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From tillrohrmann <...@git.apache.org>
Subject [GitHub] flink pull request #4569: [FLINK-7040] [REST] Add basics for REST communicat...
Date Tue, 22 Aug 2017 12:42:39 GMT
Github user tillrohrmann commented on a diff in the pull request:

    https://github.com/apache/flink/pull/4569#discussion_r134458868
  
    --- Diff: flink-runtime/src/main/java/org/apache/flink/runtime/rest/RestClientEndpoint.java
---
    @@ -0,0 +1,263 @@
    +/*
    + * 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.rest;
    +
    +import org.apache.flink.configuration.ConfigConstants;
    +import org.apache.flink.runtime.concurrent.Executors;
    +import org.apache.flink.runtime.concurrent.FutureUtils;
    +import org.apache.flink.runtime.rest.handler.PipelineErrorHandler;
    +import org.apache.flink.runtime.rest.messages.ErrorResponseBody;
    +import org.apache.flink.runtime.rest.messages.MessageHeaders;
    +import org.apache.flink.runtime.rest.messages.ParameterMapper;
    +import org.apache.flink.runtime.rest.messages.RequestBody;
    +import org.apache.flink.runtime.rest.messages.ResponseBody;
    +import org.apache.flink.runtime.rest.util.RestMapperUtils;
    +import org.apache.flink.util.Preconditions;
    +
    +import org.apache.flink.shaded.netty4.io.netty.bootstrap.Bootstrap;
    +import org.apache.flink.shaded.netty4.io.netty.buffer.ByteBuf;
    +import org.apache.flink.shaded.netty4.io.netty.buffer.ByteBufInputStream;
    +import org.apache.flink.shaded.netty4.io.netty.buffer.Unpooled;
    +import org.apache.flink.shaded.netty4.io.netty.channel.Channel;
    +import org.apache.flink.shaded.netty4.io.netty.channel.ChannelHandler;
    +import org.apache.flink.shaded.netty4.io.netty.channel.ChannelHandlerContext;
    +import org.apache.flink.shaded.netty4.io.netty.channel.ChannelInitializer;
    +import org.apache.flink.shaded.netty4.io.netty.channel.SimpleChannelInboundHandler;
    +import org.apache.flink.shaded.netty4.io.netty.channel.nio.NioEventLoopGroup;
    +import org.apache.flink.shaded.netty4.io.netty.channel.socket.SocketChannel;
    +import org.apache.flink.shaded.netty4.io.netty.channel.socket.nio.NioSocketChannel;
    +import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.DefaultFullHttpRequest;
    +import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.FullHttpRequest;
    +import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.FullHttpResponse;
    +import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.HttpClientCodec;
    +import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.HttpHeaders;
    +import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.HttpObjectAggregator;
    +import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.HttpVersion;
    +import org.apache.flink.shaded.netty4.io.netty.handler.ssl.SslHandler;
    +
    +import com.fasterxml.jackson.core.JsonParseException;
    +import com.fasterxml.jackson.core.JsonProcessingException;
    +import com.fasterxml.jackson.databind.JsonMappingException;
    +import com.fasterxml.jackson.databind.JsonNode;
    +import com.fasterxml.jackson.databind.ObjectMapper;
    +import org.slf4j.Logger;
    +import org.slf4j.LoggerFactory;
    +
    +import javax.net.ssl.SSLEngine;
    +
    +import java.io.IOException;
    +import java.io.InputStream;
    +import java.io.StringWriter;
    +import java.util.concurrent.CompletableFuture;
    +import java.util.concurrent.Executor;
    +
    +/**
    + * This client is the counter-part to the {@link RestServerEndpoint}.
    + */
    +public class RestClientEndpoint {
    +	private static final Logger LOG = LoggerFactory.getLogger(RestClientEndpoint.class);
    +
    +	private static final ObjectMapper objectMapper = RestMapperUtils.getStrictObjectMapper();
    +
    +	private final String configuredTargetAddress;
    +	private final int configuredTargetPort;
    +	private final SSLEngine sslEngine;
    +
    +	private Bootstrap bootstrap;
    +
    +	private final ClientHandler handler = new ClientHandler();
    +
    +	private CompletableFuture<?> lastFuture = CompletableFuture.completedFuture(null);
    +
    +	private final Executor directExecutor = Executors.directExecutor();
    +
    +	public RestClientEndpoint(RestClientEndpointConfiguration configuration) {
    +		this.configuredTargetAddress = configuration.getTargetRestEndpointAddress();
    +		this.configuredTargetPort = configuration.getTargetRestEndpointPort();
    +		this.sslEngine = configuration.getSslEngine();
    +	}
    +
    +	public void start() {
    +		ChannelInitializer<SocketChannel> initializer = new ChannelInitializer<SocketChannel>()
{
    +
    +			@Override
    +			protected void initChannel(SocketChannel ch) {
    +
    +				// SSL should be the first handler in the pipeline
    +				if (sslEngine != null) {
    +					ch.pipeline().addLast("ssl", new SslHandler(sslEngine));
    +				}
    +
    +				ch.pipeline()
    +					.addLast(new HttpClientCodec())
    +					.addLast(new HttpObjectAggregator(1024 * 1024))
    +					.addLast(handler)
    +					.addLast(new PipelineErrorHandler(LOG));
    +			}
    +		};
    +
    +		NioEventLoopGroup group = new NioEventLoopGroup(1);
    +
    +		bootstrap = new Bootstrap();
    +		bootstrap
    +			.group(group)
    +			.channel(NioSocketChannel.class)
    +			.handler(initializer);
    +
    +		LOG.info("Rest client endpoint started.");
    +	}
    +
    +	public void shutdown() {
    +		if (bootstrap != null) {
    +			if (bootstrap.group() != null) {
    +				bootstrap.group().shutdownGracefully();
    +			}
    +		}
    +	}
    +
    +	public <M extends MessageHeaders<R, P, U>, U extends ParameterMapper, R extends
RequestBody, P extends ResponseBody> CompletableFuture<P> sendRequest(M messageHeaders,
U urlResolver, R request) throws IOException {
    +		Preconditions.checkNotNull(messageHeaders);
    +		Preconditions.checkNotNull(request);
    +
    +		String targetUrl = ParameterMapper.resolveUrl(
    +			messageHeaders.getTargetRestEndpointURL(),
    +			urlResolver.mapPathParameters(messageHeaders.getPathParameters()),
    +			urlResolver.mapQueryParameters(messageHeaders.getQueryParameters())
    +		);
    +
    +		LOG.debug("Sending request of class {} to {}", request.getClass(), targetUrl);
    +		// serialize payload
    +		StringWriter sw = new StringWriter();
    +		objectMapper.writeValue(sw, request);
    +		ByteBuf payload = Unpooled.wrappedBuffer(sw.toString().getBytes(ConfigConstants.DEFAULT_CHARSET));
    +
    +		// create request and set headers
    +		FullHttpRequest httpRequest = new DefaultFullHttpRequest(HttpVersion.HTTP_1_1, messageHeaders.getHttpMethod().getNettyHttpMethod(),
targetUrl, payload);
    +		httpRequest.headers()
    +			.add(HttpHeaders.Names.CONTENT_LENGTH, payload.capacity())
    +			.add(HttpHeaders.Names.CONTENT_TYPE, "application/json; charset=" + ConfigConstants.DEFAULT_CHARSET.name())
    +			.set(HttpHeaders.Names.HOST, configuredTargetAddress + ":" + configuredTargetPort)
    +			.set(HttpHeaders.Names.CONNECTION, HttpHeaders.Values.CLOSE);
    +
    +		synchronized (this) {
    +			// This ensures strict sequential processing of requests.
    +			// If we send new requests immediately we can no longer make assumptions about the
order in which responses
    +			// arrive, due to which the handler cannot know which future he should complete (not
to mention what response
    +			// type to read).
    +			CompletableFuture<P> nextFuture = lastFuture
    +				.handleAsync((f, e) -> submitRequest(httpRequest, messageHeaders), directExecutor)
    +				.thenCompose((future) -> future);
    +
    +			lastFuture = nextFuture;
    +			return nextFuture;
    +		}
    +	}
    +
    +	private <M extends MessageHeaders<R, P, U>, U extends ParameterMapper, R extends
RequestBody, P extends ResponseBody> CompletableFuture<P> submitRequest(FullHttpRequest
httpRequest, M messageHeaders) {
    +		CompletableFuture<P> responseFuture = handler.expectResponse(messageHeaders.getResponseClass());
    +
    +		try {
    +			// write request
    +			Channel channel = bootstrap.connect(configuredTargetAddress, configuredTargetPort).sync().channel();
    +			channel.writeAndFlush(httpRequest);
    --- End diff --
    
    Here we could retrieve the ClientHandler via `channel.pipeline().get(ClientHandler.class)`
and then get the future of this handler back.


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