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https://issues.apache.org/jira/browse/CASSANDRA-4781?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Yuki Morishita updated CASSANDRA-4781:
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Attachment: 4781-v2.txt
Sylvain, thanks for the feedback. v2 attached.
I changed use of percentile to mean. For estimated keys, I just kept mine since
estimatedKeysForRanges might return greater value than under estimated keys
count.
bq. But all this being said, and while we should definitively fix the things
above, they will only make the estimation better, but it still an estimation.
So at least in theory, we could always end up in a case where the estimate
thinks there is enough droppable tombstones, but in practice all the droppable
tombstones are in overlapping ranges.
You are right, we need safe stopper. I followed your advice of using sstable
creation time. But I made time threshold configurable via compaction strategy
option with default value of 5 minutes, since gcGraceSecond can be set to 0,
and makes testing easy.
Speaking of schema_* columnfamilies, can we lower minimum compaction threshold
to 2? schema_* have almost always overlapped key and tombstones, and less
likely to updated.
> Sometimes Cassandra starts compacting system-shema_columns cf repeatedly
> until the node is killed
> -------------------------------------------------------------------------------------------------
>
> Key: CASSANDRA-4781
> URL: https://issues.apache.org/jira/browse/CASSANDRA-4781
> Project: Cassandra
> Issue Type: Bug
> Affects Versions: 1.2.0 beta 1
> Environment: Ubuntu 12.04, single-node Cassandra cluster
> Reporter: Aleksey Yeschenko
> Assignee: Yuki Morishita
> Fix For: 1.2.0 beta 2
>
> Attachments: 4781.txt, 4781-v2.txt
>
>
> Cassandra starts flushing system-schema_columns cf in a seemingly infinite
> loop:
> INFO [CompactionExecutor:7] 2012-10-09 17:55:46,804 CompactionTask.java
> (line 239) Compacted to
> [/var/lib/cassandra/data/system/schema_columns/system-schema_columns-ia-32107-Data.db,].
> 3,827 to 3,827 (~100% of original) bytes for 3 keys at 0.202762MB/s. Time:
> 18ms.
> INFO [CompactionExecutor:7] 2012-10-09 17:55:46,804 CompactionTask.java
> (line 119) Compacting
> [SSTableReader(path='/var/lib/cassandra/data/system/schema_columns/system-schema_columns-ia-32107-Data.db')]
> INFO [CompactionExecutor:7] 2012-10-09 17:55:46,824 CompactionTask.java
> (line 239) Compacted to
> [/var/lib/cassandra/data/system/schema_columns/system-schema_columns-ia-32108-Data.db,].
> 3,827 to 3,827 (~100% of original) bytes for 3 keys at 0.182486MB/s. Time:
> 20ms.
> INFO [CompactionExecutor:7] 2012-10-09 17:55:46,825 CompactionTask.java
> (line 119) Compacting
> [SSTableReader(path='/var/lib/cassandra/data/system/schema_columns/system-schema_columns-ia-32108-Data.db')]
> INFO [CompactionExecutor:7] 2012-10-09 17:55:46,864 CompactionTask.java
> (line 239) Compacted to
> [/var/lib/cassandra/data/system/schema_columns/system-schema_columns-ia-32109-Data.db,].
> 3,827 to 3,827 (~100% of original) bytes for 3 keys at 0.096045MB/s. Time:
> 38ms.
> INFO [CompactionExecutor:7] 2012-10-09 17:55:46,864 CompactionTask.java
> (line 119) Compacting
> [SSTableReader(path='/var/lib/cassandra/data/system/schema_columns/system-schema_columns-ia-32109-Data.db')]
> INFO [CompactionExecutor:7] 2012-10-09 17:55:46,894 CompactionTask.java
> (line 239) Compacted to
> [/var/lib/cassandra/data/system/schema_columns/system-schema_columns-ia-32110-Data.db,].
> 3,827 to 3,827 (~100% of original) bytes for 3 keys at 0.121657MB/s. Time:
> 30ms.
> INFO [CompactionExecutor:7] 2012-10-09 17:55:46,894 CompactionTask.java
> (line 119) Compacting
> [SSTableReader(path='/var/lib/cassandra/data/system/schema_columns/system-schema_columns-ia-32110-Data.db')]
> INFO [CompactionExecutor:7] 2012-10-09 17:55:46,914 CompactionTask.java
> (line 239) Compacted to
> [/var/lib/cassandra/data/system/schema_columns/system-schema_columns-ia-32111-Data.db,].
> 3,827 to 3,827 (~100% of original) bytes for 3 keys at 0.202762MB/s. Time:
> 18ms.
> INFO [CompactionExecutor:7] 2012-10-09 17:55:46,914 CompactionTask.java
> (line 119) Compacting
> [SSTableReader(path='/var/lib/cassandra/data/system/schema_columns/system-schema_columns-ia-32111-Data.db')]
> .........
> Don't know what's causing it. Don't know a way to predictably trigger this
> behaviour. It just happens sometimes.
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