private InstallSnapshotReplyProto installSnapshotImpl()

in ratis-server/src/main/java/org/apache/ratis/server/impl/SnapshotInstallationHandler.java [118:164]
38 lines of code
7 McCabe index (conditional complexity)

  private InstallSnapshotReplyProto installSnapshotImpl(InstallSnapshotRequestProto request) throws IOException {
    final RaftRpcRequestProto r = request.getServerRequest();
    final RaftPeerId leaderId = RaftPeerId.valueOf(r.getRequestorId());
    final RaftGroupId leaderGroupId = ProtoUtils.toRaftGroupId(r.getRaftGroupId());
    CodeInjectionForTesting.execute(RaftServerImpl.INSTALL_SNAPSHOT, server.getId(), leaderId, request);

    server.assertLifeCycleState(LifeCycle.States.STARTING_OR_RUNNING);
    ServerImplUtils.assertGroup(getMemberId(), leaderId, leaderGroupId);

    InstallSnapshotReplyProto reply = null;
    // Check if install snapshot from Leader is enabled
    if (installSnapshotEnabled) {
      // Leader has sent InstallSnapshot request with SnapshotInfo. Install the snapshot.
      if (request.hasSnapshotChunk()) {
        reply = checkAndInstallSnapshot(request, leaderId).join();
      }
    } else {
      // Leader has only sent a notification to install snapshot. Inform State Machine to install snapshot.
      if (request.hasNotification()) {
        reply = notifyStateMachineToInstallSnapshot(request, leaderId).join();
      }
    }

    if (reply != null) {
      if (request.hasLastRaftConfigurationLogEntryProto()) {
        // Set the configuration included in the snapshot
        final LogEntryProto proto = request.getLastRaftConfigurationLogEntryProto();
        state.truncate(proto.getIndex());
        if (!state.getRaftConf().equals(LogProtoUtils.toRaftConfiguration(proto))) {
          LOG.info("{}: set new configuration {} from snapshot", getMemberId(), proto);
          state.setRaftConf(proto);
          state.writeRaftConfiguration(proto);
          server.getStateMachine().event().notifyConfigurationChanged(
              proto.getTerm(), proto.getIndex(), proto.getConfigurationEntry());
        }
      }
      return reply;
    }

    // There is a mismatch between configurations on leader and follower.
    final InstallSnapshotReplyProto failedReply = toInstallSnapshotReplyProto(
        leaderId, getMemberId(), state.getCurrentTerm(), InstallSnapshotResult.CONF_MISMATCH);
    LOG.error("{}: Configuration Mismatch ({}): Leader {} has it set to {} but follower {} has it set to {}",
        getMemberId(), RaftServerConfigKeys.Log.Appender.INSTALL_SNAPSHOT_ENABLED_KEY,
        leaderId, request.hasSnapshotChunk(), server.getId(), installSnapshotEnabled);
    return failedReply;
  }