public static void premain()

in spectator-agent/src/main/java/com/netflix/spectator/agent/Agent.java [113:176]
43 lines of code
6 McCabe index (conditional complexity)

  public static void premain(String arg, Instrumentation instrumentation) throws Exception {
    // Setup logging
    final List<Object> resources = parseResourceList(arg);
    Config config = loadConfig(resources);
    LOGGER.debug("loaded configuration: {}", config.root().render());
    createDependencyProperties(config);

    // Setup Registry
    AtlasRegistry registry = new AtlasRegistry(Clock.SYSTEM, new AgentAtlasConfig(config));

    // Add to global registry for http stats and GC logger
    Spectator.globalRegistry().add(registry);

    // Enable GC logger
    GcLogger gcLogger = new GcLogger();
    if (config.getBoolean("collection.gc")) {
      gcLogger.start(null);
    }

    // Enable JVM data collection
    if (config.getBoolean("collection.jvm")) {
      Jmx.registerStandardMXBeans(registry);
    }

    // Enable JMX query collection
    if (config.getBoolean("collection.jmx")) {
      ScheduledExecutorService exec = Executors.newSingleThreadScheduledExecutor(r -> {
        Thread t = new Thread(r, "spectator-agent-jmx");
        t.setDaemon(true);
        return t;
      });

      // Poll the JMX data at least once per step interval unless it is less than a second
      // to avoid to much overhead
      Duration step = Duration.parse(config.getString("atlas.step"));
      long delay = Math.max(1000L, step.toMillis() / 2L);

      // Keep track of last time the configs have been loaded
      final AtomicLong lastUpdated = new AtomicLong(System.currentTimeMillis());
      final JmxPoller poller = new JmxPoller(registry);
      poller.updateConfigs(config.getConfigList("jmx.mappings"));

      exec.scheduleWithFixedDelay(() -> {
        try {
          List<File> updatedConfigs = findUpdatedConfigs(resources, lastUpdated.get());
          if (!updatedConfigs.isEmpty()) {
            LOGGER.info("detected updated config files: {}", updatedConfigs);
            lastUpdated.set(System.currentTimeMillis());
            Config cfg = loadConfig(resources);
            poller.updateConfigs(cfg.getConfigList("jmx.mappings"));
          }
        } catch (Exception e) {
          LOGGER.warn("failed to update jmx config mappings, using previous config", e);
        }
        poller.poll();
      }, delay, delay, TimeUnit.MILLISECONDS);
    }

    // Start collection for the registry
    registry.start();

    // Shutdown registry
    Runtime.getRuntime().addShutdownHook(new Thread(registry::stop, "spectator-agent-shutdown"));
  }