How to load spring application.yml from S3

Question

I have a bunch of spring application.yml properties file in S3 bucket for a different environment. I want to load the property files from the S3 bucket in order to guarantee a stateless configuration.

// Config Object
@Configuration
@ConfigurationProperties(prefix = "yaml")
public class YamlFooProperties {
    private String name;
    private List<String> aliases;
    // standard getter and setters
}

// foo.yml file located in S3 bucket
yaml:
  name: foo
  aliases:
    - abc
    - xyz

How can get my spring-boot application to load those properties and make then available when the application starts?

I'm using spring-boot version 2.2.6.RELEASE and Java 11.

Answer 1

Method 1: Write some very simple startup scripts, which first fetch (say curl) from S3 to local file (say s3-config.yaml) and then start your app normally.

Method 2: If you are using Kubernetes (which is a good idea to deploy systems), you can use other ways such as ConfigMap or Helm to deploy your app to satisfy your need of "guarantee a stateless configuration".

Method 3: If you only want Java (no script, no k8s, etc), then you may write down some simple Java code which fetches file from S3, and then call your SpringBootApplication's start with these data.

Answer 2

You don't have to store the configs in s3. The default option Spring Cloud offers is a git-backed storage, which seems more favourable to me. However, there is S3 support as well.

https://cloud.spring.io/spring-cloud-config/reference/html/#_aws_s3_backend

This way your configuration server has a EnvironmentRepository configured to use an S3 bucket as an underlaying storage.