code: public CompletionStage<ReloadableSparkeyReader> load(final File logFile) {
      checkArgument(isValidLogFile(logFile));
      CompletableFuture<ReloadableSparkeyReader> result = new CompletableFuture<>();
      this.executorService.submit(() -> {
        switchReader(logFile);
        result.complete(this);
      });
      return result;
    }
docs: Load a new log file into this reader.
  @param logFile the log file to load.
  @return A future that resolves to the sparkey reader once it has loaded the new log file.