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https://issues.apache.org/jira/browse/HADOOP-2062?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12535312
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Raghu Angadi commented on HADOOP-2062:
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> It does not appear to be used in Nutch, but it is used extensively in the dfs
> package. To be safest we might deprecate it and replace it with DaemonThread.
I think DaemonThread could just extend Daemon (or include getRunnable()) and
not require changing implementation of classes (to rename run() to innerLoop(),
extend DaemonThread instead of Runnable). This way one can just replace
Daemon(...) with DaemonThread(...).
> 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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