[HADOOP-5257] Export namenode/datanode functionality through a pluggable RPC layer - ASF JIRA

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Details

Type: New Feature
Status: Closed
Priority: Minor
Resolution: Fixed
Affects Version/s: None
Fix Version/s: 0.21.0
Component/s: None
Labels:
None

Hadoop Flags:

Reviewed
Release Note:
New plugin facility for namenode and datanode instantiates classes named in new configuration properties dfs.datanode.plugins and dfs.namenode.plugins.

Description

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:

abstract class Plugin {

    public abstract datanodeStarted(DataNode datanode);

    public abstract datanodeStopping();

    public abstract namenodeStarted(NameNode namenode);

    public abstract namenodeStopping();
}

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:

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();
        // [..]
    }

    // [..]
}