Overview
This blog will walk you through the need of consul and how to integrate with your Spring boot application.
Consul:
Consul is a distributed service mesh to connect, secure, and configure services across any runtime platform and public or private cloud
You can read more about consul here
Now, we are going to focus on key/value store in consul. KV store is one of the major feature available in consul to have all your application configuration properties in one place.
Problem:
Generally, we all are practiced to have our application related configuration in application.properties file, whenever we need to change the value, then we will be changing it in the file and have to rebuild and re-deploy the application to make changes to effect in the application.
In case, assume you are having a secret key or password in your application.properties file, then if there is any attack happened to your server and the code leaks all your critical information and your system will become vulnerable.
Solution :
Consul will actually help you to avoid the above-stated problems.
Why Consul KV:
- You will be storing all your configuration properties in consul KV store which eliminates code leakage
- Whenever there is a change in key/value, you are not required to re-deploy or reboot your server.
- Spring boot has an efficiency to reflect the values in your application instantly
- One consul Instance is sufficient to have all your environment properties like (dev, stage, production)
Install Consul
There are multiple ways to install,
- You can install it using docker Click here
- You can Download and run Click here
I have used the second approach, I have downloaded the file and extract it into your local directory
Steps to Start Consul
- Open terminal
- Go to the directory where you have extracted the consul
- Run the below commands
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root $ ./consul agent -server -bootstrap-expect=1 -data-dir=consul-data -ui -bind=127.0.0.1 |
4. Open browser and type http://localhost:8500
Now you will be seeing a consul screen
Create KV in consul
You can insert your KV in consul in two ways
- Using the command line tool
- Using Browser
Using the command line tool
- Run the below command to insert single key
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root $ ./consul kv put config/testapplication/testkey testvalue |
Note: You need to maintain the standard i.e config is mandatory followed by your application name and followed by your key name
2. Run the below command to insert multiple keys
- Create a .json file as follows
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[ { "key" : "config/testApplication/testkey", "value" : "dGVzdFZhbHVl" }, { "key" : "config/testApplication/testkey2", "value" : "dGVzdFZhbHVls", } ] |
Note: The value should be base-64 ENCODED strinG
- Then run the below commands to import data’s to consul
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1root $ ./consul kv import @/your-file-path/filename.json
To know more about consul KV commands click here
Using Browser
- open http://localhost:8500 in your browser
- click key/value from the menu
- Click Create button
- enter key as follows
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1config/testApplication/testkey
- enter the value as follow
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1test value
NOTE: You don’t have to decode the string in case of UI
That’s it, now your consul is ready to integrate with your application.
Steps to Integrate with your Spring Application:
- Assuming that you already having a spring application up and running, if not then you can create one from here
- Add the below dependency build.gradle file
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dependencies{ compile group : 'org.springframework.cloud', name :'spring-cloud-starter-consul- config' compile group : 'org.springframework.cloud', name :'spring-cloud-starter-consul-discovery' compile group : 'org.springframework.boot', name : 'spring-boot-starter-actuator' } |
Spring – actuator is mandatory so that consul will keep checking the health status of your application.
3. Add dependency management to build.gradle file
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dependencyManagement { imports { mavenBom "org.springframework.cloud:spring-cloud-dependencies:Finchley.SR1" } } |
4. Create a bootstarp.yml file under src/main/resources as follows
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spring: application: {name: 'testApplication'} cloud: consul: enabled: 'true' host: http://localhost port: 8500 discovery: {healthCheckInterval: 300s} |
Note: The application name should be matched with the folder name you created in consul under the config directory
5. User @Value annotation to bind the values from consul as follow
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@Component @RefreshScope public Class AppConfig(){ @Value("${testKey}") private String values; } |
That’s it Spring Consul will take care of binding the values from consul to your application.
Note: @RefreshScope annotation is used in the above class, which will say that, if there any changes in the consul then it will immediately refresh the values in the application without restarting. If you havent use @RefreshScope then you need to manually restart the system to apply your config changes
@RefreshScope will work with annotations like (@component, @service, @controller,@repository etc,)
Know more about @RefreshScope
6. Add @EnableDiscoveryClient into your main class
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@EnableAutoConfiguration @EnableDiscoveryClient @SpringBootApplication public class TestApplication { public static void main(String[] args) { new TestApplication(TestApplication.class).run(args); } } |
7. Now Run your application, it will look for the consul and values will be bound
Conclusion:
That’s all !!! Now you learned the importance of Consul KV store and how to integrate it with your spring boot application.
