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Date: Thu, 19 Jan 2017 23:01:26 +0000 (UTC)
From: "Sotirios Delimanolis (JIRA)" <jira@apache.org>
To: commits@cassandra.apache.org
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Subject: [jira] [Updated] (CASSANDRA-13137) nodetool disablethrift deadlocks
 if THsHaDisruptorServer is stopped while a request is being processed
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     [ https://issues.apache.org/jira/browse/CASSANDRA-13137?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Sotirios Delimanolis updated CASSANDRA-13137:
---------------------------------------------
    Summary: nodetool disablethrift deadlocks if THsHaDisruptorServer is stopped while a request is being processed  (was: nodetool disablethrift deadlocks if THsHaDisruptorServer is stopped while a read is going on)

> nodetool disablethrift deadlocks if THsHaDisruptorServer is stopped while a request is being processed
> ------------------------------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-13137
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-13137
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>         Environment: 2.2.9
>            Reporter: Sotirios Delimanolis
>
> We are using Thrift with {{rpc_server_type}} set to {{hsha}}. This creates a {{THsHaDisruptorServer}} which is a subclass of [{{TDisruptorServer}}|https://github.com/xedin/disruptor_thrift_server/blob/master/src/main/java/com/thinkaurelius/thrift/TDisruptorServer.java].
> Internally, this spawns {{number_of_cores}} number of selector threads. Each gets a {{RingBuffer}} and {{rpc_max_threads / cores}} number of worker threads (the {{RPC-Thread}} threads). As the server starts receiving requests, each selector thread adds events to its {{RingBuffer}} and the worker threads process them. 
> The _events_ are [{{Message}}|https://github.com/xedin/disruptor_thrift_server/blob/master/src/main/java/com/thinkaurelius/thrift/Message.java] instances, which have preallocated buffers for eventual IO.
> When the thrift server starts up, the corresponding {{ThriftServerThread}} joins on the selector threads, waiting for them to die. It then iterates through all the {{SelectorThread}} objects and calls their {{shutdown}} method which attempts to drain their corresponding {{RingBuffer}}. The [drain ({{drainAndHalt}})|https://github.com/LMAX-Exchange/disruptor/blob/master/src/main/java/com/lmax/disruptor/WorkerPool.java#L147] works by letting the worker pool "consumer" threads catch up to the "producer" index, ie. the selector thread.
> When we execute a {{nodetool disablethrift}}, it attempts to {{stop}} the {{THsHaDisruptorServer}}. That works by setting a {{stopped}} flag to {{true}}. When the selector threads see that, they break from their {{select()}} loop, and clean up their resources, ie. the {{Message}} objects they've created and their buffers. *However*, if one of those {{Message}} objects is currently being used by a worker pool thread to process a request, if it calls [this piece of code|https://github.com/xedin/disruptor_thrift_server/blob/master/src/main/java/com/thinkaurelius/thrift/Message.java#L317], you'll get the following {{NullPointerException}}
> {noformat}
> Jan 18, 2017 6:28:50 PM com.lmax.disruptor.FatalExceptionHandler handleEventException
> SEVERE: Exception processing: 633124 com.thinkaurelius.thrift.Message$Invocation@25c9fbeb
> java.lang.NullPointerException
>         at com.thinkaurelius.thrift.Message.getInputTransport(Message.java:338)
>         at com.thinkaurelius.thrift.Message.invoke(Message.java:308)
>         at com.thinkaurelius.thrift.Message$Invocation.execute(Message.java:90)
>         at com.thinkaurelius.thrift.TDisruptorServer$InvocationHandler.onEvent(TDisruptorServer.java:695)
>         at com.thinkaurelius.thrift.TDisruptorServer$InvocationHandler.onEvent(TDisruptorServer.java:689)
>         at com.lmax.disruptor.WorkProcessor.run(WorkProcessor.java:112)
>         at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
>         at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
>         at java.lang.Thread.run(Thread.java:745)
> {noformat}
> That fails because it tries to dereference one of the {{Message}} "cleaned up", ie. {{null}}, buffers.
> Because that call is outside the {{try}} block, the exception escapes and basically kills the worker pool thread. This has the side effect of "discarding" one of the consumers of a selector's {{RingBuffer}}. 
> *That* has the side effect of preventing the {{ThriftServerThread}} from draining the {{RingBuffer}} (and dying) since the consumers never catch up to the stopped producer. And that finally has the effect of preventing the {{nodetool disablethrift}} from proceeding since it's trying to {{join}} the {{ThriftServerThread}}. Deadlock!
> The {{ThriftServerThread}} thread looks like
> {noformat}
> "Thread-1" #2234 prio=5 os_prio=0 tid=0x00007f4ae6ff1000 nid=0x2eb6 runnable [0x00007f4729174000]
>    java.lang.Thread.State: RUNNABLE
>         at java.lang.Thread.yield(Native Method)
>         at com.lmax.disruptor.WorkerPool.drainAndHalt(WorkerPool.java:147)
>         at com.thinkaurelius.thrift.TDisruptorServer$SelectorThread.shutdown(TDisruptorServer.java:633)
>         at com.thinkaurelius.thrift.TDisruptorServer.gracefullyShutdownInvokerPool(TDisruptorServer.java:301)
>         at com.thinkaurelius.thrift.TDisruptorServer.waitForShutdown(TDisruptorServer.java:280)
>         at org.apache.thrift.server.AbstractNonblockingServer.serve(AbstractNonblockingServer.java:95)
>         at org.apache.cassandra.thrift.ThriftServer$ThriftServerThread.run(ThriftServer.java:137)
> {noformat}
> The {{nodetool disablethrift}} thread looks like
> {noformat}
> "RMI TCP Connection(18183)-127.0.0.1" #12121 daemon prio=5 os_prio=0 tid=0x00007f4ac2c61000 nid=0x5805 in Object.wait() [0x00007f4aab7ec000]
>    java.lang.Thread.State: WAITING (on object monitor)
>         at java.lang.Object.wait(Native Method)
>         at java.lang.Thread.join(Thread.java:1249)
>         - locked <0x000000055d3cb010> (a org.apache.cassandra.thrift.ThriftServer$ThriftServerThread)
>         at java.lang.Thread.join(Thread.java:1323)
>         at org.apache.cassandra.thrift.ThriftServer.stop(ThriftServer.java:70)
>         - locked <0x000000055bffb5e0> (a org.apache.cassandra.thrift.ThriftServer)
>         at org.apache.cassandra.service.StorageService.stopRPCServer(StorageService.java:337)
>         at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
>         at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
>         at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
>         at java.lang.reflect.Method.invoke(Method.java:498)
>         at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
>         at sun.reflect.GeneratedMethodAccessor8.invoke(Unknown Source)
>         at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
>         at java.lang.reflect.Method.invoke(Method.java:498)
>         at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
>         at com.sun.jmx.mbeanserver.StandardMBeanIntrospector.invokeM2(StandardMBeanIntrospector.java:112)
>         at com.sun.jmx.mbeanserver.StandardMBeanIntrospector.invokeM2(StandardMBeanIntrospector.java:46)
>         at com.sun.jmx.mbeanserver.MBeanIntrospector.invokeM(MBeanIntrospector.java:237)
>         at com.sun.jmx.mbeanserver.PerInterface.invoke(PerInterface.java:138)
>         at com.sun.jmx.mbeanserver.MBeanSupport.invoke(MBeanSupport.java:252)
>         at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
>         at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
>         at javax.management.remote.rmi.RMIConnectionImpl.doOperation(RMIConnectionImpl.java:1468)
>         at javax.management.remote.rmi.RMIConnectionImpl.access$300(RMIConnectionImpl.java:76)
>         at javax.management.remote.rmi.RMIConnectionImpl$PrivilegedOperation.run(RMIConnectionImpl.java:1309)
>         at javax.management.remote.rmi.RMIConnectionImpl.doPrivilegedOperation(RMIConnectionImpl.java:1401)
>         at javax.management.remote.rmi.RMIConnectionImpl.invoke(RMIConnectionImpl.java:829)
>         at sun.reflect.GeneratedMethodAccessor22.invoke(Unknown Source)
>         at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
>         at java.lang.reflect.Method.invoke(Method.java:498)
>         at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:324)
>         at sun.rmi.transport.Transport$1.run(Transport.java:200)
>         at sun.rmi.transport.Transport$1.run(Transport.java:197)
>         at java.security.AccessController.doPrivileged(Native Method)
>         at sun.rmi.transport.Transport.serviceCall(Transport.java:196)
>         at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:568)
>         at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:826)
>         at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$0(TCPTransport.java:683)
>         at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler$$Lambda$1/1038375559.run(Unknown Source)
>         at java.security.AccessController.doPrivileged(Native Method)
>         at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:682)
>         at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
>         at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
>         at java.lang.Thread.run(Thread.java:745)
> {noformat}
> Most of the code involved isn't part of Cassandra source, but it's an external dependency that should be fixed.


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