[MAPREDUCE-1683] Remove JNI calls from ClusterStatus cstr

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.20.2
• Fix Version/s: 0.22.0
• Component/s: jobtracker
• Hadoop Flags: Incompatible change
• Release Note: Removes JNI calls to get jvm current/max heap usage in ClusterStatus. Any instances of ClusterStatus serialized in a prior version will not be correctly deserialized using the updated class.
• Assignee: Luke Lu
• Reporter: Christopher Douglas
• Created: 07/Apr/10 06:58
• Updated: 12/Dec/11 06:18
• Resolved: 24/May/10 18:45

Description

The ClusterStatus constructor makes two JNI calls to the Runtime to fetch memory information. ClusterStatus instances are often created inside the JobTracker to obtain other, unrelated metrics (sometimes from schedulers' inner loops). Given that this information is related to the JobTracker process and not the cluster, the metrics are also available via JvmMetrics, and the jsps can gather this information for themselves: these fields can be removed from ClusterStatus

Issue Links

• incorporates: MAPREDUCE-488 JobTracker webui should report heap memory used
• is blocked by: MAPREDUCE-1779 Should we provide a way to know JobTracker's memory info from client?