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https://issues.apache.org/jira/browse/HADOOP-2062?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12535318
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Raghu Angadi commented on HADOOP-2062:
--------------------------------------
oops! this is not a drop in replacement for Daemon.. because when run()
returns, it is invoked again. Should innerLoop() be called something like
innerBlock() :) ? Also similar to Thread(), it could take a DaemonRunnable
(that requires implementation of innerLoop()) as opposed to requiring classes
to extend a Thread.
> Standardize long-running, daemon-like, threads in hadoop daemons
> ----------------------------------------------------------------
>
> Key: HADOOP-2062
> URL: https://issues.apache.org/jira/browse/HADOOP-2062
> Project: Hadoop
> Issue Type: Improvement
> Components: dfs, mapred
> Reporter: Arun C Murthy
> Assignee: Arun C Murthy
> Fix For: 0.16.0
>
>
> There are several long-running, independent, threads in hadoop daemons
> (atleast in the JobTracker - e.g. ExpireLaunchingTasks, ExpireTrackers,
> TaskCommitQueue etc.) which need to be alive as long as the daemon itself and
> hence should be impervious to various errors and exceptions (e.g.
> HADOOP-2051).
> Currently, each of them seem to be hand-crafted (again, specifically the
> JobTracker) and different from the other.
> I propose we standardize on an implementation of a long-running, impervious,
> daemon-thread which can be used all over the shop. That thread should be
> explicitly shut-down by the hadoop daemon and shouldn't be vulnerable to any
> exceptions/errors.
> This mostly likely will look like this:
> {noformat}
> public abstract class DaemonThread extends Thread {
> public static final Log LOG = LogFactory.getLog(DaemonThread.class);
> {
> setDaemon(true); // always a daemon
> }
> public abstract void innerLoop() throws InterruptedException;
>
> public final void run() {
> while (!isInterrupted()) {
> try {
> innerLoop();
> } catch (InterruptedException ie) {
> LOG.warn(getName() + " interrupted, exiting...");
> } catch (Throwable t) {
> LOG.error(getName() + " got an exception: " +
> StringUtils.stringifyException(t));
> }
> }
> }
> }
> {noformat}
> In fact, we could probably hijack org.apache.hadoop.util.Daemon since it
> isn't used anywhere (Doug is it still used in nutch?) or atleast sub-class
> that.
> Thoughts? Could someone from hdfs/hbase chime in?
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