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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