Introduction to Spring Cloud Consul
examples
01-setup
Instructions to setup consul and start service.
- The docker folder has some examples of running a consul instance container.
- The local folder has a scripts to download the consul binary (consul-binary-download.sh) and then just unzip and run it with the other script (consul-start-local.sh)
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02-example-service
This example has a demo-consul-service that uses a property (config/application/special.name) that we can set to a value like "COJUG Rocks" in the consul ui key/value section
- The service is based off Spring Boot 2.0.0M5 and Spring Cloud Consul Configuration and Spring Cloud Consul Discovery and Spring Actuator dependencies
- To create a similar project use https://start.spring.io InitializR site.
- If starting from scratch, add @EnableDiscoverClient (turn on registering the service to consul) to the Demo Application java file where @SpringBootApplication is defined.
- 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-consul-service using
./mvnw spring-boot:run - GET http://localhost:8080/hello to see the hello world message to include the default @Value from special.name: Hello World! From not-yet-special !
- Now change / create a key (config/application/specialname) / value (COJUG Rocks) in consul at http://localhost:8500/ui
- Or you can create the key / value using curl
curl -X PUT -d "COJUG Rocks" http://localhost:8500/v1/kv/application/special.name - 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.
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03-example-frontend
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-consul-service.
- Assuming you cloned the 02 project or downloaded a new one from start.spring.io, create a REST controller like set 02 above.
- Add to Demo Application java file the @EnableDiscoveryClient (register) and @EnableFeignClients (discovery for REST Template).
- Add to example REST controller @Configuration, @EnableAutoConfiguration, @RefreshScope, @RestController
This will evole for the next presentation. This is a work in progress. Enjoy!
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