From 06ad6540b3cdb8fb957f900aaebc9d1d289fabaf Mon Sep 17 00:00:00 2001
From: Stephen O'Donnell <sodonnell@cloudera.com>
Date: Fri, 13 Sep 2019 10:35:10 -0700
Subject: [PATCH] HDFS-14821. Make HDFS-14617 (fsimage sub-sections) off by
 default. Contributed by Stephen O'Donnell.

Signed-off-by: Wei-Chiu Chuang <weichiu@apache.org>
---
 .../main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java    | 2 +-
 .../hadoop-hdfs/src/main/resources/hdfs-default.xml        | 7 ++++++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java
index 6f76dc03f96..4b2058bbcf5 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java
@@ -899,7 +899,7 @@ public class DFSConfigKeys extends CommonConfigurationKeys {
 
   public static final String DFS_IMAGE_PARALLEL_LOAD_KEY =
       "dfs.image.parallel.load";
-  public static final boolean DFS_IMAGE_PARALLEL_LOAD_DEFAULT = true;
+  public static final boolean DFS_IMAGE_PARALLEL_LOAD_DEFAULT = false;
 
   public static final String DFS_IMAGE_PARALLEL_TARGET_SECTIONS_KEY =
       "dfs.image.parallel.target.sections";
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml b/hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml
index 69017dfa77f..d2ca0af59eb 100755
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml
@@ -1393,7 +1393,7 @@
 
 <property>
   <name>dfs.image.parallel.load</name>
-  <value>true</value>
+  <value>false</value>
   <description>
         If true, write sub-section entries to the fsimage index so it can
         be loaded in parallel. Also controls whether parallel loading
@@ -1403,6 +1403,11 @@
         Parallel loading is not compatible with image compression,
         so if dfs.image.compress is set to true this setting will be
         ignored and no parallel loading will occur.
+        Enabling this feature may impact rolling upgrades and downgrades if
+        the previous version does not support this feature. If the feature was
+        enabled and a downgrade is required, first set this parameter to
+        false and then save the namespace to create a fsimage with no
+        sub-sections and then perform the downgrade.
   </description>
 </property>