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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 12:42:57 GMT
Github user tillrohrmann commented on a diff in the pull request:

    https://github.com/apache/flink/pull/4569#discussion_r134464434
  
    --- Diff: flink-runtime/src/main/java/org/apache/flink/runtime/rest/handler/AbstractRestHandler.java
---
    @@ -0,0 +1,201 @@
    +/*
    + * 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.handler;
    +
    +import org.apache.flink.configuration.ConfigConstants;
    +import org.apache.flink.runtime.concurrent.FutureUtils;
    +import org.apache.flink.runtime.rest.HttpMethodWrapper;
    +import org.apache.flink.runtime.rest.messages.ErrorResponseBody;
    +import org.apache.flink.runtime.rest.messages.MessageHeaders;
    +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.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.ChannelFuture;
    +import org.apache.flink.shaded.netty4.io.netty.channel.ChannelFutureListener;
    +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.SimpleChannelInboundHandler;
    +import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.DefaultHttpResponse;
    +import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.FullHttpRequest;
    +import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.HttpHeaders;
    +import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.HttpRequest;
    +import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.HttpResponse;
    +import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.HttpResponseStatus;
    +import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.LastHttpContent;
    +import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.router.Routed;
    +
    +import com.fasterxml.jackson.core.JsonParseException;
    +import com.fasterxml.jackson.databind.JsonMappingException;
    +import com.fasterxml.jackson.databind.ObjectMapper;
    +import org.slf4j.Logger;
    +import org.slf4j.LoggerFactory;
    +
    +import javax.annotation.Nonnull;
    +
    +import java.io.IOException;
    +import java.io.StringWriter;
    +import java.util.concurrent.CompletableFuture;
    +
    +import static org.apache.flink.shaded.netty4.io.netty.handler.codec.http.HttpHeaders.Names.CONNECTION;
    +import static org.apache.flink.shaded.netty4.io.netty.handler.codec.http.HttpHeaders.Names.CONTENT_TYPE;
    +import static org.apache.flink.shaded.netty4.io.netty.handler.codec.http.HttpVersion.HTTP_1_1;
    +
    +/**
    + * Super class for netty-based handlers that work with {@link RequestBody}s and {@link
ResponseBody}s.
    + *
    + * <p>Subclasses must be thread-safe.
    + *
    + * @param <R> type of incoming requests
    + * @param <P> type of outgoing responses
    + */
    +@ChannelHandler.Sharable
    +public abstract class AbstractRestHandler<R extends RequestBody, P extends ResponseBody>
extends SimpleChannelInboundHandler<Routed> {
    +	protected final Logger log = LoggerFactory.getLogger(getClass());
    +
    +	private static final ObjectMapper mapper = RestMapperUtils.getStrictObjectMapper();
    +
    +	private final MessageHeaders<R, P, ?> messageHeaders;
    +
    +	protected AbstractRestHandler(MessageHeaders<R, P, ?> messageHeaders) {
    +		this.messageHeaders = messageHeaders;
    +	}
    +
    +	public MessageHeaders<R, P, ?> getMessageHeaders() {
    +		return messageHeaders;
    +	}
    +
    +	@Override
    +	protected void channelRead0(final ChannelHandlerContext ctx, Routed routed) throws Exception
{
    +		log.debug("Received request.");
    +		final HttpRequest httpRequest = routed.request();
    +
    +		try {
    +			if (!(httpRequest instanceof FullHttpRequest)) {
    +				log.error("Implementation error: Received a request that wasn't a FullHttpResponse.");
    +				sendErrorResponse(new ErrorResponseBody("Bad request received."), HttpResponseStatus.BAD_REQUEST,
ctx, httpRequest);
    +				return;
    +			}
    +
    +			ByteBuf msgContent = ((FullHttpRequest) httpRequest).content();
    +
    +			R request;
    +			if (msgContent.capacity() == 0 || messageHeaders.getHttpMethod() == HttpMethodWrapper.GET)
{
    +				try {
    +					request = mapper.readValue("{}", messageHeaders.getRequestClass());
    +				} catch (JsonParseException | JsonMappingException je) {
    +					log.error("Implementation error: Get request bodies must have a no-argument constructor.",
je);
    +					sendErrorResponse(new ErrorResponseBody("Internal server error."), HttpResponseStatus.INTERNAL_SERVER_ERROR,
ctx, httpRequest);
    +					return;
    +				}
    +			} else {
    +				try {
    +					ByteBufInputStream in = new ByteBufInputStream(msgContent);
    +					request = mapper.readValue(in, messageHeaders.getRequestClass());
    +				} catch (JsonParseException | JsonMappingException je) {
    +					log.error("Failed to read request.", je);
    +					sendErrorResponse(new ErrorResponseBody(String.format("Request did not match expected
format %s.", messageHeaders.getRequestClass().getSimpleName())), HttpResponseStatus.BAD_REQUEST,
ctx, httpRequest);
    +					return;
    +				}
    +			}
    +
    +			CompletableFuture<HandlerResponse<P>> response;
    +			try {
    +				HandlerRequest<R> handlerRequest = new HandlerRequest<>(request, routed.pathParams(),
routed.queryParams());
    +				response = handleRequest(handlerRequest);
    +			} catch (Exception e) {
    +				response = FutureUtils.completedExceptionally(e);
    +			}
    +
    +			response.whenComplete((HandlerResponse<P> resp, Throwable error) -> {
    +				try {
    +					if (error != null) {
    +						log.error("Implementation error: Unhandled exception.", error);
    +						sendErrorResponse(new ErrorResponseBody("Internal server error."), HttpResponseStatus.INTERNAL_SERVER_ERROR,
ctx, httpRequest);
    +					} else {
    +						if (resp.wasSuccessful()) {
    +							sendResponse(messageHeaders, resp.getResponse(), ctx, httpRequest);
    +						} else {
    +							sendErrorResponse(new ErrorResponseBody(resp.getErrorMessage()), resp.getErrorCode(),
ctx, httpRequest);
    +						}
    +					}
    +				} catch (Exception e) {
    +					log.error("Critical error while sending a response.", e);
    --- End diff --
    
    I think the only reason for an exception here is the failed transformation of the (error)response
to a string. If this should happen, then we should still be able to send something to the
client. We should let him also know in this case.


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