[FLUME-1124] Lifecycle supervisor can cause thread contention, sometimes causing components to not startup.

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.1.0
• Fix Version/s: 1.2.0
• Component/s: Sinks+Sources
• Assignee: Hari Shreedharan
• Reporter: Hari Shreedharan
• Created: 17/Apr/12 00:24
• Updated: 18/Apr/12 19:28
• Resolved: 18/Apr/12 18:47

Description

Based on Brock's review of my patch, the following issues have been added to this jira:

This isn't your code but it looks like there are a few problems here.

1) monitorService on MonitorRunnable is not set so an NPE (which is not being logged is thrown:

java.lang.NullPointerException
at org.apache.flume.lifecycle.LifecycleSupervisor$MonitorRunnable.run(LifecycleSupervisor.java:255)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:317)
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:150)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$101(ScheduledThreadPoolExecutor.java:98)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.runPeriodic(ScheduledThreadPoolExecutor.java:180)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:204)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)

2) The NPE is not being logged.
3) If the NPE did not occur we'd have a bigger issue as scheduleAtFixedRate is called here but the runnable reschedules itself.
4) Calling first supervise() and then start() creates two threads monitoring this service.