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From bus...@apache.org
Subject hbase git commit: HBASE-15985 clarify promises about edits from replication in ref guide
Date Tue, 05 Jul 2016 18:04:22 GMT
Repository: hbase
Updated Branches:
  refs/heads/master d016338e4 -> 29c46c483

HBASE-15985 clarify promises about edits from replication in ref guide

Signed-off-by: Andrew Purtell <apurtell@apache.org>

Project: http://git-wip-us.apache.org/repos/asf/hbase/repo
Commit: http://git-wip-us.apache.org/repos/asf/hbase/commit/29c46c48
Tree: http://git-wip-us.apache.org/repos/asf/hbase/tree/29c46c48
Diff: http://git-wip-us.apache.org/repos/asf/hbase/diff/29c46c48

Branch: refs/heads/master
Commit: 29c46c4834a3f96e9fca33cb16bc7f3748fcd60c
Parents: d016338
Author: Sean Busbey <busbey@apache.org>
Authored: Tue Jun 7 17:16:55 2016 -0500
Committer: Sean Busbey <busbey@apache.org>
Committed: Tue Jul 5 13:03:18 2016 -0500

 src/main/asciidoc/_chapters/ops_mgt.adoc | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/main/asciidoc/_chapters/ops_mgt.adoc b/src/main/asciidoc/_chapters/ops_mgt.adoc
index 13449c1..6e84237 100644
--- a/src/main/asciidoc/_chapters/ops_mgt.adoc
+++ b/src/main/asciidoc/_chapters/ops_mgt.adoc
@@ -1320,6 +1320,14 @@ The master cluster relies on randomization to attempt to balance the
stream of r
 It is expected that the slave cluster has storage capacity to hold the replicated data, as
well as any data it is responsible for ingesting.
 If a slave cluster does run out of room, or is inaccessible for other reasons, it throws
an error and the master retains the WAL and retries the replication at intervals.
+.Consistency Across Replicated Clusters
+How your application builds on top of the HBase API matters when replication is in play.
HBase's replication system provides at-least-once delivery of client edits for an enabled
column family to each configured destination cluster. In the event of failure to reach a given
destination, the replication system will retry sending edits in a way that might repeat a
given message. Further more, there is not a guaranteed order of delivery for client edits.
In the event of a RegionServer failing, recovery of the replication queue happens independent
of recovery of the individual regions that server was previously handling. This means that
it is possible for the not-yet-replicated edits to be serviced by a RegionServer that is currently
slower to replicate than the one that handles edits from after the failure.
+The combination of these two properties (at-least-once delivery and the lack of message ordering)
means that some destination clusters may end up in a different state if your application makes
use of operations that are not idempotent, e.g. Increments.
 .Terminology Changes

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