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.fnexecution.control;
  
  import static org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Preconditions.checkState;
  
  import java.util.HashMap;
  import java.util.Map;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  import javax.annotation.concurrent.GuardedBy;
  import org.apache.beam.model.fnexecution.v1.BeamFnApi;
  import org.apache.beam.model.fnexecution.v1.BeamFnControlGrpc;
  import org.apache.beam.sdk.fn.server.FnService;
  import org.apache.beam.sdk.fn.server.HeaderAccessor;
  import org.apache.beam.vendor.grpc.v1p69p0.io.grpc.Status;
  import org.apache.beam.vendor.grpc.v1p69p0.io.grpc.StatusException;
  import org.apache.beam.vendor.grpc.v1p69p0.io.grpc.stub.StreamObserver;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /** A Fn API control service which adds incoming SDK harness connections to a sink. */
  public class FnApiControlClientPoolService extends BeamFnControlGrpc.BeamFnControlImplBase
      implements FnService {
    private static final Logger LOG = LoggerFactory.getLogger(FnApiControlClientPoolService.class);
  
    private final Object lock = new Object();
    private final ControlClientPool.Sink clientSink;
    private final HeaderAccessor headerAccessor;
    private final ConcurrentMap<String, BeamFnApi.ProcessBundleDescriptor> processBundleDescriptors =
        new ConcurrentHashMap<>();
  
    @GuardedBy("lock")
    private final Map<String, FnApiControlClient> vendedClients = new HashMap<>();
  
    @GuardedBy("lock")
    private boolean closed = false;
  
    private FnApiControlClientPoolService(
        ControlClientPool.Sink clientSink, HeaderAccessor headerAccessor) {
      this.clientSink = clientSink;
      this.headerAccessor = headerAccessor;
    }
  
    /**
     * Creates a new {@link FnApiControlClientPoolService} which will enqueue and vend new SDK harness
     * connections.
     *
     * <p>Clients placed into the {@code clientSink} are owned by whoever consumes them from the other
     * end of the pool. That consumer is responsible for closing the clients when they are no longer
     * needed.
     */
    public static FnApiControlClientPoolService offeringClientsToPool(
        ControlClientPool.Sink clientPool, HeaderAccessor headerAccessor) {
      return new FnApiControlClientPoolService(clientPool, headerAccessor);
    }
  
    /**
     * Called by gRPC for each incoming connection from an SDK harness, and enqueue an available SDK
     * harness client.
     *
     * <p>Note: currently does not distinguish what sort of SDK it is, so a separate instance is
     * required for each.
     */
    @Override
    public StreamObserver<BeamFnApi.InstructionResponse> control(
        StreamObserver<BeamFnApi.InstructionRequest> requestObserver) {
      final String workerId = headerAccessor.getSdkWorkerId();
      LOG.info("Beam Fn Control client connected with id {}", workerId);
      FnApiControlClient newClient =
          FnApiControlClient.forRequestObserver(workerId, requestObserver, processBundleDescriptors);
      try {
        // Add the client to the pool of vended clients before making it available - we should close
        // the client when we close even if no one has picked it up yet. This can occur after the
        // service is closed, in which case the client will be discarded when the service is
        // discarded, which should be performed by a call to #shutdownNow. The remote caller must be
        // able to handle an unexpectedly terminated connection.
        synchronized (lock) {
          checkState(
              !closed, "%s already closed", FnApiControlClientPoolService.class.getSimpleName());
          // TODO: https://github.com/apache/beam/issues/18790: Prevent stale client references
          // from leaking.
          vendedClients.put(workerId, newClient);
        }
        // We do not attempt to transactionally add the client to our internal list and offer it to
        // the sink.
        clientSink.put(headerAccessor.getSdkWorkerId(), newClient);
      } catch (Exception e) {
        throw new RuntimeException(e);
      }
      return newClient.asResponseObserver();
    }
  
    @Override
    public void getProcessBundleDescriptor(
        BeamFnApi.GetProcessBundleDescriptorRequest request,
        StreamObserver<BeamFnApi.ProcessBundleDescriptor> responseObserver) {
      String bundleDescriptorId = request.getProcessBundleDescriptorId();
      LOG.info("getProcessBundleDescriptor request with id {}", bundleDescriptorId);
      BeamFnApi.ProcessBundleDescriptor descriptor = processBundleDescriptors.get(bundleDescriptorId);
      if (descriptor == null) {
        String msg =
            String.format("ProcessBundleDescriptor with id %s not found", bundleDescriptorId);
        responseObserver.onError(new StatusException(Status.NOT_FOUND.withDescription(msg)));
        LOG.error(msg);
      } else {
        responseObserver.onNext(descriptor);
        responseObserver.onCompleted();
      }
    }
  
    @Override
    public void close() {
      synchronized (lock) {
        if (!closed) {
          closed = true;
          for (FnApiControlClient vended : vendedClients.values()) {
            vended.close();
          }
        }
      }
    }
  }
  