content: /*
   * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
   * (the "License"). You may not use this work except in compliance with the License, which is
   * available at www.apache.org/licenses/LICENSE-2.0
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied, as more fully set forth in the License.
   *
   * See the NOTICE file distributed with this work for information regarding copyright ownership.
   */
  
  package alluxio.master.journal.raft;
  
  import alluxio.AbstractMasterClient;
  import alluxio.ClientContext;
  import alluxio.Constants;
  import alluxio.conf.Configuration;
  import alluxio.conf.PropertyKey;
  import alluxio.grpc.LatestSnapshotInfoPRequest;
  import alluxio.grpc.RaftJournalServiceGrpc;
  import alluxio.grpc.ServiceType;
  import alluxio.grpc.SnapshotData;
  import alluxio.grpc.SnapshotMetadata;
  import alluxio.master.MasterClientContext;
  import alluxio.master.selectionpolicy.MasterSelectionPolicy;
  import alluxio.retry.RetryPolicy;
  
  import java.util.Iterator;
  import java.util.concurrent.TimeUnit;
  import java.util.function.Supplier;
  
  /**
   * A client for raft journal service.
   */
  public class RaftJournalServiceClient extends AbstractMasterClient {
    private final long mRequestInfoTimeoutMs =
        Configuration.getMs(PropertyKey.MASTER_JOURNAL_REQUEST_INFO_TIMEOUT);
  
    private RaftJournalServiceGrpc.RaftJournalServiceBlockingStub mBlockingClient = null;
  
    /**
     * Create a client that talks to a specific master.
     * @param selectionPolicy specifies which master is targeted
     * @param retryPolicySupplier the retry policy to use when connecting to another master
     */
    public RaftJournalServiceClient(MasterSelectionPolicy selectionPolicy,
                                    Supplier<RetryPolicy> retryPolicySupplier) {
      super(MasterClientContext.newBuilder(ClientContext.create(Configuration.global())).build(),
          selectionPolicy, retryPolicySupplier);
    }
  
    @Override
    protected ServiceType getRemoteServiceType() {
      return ServiceType.RAFT_JOURNAL_SERVICE;
    }
  
    @Override
    protected String getServiceName() {
      return Constants.RAFT_JOURNAL_SERVICE_NAME;
    }
  
    @Override
    protected long getServiceVersion() {
      return Constants.RAFT_JOURNAL_SERVICE_VERSION;
    }
  
    @Override
    protected void beforeConnect() {
      // the default behavior of this method is to search for the primary master
      // in our case we do no care which one is the primary master as MasterSelectionPolicy is
      // explicitly specified
    }
  
    @Override
    protected void afterConnect() {
      mBlockingClient = RaftJournalServiceGrpc.newBlockingStub(mChannel);
    }
  
    /**
     * @return {@link SnapshotMetadata} from specified master
     */
    public SnapshotMetadata requestLatestSnapshotInfo() {
      return mBlockingClient.withDeadlineAfter(mRequestInfoTimeoutMs, TimeUnit.MILLISECONDS)
          .requestLatestSnapshotInfo(LatestSnapshotInfoPRequest.getDefaultInstance());
    }
  
    /**
     * Receive snapshot data from specified follower.
     *
     * @param request the request detailing which file to download
     * @return an iterator containing the snapshot data
     */
    public Iterator<SnapshotData> requestLatestSnapshotData(SnapshotMetadata request) {
      return mBlockingClient.requestLatestSnapshotData(request);
    }
  }
  