[CURATOR-240] Severe memory leak in TreeCache when path does not exist

• Type: Bug
• Status: Resolved
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 2.8.0
• Fix Version/s: 2.9.0
• Component/s: Recipes
• Labels: memory-leak
• Environment: java version "1.7.0_71"; Java(TM) SE Runtime Environment (build 1.7.0_71-b14); Java HotSpot(TM) 64-Bit Server VM (build 24.71-b01, mixed mode); ; OSX Yosemite
• Assignee: Scott Blum
• Reporter: Joe Littlejohn
• Created: 31/Jul/15 13:25
• Updated: 05/Aug/15 07:57
• Resolved: 31/Jul/15 21:21

Description

When creating a TreeCache, if the path supplied does not exist in Zookeeper then the heap is quickly exhausted. The problem appears to be instances of org.apache.curator.framework.imps.NamespaceWatcher.

Try running the following test:

package org.apache.curator.framework.recipes.cache;

import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.recipes.cache.TreeCache;
import org.apache.curator.retry.RetryOneTime;
import org.apache.curator.test.TestingServer;

public class TreeCacheLeak {

    public static void main(String[] args) throws Exception {

        TestingServer server = new TestingServer();
        
        final CuratorFramework curatorFramework = CuratorFrameworkFactory.newClient(server.getConnectString(), new RetryOneTime(1));
        curatorFramework.start();

        final TreeCache cache = new TreeCache(curatorFramework, "/foo/bar/baz");
        cache.start();

        try {
            while (true) {
                Thread.sleep(1000);
            }
        } finally {
            cache.close();
            server.close();
        }
    }

}

Launch the class then connect e.g. jvisualvm. You'll see the heap growing and if you watch for a few minutes then take a heap dump, you'll see millions of instances of org.apache.curator.framework.imps.NamespaceWatcher are present.