Hi,
I apologize for the broadcasting. I searched the archive before I send this
email to the mailing list.
We are using Cages library + Zookeeper 3.3.3 to synchronize creation of forum
user name (which needs to be unique).
This is the only use case that we write in ZooKeeper.
We used Cages ZkWriteLock to obtain write lock and below is the code (which
is very straightforward):
org.wyki.zookeeper.cages.ZkWriteLock lock = new
org.wyki.zookeeper.cages.ZkWriteLock("/User/ForumUsername/" + forumUsername);
try {
boolean lockAcquired = lock.acquire(5, TimeUnit.SECONDS);
......
} finally {
lock.release();
}
In our load test (1 single Zookeeper server), even with 3GB max heap size,
ZooKeeper runs out of memory after ~3 hours.
So I decided to profile Zookeeper with YourKit Jave profile (9.5) against one
Zookeeper server. After every 6 above calls to ZooKeeper (I randomly picked
6), I saw the memory usage increased ~200K (in Yourkit retained size increased
~220K and shallow size increased
Even after 1 hour or more, even if I forced garbage collection (done in
YourKit), the memory increased due to the 6 calls didn't get released. I ran
the 6 calls for a few times and observed the same. So I suspect there is a
memory leak (and that is why we got OutOfMemory in load test)
Looking further at the hotspot using Yourkit, the memory increase are in the
form of String, char[], Class, HashMap$Entry (java classes or types) and maily
from below method invocation:
org.apache.zookeeper.server.FinalRequestProcessor.processRequest(Request)
org.apache.zookeeper.server.PrepRequestProcessor.pRequest(Request)
org.apache.zookeeper.server.NIOServerCnxn$Factory.run()
But from the code, leakage is not obvious.
We used below JVM (for ZooKeeper) startup options/flags:
-server -Xms1536m -Xmx3072m -Xloggc:/var/zookeeper/logs/gc.log
-XX:+PrintGCApplicationStoppedTime -XX:+PrintGCApplicationConcurrentTime
-XX:+PrintGC -XX:+PrintGCTimeStamps -XX:+PrintGCDetails -XX:ParallelGCThreads=8
-XX:+UseConcMarkSweepGC -Dcom.sun.management.jmxremote
-Dcom.sun.management.jmxremote.authenticate=false
-Dcom.sun.management.jmxremote.ssl=false
-Dcom.sun.management.jmxremote.port=54321 -Dcom.sun.management.jmxremote
-Dcom.sun.management.jmxremote.local.only=false
I looked at ZooKeeper documentation thoroughly (especially the
administration guide), but couldn't find a way to tune this (to avoid above
suspected memory leak)
Is there a memory leak in Zookeeper 3.3.3 (or 3.3.2)? If there is, How could
we configure ZooKeeper to avoid/reduce that leak? What is the stable version
to use? did we misconfigure anything?
Please advise or help. Thanks a lot!
Victor
