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From tillrohrmann <...@git.apache.org>
Subject [GitHub] flink pull request #2357: [FLINK-4362] [rpc] Auto generate rpc gateways via ...
Date Thu, 11 Aug 2016 15:22:22 GMT
Github user tillrohrmann commented on a diff in the pull request:

    https://github.com/apache/flink/pull/2357#discussion_r74443020
  
    --- Diff: flink-runtime/src/main/java/org/apache/flink/runtime/rpc/akka/AkkaRpcActor.java
---
    @@ -0,0 +1,176 @@
    +/*
    + * Licensed to the Apache Software Foundation (ASF) under one
    + * or more contributor license agreements.  See the NOTICE file
    + * distributed with this work for additional information
    + * regarding copyright ownership.  The ASF licenses this file
    + * to you under the Apache License, Version 2.0 (the
    + * "License"); you may not use this file except in compliance
    + * with the License.  You may obtain a copy of the License at
    + *
    + *     http://www.apache.org/licenses/LICENSE-2.0
    + *
    + * Unless required by applicable law or agreed to in writing, software
    + * distributed under the License is distributed on an "AS IS" BASIS,
    + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    + * See the License for the specific language governing permissions and
    + * limitations under the License.
    + */
    +
    +package org.apache.flink.runtime.rpc.akka;
    +
    +import akka.actor.Status;
    +import akka.actor.UntypedActor;
    +import akka.pattern.Patterns;
    +import org.apache.flink.runtime.rpc.RpcEndpoint;
    +import org.apache.flink.runtime.rpc.RpcGateway;
    +import org.apache.flink.runtime.rpc.akka.messages.CallAsync;
    +import org.apache.flink.runtime.rpc.akka.messages.RpcInvocation;
    +import org.apache.flink.runtime.rpc.akka.messages.RunAsync;
    +import org.apache.flink.util.Preconditions;
    +import org.slf4j.Logger;
    +import org.slf4j.LoggerFactory;
    +import scala.concurrent.Future;
    +
    +import java.lang.reflect.Method;
    +import java.util.concurrent.Callable;
    +
    +/**
    + * Akka rpc actor which receives {@link RpcInvocation}, {@link RunAsync} and {@link CallAsync}
    + * messages.
    + * <p>
    + * The {@link RpcInvocation} designates a rpc and is dispatched to the given {@link RpcEndpoint}
    + * instance.
    + * <p>
    + * The {@link RunAsync} and {@link CallAsync} messages contain executable code which
is executed
    + * in the context of the actor thread.
    + *
    + * @param <C> Type of the {@link RpcGateway} associated with the {@link RpcEndpoint}
    + * @param <T> Type of the {@link RpcEndpoint}
    + */
    +class AkkaRpcActor<C extends RpcGateway, T extends RpcEndpoint<C>> extends
UntypedActor {
    +	private static final Logger LOG = LoggerFactory.getLogger(AkkaRpcActor.class);
    +
    +	private final T rpcEndpoint;
    +
    +	AkkaRpcActor(final T rpcEndpoint) {
    +		this.rpcEndpoint = Preconditions.checkNotNull(rpcEndpoint, "rpc endpoint");
    +	}
    +
    +	@Override
    +	public void onReceive(final Object message)  {
    +		if (message instanceof RunAsync) {
    +			handleRunAsync((RunAsync) message);
    +		} else if (message instanceof CallAsync) {
    +			handleCallAsync((CallAsync) message);
    +		} else if (message instanceof RpcInvocation) {
    +			handleRpcInvocation((RpcInvocation) message);
    +		} else {
    +			throw new RuntimeException("Encountered unknown message type " + message.getClass()
+
    +				" with value " + message + '.');
    +		}
    +	}
    +
    +	/**
    +	 * Handle rpc invocations by looking up the rpc method on the rpc endpoint and calling
this
    +	 * method with the provided method arguments. If the method has a return value, it is
returned
    +	 * to the sender of the call.
    +	 *
    +	 * @param rpcInvocation Rpc invocation message
    +	 */
    +	private void handleRpcInvocation(RpcInvocation rpcInvocation) {
    +		Method rpcMethod = null;
    +
    +		try {
    +			rpcMethod = lookupRpcMethod(rpcInvocation.getMethodName(), rpcInvocation.getParameterTypes());
    +		} catch (final NoSuchMethodException e) {
    +			LOG.error("Could not find rpc method for rpc invocation: {}.", rpcInvocation, e);
    +		}
    +
    +		if (rpcMethod != null) {
    +			if (rpcMethod.getReturnType().equals(Void.TYPE)) {
    +				// No return value to send back
    +				try {
    +					rpcMethod.invoke(rpcEndpoint, rpcInvocation.getArgs());
    +				} catch (Throwable e) {
    +					LOG.error("Error while executing remote procedure call {}.", rpcMethod, e);
    +				}
    +			} else {
    +				try {
    +					Object result = rpcMethod.invoke(rpcEndpoint, rpcInvocation.getArgs());
    +
    +					if (result instanceof Future) {
    +						// pipe result to sender
    +						Patterns.pipe((Future<?>) result, getContext().dispatcher()).to(getSender());
    +					} else {
    +						// tell the sender the result of the computation
    +						getSender().tell(new Status.Success(result), getSelf());
    +					}
    +				} catch (Throwable e) {
    +					// tell the sender about the failure
    +					getSender().tell(new Status.Failure(e), getSelf());
    +				}
    +			}
    +		}
    +	}
    +
    +	/**
    +	 * Handle asynchronous {@link Callable}. This method simply executes the given {@link
Callable}
    +	 * in the context of the actor thread.
    +	 *
    +	 * @param callAsync Call async message
    +	 */
    +	private void handleCallAsync(CallAsync callAsync) {
    +		if (callAsync.getCallable() == null) {
    +			final String result = "Received a " + callAsync.getClass().getName() + " message with
an empty " +
    --- End diff --
    
    Yes exactly. This branch should never be reached but I included it to treat the case that
local messages get serialized (if Akka is instructed to do so).


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