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From Daniel M Garland <daniel.garl...@titanemail.com>
Subject Re: DeltaManager cannot receive message through TCP channel in Tomcat cluster
Date Mon, 01 Oct 2007 10:09:42 GMT
OK I've figured out what's happening, but not how to fix it!

I'm running a single Tomcat instance that is hosting some virtual hosts, 
and we have three Tapestry web applications. For those unfamiliar with 
Tapestry, a Visit object is defined to represent the user's session and 
is sort of a facade to avoid working directly with HttpSession. Hence in 
a cluster this Visit object is propagated around the cluster.

Now, what seems to be the case is that Tomcat is getting muddled up with 
the different Visit classes in each separate application; which is not 
good. Not only are the classes in different java packages, but they have 
unique serialVersionIDs. This then gives me the error:

java.io.InvalidClassException: com.mydomain.Visit; local class 
incompatible: stream classdesc serialVersionUID = -139355480
5485899996, local class serialVersionUID = 8444624889687850885

and it turns out that -1393554805485899996 is the Visit object from a 
completely different web application.

I'm trying to figure out what changes to my config I made when I went 
from my old hardware to a new setup, and I believe that the only change 
is that we configured each virtual host to use its own <cluster> 
element, rather than having a single cluster for the engine; but I 
would've thought that having three seperate clusters on different ports/ 
addresses would help to prevent this sort of thing happening, rather 
than cause it?

Any other reasons why my serialized objects are being confused in this 
way?

Daniel M Garland wrote:
> Hi all,
> 
> I've been running two Tomcat 5.5.20 servers in a cluster for some time 
> on Mac OSx but we've recently moved to 64-bit architecture (Debian etch) 
> . I tried as far as possible to keep the config the same, so only the OS 
> has changed (and I also got the Apache Portable Runtime going). However 
> since moving to this new setup I'm starting to see the following 
> messages in my catalina.out:
> 
> 25-Sep-2007 16:35:11 org.apache.catalina.cluster.session.DeltaManager 
> messageReceived
> SEVERE: Manager []: Unable to receive message through TCP channel
> java.lang.ClassNotFoundException:
> com.mycompany.someSerialiazbleObject
> 
> and sometimes in other web apps I see instead of ClassNotFoundException:
> 
> java.io.InvalidClassException: 
> org.mycomapny.someOtherSerializableObject; local class incompatible: 
> stream classdesc serialVersionUID = -1393554805485899996, local class 
> serialVersionUID = 8444624889687850885
> 
> Now I did some homework here and I've tried the following without success:
> 
> 1) I've compiled the java files on the server's themselves, so I am sure 
> that the correct class versions are being used
> 2) The object implements java.io.Serializable, and has a generated 
> serial ID from Eclipse. Incidentally, this Long value matches the local 
> class serialVersionUID, so I have no idea where the 'stream' 
> serialVersionUID comes from.
> 3) I have the same code running on both the Tomcat servers.
> 
> What I would like to know is where I am supposed to look next for some 
> answers to this problem. Is there any more information from my config 
> that would be relevant to post here?
> 
> Thanks in advance, my first 'tomcat-users' post :)
> 
> Dan Garland
> daniel.garland@NO-SPAMtitanemail.com
> 
> -- Stack Trace --
> 25-Sep-2007 16:35:11 org.apache.catalina.cluster.session.DeltaManager 
> messageReceived
> SEVERE: Manager []: Unable to receive message through TCP channel
> java.lang.ClassNotFoundException:
> com.mycompany.someSerialiazbleObject
>         at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
>         at java.security.AccessController.doPrivileged(Native Method)
>         at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
>         at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
>         at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
>         at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
>         at java.lang.Class.forName0(Native Method)
>         at java.lang.Class.forName(Class.java:242)
>         at 
> java.io.ObjectInputStream.resolveClass(ObjectInputStream.java:574)
>         at 
> org.apache.catalina.cluster.session.ReplicationStream.resolveClass(ReplicationStream.java:84)

> 
>         at 
> java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1538)
>         at 
> java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1460)
>         at 
> java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1693)
>         at 
> java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1299)
>         at java.io.ObjectInputStream.readObject(ObjectInputStream.java:339)
>         at 
> org.apache.catalina.cluster.session.DeltaRequest$AttributeInfo.readExternal(DeltaRequest.java:334)

> 
>         at 
> org.apache.catalina.cluster.session.DeltaRequest.readExternal(DeltaRequest.java:246)

> 
>         at 
> org.apache.catalina.cluster.session.DeltaManager.loadDeltaRequest(DeltaManager.java:697)

> 
>         at 
> org.apache.catalina.cluster.session.DeltaManager.handleSESSION_DELTA(DeltaManager.java:1572)

> 
>         at 
> org.apache.catalina.cluster.session.DeltaManager.messageReceived(DeltaManager.java:1522)

> 
>         at 
> org.apache.catalina.cluster.session.DeltaManager.messageDataReceived(DeltaManager.java:1271)

> 
>         at 
> org.apache.catalina.cluster.session.ClusterSessionListener.messageReceived(ClusterSessionListener.java:85)

> 
>         at 
> org.apache.catalina.cluster.tcp.SimpleTcpCluster.receive(SimpleTcpCluster.java:1167)

> 
>         at 
> org.apache.catalina.cluster.tcp.ClusterReceiverBase.messageDataReceived(ClusterReceiverBase.java:426)

> 
>         at 
> org.apache.catalina.cluster.io.ObjectReader.execute(ObjectReader.java:107)
>         at 
> org.apache.catalina.cluster.tcp.TcpReplicationThread.drainChannel(TcpReplicationThread.java:138)

> 
>         at 
> org.apache.catalina.cluster.tcp.TcpReplicationThread.run(TcpReplicationThread.java:69)

> 
> 
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