JobTracker's processHeartbeat() should not call System.currentTimeMillis()
everytime
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Key: HADOOP-3524
URL: https://issues.apache.org/jira/browse/HADOOP-3524
Project: Hadoop Core
Issue Type: Improvement
Components: mapred
Reporter: Amar Kamat
Consider the following
{code:title=JobTracker.java|borderStyle=solid}
private synchronized boolean processHeartbeat(
TaskTrackerStatus
trackerStatus, boolean initialContact) {
String trackerName = trackerStatus.getTrackerName();
trackerStatus.setLastSeen(System.currentTimeMillis());
{code}
Here, the call to {{System.currentTimeMillis()}} on every call to
{{JobTracker.processHeartbeat()}} might prove costly. While
testing/benchmarking HADOOP-2119, we recorded that the JobTracker was able to
serve ~130 tasks/sec. So that means we might make ~130 calls to
{{System.currentTimeMillis()}} per second. I think in these cases
(_last-seen-status_ etc) such a high level of accuracy in terms of timestamp is
unnecessary and hence can be avoided.
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