[KAFKA-3501] Console consumer process hangs on SIGINT

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.9.0.0
• Fix Version/s: 0.10.1.0
• Component/s: consumer, core
• Environment: Ubuntu 12.04.5 LTS; OpenJDK Runtime Environment (IcedTea 2.6.3) (7u91-2.6.3-0ubuntu0.12.04.1); OpenJDK 64-Bit Server VM (build 24.91-b01, mixed mode)
• Flags: Patch
• Assignee: Neha Narkhede
• Reporter: Sébastien Launay
• Created: 04/Apr/16 20:21
• Updated: 07/Jun/16 04:35
• Resolved: 07/Jun/16 04:35

Description

Sometimes when running the `kafka-console-consumer` script inside a pipe and trying to stop it with a `SIGINT` (`ctrl+c`), the process will not stop.

ubuntu@xxx:~$ kafka-console-consumer --zookeeper localhost --topic topic --from-beginning | grep "pattern"
record1
...
recordN
^CUnable to write to standard out, closing consumer.
 ^C
# process is still running

When looking at the various threads running on the JVM, I noticed that one user thread is waiting on a latch preventing the JVM from shutting down:

...
"Thread-6" prio=10 tid=0x00007f258c016000 nid=0x289f waiting on condition [0x00007f259aee3000]
   java.lang.Thread.State: WAITING (parking)
	at sun.misc.Unsafe.park(Native Method)
	- parking to wait for  <0x00000000d6640c80> (a java.util.concurrent.CountDownLatch$Sync)
	at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)
	at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:834)
	at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(AbstractQueuedSynchronizer.java:994)
	at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1303)
	at java.util.concurrent.CountDownLatch.await(CountDownLatch.java:236)
	at kafka.tools.ConsoleConsumer$$anon$1.run(ConsoleConsumer.scala:101)
...
"main" prio=10 tid=0x00007f25c400e000 nid=0x2878 waiting for monitor entry [0x00007f25cbefc000]
   java.lang.Thread.State: BLOCKED (on object monitor)
	at java.lang.Shutdown.exit(Shutdown.java:212)
	- waiting to lock <0x00000000d6974308> (a java.lang.Class for java.lang.Shutdown)
	at java.lang.Runtime.exit(Runtime.java:109)
	at java.lang.System.exit(System.java:962)
	at kafka.tools.ConsoleConsumer$.checkErr(ConsoleConsumer.scala:149)
	at kafka.tools.ConsoleConsumer$.process(ConsoleConsumer.scala:136)
	at kafka.tools.ConsoleConsumer$.run(ConsoleConsumer.scala:69)
	at kafka.tools.ConsoleConsumer$.main(ConsoleConsumer.scala:47)
	at kafka.tools.ConsoleConsumer.main(ConsoleConsumer.scala)

I believe the standard output linked to the defunct grep process get closed and triggers a `System.exit(1)` that prevents the latch from getting count down and therefore the main thread to hang on forever:

def checkErr(formatter: MessageFormatter) {
if (System.out.checkError())

{ // This means no one is listening to our output stream any more, time to shutdown System.err.println("Unable to write to standard out, closing consumer.") formatter.close() System.exit(1) }

}

This only happens when `System.out` is checked for errors after consuming a message and before the consumer get closed, definitely a race condition that is most likely to happen when messages are consumed at a high throughput.

Issue Links

• links to: GitHub Pull Request #1185