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https://issues.apache.org/jira/browse/HDFS-528?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Todd Lipcon updated HDFS-528:
-----------------------------
Attachment: hdfs-528.txt
This patch implements dfsadmin -waitDatanodes.
For testing, I augmented TestHDFSCLI and also ran through the following on the
command line:
{noformat}
$ ./bin/hdfs dfsadmin -help waitDatanodes
-waitDatanodes [timeout] [numNodes]: Wait for datanodes to report.
Waits for the specified number of Datanodes to report as alive
to the
Namenode. A timeout can be specified in seconds - if the
specified
number of nodes do not report within the timeout, returns a
non-zero
exit code. If the number of nodes is not specified, defaults to
the
value of dfs.replication.min. If the timeout is not specified,
defaults
to 5 minutes.
$ ./bin/hdfs dfsadmin -waitDatanodes
SUCCESS: 1 datanodes have reported.
$ echo $?
0
$ ./bin/hdfs dfsadmin -waitDatanodes 5 10
Timed out waiting for 10 datanodes after 5 seconds
$ echo $?
1
{noformat}
One example use case for this tool is in the EC2 scripts - even though the
master has started up, the user needs to wait until at least a few DNs have
reported before he or she can start writing to the cluster.
> Add dfsadmin -waitDatanodes feature to block until DNs have reported
> --------------------------------------------------------------------
>
> Key: HDFS-528
> URL: https://issues.apache.org/jira/browse/HDFS-528
> Project: Hadoop HDFS
> Issue Type: New Feature
> Components: scripts
> Affects Versions: 0.21.0
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
> Attachments: 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.
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