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https://issues.apache.org/jira/browse/HBASE-14468?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14940214#comment-14940214
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Vladimir Rodionov commented on HBASE-14468:
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[~tedyu]
{quote}
think support for purging expired files is already in code base.
If TTL is short, user can achieve FIFO compaction by adjusting existing
compaction parameters.
{quote}
Yes, it looks like we can achieve FIFO behavior by using existing
ExlporingCompactionPolicy. We have to set CF TTL, disable periodic major
compactions and set minimum files to compact to very large value. But even if
it works, I would prefer to use separate policy - it is self explaining, at
least.
> Compaction improvements: FIFO compaction policy
> -----------------------------------------------
>
> Key: HBASE-14468
> URL: https://issues.apache.org/jira/browse/HBASE-14468
> Project: HBase
> Issue Type: Improvement
> Reporter: Vladimir Rodionov
> Assignee: Vladimir Rodionov
> Fix For: 2.0.0
>
> Attachments: HBASE-14468-v1.patch, HBASE-14468-v2.patch,
> HBASE-14468-v3.patch, HBASE-14468-v4.patch
>
>
> h2. FIFO Compaction
> h3. Introduction
> FIFO compaction policy selects only files which have all cells expired. The
> column family MUST have non-default TTL.
> Essentially, FIFO compactor does only one job: collects expired store files.
> I see many applications for this policy:
> # use it for very high volume raw data which has low TTL and which is the
> source of another data (after additional processing). Example: Raw
> time-series vs. time-based rollup aggregates and compacted time-series. We
> collect raw time-series and store them into CF with FIFO compaction policy,
> periodically we run task which creates rollup aggregates and compacts
> time-series, the original raw data can be discarded after that.
> # use it for data which can be kept entirely in a a block cache (RAM/SSD).
> Say we have local SSD (1TB) which we can use as a block cache. No need for
> compaction of a raw data at all.
> Because we do not do any real compaction, we do not use CPU and IO (disk and
> network), we do not evict hot data from a block cache. The result: improved
> throughput and latency both write and read.
> See: https://github.com/facebook/rocksdb/wiki/FIFO-compaction-style
> h3. To enable FIFO compaction policy
> For table:
> {code}
> HTableDescriptor desc = new HTableDescriptor(tableName);
>
> desc.setConfiguration(DefaultStoreEngine.DEFAULT_COMPACTION_POLICY_CLASS_KEY,
> FIFOCompactionPolicy.class.getName());
> {code}
> For CF:
> {code}
> HColumnDescriptor desc = new HColumnDescriptor(family);
>
> desc.setConfiguration(DefaultStoreEngine.DEFAULT_COMPACTION_POLICY_CLASS_KEY,
> FIFOCompactionPolicy.class.getName());
> {code}
> h3. Limitations
> Do not use FIFO compaction if :
> * Table/CF has MIN_VERSION > 0
> * Table/CF has TTL = FOREVER (HColumnDescriptor.DEFAULT_TTL)
> * Table/CF is MOB
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