content: /*
   * 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.beam.runners.dataflow.worker.windmill.client.grpc;
  
  import com.google.errorprone.annotations.concurrent.GuardedBy;
  import java.io.PrintWriter;
  import java.time.Duration;
  import java.time.Instant;
  import java.util.Optional;
  import java.util.Set;
  import java.util.concurrent.ScheduledExecutorService;
  import java.util.function.Consumer;
  import java.util.function.Function;
  import org.apache.beam.runners.dataflow.worker.windmill.Windmill.JobHeader;
  import org.apache.beam.runners.dataflow.worker.windmill.Windmill.WorkerMetadataRequest;
  import org.apache.beam.runners.dataflow.worker.windmill.Windmill.WorkerMetadataResponse;
  import org.apache.beam.runners.dataflow.worker.windmill.WindmillEndpoints;
  import org.apache.beam.runners.dataflow.worker.windmill.client.AbstractWindmillStream;
  import org.apache.beam.runners.dataflow.worker.windmill.client.WindmillStream.GetWorkerMetadataStream;
  import org.apache.beam.runners.dataflow.worker.windmill.client.WindmillStreamShutdownException;
  import org.apache.beam.runners.dataflow.worker.windmill.client.grpc.observers.StreamObserverFactory;
  import org.apache.beam.sdk.util.BackOff;
  import org.apache.beam.vendor.grpc.v1p69p0.io.grpc.Status;
  import org.apache.beam.vendor.grpc.v1p69p0.io.grpc.stub.StreamObserver;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  public final class GrpcGetWorkerMetadataStream
      extends AbstractWindmillStream<WorkerMetadataRequest, WorkerMetadataResponse>
      implements GetWorkerMetadataStream {
    private static final Logger LOG = LoggerFactory.getLogger(GrpcGetWorkerMetadataStream.class);
    private static final WorkerMetadataRequest HEALTH_CHECK_REQUEST =
        WorkerMetadataRequest.getDefaultInstance();
    private final WorkerMetadataRequest workerMetadataRequest;
    private final Consumer<WindmillEndpoints> serverMappingConsumer;
    private final Object metadataLock;
  
    @GuardedBy("metadataLock")
    private WorkerMetadataResponse latestResponse;
  
    @GuardedBy("metadataLock")
    private Instant latestResponseReceived = Instant.EPOCH;
  
    private GrpcGetWorkerMetadataStream(
        Function<StreamObserver<WorkerMetadataResponse>, StreamObserver<WorkerMetadataRequest>>
            startGetWorkerMetadataRpcFn,
        BackOff backoff,
        StreamObserverFactory streamObserverFactory,
        Set<AbstractWindmillStream<?, ?>> streamRegistry,
        int logEveryNStreamFailures,
        JobHeader jobHeader,
        Consumer<WindmillEndpoints> serverMappingConsumer,
        Duration halfClosePhysicalStreamAfter,
        ScheduledExecutorService executorService) {
      super(
          LOG,
          startGetWorkerMetadataRpcFn,
          backoff,
          streamObserverFactory,
          streamRegistry,
          logEveryNStreamFailures,
          "",
          halfClosePhysicalStreamAfter,
          executorService);
      this.workerMetadataRequest = WorkerMetadataRequest.newBuilder().setHeader(jobHeader).build();
      this.serverMappingConsumer = serverMappingConsumer;
      this.latestResponse = WorkerMetadataResponse.getDefaultInstance();
      this.metadataLock = new Object();
    }
  
    public static GrpcGetWorkerMetadataStream create(
        Function<StreamObserver<WorkerMetadataResponse>, StreamObserver<WorkerMetadataRequest>>
            startGetWorkerMetadataRpcFn,
        BackOff backoff,
        StreamObserverFactory streamObserverFactory,
        Set<AbstractWindmillStream<?, ?>> streamRegistry,
        int logEveryNStreamFailures,
        JobHeader jobHeader,
        Consumer<WindmillEndpoints> serverMappingUpdater,
        Duration halfClosePhysicalStreamAfter,
        ScheduledExecutorService executorService) {
      return new GrpcGetWorkerMetadataStream(
          startGetWorkerMetadataRpcFn,
          backoff,
          streamObserverFactory,
          streamRegistry,
          logEveryNStreamFailures,
          jobHeader,
          serverMappingUpdater,
          halfClosePhysicalStreamAfter,
          executorService);
    }
  
    /**
     * Acquires the {@link #metadataLock} Returns {@link Optional<WindmillEndpoints>} if the
     * metadataVersion in the response is not stale (older or equal to current {@link
     * WorkerMetadataResponse#getMetadataVersion()}), else returns empty {@link Optional}.
     */
    private Optional<WindmillEndpoints> extractWindmillEndpointsFrom(
        WorkerMetadataResponse response) {
      synchronized (metadataLock) {
        if (response.getMetadataVersion() > latestResponse.getMetadataVersion()) {
          this.latestResponse = response;
          this.latestResponseReceived = Instant.now();
          return Optional.of(WindmillEndpoints.from(response));
        } else {
          // If the currentMetadataVersion is greater than or equal to one in the response, the
          // response data is stale, and we do not want to do anything.
          LOG.debug(
              "Received metadata version={}; Current metadata version={}. "
                  + "Skipping update because received stale metadata",
              response.getMetadataVersion(),
              latestResponse.getMetadataVersion());
        }
      }
  
      return Optional.empty();
    }
  
    @Override
    protected PhysicalStreamHandler newResponseHandler() {
      return new PhysicalStreamHandler() {
  
        @Override
        public void onResponse(WorkerMetadataResponse response) {
          extractWindmillEndpointsFrom(response).ifPresent(serverMappingConsumer);
        }
  
        @Override
        public boolean hasPendingRequests() {
          return false;
        }
  
        @Override
        public void onDone(Status status) {}
  
        @Override
        public void appendHtml(PrintWriter writer) {}
      };
    }
  
    @Override
    protected void onFlushPending(boolean isNewStream) throws WindmillStreamShutdownException {
      if (isNewStream) {
        trySend(workerMetadataRequest);
      }
    }
  
    @Override
    protected void sendHealthCheck() throws WindmillStreamShutdownException {
      trySend(HEALTH_CHECK_REQUEST);
    }
  
    @Override
    protected void appendSpecificHtml(PrintWriter writer) {
      synchronized (metadataLock) {
        writer.format(
            "GetWorkerMetadataStream:  job_header=[%s], current_metadata=[%s] received_at=[%s]",
            workerMetadataRequest.getHeader(), latestResponse, latestResponseReceived);
      }
    }
  }
  