Standardize long-running, daemon-like, threads in hadoop daemons
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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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