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https://issues.apache.org/jira/browse/CASSANDRA-1610?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13046177#comment-13046177
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Jonathan Ellis commented on CASSANDRA-1610:
-------------------------------------------
- I think Ben's selection of methods for the CompactionStrategy is an
improvement, but I do like having an abstract class so it's obvious what the
contract is for us vs having to inject parameters post-construction.
- I'd like to move away from minor/major terms as too tied to the old
compaction internals. Perhaps background/maximal instead?
- We should also make user defined compactions part of ACS -- for some
strategies (e.g. leveldb) we want to be able to reject user requests that would
break strategy invariants. Note that this should probably return a single
Task, rather than a list. ("Maximal" will also usually return a single task,
but it's cleaner to represent "nothing to do" as an empty list, than as null.)
- handleInsufficientSpaceForCompaction is a bad encapsulation; it means both it
and its caller have to deal with "find a place for an sstable." suggest
leaving it up to CT.execute to deal with.
Here's what I think ACS should end up looking like with these changes:
{code}
/**
* Puggable compaction strategy determines how SSTables get merged.
*
* There are two main goals:
* - perform background compaction constantly as needed; this typically makes
a tradeoff between
* i/o done by compaction, and merging done at read time.
* - perform a full (maximum possible) compaction if requested by the user
*/
public abstract class AbstractCompactionStrategy
{
protected final ColumnFamilyStore cfs;
protected final Map<String, String> options;
protected AbstractCompactionStrategy(ColumnFamilyStore cfs, Map<String,
String> options)
{
this.cfs = cfs;
this.options = options;
}
/**
* @return a list of compaction tasks that should run in the background to
get the sstable
* count down to desired parameters.
* @param gcBefore throw away tombstones older than this
*/
public abstract List<AbstractCompactionTask> getBackgroundTasks(final int
gcBefore);
/**
* @return the number of background tasks estimated to still be needed for
this columnfamilystore
*/
public abstract int getEstimatedRemainingTasks();
/**
* @return a list of compaction tasks that should be run to compact this
columnfamilystore
* as much as possible.
* @param gcBefore throw away tombstones older than this
*/
public abstract List<AbstractCompactionTask> getMaximalTasks(final int
gcBefore);
/**
* @return a compaction task corresponding to the requested sstables
* @param gcBefore throw away tombstones older than this
*/
public abstract AbstractCompactionTask
getUserDefinedTasks(List<SSTableReader> sstables, final int gcBefore);
}
{code}
- Finally, can you update to conform with
http://wiki.apache.org/cassandra/CodeStyle, especially the part about multiline
statements?
> Pluggable Compaction
> --------------------
>
> Key: CASSANDRA-1610
> URL: https://issues.apache.org/jira/browse/CASSANDRA-1610
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Chris Goffinet
> Assignee: Alan Liang
> Priority: Minor
> Labels: compaction
> Fix For: 1.0
>
> Attachments: 0001-move-compaction-code-into-own-package.patch,
> 0001-move-compaction-code-into-own-package.patch,
> 0001-move-compaction-code-into-own-package.patch,
> 0001-move-compaction-code-into-own-package.patch,
> 0001-move-compaction-code-into-own-package.patch,
> 0001-move-compaction-code-into-own-package.patch,
> 0001-pluggable-compaction.patch,
> 0002-Pluggable-Compaction-and-Expiration.patch,
> 0002-pluggable-compaction.patch, 0002-pluggable-compaction.patch,
> 0002-pluggable-compaction.patch, 0002-pluggable-compaction.patch,
> 0002-pluggable-compaction.patch, 0002-pluggable-compaction.patch,
> 0002-pluggable-compaction.patch
>
>
> In CASSANDRA-1608, I proposed some changes on how compaction works. I think
> it also makes sense to allow the ability to have pluggable compaction per CF.
> There could be many types of workloads where this makes sense. One example we
> had at Digg was to completely throw away certain SSTables after N days.
> This ticket addresses making compaction pluggable only.
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