code: @Override
  	public void start() {
  		try {
  			url = new URL(getStringSetting(SETTING_URL, DEFAULT_STACKDRIVER_API_URL));
  		} catch (MalformedURLException e) {
  			throw new EmbeddedJmxTransException(e);
  		}
  
  		apiKey = getStringSetting(SETTING_TOKEN);
  
  		if (getStringSetting(SETTING_PROXY_HOST, null) != null && !getStringSetting(SETTING_PROXY_HOST).isEmpty()) {
  			proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress(getStringSetting(SETTING_PROXY_HOST), getIntSetting(SETTING_PROXY_PORT)));
  		}
  		
  		logger.info("Starting Stackdriver writer connected to '{}', proxy {} ...", url, proxy);
  		
  
  		stackdriverApiTimeoutInMillis = getIntSetting(SETTING_STACKDRIVER_API_TIMEOUT_IN_MILLIS, DEFAULT_STACKDRIVER_API_TIMEOUT_IN_MILLIS);
  
  		// try to get and instance ID
  		if (getStringSetting(SETTING_SOURCE_INSTANCE, null) != null && !getStringSetting(SETTING_SOURCE_INSTANCE).isEmpty()) {
  			// if one is set directly use that
  			instanceId = getStringSetting(SETTING_SOURCE_INSTANCE);
  			logger.info("Using instance ID {} from setting {}", instanceId, SETTING_SOURCE_INSTANCE);
  		} else if (getStringSetting(SETTING_DETECT_INSTANCE, null) != null && "AWS".equalsIgnoreCase(getStringSetting(SETTING_DETECT_INSTANCE))) {
  			// if setting is to detect, look on the local machine URL
  			logger.info("Detect instance set to AWS, trying to determine AWS instance ID");
  			instanceId = getLocalAwsInstanceId();
  			if (instanceId != null) {
  				logger.info("Detected instance ID as {}", instanceId);
  			} else {
  				logger.info("Unable to detect AWS instance ID for this machine, sending metrics without an instance ID");
  			}
  		} else {
  			// no instance ID, the metrics will be sent as "bare" custom metrics and not associated with an instance
  			instanceId = null;
  			logger.info("No source instance ID passed, and not set to detect, sending metrics without and instance ID");
  		}
  		
  	}
docs: Initial setup for the writer class. Loads in settings and initializes one-time setup variables like instanceId.