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https://issues.apache.org/jira/browse/CASSANDRA-13418?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16144901#comment-16144901
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Romain GERARD edited comment on CASSANDRA-13418 at 8/29/17 8:15 AM:
--------------------------------------------------------------------
bq. 2. only enabling unsafe_aggressive_sstable_expiration
When looking for sstables expired, you will *ignore* the overlaps and only look
locally if the current sstable is eligible.
When looking for sstables to compact, you will *not ignore* the overlaps and
look globally if the current sstable is eligible.
In this case, you will most likely not trigger any compaction to purge
tombstone if you run into an overlaps.
bq. 1. enabling both
When looking for sstables expired, you will *ignore* the overlaps and only look
locally if the current sstable is eligible.
When looking for sstables to compact, you will *ignore* the overlaps and look
locally if the current sstable is eligible.
In this case, you will always trigger compaction to purge tombstone even if you
run into an overlaps.
-----
I made a new version of the patch with uncheckedTombstoneCompaction disabled
and a warning message.
https://github.com/criteo-forks/cassandra/commit/1800b23ddfbb308645c44022e15c1760a0124025
the diff
{noformat}
diff --git
a/src/java/org/apache/cassandra/db/compaction/TimeWindowCompactionStrategy.java
b/src/java/org/apache/cassandra/db/compaction/TimeWindowCompactionStrategy.java
index 43c90c7042..d21222c484 100644
---
a/src/java/org/apache/cassandra/db/compaction/TimeWindowCompactionStrategy.java
+++
b/src/java/org/apache/cassandra/db/compaction/TimeWindowCompactionStrategy.java
@@ -67,9 +67,9 @@ public class TimeWindowCompactionStrategy extends
AbstractCompactionStrategy
else
logger.debug("Enabling tombstone compactions for TWCS");
- if (this.options.ignoreOverlaps)
- this.uncheckedTombstoneCompaction = true;
-
+ if(this.options.ignoreOverlaps && !this.uncheckedTombstoneCompaction) {
+ logger.warn("You are running with sstables overlapping checks
disabled but without unchecked tombstone compaction, check that this is what
you want");
+ }
}
{noformat}
was (Author: rgerard):
bq. 2. only enabling unsafe_aggressive_sstable_expiration
When looking for sstables expired, you will *ignore* the overlaps and only look
locally if the current sstable is eligible.
When looking for sstables to compact, you will *not ignore* the overlaps and
look globally if the current sstable is eligible.
bq. 1. enabling both
When looking for sstables expired, you will *ignore* the overlaps and only look
locally if the current sstable is eligible.
When looking for sstables to compact, you will *ignore* the overlaps and look
locally if the current sstable is eligible.
-----
I made a new version of the patch with uncheckedTombstoneCompaction disabled
and a warning message.
https://github.com/criteo-forks/cassandra/commit/1800b23ddfbb308645c44022e15c1760a0124025
the diff
{noformat}
diff --git
a/src/java/org/apache/cassandra/db/compaction/TimeWindowCompactionStrategy.java
b/src/java/org/apache/cassandra/db/compaction/TimeWindowCompactionStrategy.java
index 43c90c7042..d21222c484 100644
---
a/src/java/org/apache/cassandra/db/compaction/TimeWindowCompactionStrategy.java
+++
b/src/java/org/apache/cassandra/db/compaction/TimeWindowCompactionStrategy.java
@@ -67,9 +67,9 @@ public class TimeWindowCompactionStrategy extends
AbstractCompactionStrategy
else
logger.debug("Enabling tombstone compactions for TWCS");
- if (this.options.ignoreOverlaps)
- this.uncheckedTombstoneCompaction = true;
-
+ if(this.options.ignoreOverlaps && !this.uncheckedTombstoneCompaction) {
+ logger.warn("You are running with sstables overlapping checks
disabled but without unchecked tombstone compaction, check that this is what
you want");
+ }
}
{noformat}
> Allow TWCS to ignore overlaps when dropping fully expired sstables
> ------------------------------------------------------------------
>
> Key: CASSANDRA-13418
> URL: https://issues.apache.org/jira/browse/CASSANDRA-13418
> Project: Cassandra
> Issue Type: Improvement
> Components: Compaction
> Reporter: Corentin Chary
> Labels: twcs
> Attachments: twcs-cleanup.png
>
>
> http://thelastpickle.com/blog/2016/12/08/TWCS-part1.html explains it well. If
> you really want read-repairs you're going to have sstables blocking the
> expiration of other fully expired SSTables because they overlap.
> You can set unchecked_tombstone_compaction = true or tombstone_threshold to a
> very low value and that will purge the blockers of old data that should
> already have expired, thus removing the overlaps and allowing the other
> SSTables to expire.
> The thing is that this is rather CPU intensive and not optimal. If you have
> time series, you might not care if all your data doesn't exactly expire at
> the right time, or if data re-appears for some time, as long as it gets
> deleted as soon as it can. And in this situation I believe it would be really
> beneficial to allow users to simply ignore overlapping SSTables when looking
> for fully expired ones.
> To the question: why would you need read-repairs ?
> - Full repairs basically take longer than the TTL of the data on my dataset,
> so this isn't really effective.
> - Even with a 10% chances of doing a repair, we found out that this would be
> enough to greatly reduce entropy of the most used data (and if you have
> timeseries, you're likely to have a dashboard doing the same important
> queries over and over again).
> - LOCAL_QUORUM is too expensive (need >3 replicas), QUORUM is too slow.
> I'll try to come up with a patch demonstrating how this would work, try it on
> our system and report the effects.
> cc: [~adejanovski], [~rgerard] as I know you worked on similar issues already.
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