five minutes): 0.8139232271871242
> 		Average tombstones per slice (last five minutes): 0.5493417148555677
> {code}
> Is there anything else that I can provide?
> Thanks!
> DD



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