code: @Override
      public synchronized void start() {
          Preconditions.checkNotNull(getServer());
  
          String osName = System.getProperty("os.name");
          String osVersion = System.getProperty("os.version");
          log.info("Bootstrapping {} ({})", settings.getApplicationName(), settings.getApplicationVersion());
          Util.logSetting(log, "Fathom", Constants.getVersion());
          Util.logSetting(log, "Mode", settings.getMode().toString());
          Util.logSetting(log, "Operating System", String.format("%s (%s)", osName, osVersion));
          Util.logSetting(log, "Available processors", Runtime.getRuntime().availableProcessors());
          Util.logSetting(log, "Available heap", (Runtime.getRuntime().maxMemory() / (1024 * 1024)) + " MB");
  
          SimpleDateFormat df = new SimpleDateFormat("z Z");
          df.setTimeZone(TimeZone.getDefault());
          String offset = df.format(new Date());
          Util.logSetting(log, "JVM timezone", String.format("%s (%s)", TimeZone.getDefault().getID(), offset));
          Util.logSetting(log, "JVM locale", Locale.getDefault());
  
          long startTime = System.nanoTime();
          getServer().start();
  
          String contextPath = settings.getContextPath();
  
          if (settings.getHttpsPort() > 0) {
              log.info("https://{}:{}{}", settings.getHttpsListenAddress(), settings.getHttpsPort(), contextPath);
          }
          if (settings.getHttpPort() > 0) {
              log.info("http://{}:{}{}", settings.getHttpListenAddress(), settings.getHttpPort(), contextPath);
          }
          if (settings.getAjpPort() > 0) {
              log.info("ajp://{}:{}{}", settings.getAjpListenAddress(), settings.getAjpPort(), contextPath);
          }
  
          long delta = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startTime);
          String duration;
          if (delta < 1000L) {
              duration = String.format("%s ms", delta);
          } else {
              duration = String.format("%.1f seconds", (delta / 1000f));
          }
          log.info("Fathom bootstrapped {} mode in {}", settings.getMode().toString(), duration);
          log.info("READY.");
  
      }
docs: Starts Fathom synchronously.