@Override
  public Optional<RemoteOperation> remoteCallBuild(MasterProcedureEnv env, ServerName remote) {
    ReplaySyncReplicationWALParameter.Builder builder =
      ReplaySyncReplicationWALParameter.newBuilder();
    builder.setPeerId(peerId);
    wals.stream().forEach(builder::addWal);
    return Optional
      .of(new ServerOperation(this, getProcId(), ReplaySyncReplicationWALCallable.class,
        builder.build().toByteArray(), env.getMasterServices().getMasterActiveTime()));
  }
A remote procedure which is used to send replaying remote wal work to region server.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/replication/SyncReplicationReplayWALRemoteProcedure.java