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https://issues.apache.org/jira/browse/AMQ-4977?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13876117#comment-13876117
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Alexander Suslov commented on AMQ-4977:
---------------------------------------
Test shows that cache size now stable, does not grow with time as before:
{noformat:title=Now}
2014-01-20 11:05:26 WARN ConnectionStateTrackerMemoryLeakTest - Cache size:
131200, 328 elements, memory: 21556KB
2014-01-20 11:05:31 WARN ConnectionStateTrackerMemoryLeakTest - Cache size:
131200, 328 elements, memory: 15535KB
2014-01-20 11:05:36 WARN ConnectionStateTrackerMemoryLeakTest - Cache size:
131200, 328 elements, memory: 17671KB
2014-01-20 11:05:41 WARN ConnectionStateTrackerMemoryLeakTest - Cache size:
131200, 328 elements, memory: 33767KB
2014-01-20 11:05:46 WARN ConnectionStateTrackerMemoryLeakTest - Cache size:
131200, 328 elements, memory: 43187KB
{noformat}
{noformat:title=Before}
2014-01-20 11:08:28 WARN ConnectionStateTrackerMemoryLeakTest - Cache size:
6398000, 31 elements, memory: 10546KB
2014-01-20 11:08:33 WARN ConnectionStateTrackerMemoryLeakTest - Cache size:
21079200, 31 elements, memory: 16294KB
2014-01-20 11:08:38 WARN ConnectionStateTrackerMemoryLeakTest - Cache size:
40870000, 31 elements, memory: 15740KB
2014-01-20 11:08:43 WARN ConnectionStateTrackerMemoryLeakTest - Cache size:
60265200, 31 elements, memory: 27111KB
2014-01-20 11:08:48 WARN ConnectionStateTrackerMemoryLeakTest - Cache size:
79071200, 31 elements, memory: 8817KB
{noformat}
> Memory leak in ConnectionStateTracker when browsing non-empty queues
> --------------------------------------------------------------------
>
> Key: AMQ-4977
> URL: https://issues.apache.org/jira/browse/AMQ-4977
> Project: ActiveMQ
> Issue Type: Bug
> Affects Versions: 5.6.0, 5.7.0, 5.8.0, 5.9.0
> Reporter: Georgi Danov
> Assignee: Timothy Bish
> Fix For: 5.10.0
>
> Attachments: ConnectionStateTrackerMemoryLeakTest.java
>
>
> I think I found case that is not handled by the fix AMQ-3316. We see memory
> leaks connected to this bug and after good amount of headbanging I think the
> problem is in how two methods work together - processMessagePull and
> trackBack. The first one has this piece of code:
> {code}
> // leave a single instance in the cache
> final String id = pull.getDestination() + "::" +
> pull.getConsumerId();
> messageCache.put(id.intern(), pull);
> {code}
> while the second one unconditionally increases the currentCacheSize -
> regardless if the previous method added or replaced entry in the cache.
> The situation where entries will be replaced (and not added) and the
> currentCacheSize will grow very fast until it wraps around and becomes
> negative is the following:
> * have some logic that frequently creates queue browser and iterates through
> all the entries
> * have the queue most of the time with at least one message. The more
> messages in the queue the faster currentCacheSize grows.
> The reason is that processMessagePull reuses the consumer and destination ID
> for each browsed message in the queue when
> org.apache.activemq.ActiveMQQueueBrowser#hasMoreElements is invoked.
> trackBack is ignorant of this and keeps adding to the size regardless that
> the cache size stays the same.
> Here is log from reproducing the issue as a proof:
> {code}
> 2014-01-16 23:05:14 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 10000, 5 elements, pending scans:10, memory: 8951KB
> 2014-01-16 23:05:14 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 20000, 10 elements, pending scans:10, memory: 10845KB
> 2014-01-16 23:05:14 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 30000, 15 elements, pending scans:10, memory: 12645KB
> 2014-01-16 23:05:14 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 40000, 20 elements, pending scans:10, memory: 10363KB
> 2014-01-16 23:05:14 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 50000, 25 elements, pending scans:10, memory: 12169KB
> 2014-01-16 23:05:14 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 60000, 30 elements, pending scans:10, memory: 9852KB
> 2014-01-16 23:05:14 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 70000, 35 elements, pending scans:10, memory: 11657KB
> 2014-01-16 23:05:14 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 80000, 40 elements, pending scans:10, memory: 9401KB
> 2014-01-16 23:05:14 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 90000, 45 elements, pending scans:10, memory: 11222KB
> 2014-01-16 23:05:14 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 100000, 50 elements, pending scans:10, memory: 13047KB
> 2014-01-16 23:05:14 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 110000, 55 elements, pending scans:10, memory: 10767KB
> 2014-01-16 23:05:14 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 120000, 60 elements, pending scans:10, memory: 12567KB
> 2014-01-16 23:05:14 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 130000, 65 elements, pending scans:10, memory: 10256KB
> 2014-01-16 23:05:14 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 138800, 67 elements, pending scans:10, memory: 12085KB
> 2014-01-16 23:05:14 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 146800, 67 elements, pending scans:10, memory: 9745KB
> 2014-01-16 23:05:14 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 154800, 67 elements, pending scans:10, memory: 11566KB
> 2014-01-16 23:05:14 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 162800, 67 elements, pending scans:10, memory: 9225KB
> 2014-01-16 23:05:14 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 170800, 67 elements, pending scans:10, memory: 11013KB
> 2014-01-16 23:05:14 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 178800, 67 elements, pending scans:10, memory: 12812KB
> 2014-01-16 23:05:14 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 186800, 67 elements, pending scans:10, memory: 10522KB
> 2014-01-16 23:05:14 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 194800, 67 elements, pending scans:10, memory: 12328KB
> 2014-01-16 23:05:14 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 202800, 67 elements, pending scans:10, memory: 9999KB
> 2014-01-16 23:05:15 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 210800, 67 elements, pending scans:10, memory: 11805KB
> 2014-01-16 23:05:15 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 218800, 67 elements, pending scans:10, memory: 9496KB
> 2014-01-16 23:05:15 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 226800, 67 elements, pending scans:10, memory: 11316KB
> 2014-01-16 23:05:15 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 234800, 67 elements, pending scans:10, memory: 13100KB
> 2014-01-16 23:05:15 WARN ActiveMqMemoryLeakTest - MaxCacheSize: 131072,
> currentCacheSize: 242800, 67 elements, pending scans:10, memory: 10754KB
> {code}
> One can see that the garbage collection works well (cache does not grow) but
> the currentCacheSize keeps increasing
> Unfortunately I cannot easily extract the original code and provide it. Hope
> the explanation is clear enough.
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