[HADOOP-4232] Race condition in JVM reuse when more than one slot becomes free

• Type: Bug
• Status: Closed
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 0.19.0
• Fix Version/s: 0.19.0
• Hadoop Flags: Reviewed
• Assignee: Devaraj Das
• Reporter: Devaraj Das
• Created: 20/Sep/08 06:59
• Updated: 08/Jul/09 16:53
• Resolved: 30/Sep/08 23:15

Description

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.