Server IPC Version 9 Can't Communicate With Client Version 4
Server IPC Version 9 Can't Communicate With Client Version 4
Check out how Mark Needham got past a version incompatibility problem using Mahout.
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I’ve been working my way through Dragan Milcevski’s mini tutorial on using Mahout to do content based filtering on documents and reached the final step where I needed to read in the generated item-similarity files.
I got the example compiling by using the following Maven dependency:
<dependency>
<groupId>org.apache.mahout</groupId>
<artifactId>mahout-core</artifactId>
<version>0.9</version>
</dependency>Unfortunately, when I ran the code I ran into a version incompatibility problem:
Exception in thread "main" org.apache.hadoop.ipc.RemoteException: Server IPC version 9 cannot communicate with client version 4
at org.apache.hadoop.ipc.Client.call(Client.java:1113)
at org.apache.hadoop.ipc.RPC$Invoker.invoke(RPC.java:229)
at com.sun.proxy.$Proxy1.getProtocolVersion(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:85)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:62)
at com.sun.proxy.$Proxy1.getProtocolVersion(Unknown Source)
at org.apache.hadoop.ipc.RPC.checkVersion(RPC.java:422)
at org.apache.hadoop.hdfs.DFSClient.createNamenode(DFSClient.java:183)
at org.apache.hadoop.hdfs.DFSClient.<init>(DFSClient.java:281)
at org.apache.hadoop.hdfs.DFSClient.<init>(DFSClient.java:245)
at org.apache.hadoop.hdfs.DistributedFileSystem.initialize(DistributedFileSystem.java:100)
at org.apache.hadoop.fs.FileSystem.createFileSystem(FileSystem.java:1446)
at org.apache.hadoop.fs.FileSystem.access$200(FileSystem.java:67)
at org.apache.hadoop.fs.FileSystem$Cache.get(FileSystem.java:1464)
at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:263)
at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:124)
at com.markhneedham.mahout.Similarity.getDocIndex(Similarity.java:86)
at com.markhneedham.mahout.Similarity.main(Similarity.java:25)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)Version 0.9.0 of mahout-core was published in early 2014 so I expect it was built against an earlier version of Hadoop than I’m using (2.7.2).
I tried updating the Hadoop dependencies that were being called in the stack trace to no avail.
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-client</artifactId>
<version>2.7.2</version>
</dependency>
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-hdfs</artifactId>
<version>2.7.2</version>
</dependency>When stepping through the stack trace I noticed that my program was still using an old version of hadoop-core, so with one last throw of the dice I decided to try explicitly excluding that:
<dependency>
<groupId>org.apache.mahout</groupId>
<artifactId>mahout-core</artifactId>
<version>0.9</version>
<exclusions>
<exclusion>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-core</artifactId>
</exclusion>
</exclusions>
</dependency>And amazingly it worked. Now, finally, I can see how similar my documents are!
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