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Date: Fri, 16 Dec 2011 09:08:30 +0000 (UTC)
From: "Aaron T. Myers (Created) (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
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 <231197017.18798.1324026510904.JavaMail.tomcat@hel.zones.apache.org>
Subject: [jira] [Created] (HDFS-2694) Removal of Avro broke non-PB NN
 services
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Removal of Avro broke non-PB NN services
----------------------------------------

                 Key: HDFS-2694
                 URL: https://issues.apache.org/jira/browse/HDFS-2694
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: name-node
    Affects Versions: 0.24.0
            Reporter: Aaron T. Myers
            Assignee: Aaron T. Myers


RpcEngine implementations have to register themselves associated with an RpcKind. Both WritableRpcEngine and ProtobufRpcEngine do this registration in static initialization blocks. It used to be that the static initializer block for WritableRpcEngine was triggered when AvroRpcEngine was initialized, since this instantiated a WritableRpcEngine object. With AvroRpcEngine gone, there's nothing in the NN to trigger the WritableRpcEngine static initialization block. Therefore, those RPC services which still use Writable and not PB no longer work.

For example, if I try to run `hdfs groups' on trunk, which uses the GetUserMappingsProtocol, this error gets spit out:

{noformat}
$ hdfs groups
log4j:ERROR Could not find value for key log4j.appender.NullAppender
log4j:ERROR Could not instantiate appender named "NullAppender".
Exception in thread "main" java.io.IOException: Unknown rpc kind RPC_WRITABLE
	at org.apache.hadoop.ipc.Client.call(Client.java:1136)
	at org.apache.hadoop.ipc.WritableRpcEngine$Invoker.invoke(WritableRpcEngine.java:205)
	at $Proxy6.getGroupsForUser(Unknown Source)
	at org.apache.hadoop.tools.GetGroupsBase.run(GetGroupsBase.java:71)
	at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:69)
	at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:83)
	at org.apache.hadoop.hdfs.tools.GetGroups.main(GetGroups.java:56)
{noformat}

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