From 705b172b95db345a99adf088fca83c67bd13a691 Mon Sep 17 00:00:00 2001 From: Ayush Saxena Date: Fri, 6 Dec 2019 23:04:09 +0530 Subject: [PATCH] HDFS-14998. [SBN read] Update Observer Namenode doc for ZKFC after HDFS-14130. Contributed by Fei Hui. --- .../src/site/markdown/ObserverNameNode.md | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) 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 16cb2be6a73..00aeb5bd2e0 100644 --- a/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/ObserverNameNode.md +++ b/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/ObserverNameNode.md @@ -224,10 +224,10 @@ Observer NameNode, which transition it to the standby state. **NOTE**: the feature for Observer NameNode to participate in failover is not implemented yet. Therefore, as described in the next section, you -should only use **transitionToObserver** to bring up an observer and put -it outside the ZooKeeper controlled failover group. You should not use -**transitionToStandby** since the host for the Observer NameNode cannot -have ZKFC running. +should only use **transitionToObserver** to bring up an observer. ZKFC +could be turned on the Observer NameNode, but it doesn't do anything when +the NameNode is in Observer state. ZKFC will participate in the election of +Active after the NameNode is transitioned to standby state. ### Deployment details @@ -240,9 +240,11 @@ on the intensity of read requests and HA requirements. Note that currently Observer NameNode doesn't integrate fully when automatic failover is enabled. If the -**dfs.ha.automatic-failover.enabled** is turned on, you'll also need to -disable ZKFC on the namenode for observer. In addition to that, you'll -also need to add **forcemanual** flag to the **transitionToObserver** +**dfs.ha.automatic-failover.enabled** is turned on, the only benefit for +running ZKFC on Observer NameNode is that it will automatically join election +of Active after you transition the NameNode to Standby. If this is not desired, +you can disable ZKFC on the Observer NameNode. In addition to that, you'll also +need to add **forcemanual** flag to the **transitionToObserver** command: haadmin -transitionToObserver -forcemanual