ServiceWatch for discovery is missing

Hello

I found out, that in the consul-discovery-module is no watch-job like in the consul-config-module, which publishes a "RefreshEvent" when a service at consul is changed. I build it now on my own, but I think it would be helpful for other dev-guys when it is inside of the discovery-module.

This is my current way, I have implemented this watch. Perhaps it makes it faster to integrate.

Thank you.

        /**
	 * This method uses the "consul.getAgentServices" to get the current list of services
	 * which are registered at consul.
	 *
	 * If some service is changed a "Refresh"-Event is published, that all "RefreshScoped"
	 * Beans will be build again. To set the delay between the sync set the
	 * spring.consul.discovery.watchDelay property. Default is 1000 milisecounds.
	 */
	@Scheduled(fixedDelayString = "${spring.consul.discovery.watchDelay:1000}")
	public void watchServices() {
		if (this.running.get()) {
			try {
				if (firstTime) {
					log.info("Load baseline of consul services.");
					Response<Map<String, Service>> response = consul.getAgentServices();
					if (response.getValue() != null) {
						response.getValue().keySet().forEach(key -> currentStoredServices
								.put(key, response.getValue().get(key)));
					}
					firstTime = false;
				}
				else {

					Response<Map<String, Service>> response = null;

					response = this.consul.getAgentServices();
					if (response.getValue() != null && !response.getValue().isEmpty()) {
						Map<String, Service> remoteServices = response.getValue();

						remoteServices.keySet().forEach(key -> {
							if (!remoteServices.get(key).getId()
									.startsWith(instanceId)
									&& (!currentStoredServices.containsKey(key)
											|| !remoteServices.get(key).toString()
													.equals(currentStoredServices.get(key)
															.toString()))) {
								if (log.isDebugEnabled()) {
									log.debug(
											"Services changed, fire refresh event. New:{} Old: {}",
											remoteServices.get(key).toString(),
											currentStoredServices.get(key));
								}
								else {
									log.info("Services changed, fire refresh event.");
								}
								RefreshEventData data = new RefreshEventData(key,
										currentStoredServices.get(key),
										remoteServices.get(key));

								this.publisher.publishEvent(
										new RefreshEvent(this, data, data.toString()));

								this.currentStoredServices.put(key,
										remoteServices.get(key));
							}

						});
					}
				}

			}
			catch (Exception e) {
				// only fail fast on the initial query, otherwise just log the error
				if (firstTime && this.properties.isFailFast()) {
					log.error(
							"Fail fast is set and there was an error reading services from consul.");
					ReflectionUtils.rethrowRuntimeException(e);
				}
				else if (log.isDebugEnabled()) {
					log.debug("Error querying services from consul.  ", e);
				}
				else if (log.isWarnEnabled()) {
					// simplified one line log message in the event of an agent
					// failure
					log.warn("Error querying services from consul. Message: "
							+ e.getMessage());
				}
			}
		}
	}

    @Data
    static class RefreshEventData {

        private final String context;
        private final Service prevService;
        private final Service newService;

    }

Compare the consul-discovery-module with the watch-job in the consul-config-module, starting with the existing getAgentServices and RefreshEvent usage shown in the issue. Add discovery service watching with the proposed delay and baseline behavior, then verify that service changes publish refresh events without disrupting startup error handling.