#Leveraging Spring Cloud Consul for Discovery - CodeMash 2018
by David Lucas @DavidDLucas
examples
01-setup
- Instructions to setup and start consul
- Directory breakdown:
- The docker folder has some examples of running a docker instance of consul
- The local folder has scripts to download the consul binary (consul-binary-download.sh) and start it (consul-start-local.sh)
- The load folder contains scripts to load / save key value pairs
--
02-demo-service
This example has a demo-service that have a /foo method and /hello/ method to demonstrate it is taking requests. This also using properties found under consul like "/config/application/foo with a value that will replace the default in the DemoController.
- If starting from scratch, add a REST controller and include the @Configuration, @EnableAutoConfiguration, @RefreshScope , @RestController .
- @RefreshScope is key to reloading properties from consul posting to Actuator's refresh endpoint
- Start the demo-service using
./mvnw spring-boot:run - GET http://localhost:8080/hello to see the hello world message to include the default @Value.
- Now change / create a key (config/application/foo) / value (CodeMash Rocks) in consul at http://localhost:8500/ui under Key / Value tab and create / navigate to /config/application/foo
- Or you can create the key / value using curl
curl -X PUT -d "CodeMash Rocks" http://localhost:8500/v1/kv/application/foo - In order to refresh the properties in the service when they are changed in consul, one just needs to POST the refresh endpoint
- Example using curl:
curl -s -X POST http://localhost:8080/application/refresh -o- - There is a script (refresh.sh) that can be used to execute the refresh POST.
--
03-demo-application
This example is from the point of view of an application looking up the service and making a call. The actual code base just delegates its work to the original demo-service for a message.
- This example uses Kotlin and delegates to the "demo-service" by making a call via the Spring RestTemplate to "http://demo-service". Using the @LoadBalanced annotation on the RestTemplate @Bean creation will help it discover the host port behind the scene.
- Add to Demo Application class the @EnableDiscoveryClient (register) ( and optional @EnableFeignClients discovery for REST Template).
- Add to example REST controller @Configuration, @EnableAutoConfiguration, @RefreshScope, @RestController
04-gateway-server
This example is to show how to add the zuul server (a type of api gateway) to the mix.
- Annotations to add to enable gateway zuul server:
- @EnableDiscoveryClient
- @EnableFeignClients
- @EnableZuulProxy
Slides
Please review the slides in the slides folder to read through what was attempted in the demo that might help understand. You can always reach out to me at @DavidDLucas or via github.com/lseinc issue.
slides/Spring-Cloud-Consul-CM2018.pdf
This will most likely change with the upcoming Spring Boot 2 release. But it should be close to how it will be without any major changes.
This is a work in progress. This is not a secure example and should be changed to secure actuator and provide authentication.
Enjoy!
2018-01-12