[ https://issues.apache.org/jira/browse/HDFS-528?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
dhruba borthakur updated HDFS-528: ---------------------------------- Status: Open (was: Patch Available) It appears that this functionality can be achieved by some code outside the namenode. 1. start the NN with a dfs.safemode.threshold.pct 1.5 i.e. NN will never exit safemode by itself. 2. write a script that periodically invokes "bin/hadoop dfsadmin -report" and counts the number of datanodes that have checked in with the NN. 3. The script can explicitly exit safemode whenever it desires. This approach allows different policies of when-to-exit-safemode be implemented outside the NN. If you agree, then we can make this JIRA expose a new API from the NN that exposes the safeBlockCount and totalBlockCount from the NN. > Add ability for safemode to wait for a minimum number of live datanodes > ----------------------------------------------------------------------- > > Key: HDFS-528 > URL: https://issues.apache.org/jira/browse/HDFS-528 > Project: Hadoop HDFS > Issue Type: New Feature > Components: scripts > Affects Versions: 0.22.0 > Reporter: Todd Lipcon > Assignee: Todd Lipcon > Attachments: hdfs-528-v2.txt, hdfs-528-v3.txt, hdfs-528.txt, > hdfs-528.txt > > > When starting up a fresh cluster programatically, users often want to wait > until DFS is "writable" before continuing in a script. "dfsadmin -safemode > wait" doesn't quite work for this on a completely fresh cluster, since when > there are 0 blocks on the system, 100% of them are accounted for before any > DNs have reported. > This JIRA is to add a command which waits until a certain number of DNs have > reported as alive to the NN. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.