Race condition in JVM reuse when more than one slot becomes free
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Key: HADOOP-4232
URL: https://issues.apache.org/jira/browse/HADOOP-4232
Project: Hadoop Core
Issue Type: Bug
Components: mapred
Affects Versions: 0.19.0
Reporter: Devaraj Das
Assignee: Devaraj Das
Priority: Blocker
Fix For: 0.19.0
A race condition exists where there are two or more slots free and there are
two or more tasks waiting to run. As an example, consider a case where there
are two free slots and there are two tasks waiting to run. JVM_job1 and
JVM_job2 are the two idle jvms in memory. A waiting task, task job1_t1, kills
the JVM_job2 and spawns a new one, JVM_1_job1. While JVM_1_job1 is initializing
(it is marked busy during initialization), JVM_job1 picks this task up and
hence this becomes busy as well. Another waiting task, job3_t1 finds both the
JVMs busy and doesn't spawn a new JVM.
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