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Posted to commits@hbase.apache.org by ch...@apache.org on 2017/12/19 15:39:26 UTC
hbase git commit: HBASE-18504 Add documentation for WAL compression
Repository: hbase
Updated Branches:
refs/heads/branch-2 6a3af2e52 -> 35296e590
HBASE-18504 Add documentation for WAL compression
Signed-off-by: Michael Stack <st...@apache.org>
Signed-off-by: Chia-Ping Tsai <ch...@gmail.com>
Project: http://git-wip-us.apache.org/repos/asf/hbase/repo
Commit: http://git-wip-us.apache.org/repos/asf/hbase/commit/35296e59
Tree: http://git-wip-us.apache.org/repos/asf/hbase/tree/35296e59
Diff: http://git-wip-us.apache.org/repos/asf/hbase/diff/35296e59
Branch: refs/heads/branch-2
Commit: 35296e5902f324afd2cf8075a5ae5a1cf8eea9bb
Parents: 6a3af2e
Author: Peter Somogyi <ps...@cloudera.com>
Authored: Wed Aug 2 17:00:52 2017 +0200
Committer: Chia-Ping Tsai <ch...@gmail.com>
Committed: Tue Dec 19 23:39:13 2017 +0800
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src/main/asciidoc/_chapters/architecture.adoc | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
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http://git-wip-us.apache.org/repos/asf/hbase/blob/35296e59/src/main/asciidoc/_chapters/architecture.adoc
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diff --git a/src/main/asciidoc/_chapters/architecture.adoc b/src/main/asciidoc/_chapters/architecture.adoc
index 9a3cbd9..1c9671d 100644
--- a/src/main/asciidoc/_chapters/architecture.adoc
+++ b/src/main/asciidoc/_chapters/architecture.adoc
@@ -1184,6 +1184,22 @@ A possible downside to WAL compression is that we lose more data from the last b
mid-write. If entries in this last block were added with new dictionary entries but we failed persist the amended
dictionary because of an abrupt termination, a read of this last block may not be able to resolve last-written entries.
+[[wal.compression]]
+==== WAL Compression ====
+
+The content of the WAL can be compressed using LRU Dictionary compression.
+This can be used to speed up WAL replication to different datanodes.
+The dictionary can store up to 2^15^ elements; eviction starts after this number is exceeded.
+
+To enable WAL compression, set the `hbase.regionserver.wal.enablecompression` property to `true`.
+The default value for this property is `false`.
+By default, WAL tag compression is turned on when WAL compression is enabled.
+You can turn off WAL tag compression by setting the `hbase.regionserver.wal.tags.enablecompression` property to 'false'.
+
+A possible downside to WAL compression is that we lose more data from the last block in the WAL if it ill-terminated
+mid-write. If entries in this last block were added with new dictionary entries but we failed persist the amended
+dictionary because of an abrupt termination, a read of this last block may not be able to resolve last-written entries.
+
[[wal.disable]]
==== Disabling the WAL