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commit 9c1c73a0d572d58cdde5aeaa552229309edc8d8c
Author: Chao Sun <sunc...@apache.org>
AuthorDate: Wed Dec 19 22:20:31 2018 -0800
HDFS-14154. [SBN read] Document dfs.ha.tail-edits.period in user guide.
Contributed by Chao Sun.
---
.../src/site/markdown/HDFSHighAvailabilityWithQJM.md | 7 ++++++-
.../hadoop-hdfs/src/site/markdown/ObserverNameNode.md | 18 ++++++++++++++++--
2 files changed, 22 insertions(+), 3 deletions(-)
diff --git
a/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HDFSHighAvailabilityWithQJM.md
b/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HDFSHighAvailabilityWithQJM.md
index 3b5157f..9557018 100644
---
a/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HDFSHighAvailabilityWithQJM.md
+++
b/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HDFSHighAvailabilityWithQJM.md
@@ -27,7 +27,12 @@ This document assumes that the reader has a general
understanding of general com
Note: Using the Quorum Journal Manager or Conventional Shared Storage
---------------------------------------------------------------------
-This guide discusses how to configure and use HDFS HA using the Quorum Journal
Manager (QJM) to share edit logs between the Active and Standby NameNodes. For
information on how to configure HDFS HA using NFS for shared storage instead of
the QJM, please see [this alternative
guide.](./HDFSHighAvailabilityWithNFS.html)
+This guide discusses how to configure and use HDFS HA using the Quorum
+Journal Manager (QJM) to share edit logs between the Active and Standby
+NameNodes. For information on how to configure HDFS HA using NFS for
+shared storage instead of the QJM, please see [this alternative
+guide.](./HDFSHighAvailabilityWithNFS.html). For information on how to
+configure HDFS HA with Observer NameNode, please see [this
guide](./ObserverNameNode.html)
Background
----------
diff --git
a/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/ObserverNameNode.md
b/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/ObserverNameNode.md
index 2548315..d93256c 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/ObserverNameNode.md
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/ObserverNameNode.md
@@ -23,13 +23,13 @@ Purpose
This guide provides an overview of the HDFS Observer NameNode feature
and how to configure/install it in a typical HA-enabled cluster. For a
detailed technical design overview, please check the doc attached to
-HDFS-12943.
+[HDFS-12943](https://issues.apache.org/jira/browse/HDFS-12943).
Background
-----------
In a HA-enabled HDFS cluster (for more information, check
-[HDFSHighAvailabilityWithQJM](./HDFSHighAvailabilityWithQJM.md)), there
+[HDFSHighAvailabilityWithQJM](./HDFSHighAvailabilityWithQJM.html)), there
is a single Active NameNode and one or more Standby NameNode(s). The
Active NameNode is responsible for serving all client requests, while
Standby NameNode just keep the up-to-date information regarding the
@@ -104,6 +104,20 @@ few configurations to your **hdfs-site.xml**:
<value>true</value>
</property>
+* **dfs.ha.tail-edits.period** - how often Standby/Observer NameNodes
+ should fetch edits from JournalNodes.
+
+ This determines the staleness of Observer NameNode w.r.t the Active.
+ If too large, RPC time will increase as client requests will wait
+ longer in the RPC queue before Observer tails edit logs and catches
+ up the latest state of Active. The default value is 1min. It is
+ **highly recommend** to configure this to a much lower value.
+
+ <property>
+ <name>dfs.ha.tail-edits.period</name>
+ <value>0ms</value>
+ </property>
+
* **dfs.journalnode.edit-cache-size.bytes** - the in-memory cache size,
in bytes, on the JournalNodes.
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