alluxio-master-2.x/core/server/common/src/main/java/alluxio/master/journal/raft/RaftJournalServiceClient.java
/*
 * 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);
  }
}
