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From cli...@apache.org
Subject [hadoop] 43/50: HDFS-14154. [SBN read] Document dfs.ha.tail-edits.period in user guide. Contributed by Chao Sun.
Date Fri, 28 Jun 2019 23:06:46 GMT
This is an automated email from the ASF dual-hosted git repository.

cliang pushed a commit to branch branch-3.2
in repository https://gitbox.apache.org/repos/asf/hadoop.git

commit 720eed9ef9e230c026e3389d1bc188036e88be7e
Author: Chao Sun <sunchao@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 76a9837..4f3df27 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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