private void generateSnapshotCheckpoint()

in hadoop-hdds/framework/src/main/java/org/apache/hadoop/hdds/utils/DBCheckpointServlet.java [151:277]
117 lines of code
18 McCabe index (conditional complexity)

  private void generateSnapshotCheckpoint(HttpServletRequest request,
      HttpServletResponse response, boolean isFormData) {
    if (dbStore == null) {
      LOG.error(
          "Unable to process metadata snapshot request. DB Store is null");
      response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
      return;
    }

    // Check ACL for dbCheckpoint only when global Ozone ACL is enabled
    if (aclEnabled) {
      final java.security.Principal userPrincipal = request.getUserPrincipal();
      if (userPrincipal == null) {
        final String remoteUser = request.getRemoteUser();
        LOG.error("Permission denied: Unauthorized access to /dbCheckpoint,"
                + " no user principal found. Current login user is {}.",
            remoteUser != null ? "'" + remoteUser + "'" : "UNKNOWN");
        response.setStatus(HttpServletResponse.SC_FORBIDDEN);
        return;
      } else {
        final String userPrincipalName = userPrincipal.getName();
        UserGroupInformation ugi =
            UserGroupInformation.createRemoteUser(userPrincipalName);
        if (!hasPermission(ugi)) {
          LOG.error("Permission denied: User principal '{}' does not have"
                  + " access to /dbCheckpoint.\nThis can happen when Ozone"
                  + " Manager is started with a different user.\n"
                  + " Please append '{}' to OM 'ozone.administrators'"
                  + " config and restart OM to grant current"
                  + " user access to this endpoint.",
              userPrincipalName, userPrincipalName);
          response.setStatus(HttpServletResponse.SC_FORBIDDEN);
          return;
        }
        LOG.debug("Granted user principal '{}' access to /dbCheckpoint.",
            userPrincipalName);
      }
    }

    DBCheckpoint checkpoint = null;

    boolean flush = false;
    String flushParam =
        request.getParameter(OZONE_DB_CHECKPOINT_REQUEST_FLUSH);
    if (StringUtils.isNotEmpty(flushParam)) {
      flush = Boolean.parseBoolean(flushParam);
    }

    List<String> receivedSstList = new ArrayList<>();
    List<String> excludedSstList = new ArrayList<>();
    String[] sstParam = isFormData ?
        parseFormDataParameters(request) : request.getParameterValues(
        OZONE_DB_CHECKPOINT_REQUEST_TO_EXCLUDE_SST);
    if (sstParam != null) {
      receivedSstList.addAll(
          Arrays.stream(sstParam)
              .filter(s -> s.endsWith(ROCKSDB_SST_SUFFIX))
              .distinct()
              .collect(Collectors.toList()));
      logSstFileList(receivedSstList,
          "Received list of {} SST files to be excluded{}: {}", 5);
    }

    Path tmpdir = null;
    try (BootstrapStateHandler.Lock lock = getBootstrapStateLock().lock()) {
      tmpdir = Files.createTempDirectory(bootstrapTempData.toPath(),
          "bootstrap-data-");
      checkpoint = getCheckpoint(tmpdir, flush);
      if (checkpoint == null || checkpoint.getCheckpointLocation() == null) {
        LOG.error("Unable to process metadata snapshot request. " +
            "Checkpoint request returned null.");
        response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
        return;
      }
      dbMetrics.setLastCheckpointCreationTimeTaken(
          checkpoint.checkpointCreationTimeTaken());

      Path file = checkpoint.getCheckpointLocation().getFileName();
      if (file == null) {
        return;
      }
      response.setContentType("application/x-tar");
      response.setHeader("Content-Disposition",
          "attachment; filename=\"" +
               file + ".tar\"");

      Instant start = Instant.now();
      writeDbDataToStream(checkpoint, request,
          response.getOutputStream(), receivedSstList, excludedSstList, tmpdir);
      Instant end = Instant.now();

      long duration = Duration.between(start, end).toMillis();
      LOG.info("Time taken to write the checkpoint to response output " +
          "stream: {} milliseconds", duration);
      logSstFileList(excludedSstList,
          "Excluded {} SST files from the latest checkpoint{}: {}", 5);
      if (!excludedSstList.isEmpty()) {
        dbMetrics.incNumIncrementalCheckpoint();
      }
      dbMetrics.setLastCheckpointStreamingNumSSTExcluded(
          excludedSstList.size());
      dbMetrics.setLastCheckpointStreamingTimeTaken(duration);
      dbMetrics.incNumCheckpoints();
    } catch (Exception e) {
      LOG.error(
          "Unable to process metadata snapshot request. ", e);
      response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
      dbMetrics.incNumCheckpointFails();
    } finally {
      try {
        if (tmpdir != null) {
          FileUtils.deleteDirectory(tmpdir.toFile());
        }
      } catch (IOException e) {
        LOG.error("unable to delete: " + tmpdir);
      }

      if (checkpoint != null) {
        try {
          checkpoint.cleanupCheckpoint();
        } catch (IOException e) {
          LOG.error("Error trying to clean checkpoint at {} .",
              checkpoint.getCheckpointLocation().toString());
        }
      }
    }
  }