From 3915d1afc7c2189b788f0e773949895d1ab0780b Mon Sep 17 00:00:00 2001
From: Ayush Saxena <ayushsaxena@apache.org>
Date: Sat, 16 May 2020 16:35:06 +0530
Subject: [PATCH] HDFS-15356. Unify configuration `dfs.ha.allow.stale.reads` to
 DFSConfigKeys. Contributed by Xiaoqiao He.

(cherry picked from commit 178336f8a8bb291eb355bede729082f2f0382216)
---
 .../main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java  | 3 +++
 .../src/main/java/org/apache/hadoop/hdfs/HAUtil.java     | 7 +++++--
 .../hadoop-hdfs/src/main/resources/hdfs-default.xml      | 9 +++++++++
 3 files changed, 17 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 2e2b7db1d0..e4a710f24f 100755
--- 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
@@ -1168,6 +1168,9 @@ public class DFSConfigKeys extends CommonConfigurationKeys {
       "dfs.ha.nn.not-become-active-in-safemode";
   public static final boolean DFS_HA_NN_NOT_BECOME_ACTIVE_IN_SAFEMODE_DEFAULT =
       false;
+  public static final String DFS_HA_ALLOW_STALE_READ_KEY =
+      "dfs.ha.allow.stale.reads";
+  public static final boolean DFS_HA_ALLOW_STALE_READ_DEFAULT = false;
 
   // Security-related configs
   public static final String DFS_ENCRYPT_DATA_TRANSFER_KEY = "dfs.encrypt.data.transfer";
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/HAUtil.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/HAUtil.java
index aebc28aa79..43e76c79e2 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/HAUtil.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/HAUtil.java
@@ -17,6 +17,8 @@
  */
 package org.apache.hadoop.hdfs;
 
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_HA_ALLOW_STALE_READ_DEFAULT;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_HA_ALLOW_STALE_READ_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_HA_NAMENODE_ID_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_HTTPS_ADDRESS_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_HTTPS_BIND_HOST_KEY;
@@ -220,11 +222,12 @@ public class HAUtil {
    * @return true if the NN should allow read operations while in standby mode.
    */
   public static boolean shouldAllowStandbyReads(Configuration conf) {
-    return conf.getBoolean("dfs.ha.allow.stale.reads", false);
+    return conf.getBoolean(DFS_HA_ALLOW_STALE_READ_KEY,
+        DFS_HA_ALLOW_STALE_READ_DEFAULT);
   }
   
   public static void setAllowStandbyReads(Configuration conf, boolean val) {
-    conf.setBoolean("dfs.ha.allow.stale.reads", val);
+    conf.setBoolean(DFS_HA_ALLOW_STALE_READ_KEY, val);
   }
 
   /**
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 7c42e0d879..9c31c1814d 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
@@ -4622,6 +4622,15 @@
   </description>
 </property>
 
+<property>
+  <name>dfs.ha.allow.stale.reads</name>
+  <value>false</value>
+  <description>
+    If true, a NameNode in Standby state can process read request and the result
+    could be stale.
+  </description>
+</property>
+
 <property>
   <name>dfs.journalnode.edits.dir</name>
   <value>/tmp/hadoop/dfs/journalnode/</value>