lab_circuitbreaker.md

Creating the Circuit Breaker Dashboard.

Cloud-native architectures are typically composed of multiple layers of distributed services. End-user requests may comprise multiple calls to these services, and if a lower-level service fails, the failure can cascade up to the end user and spread to other dependent services. Heavy traffic to a failing service can also make it difficult to repair. Using Circuit Breaker Dashboard, you can monitor a service for failure, prevent failures from cascading, and supply dependent services until the failing service is operable again.

The code to create a circuit breaker involved providing a fallback method. For example:

  @HystrixCommand(fallbackMethod = "getCompaniesFallback")
	public List<CompanyInfo> getCompanies(String name) {
		logger.debug("Fetching companies with name or symbol matching: " + name);
		CompanyInfo[] infos = restTemplate.getForObject("http://quotes/company/{name}", CompanyInfo[].class, name);
		return Arrays.asList(infos);
	}

	private List<CompanyInfo> getCompaniesFallback(String name) {
		List<CompanyInfo> infos = new ArrayList<>();
		return infos;
	}

It is useful to know when the circuits are open as it may suggest a problem with the dependent services. Spring Cloud Services for Pivotal Cloud Foundry provides a centralised dashboard to collect all the statistics from circuit breakers and visualize them in one place.

Underneath the covers, this circuit breaker pattern is implemented using the Spring Cloud Netflix - Hystrix.

In order to make use of the dashboard, we need to create an instance of the service to bind it to our applications.

Exercise

1. Log in to the Apps Manager through your browser. The URL will be: https://console.<your_cloud_foundry_url>/

Go the Marketplace and choose a Circuit Breaker for Pivotal Cloud Foundry standard.

When prompted for the name of the service, insert "circuit-breaker-dashboard" and bind it to the space you are using to deploy your applications.

You can pick any name of the service, however, the service is already specified in the manifest files, so it is easier to re-use that name. If you do modify the name, ensure you modify it in the manifest files as well.

Summary

The circuit breaker dashboard can be accessed on the link provided in the console UI. Find the circuit breaker service you created and click on Manage.

You can now move on to creating the configuration service