Sébastien Launay created KAFKA-3501:
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Summary: Console consumer process hangs on SIGINT
Key: KAFKA-3501
URL: https://issues.apache.org/jira/browse/KAFKA-3501
Project: Kafka
Issue Type: Bug
Components: consumer, core
Affects Versions: 0.9.0.0
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)
Reporter: Sébastien Launay
Assignee: Neha Narkhede
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.
{noformat}
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
{noformat}
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:
{noformat}
...
"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)
{noformat}
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:
{code:scala}
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)
}
}
{code:java}
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.
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