[ https://issues.apache.org/jira/browse/HDFS-7714?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14313590#comment-14313590 ]
Vinayakumar B commented on HDFS-7714: ------------------------------------- Thanks [~cnauroth] for the review. Committed to trunk and branch-2 > Simultaneous restart of HA NameNodes and DataNode can cause DataNode to > register successfully with only one NameNode. > --------------------------------------------------------------------------------------------------------------------- > > Key: HDFS-7714 > URL: https://issues.apache.org/jira/browse/HDFS-7714 > Project: Hadoop HDFS > Issue Type: Bug > Components: datanode > Affects Versions: 2.6.0 > Reporter: Chris Nauroth > Assignee: Vinayakumar B > Fix For: 2.7.0 > > Attachments: HDFS-7714-001.patch, HDFS-7714-002.patch > > > In an HA deployment, DataNodes must register with both NameNodes and send > periodic heartbeats and block reports to both. However, if NameNodes and > DataNodes are restarted simultaneously, then this can trigger a race > condition in registration. The end result is that the {{BPServiceActor}} for > one NameNode terminates, but the {{BPServiceActor}} for the other NameNode > remains alive. The DataNode process is then in a "half-alive" state where it > only heartbeats and sends block reports to one of the NameNodes. This could > cause a loss of storage capacity after an HA failover. The DataNode process > would have to be restarted to resolve this. -- This message was sent by Atlassian JIRA (v6.3.4#6332)