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https://issues.apache.org/jira/browse/XMLRPC-168?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jochen Wiedmann updated XMLRPC-168:
-----------------------------------
Attachment: ThreadPool.java
Client.java
Thanks for the hint to jps and jstack. It showed me that the patched version of
the ThreadPool at least did indeed decouple the ThreadPool and the Poolable
class. With that knowledge it was easy to deduce a fix: By declaring the
variables Poolable.shuttingDown and Poolable.task as volatile I could remove
the synchronized keyword from several Poolable methods.
With the new version of ThreadPool and a slightly more interesting version of
the Client, I was able to perform 1000000 calls to the server from 10
concurrent clients. No client ceased to work.
> XML-RPC server deadlocks under heavy load
> -----------------------------------------
>
> Key: XMLRPC-168
> URL: https://issues.apache.org/jira/browse/XMLRPC-168
> Project: XML-RPC
> Issue Type: Bug
> Components: Source
> Affects Versions: 3.1.2
> Environment: Soalris
> Reporter: Alan Burlison
> Attachments: Client.java, Client.java, Server.java, ThreadPool.java,
> ThreadPool.java
>
>
> When running a XML-RPC server under heavy load, it eventually deadlocks
> inside the thread pool that manages the 'worker' threads which handle the
> individual XML-RPC requests - the classes involved are
> org.apache.xmlrpc.util.ThreadPool and
> org.apache.xmlrpc.util.ThreadPool$Poolable. jstack on the hung process shows:
> ----------
> Found one Java-level deadlock:
> =============================
> "XML-RPC-13":
> waiting to lock monitor 0x08d10bec (object 0xbb6959c0, a
> org.apache.xmlrpc.util.ThreadPool),
> which is held by "XML-RPC Weblistener"
> "XML-RPC Weblistener":
> waiting to lock monitor 0x08d1186c (object 0xbd2ed340, a
> org.apache.xmlrpc.util.ThreadPool$Poolable$1),
> which is held by "XML-RPC-2"
> "XML-RPC-2":
> waiting to lock monitor 0x08d112f4 (object 0xbd2ed570, a
> org.apache.xmlrpc.util.ThreadPool$Poolable),
> which is held by "XML-RPC Weblistener"
> Java stack information for the threads listed above:
> ===================================================
> "XML-RPC-13":
> at org.apache.xmlrpc.util.ThreadPool.repool(Unknown Source)
> - waiting to lock <0xbb6959c0> (a org.apache.xmlrpc.util.ThreadPool)
> at org.apache.xmlrpc.util.ThreadPool$Poolable$1.run(Unknown Source)
> "XML-RPC Weblistener":
> at org.apache.xmlrpc.util.ThreadPool$Poolable.start(Unknown Source)
> - waiting to lock <0xbd2ed340> (a
> org.apache.xmlrpc.util.ThreadPool$Poolable$1)
> - locked <0xbd2ed570> (a org.apache.xmlrpc.util.ThreadPool$Poolable)
> at org.apache.xmlrpc.util.ThreadPool.startTask(Unknown Source)
> - locked <0xbb6959c0> (a org.apache.xmlrpc.util.ThreadPool)
> at org.apache.xmlrpc.webserver.WebServer.run(Unknown Source)
> at java.lang.Thread.run(Thread.java:619)
> "XML-RPC-2":
> at org.apache.xmlrpc.util.ThreadPool$Poolable.isShuttingDown(Unknown
> Source)
> - waiting to lock <0xbd2ed570> (a
> org.apache.xmlrpc.util.ThreadPool$Poolable)
> at org.apache.xmlrpc.util.ThreadPool$Poolable.access$000(Unknown Source)
> at org.apache.xmlrpc.util.ThreadPool$Poolable$1.run(Unknown Source)
> - locked <0xbd2ed340> (a org.apache.xmlrpc.util.ThreadPool$Poolable$1)
> Found 1 deadlock.
> ----------
> And another slight variant on the above, from a debug build of revision
> 769436.
> ----------
> Found one Java-level deadlock:
> =============================
> "XML-RPC-6":
> waiting to lock monitor 0x0870d8ec (object 0xbac020f8, a
> org.apache.xmlrpc.util.ThreadPool),
> which is held by "XML-RPC Weblistener"
> "XML-RPC Weblistener":
> waiting to lock monitor 0x0814de4c (object 0xbad73820, a
> org.apache.xmlrpc.util.ThreadPool$Poolable$1),
> which is held by "XML-RPC-5"
> "XML-RPC-5":
> waiting to lock monitor 0x0814eacc (object 0xbad73b48, a
> org.apache.xmlrpc.util.ThreadPool$Poolable),
> which is held by "XML-RPC Weblistener"
> Java stack information for the threads listed above:
> ===================================================
> "XML-RPC-6":
> at org.apache.xmlrpc.util.ThreadPool.repool(ThreadPool.java:136)
> - waiting to lock <0xbac020f8> (a org.apache.xmlrpc.util.ThreadPool)
> at org.apache.xmlrpc.util.ThreadPool$Poolable$1.run(ThreadPool.java:70)
> "XML-RPC Weblistener":
> at org.apache.xmlrpc.util.ThreadPool$Poolable.start(ThreadPool.java:106)
> - waiting to lock <0xbad73820> (a
> org.apache.xmlrpc.util.ThreadPool$Poolable$1)
> - locked <0xbad73b48> (a org.apache.xmlrpc.util.ThreadPool$Poolable)
> at org.apache.xmlrpc.util.ThreadPool.startTask(ThreadPool.java:168)
> - locked <0xbac020f8> (a org.apache.xmlrpc.util.ThreadPool)
> at org.apache.xmlrpc.webserver.WebServer.run(WebServer.java:338)
> at java.lang.Thread.run(Thread.java:619)
> "XML-RPC-5":
> at
> org.apache.xmlrpc.util.ThreadPool$Poolable.getTask(ThreadPool.java:99)
> - waiting to lock <0xbad73b48> (a
> org.apache.xmlrpc.util.ThreadPool$Poolable)
> at
> org.apache.xmlrpc.util.ThreadPool$Poolable.access$100(ThreadPool.java:47)
> at org.apache.xmlrpc.util.ThreadPool$Poolable$1.run(ThreadPool.java:59)
> - locked <0xbad73820> (a org.apache.xmlrpc.util.ThreadPool$Poolable$1)
> Found 1 deadlock.
> ----------
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