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https://issues.apache.org/jira/browse/OAK-3153?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14653187#comment-14653187
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Thomas Mueller commented on OAK-3153:
-------------------------------------
I'm not quite sure what problem we wanted to solve with recording the stack
trace. If we want to find session leaks, then it's not clear to me what kind of
leak: (a) more and more sessions are referenced in memory, or (b) do we want to
track those where logout was not called.
Depending on that, it may or may not make sense to make it configurable. Making
it configurable, and disabled by default, would slow down solving the problem
because people would first have to manually enable the feature. It would be
better if this feature is automatically enabled in some way. To enable it
automatically, we could count the live sessions and enable it after we have
more than 2000 sessions (for example). To count live sessions,
PhantomReferences can be used as follows:
{noformat}
import java.lang.ref.PhantomReference;
import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.util.HashSet;
import java.util.LinkedList;
public class Test {
public static void main(String... a) {
System.out.println("create & gc 1000 sessions...");
for (int i = 0; i < 1000; i++) {
new Session();
if (i % 100 == 0) {
System.gc();
}
}
System.out.println("create & keep 1000 sessions...");
LinkedList<Session> list = new LinkedList<Session>();
for (int i = 0; i < 1000; i++) {
list.add(new Session());
}
}
static class Session {
static HashSet<Reference<Session>> references =
new HashSet<Reference<Session>>();
static ReferenceQueue<Session> queue =
new ReferenceQueue<Session>();
byte[] data = new byte[1024 * 1024];
{
synchronized (Session.class) {
Reference<Session> ref =
new PhantomReference<Session>(this, queue);
references.add(ref);
while (true) {
Reference<? extends Session> r = queue.poll();
if (r == null) {
break;
}
references.remove(r);
}
int s = references.size();
if (s > 100 && s % 100 == 0) {
System.out.println("size: about " + s);
}
}
}
}
}
{noformat}
> Make it possible to disable recording of stack trace in SessionStats
> --------------------------------------------------------------------
>
> Key: OAK-3153
> URL: https://issues.apache.org/jira/browse/OAK-3153
> Project: Jackrabbit Oak
> Issue Type: Improvement
> Components: core
> Affects Versions: 1.3.3
> Reporter: Joel Richard
> Labels: performance
>
> For the rendering of some pages we have to create a lot of sessions. Around
> 9% of the rendering time is spent inside of RepositoryImpl.login. Half of
> this time is spent creating the exception in SessionStats. Therefore, it
> would be useful if the recording of the exception could be disabled to
> improve the performance.
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