[jira] Commented: (HADOOP-5257) Export namenode/datanode functionality through a pluggable RPC layer

["dhruba borthakur (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-5257?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12681927#action_12681927 ] 

dhruba borthakur commented on HADOOP-5257:
------------------------------------------

This looks good.

Since these are kinda-APIs to namenode/datanode, they should probably reside in src/hdfs/org/apache/hadoop/hdfs/server/protocol. Also, there could be just one Interface (instead of two), both the namenode and datanode should be able to use the same interface. The Interface would have two methods, start and stop. Please let me know if this sounds ok to you.

> Export namenode/datanode functionality through a pluggable RPC layer
> --------------------------------------------------------------------
>
>                 Key: HADOOP-5257
>                 URL: https://issues.apache.org/jira/browse/HADOOP-5257
>             Project: Hadoop Core
>          Issue Type: New Feature
>          Components: dfs
>            Reporter: Carlos Valiente
>            Priority: Minor
>         Attachments: HADOOP-5257-v2.patch, HADOOP-5257-v3.patch, HADOOP-5257.patch
>
>
> Adding support for pluggable components would allow exporting DFS functionallity using arbitrary protocols, like Thirft or Protocol Buffers. I'm opening this issue on Dhruba's suggestion in HADOOP-4707.
> Plug-in implementations would extend this base class:
> {code}abstract class Plugin {
>     public abstract datanodeStarted(DataNode datanode);
>     public abstract datanodeStopping();
>     public abstract namenodeStarted(NameNode namenode);
>     public abstract namenodeStopping();
> }{code}
> Name node instances would then start the plug-ins according to a configuration object, and would also shut them down when the node goes down:
> {code}public class NameNode {
>     // [..]
>     private void initialize(Configuration conf)
>         // [...]
>         for (Plugin p: PluginManager.loadPlugins(conf))
>           p.namenodeStarted(this);
>     }
>     // [..]
>     public void stop() {
>         if (stopRequested)
>             return;
>         stopRequested = true;
>         for (Plugin p: plugins) 
>             p.namenodeStopping();
>         // [..]
>     }
>     // [..]
> }{code}
> Data nodes would do a similar thing in {{DataNode.startDatanode()}} and {{DataNode.shutdown}}

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