Some blocked threads in thread dump

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pratts
Posts: 34
Joined: 23 Aug 2016, 17:46

Some blocked threads in thread dump

Postby pratts » 14 Mar 2017, 12:41

Hello,
I just found some threads in blocked state in thread dump:
"qtp1185674740-67-acceptor-7-ServerConnector@7ffc64c8{HTTP/1.1}{0.0.0.0:8080}" prio=10 tid=0x00007f9be4001000 nid=0xe73 waiting for monitor entry [0x00007f9cecc56000]
java.lang.Thread.State: BLOCKED (on object monitor)
at sun.nio.ch.ServerSocketChannelImpl.accept(Unknown Source)
- waiting to lock <0x00000006439b8070> (a java.lang.Object)
at org.eclipse.jetty.server.ServerConnector.accept(ServerConnector.java:336)
at org.eclipse.jetty.server.AbstractConnector$Acceptor.run(AbstractConnector.java:466)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:607)
at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:536)
at java.lang.Thread.run(Unknown Source)

"qtp1185674740-65-acceptor-5-ServerConnector@7ffc64c8{HTTP/1.1}{0.0.0.0:8080}" prio=10 tid=0x00007f9bec001000 nid=0xe71 waiting for monitor entry [0x00007f9cece58000]
java.lang.Thread.State: BLOCKED (on object monitor)
at sun.nio.ch.ServerSocketChannelImpl.accept(Unknown Source)
- waiting to lock <0x00000006439b8070> (a java.lang.Object)
at org.eclipse.jetty.server.ServerConnector.accept(ServerConnector.java:336)
at org.eclipse.jetty.server.AbstractConnector$Acceptor.run(AbstractConnector.java:466)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:607)
at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:536)
at java.lang.Thread.run(Unknown Source)

"qtp1185674740-64-acceptor-4-ServerConnector@7ffc64c8{HTTP/1.1}{0.0.0.0:8080}" prio=10 tid=0x00007f9be8001000 nid=0xe70 waiting for monitor entry [0x00007f9cecf59000]
java.lang.Thread.State: BLOCKED (on object monitor)
at sun.nio.ch.ServerSocketChannelImpl.accept(Unknown Source)
- waiting to lock <0x00000006439b8070> (a java.lang.Object)
at org.eclipse.jetty.server.ServerConnector.accept(ServerConnector.java:336)
at org.eclipse.jetty.server.AbstractConnector$Acceptor.run(AbstractConnector.java:466)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:607)
at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:536)
at java.lang.Thread.run(Unknown Source)

"qtp1185674740-63-acceptor-3-ServerConnector@7ffc64c8{HTTP/1.1}{0.0.0.0:8080}" prio=10 tid=0x00007f9bf4001000 nid=0xe6f waiting for monitor entry [0x00007f9ced05a000]
java.lang.Thread.State: BLOCKED (on object monitor)
at sun.nio.ch.ServerSocketChannelImpl.accept(Unknown Source)
- waiting to lock <0x00000006439b8070> (a java.lang.Object)
at org.eclipse.jetty.server.ServerConnector.accept(ServerConnector.java:336)
at org.eclipse.jetty.server.AbstractConnector$Acceptor.run(AbstractConnector.java:466)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:607)
at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:536)
at java.lang.Thread.run(Unknown Source)

"qtp1185674740-62-acceptor-2-ServerConnector@7ffc64c8{HTTP/1.1}{0.0.0.0:8080}" prio=10 tid=0x00007f9bf0001000 nid=0xe6e waiting for monitor entry [0x00007f9ced15b000]
java.lang.Thread.State: BLOCKED (on object monitor)
at sun.nio.ch.ServerSocketChannelImpl.accept(Unknown Source)
- waiting to lock <0x00000006439b8070> (a java.lang.Object)
at org.eclipse.jetty.server.ServerConnector.accept(ServerConnector.java:336)
at org.eclipse.jetty.server.AbstractConnector$Acceptor.run(AbstractConnector.java:466)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:607)
at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:536)
at java.lang.Thread.run(Unknown Source)

"qtp1185674740-61-acceptor-1-ServerConnector@7ffc64c8{HTTP/1.1}{0.0.0.0:8080}" prio=10 tid=0x00007f9bfc001000 nid=0xe6d waiting for monitor entry [0x00007f9ced25c000]
java.lang.Thread.State: BLOCKED (on object monitor)
at sun.nio.ch.ServerSocketChannelImpl.accept(Unknown Source)
- waiting to lock <0x00000006439b8070> (a java.lang.Object)
at org.eclipse.jetty.server.ServerConnector.accept(ServerConnector.java:336)
at org.eclipse.jetty.server.AbstractConnector$Acceptor.run(AbstractConnector.java:466)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:607)
at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:536)
at java.lang.Thread.run(Unknown Source)

"qtp1185674740-60-acceptor-0-ServerConnector@7ffc64c8{HTTP/1.1}{0.0.0.0:8080}" prio=10 tid=0x00007f9bf8001000 nid=0xe6c waiting for monitor entry [0x00007f9ced35d000]
java.lang.Thread.State: BLOCKED (on object monitor)
at sun.nio.ch.ServerSocketChannelImpl.accept(Unknown Source)
- waiting to lock <0x00000006439b8070> (a java.lang.Object)
at org.eclipse.jetty.server.ServerConnector.accept(ServerConnector.java:336)
at org.eclipse.jetty.server.AbstractConnector$Acceptor.run(AbstractConnector.java:466)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:607)
at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:536)
at java.lang.Thread.run(Unknown Source)

What are these threads ? Are they somehow related to smartfox admin panel ?
User avatar
Lapo
Site Admin
Posts: 23008
Joined: 21 Mar 2005, 09:50
Location: Italy

Re: Some blocked threads in thread dump

Postby Lapo » 14 Mar 2017, 15:19

Hi,
these threads pertain to the HTTP server (Jetty), and their state (BLOCKED) is not indication of a problem. A thread will be in "Blocked" state when it's waiting for another thread to release a shared lock.

This is not enough to say if a thread (or more) are in a deadlock state. Given the specific stack trace of each thread I think they're just working fine, but if you want to investigate more you can check with jstack (or visualvm) which can report deadlocks.

Here's an overview of thread states:
https://dzone.com/articles/how-analyze- ... read-dumps

and here's our troubleshooting guide for live servers:
http://docs2x.smartfoxserver.com/Advanc ... ive-server

hope it helps
Lapo
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