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https://issues.apache.org/jira/browse/HADOOP-3628?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12624893#action_12624893
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Jim Kellerman commented on HADOOP-3628:
---------------------------------------
HBase uses the following to determine when Hadoop exits safe mode:
{code}
if (this.fs instanceof DistributedFileSystem) {
// Make sure dfs is not in safe mode
String message = "Waiting for dfs to exit safe mode...";
while (((DistributedFileSystem) fs).setSafeMode(
FSConstants.SafeModeAction.SAFEMODE_GET)) {
LOG.info(message);
try {
Thread.sleep(this.threadWakeFrequency);
} catch (InterruptedException e) {
//continue
}
}
}
{code}
> Add a lifecycle interface for Hadoop components: namenodes, job clients, etc.
> -----------------------------------------------------------------------------
>
> Key: HADOOP-3628
> URL: https://issues.apache.org/jira/browse/HADOOP-3628
> Project: Hadoop Core
> Issue Type: Improvement
> Components: dfs, mapred
> Affects Versions: 0.19.0
> Reporter: Steve Loughran
> Assignee: Steve Loughran
> Attachments: AbstractHadoopComponent.java, hadoop-3628.patch,
> hadoop-3628.patch, hadoop-3628.patch, hadoop-3628.patch, hadoop-3628.patch,
> hadoop-3628.patch, hadoop-3628.patch, hadoop-3628.patch, hadoop-3628.patch,
> hadoop-3628.patch
>
>
> I'd like to propose we have a standard interface for hadoop components, the
> things that get started or stopped when you bring up a namenode. currently,
> some of these classes have a stop() or shutdown() method, with no standard
> name/interface, but no way of seeing if they are live, checking their health
> of shutting them down reliably. Indeed, there is a tendency for the spawned
> threads to not want to die; to require the entire process to be killed to
> stop the workers.
> Having a standard interface would make it easier for
> * management tools to manage the different things
> * monitoring the state of things
> * subclassing
> The latter is interesting as right now TaskTracker and JobTracker start up
> threads in their constructor; that's very dangerous as subclasses may have
> their methods called before they are full initialised. Adding this interface
> would be the right time to clean up the startup process so that subclassing
> is less risky.
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