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https://issues.apache.org/jira/browse/HAMA-378?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13021045#comment-13021045
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Thomas Jungblut commented on HAMA-378:
--------------------------------------
Hey, I think I have found a related issue with the classloader:
Since message patch the user can implement his own message type. Running with
this message tells me on the grooms:
{noformat}
2011-04-18 16:23:37,619 INFO org.apache.hadoop.ipc.Server: IPC Server listener
on 58648: readAndProcess threw exception java.lang.RuntimeException: readObject
can't find class de.jungblut.hama.model.IntegerDoubleMessage. Count of bytes
read: 0
java.lang.RuntimeException: readObject can't find class
de.jungblut.hama.model.IntegerDoubleMessage
at
org.apache.hadoop.io.ObjectWritable.readObject(ObjectWritable.java:233)
at org.apache.hadoop.ipc.RPC$Invocation.readFields(RPC.java:103)
at org.apache.hadoop.ipc.Server$Connection.processData(Server.java:908)
at
org.apache.hadoop.ipc.Server$Connection.readAndProcess(Server.java:847)
at org.apache.hadoop.ipc.Server$Listener.doRead(Server.java:421)
at org.apache.hadoop.ipc.Server$Listener.run(Server.java:330)
Caused by: java.lang.ClassNotFoundException:
de.jungblut.hama.model.IntegerDoubleMessage
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:247)
at
org.apache.hadoop.conf.Configuration.getClassByName(Configuration.java:762)
at
org.apache.hadoop.io.ObjectWritable.readObject(ObjectWritable.java:231)
... 5 more
{noformat}
Obviously the jar contains this class, the jar has been transfered to the
grooms and got unpacked:
{noformat}
hadoop@raynor:/usr/local$
/srv/hama/bsp/local/groomServer/attempt_201104181622_0001_000001_0/
job.jar job.xml work/
hadoop@raynor:/usr/local$
/srv/hama/bsp/local/groomServer/attempt_201104181622_0001_000001_0/work/
de/ META-INF/
hadoop@raynor:/usr/local$
/srv/hama/bsp/local/groomServer/attempt_201104181622_0001_000001_0/work/de/jungblut/
graph/ hama/ mapreduce/
hadoop@raynor:/usr/local$
/srv/hama/bsp/local/groomServer/attempt_201104181622_0001_000001_0/work/de/jungblut/hama/
bsp/ graph/ mapreduce/ model/ partioning/
hadoop@raynor:/usr/local$ ls
/srv/hama/bsp/local/groomServer/attempt_201104181622_0001_000001_0/work/de/jungblut/hama/model/
BooleanMessage.class IntegerDoubleMessage.class WeightedVertex.class
FullIntegerMessage.class IntegerMessage.class
hadoop@raynor:/usr/local$ ls
/srv/hama/bsp/local/groomServer/attempt_201104181622_0001_000001_0/work/de/jungblut/hama/model/
BooleanMessage.class IntegerDoubleMessage.class WeightedVertex.class
FullIntegerMessage.class IntegerMessage.class
{noformat}
Looking at the stacktrace reveals the AppClassLoader too.
> Lost connection to BSP Master [host/ip:port]. Retrying...
> -----------------------------------------------------------
>
> Key: HAMA-378
> URL: https://issues.apache.org/jira/browse/HAMA-378
> Project: Hama
> Issue Type: Improvement
> Components: bsp
> Reporter: ChiaHung Lin
> Priority: Minor
>
> When submitting a job, at the server side the GroomServer reports message
> Lost connection to BSP Master [host/ip:port]. Retrying...
> java.lang.NullPointerException
> This seems because the script hama only includes jar files (such as
> hama-0.3.0-examples.jar) located under basedir, the same folder as build.xml.
> Also, a quick check shows that when submitting a job, the ClassLader used is
> sun.misc.Launcher$AppClassLoader, instead of java.net.URLClassLoader. This
> might not be the root cause, but a further investigation may be required.
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