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https://issues.apache.org/jira/browse/HADOOP-4977?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Vivek Ratan updated HADOOP-4977:
--------------------------------
Attachment: 4977.3.patch
Valid points, Amar. I did some extra refactoring at the end and didn't realize
the confusing calls. I do want to keep the update of the QSI objects separate
from the fetching of the cluster status, as both these can come under different
synchronization calls, if required. So each of the three callers:
assignTasks(), reclaimCapacity, and the test cases, get the cluster stats on
their own and then call updateQSIObjects(). See attached patch (4977.3.patch).
The method printQSIs() is useful for printing debug information. We don't call
it right now (we did, earlier), but I wanted to keep it around as it can prove
quite useful.
> Deadlock between reclaimCapacity and assignTasks
> ------------------------------------------------
>
> Key: HADOOP-4977
> URL: https://issues.apache.org/jira/browse/HADOOP-4977
> Project: Hadoop Core
> Issue Type: Bug
> Components: contrib/capacity-sched
> Affects Versions: 0.19.0
> Reporter: Matei Zaharia
> Assignee: Vivek Ratan
> Priority: Blocker
> Fix For: 0.20.0
>
> Attachments: 4977.1.patch, 4977.2.patch, 4977.3.patch, jstack.txt
>
>
> I was running the latest trunk with the capacity scheduler and saw the
> JobTracker lock up with the following deadlock reported in jstack:
> Found one Java-level deadlock:
> =============================
> "18107...@qtp0-4":
> waiting to lock monitor 0x08085b40 (object 0x56605100, a
> org.apache.hadoop.mapred.JobTracker),
> which is held by "IPC Server handler 4 on 54311"
> "IPC Server handler 4 on 54311":
> waiting to lock monitor 0x0808594c (object 0x5660e518, a
> org.apache.hadoop.mapred.CapacityTaskScheduler$MapSchedulingMgr),
> which is held by "reclaimCapacity"
> "reclaimCapacity":
> waiting to lock monitor 0x08085b40 (object 0x56605100, a
> org.apache.hadoop.mapred.JobTracker),
> which is held by "IPC Server handler 4 on 54311"
> Java stack information for the threads listed above:
> ===================================================
> "18107...@qtp0-4":
> at
> org.apache.hadoop.mapred.JobTracker.getClusterStatus(JobTracker.java:2695)
> - waiting to lock <0x56605100> (a org.apache.hadoop.mapred.JobTracker)
> at
> org.apache.hadoop.mapred.jobtracker_jsp._jspService(jobtracker_jsp.java:93)
> at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
> at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
> at
> org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:502)
> at
> org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:363)
> at
> org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
> at
> org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:181)
> at
> org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:766)
> at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:417)
> at
> org.mortbay.jetty.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:230)
> at
> org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
> at org.mortbay.jetty.Server.handle(Server.java:324)
> at
> org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:534)
> at
> org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:864)
> at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:533)
> at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:207)
> at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:403)
> at
> org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
> at
> org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:522)
> "IPC Server handler 4 on 54311":
> at
> org.apache.hadoop.mapred.CapacityTaskScheduler$TaskSchedulingMgr.updateQSIObjects(CapacityTaskScheduler.java:564)
> - waiting to lock <0x5660e518> (a
> org.apache.hadoop.mapred.CapacityTaskScheduler$MapSchedulingMgr)
> at
> org.apache.hadoop.mapred.CapacityTaskScheduler$TaskSchedulingMgr.assignTasks(CapacityTaskScheduler.java:855)
> at
> org.apache.hadoop.mapred.CapacityTaskScheduler$TaskSchedulingMgr.access$1000(CapacityTaskScheduler.java:294)
> at
> org.apache.hadoop.mapred.CapacityTaskScheduler.assignTasks(CapacityTaskScheduler.java:1336)
> - locked <0x5660dd20> (a org.apache.hadoop.mapred.CapacityTaskScheduler)
> at org.apache.hadoop.mapred.JobTracker.heartbeat(JobTracker.java:2288)
> - locked <0x56605100> (a org.apache.hadoop.mapred.JobTracker)
> at sun.reflect.GeneratedMethodAccessor16.invoke(Unknown Source)
> at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
> at java.lang.reflect.Method.invoke(Method.java:597)
> at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:508)
> at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:959)
> Unfortunately I didn't manage to select all of the output by mistake, so some
> is missing, but it appears that reclaimCapacity locks the MapSchedulingMgr
> and then tries to lock the JobTracker, whereas the updateQSIObjects called in
> assignTasks holds a lock on the JobTracker (the JobTracker grabs this lock
> when it calls assignTasks) and then tries to lock the MapSchedulingMgr. The
> other thread listed there is a Jetty thread for the web interface and isn't
> part of the circular locking. The solution to this would be to lock the
> JobTracker in reclaimCapacity before locking anything else.
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