Hadoop YARN RPC (part I)

I have spent some time digging into YARN RPC source codes. Personally, I like the use of Factory pattern to inject different RPC proxy client protocol and server implementations to the framework. It looks way cleaner and better compared to the older versions of Hadoop.

For example: RpcServerFactoryPBImpl is the implementation of RpcServerFactory interface to create Protobuf RPC Server. Basically, it delegates the creation using the standard Hadoop RPC class.

Look at the following snippet in RpcServerFactoryPBImpl,

private Server createServer(Class<?> pbProtocol, InetSocketAddress addr, Configuration conf, 
      SecretManager<? extends TokenIdentifier> secretManager, int numHandlers, 
      BlockingService blockingService, String portRangeConfig) throws IOException {
    RPC.setProtocolEngine(conf, pbProtocol, ProtobufRpcEngine.class);
    RPC.Server server = RPC.getServer(pbProtocol, blockingService, 
        addr.getHostName(), addr.getPort(), numHandlers, false, conf, 
        secretManager, portRangeConfig);
    LOG.info("Adding protocol "+pbProtocol.getCanonicalName()+" to the server");
    server.addProtocol(RPC.RpcKind.RPC_PROTOCOL_BUFFER, pbProtocol, blockingService);
    return server;

We could create a new type of RPC Server Factory called RpcServerFactoryMyOwnImpl that implements the above createServer method which would return our own RPC Server.

In YARN framework, HadoopYarnProtoRPC is the class uses these factories.
Basically, it calls RpcFactoryProvider.getServerFactory(conf) to get the right RpcServerFactory implementation.

public class HadoopYarnProtoRPC extends YarnRPC {

  private static final Log LOG = LogFactory.getLog(HadoopYarnProtoRPC.class);

  public Object getProxy(Class protocol, InetSocketAddress addr,
      Configuration conf) {
    LOG.debug("Creating a HadoopYarnProtoRpc proxy for protocol " + protocol);
    return RpcFactoryProvider.getClientFactory(conf).getClient(protocol, 1,
        addr, conf);

  public void stopProxy(Object proxy, Configuration conf) {

  public Server getServer(Class protocol, Object instance,
      InetSocketAddress addr, Configuration conf,
      SecretManager<? extends TokenIdentifier> secretManager,
      int numHandlers, String portRangeConfig) {
    LOG.debug("Creating a HadoopYarnProtoRpc server for protocol " + protocol + 
        " with " + numHandlers + " handlers");
    return RpcFactoryProvider.getServerFactory(conf).getServer(protocol, 
        instance, addr, conf, secretManager, numHandlers, portRangeConfig);



To be continued…

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