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https://issues.apache.org/jira/browse/CURATOR-167?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14710132#comment-14710132
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Scott Blum commented on CURATOR-167:
------------------------------------
Sorry for being dumb, can someone give me the short version of why NodeCache
would have this problem, but TreeCache and PathChildrenCache would not?
> All registered watchers should be cleared on close
> --------------------------------------------------
>
> Key: CURATOR-167
> URL: https://issues.apache.org/jira/browse/CURATOR-167
> Project: Apache Curator
> Issue Type: Bug
> Components: Client
> Affects Versions: 2.6.0
> Environment: Linux 3.13.0-37-generic #64~precise1-Ubuntu SMP Wed Sep
> 24 21:39:43 UTC 2014 i686 i686 i386 GNU/Linux
> java version "1.7.0_13"
> Java(TM) SE Runtime Environment (build 1.7.0_13-b20)
> Java HotSpot(TM) Server VM (build 23.7-b01, mixed mode)
> Reporter: Craig McNally
> Assignee: Cameron McKenzie
> Priority: Critical
> Labels: heap, memory-leak, node-cache
> Fix For: 2.9.0
>
> Attachments: heap.png, yourKit_NodeCacheMemoryLeakTest.png,
> yourKit_NodeCache_ConnectionListenerLeak.png
>
>
> There's a memory leak in NodeCache. I was able to reliably reproduce the
> problem using a very simple test that performs the following:
> 1) Creates a CuratorFramework instance and starts it.
> 2) in a loop: Creates a NodeCache and starts it, then closes it.
> Eventually you get a java.lang.OutOfMemoryError: Java heap space. This
> happens regardless of the heap size, though it happens much faster with a
> small heap.
> Upon furher investigation w/ a profiler, I can see that each NodeCache is
> being referenced by the NamespaceWatcherMap.
> Here's the test code:
> {code:title=NodeCacheLeakTest.java|borderStyle=solid}
> import java.util.Date;
> import org.apache.curator.framework.CuratorFramework;
> import org.apache.curator.framework.CuratorFrameworkFactory;
> import org.apache.curator.framework.recipes.cache.NodeCache;
> import org.apache.curator.retry.ExponentialBackoffRetry;
> public class NodeCacheLeakTest {
> public static void main(String[] args) throws Exception {
> String zkConnect;
> if (args.length > 0 && args[0] != null)
> zkConnect = args[0];
> else
> zkConnect = "localhost:2181/test";
> CuratorFramework curator =
> CuratorFrameworkFactory.newClient(zkConnect,
> new ExponentialBackoffRetry(500, 10));
> curator.start();
> int count = 0;
> while (true) {
> String nodePath = "/foo/node-" + (count);
> NodeCache cache = new NodeCache(curator, nodePath);
> cache.start(true);
> cache.close();
> count++;
> if (count % 1000 == 0)
> System.out.println(new Date() + " Started and
> Closed " + count
> + " NodeCache instances");
> }
> }
> }
> {code}
> And here's the output/OOM Error when using (-Xms10m -Xmx10m -XX:+UseG1GC):
> {noformat}
> log4j:WARN No appenders could be found for logger
> (org.apache.curator.framework.imps.CuratorFrameworkImpl).
> log4j:WARN Please initialize the log4j system properly.
> log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more
> info.
> Tue Nov 18 15:59:12 GMT+00:00 2014 Started and Closed 1000 NodeCache instances
> Tue Nov 18 15:59:16 GMT+00:00 2014 Started and Closed 2000 NodeCache instances
> Tue Nov 18 15:59:20 GMT+00:00 2014 Started and Closed 3000 NodeCache instances
> Tue Nov 18 15:59:23 GMT+00:00 2014 Started and Closed 4000 NodeCache instances
> Tue Nov 18 15:59:27 GMT+00:00 2014 Started and Closed 5000 NodeCache instances
> Tue Nov 18 15:59:31 GMT+00:00 2014 Started and Closed 6000 NodeCache instances
> Tue Nov 18 15:59:36 GMT+00:00 2014 Started and Closed 7000 NodeCache instances
> Tue Nov 18 15:59:40 GMT+00:00 2014 Started and Closed 8000 NodeCache instances
> Tue Nov 18 15:59:45 GMT+00:00 2014 Started and Closed 9000 NodeCache instances
> Tue Nov 18 15:59:49 GMT+00:00 2014 Started and Closed 10000 NodeCache
> instances
> Tue Nov 18 16:00:01 GMT+00:00 2014 Started and Closed 11000 NodeCache
> instances
> java.lang.OutOfMemoryError: Java heap space
> at java.io.BufferedWriter.<init>(BufferedWriter.java:105)
> at java.io.BufferedWriter.<init>(BufferedWriter.java:88)
> at java.io.PrintStream.<init>(PrintStream.java:112)
> at java.io.PrintStream.<init>(PrintStream.java:175)
> at org.apache.jute.CsvOutputArchive.<init>(CsvOutputArchive.java:57)
> at
> org.apache.zookeeper.proto.RequestHeader.toString(RequestHeader.java:62)
> at java.lang.String.valueOf(String.java:2854)
> at java.lang.StringBuilder.append(StringBuilder.java:128)
> at org.apache.zookeeper.ClientCnxn$Packet.toString(ClientCnxn.java:308)
> at java.lang.String.valueOf(String.java:2854)
> at java.lang.StringBuilder.append(StringBuilder.java:128)
> at
> org.apache.zookeeper.ClientCnxn$SendThread.readResponse(ClientCnxn.java:815)
> at
> org.apache.zookeeper.ClientCnxnSocketNIO.doIO(ClientCnxnSocketNIO.java:94)
> at
> org.apache.zookeeper.ClientCnxnSocketNIO.doTransport(ClientCnxnSocketNIO.java:355)
> at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1068)
> java.lang.OutOfMemoryError: Java heap space
> at java.io.BufferedWriter.<init>(BufferedWriter.java:105)
> at java.io.BufferedWriter.<init>(BufferedWriter.java:88)
> at java.io.PrintStream.<init>(PrintStream.java:112)
> at java.io.PrintStream.<init>(PrintStream.java:175)
> at org.apache.jute.CsvOutputArchive.<init>(CsvOutputArchive.java:57)
> at
> org.apache.zookeeper.proto.RequestHeader.toString(RequestHeader.java:62)
> at java.lang.String.valueOf(String.java:2854)
> at java.lang.StringBuilder.append(StringBuilder.java:128)
> at org.apache.zookeeper.ClientCnxn$Packet.toString(ClientCnxn.java:308)
> at java.lang.String.valueOf(String.java:2854)
> at java.lang.StringBuilder.append(StringBuilder.java:128)
> at
> org.apache.zookeeper.ClientCnxn$SendThread.readResponse(ClientCnxn.java:815)
> at
> org.apache.zookeeper.ClientCnxnSocketNIO.doIO(ClientCnxnSocketNIO.java:94)
> at
> org.apache.zookeeper.ClientCnxnSocketNIO.doTransport(ClientCnxnSocketNIO.java:355)
> at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1068)
> java.lang.OutOfMemoryError: Java heap space
> at java.io.BufferedWriter.<init>(BufferedWriter.java:105)
> at java.io.BufferedWriter.<init>(BufferedWriter.java:88)
> at java.io.PrintStream.<init>(PrintStream.java:112)
> at java.io.PrintStream.<init>(PrintStream.java:175)
> at org.apache.jute.CsvOutputArchive.<init>(CsvOutputArchive.java:57)
> at
> org.apache.zookeeper.proto.RequestHeader.toString(RequestHeader.java:62)
> at java.lang.String.valueOf(String.java:2854)
> at java.lang.StringBuilder.append(StringBuilder.java:128)
> at org.apache.zookeeper.ClientCnxn$Packet.toString(ClientCnxn.java:308)
> at java.lang.String.valueOf(String.java:2854)
> at java.lang.StringBuilder.append(StringBuilder.java:128)
> at
> org.apache.zookeeper.ClientCnxn$SendThread.readResponse(ClientCnxn.java:815)
> at
> org.apache.zookeeper.ClientCnxnSocketNIO.doIO(ClientCnxnSocketNIO.java:94)
> at
> org.apache.zookeeper.ClientCnxnSocketNIO.doTransport(ClientCnxnSocketNIO.java:355)
> at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1068)
> java.lang.OutOfMemoryError: Java heap space
> at java.io.BufferedWriter.<init>(BufferedWriter.java:105)
> at java.io.BufferedWriter.<init>(BufferedWriter.java:88)
> at java.io.PrintStream.<init>(PrintStream.java:112)
> at java.io.PrintStream.<init>(PrintStream.java:175)
> at org.apache.jute.CsvOutputArchive.<init>(CsvOutputArchive.java:57)
> at
> org.apache.zookeeper.proto.RequestHeader.toString(RequestHeader.java:62)
> at java.lang.String.valueOf(String.java:2854)
> at java.lang.StringBuilder.append(StringBuilder.java:128)
> at org.apache.zookeeper.ClientCnxn$Packet.toString(ClientCnxn.java:308)
> at java.lang.String.valueOf(String.java:2854)
> at java.lang.StringBuilder.append(StringBuilder.java:128)
> at
> org.apache.zookeeper.ClientCnxn$SendThread.readResponse(ClientCnxn.java:815)
> at
> org.apache.zookeeper.ClientCnxnSocketNIO.doIO(ClientCnxnSocketNIO.java:94)
> at
> org.apache.zookeeper.ClientCnxnSocketNIO.doTransport(ClientCnxnSocketNIO.java:355)
> at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1068)
> Exception: java.lang.OutOfMemoryError thrown from the
> UncaughtExceptionHandler in thread "main"
> {noformat}
> Additional Notes:
> * When I don't specify the G1 collector I still get OutOfMemoryErrors, only
> the cause is "GC overhead limit exceeded".
> {noformat}java.lang.OutOfMemoryError: GC overhead limit exceeded
> at java.io.BufferedWriter.<init>(BufferedWriter.java:105)
> at java.io.BufferedWriter.<init>(BufferedWriter.java:88)
> at java.io.PrintStream.<init>(PrintStream.java:112)
> at java.io.PrintStream.<init>(PrintStream.java:175)
> at org.apache.jute.CsvOutputArchive.<init>(CsvOutputArchive.java:57)
> at
> org.apache.zookeeper.proto.GetDataRequest.toString(GetDataRequest.java:62)
> at java.lang.String.valueOf(String.java:2854)
> at java.lang.StringBuilder.append(StringBuilder.java:128)
> at org.apache.zookeeper.ClientCnxn$Packet.toString(ClientCnxn.java:310)
> at java.lang.String.valueOf(String.java:2854)
> at java.lang.StringBuilder.append(StringBuilder.java:128)
> at
> org.apache.zookeeper.ClientCnxn$SendThread.readResponse(ClientCnxn.java:815)
> at
> org.apache.zookeeper.ClientCnxnSocketNIO.doIO(ClientCnxnSocketNIO.java:94)
> at
> org.apache.zookeeper.ClientCnxnSocketNIO.doTransport(ClientCnxnSocketNIO.java:355)
> at
> org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1068){noformat}
> * This has been around for a while as I first noticed it with v1.3.3. I
> upgraded to v2.6.0 and re-ran the test, but as you can see this still appears
> to be an issue.
> * I ran this test on a x86_64 Ubuntu 10.043 system and observed the same
> behavior
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