spring-cloud-config-examples
The two Spring projects included here are a Spring Cloud Config Server and a Spring Cloud Config Client, as described in the Spring Cloud Config Documentation
The configuration of the two projects serves as working example of using the Spring Cloud Config Server to externalize a client's configuration (like application.properties), and enable changes to that configuration at runtime, without having to restart/reload the client service. The mechanism works by utilizing the Spring Cloud Bus
The two maven projects here are just barebones Spring Boot Apps. The cloud-config-server project is just as described here in the Spring documentation, with the addition of the spring-cloud-config-monitor dependency--the need for which is described below in the Notes section
The spring-cloud-config-client configuration file is externalized via the Spring Cloud Config Server, and lives in this git repository as file spring-cloud-config-client.properties. As you'll find in the Spring Cloud Config Documentation, you can have different profiles/labels of this configuration as needed for your project (spring-cloud-config-client-production.properties, spring-cloud-config-client-development.properties, etc)
The spring-cloud-config-client Spring Boot app is a very simple app that does two things:
-
it has an endpoint /testProperty, which outputs the current
test.propertyvalue as found in the project's configuration -
it runs a background scheduled job that logs the value of
test.propertyon an interval defined by thetest.property.cronvalue in the project's configuration
By looking at the output of 1), or the output of 2) in the logs, you can verify that changing the project's configuration at runtime changes the value and interval used by the running service.
The relevant code for 1) and 2) is in RuntimePropertyChangeExample.java
Spring Cloud services talk to each other over Spring Cloud Bus, which passes messages under the hood over RabbitMQ. For the spring-cloud-config-server and spring-cloud-config-client services to talk to each other over Spring Cloud Bus, there is a running RabbitMQ instance at this address 52.87.208.69. You'll find this address is configured in both the spring-cloud-config-server's application.properties file, as well as the spring-cloud-config-client's bootstrap.properties file. To use this mechanism in your own project, you'll want to have your own instance of RabbitMQ running, and point the Spring Cloud Config Server and the Spring Cloud Config Client to it in their configuration files similarly.
To run the example:
cd cloud-config-client
mvn clean package
make sure you have java 8 to run this
java -jar target/spring-cloud-config-client-0.0.1-SNAPSHOT.jar
After the application loads, you should see output like this:
Mon Mar 07 17:25:00 CST 2016 test.property value is : change me
Mon Mar 07 17:25:10 CST 2016 test.property value is : change me
Mon Mar 07 17:25:20 CST 2016 test.property value is : change me
Mon Mar 07 17:25:30 CST 2016 test.property value is : change me
As shown, the value of test.property is logged every interval as configured in test.property.cron in spring-cloud-config-client.properties
If you were now to change the test.property or test.property.cron values in spring-cloud-config-client.properties, you should see your changes reflect in the output of the application without a restart.
summary
The two projects in this repo demonstrate how to externalize the configuration of a Spring Boot Application to a Spring Cloud Config Server's GIT repository. That Spring configuration of the app can then be changed at runtime without having to restart/reload it.
Notes
The Push notification mechanism works by creating a GitHub Webhook to notify the http://cloud-config-server-host/monitor URL whenever the configuration changes in GIT. You can read more about it here: Push Notifications and Spring Cloud Bus. You can set up a similar webhook in your GitHub repository which backs your Spring Cloud Config Server.