[GitHub] [flink] tillrohrmann commented on a change in pull request #12037: [FLINK-14807][runtime][client] Introduce communication through REST API between the clients and the operator coordinators

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tillrohrmann commented on a change in pull request #12037:
URL: https://github.com/apache/flink/pull/12037#discussion_r424914569



##########
File path: flink-runtime/src/main/java/org/apache/flink/runtime/rest/handler/job/coordination/ClientCoordinationHandler.java
##########
@@ -0,0 +1,84 @@
+/*
+ * 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.job.coordination;
+
+import org.apache.flink.api.common.JobID;
+import org.apache.flink.api.common.time.Time;
+import org.apache.flink.runtime.jobgraph.OperatorID;
+import org.apache.flink.runtime.operators.coordination.CoordinationRequest;
+import org.apache.flink.runtime.operators.coordination.CoordinationResponse;
+import org.apache.flink.runtime.rest.handler.AbstractRestHandler;
+import org.apache.flink.runtime.rest.handler.HandlerRequest;
+import org.apache.flink.runtime.rest.handler.RestHandlerException;
+import org.apache.flink.runtime.rest.messages.JobIDPathParameter;
+import org.apache.flink.runtime.rest.messages.MessageHeaders;
+import org.apache.flink.runtime.rest.messages.OperatorIDPathParameter;
+import org.apache.flink.runtime.rest.messages.job.coordination.ClientCoordinationMessageParameters;
+import org.apache.flink.runtime.rest.messages.job.coordination.ClientCoordinationRequestBody;
+import org.apache.flink.runtime.rest.messages.job.coordination.ClientCoordinationResponseBody;
+import org.apache.flink.runtime.webmonitor.RestfulGateway;
+import org.apache.flink.runtime.webmonitor.retriever.GatewayRetriever;
+import org.apache.flink.util.SerializedValue;
+
+import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.HttpResponseStatus;
+
+import javax.annotation.Nonnull;
+
+import java.io.IOException;
+import java.util.Map;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionException;
+
+/**
+ * Handler that receives the coordination requests from the client and returns the response from the coordinator.
+ */
+public class ClientCoordinationHandler extends AbstractRestHandler<RestfulGateway, ClientCoordinationRequestBody, ClientCoordinationResponseBody, ClientCoordinationMessageParameters> {
+
+	public ClientCoordinationHandler(
+			GatewayRetriever<? extends RestfulGateway> leaderRetriever,
+			Time timeout,
+			Map<String, String> responseHeaders,
+			MessageHeaders<ClientCoordinationRequestBody, ClientCoordinationResponseBody, ClientCoordinationMessageParameters> messageHeaders) {
+		super(leaderRetriever, timeout, responseHeaders, messageHeaders);
+	}
+
+	@Override
+	protected CompletableFuture<ClientCoordinationResponseBody> handleRequest(
+			@Nonnull HandlerRequest<ClientCoordinationRequestBody, ClientCoordinationMessageParameters> request,
+			@Nonnull RestfulGateway gateway) throws RestHandlerException {
+		JobID jobId = request.getPathParameter(JobIDPathParameter.class);
+		OperatorID operatorId = request.getPathParameter(OperatorIDPathParameter.class);
+		SerializedValue<CoordinationRequest> serializedRequest =
+			request.getRequestBody().getSerializedCoordinationRequest();
+		CompletableFuture<CoordinationResponse> responseFuture =
+			gateway.deliverCoordinationRequestToCoordinator(jobId, operatorId, serializedRequest, timeout);
+		return responseFuture.thenApply(
+			coordinationResponse -> {
+				try {
+					return new ClientCoordinationResponseBody(new SerializedValue<>(coordinationResponse));

Review comment:
       Makes sense. I guess we will use another layer of `SerializedValue` if the user requests a user code object from the `OperatorCoordinator` which is then initialized on the JM.




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