Sotirios Delimanolis created CASSANDRA-13137:
------------------------------------------------
Summary: nodetool disablethrift deadlocks if THsHaDisruptorServer
is stopped while a read is going on
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 {{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 threads catch up to the "producer" index, ie.
the selector thread.
When we execute a {{nodetool disablethrift}}, this 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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