spring.cloud.gcp.sql.enabled is ignored if specified in application.properties

Describe the bug Introduced in https://github.com/GoogleCloudPlatform/spring-cloud-gcp/pull/131

The spring.cloud.gcp.sql.enabled variable is ignored if it’s set using application.properties. I’m not sure if this is a deliberate design choice since EnvironmentPostProcessor runs before those properties are applied.

[snicoll]

If the EnvironmentPostProcessor runs in the bootstrap context, it can only see what Spring Cloud has initiated. At that point, the application actually hasn’t even started and none of the usual environment preparation has happened yet.

This is unfortunately a limitation of how the bootstrap context was designed and that lead to significant issues when using this feature with Spring Cloud Config Server (see https://github.com/spring-cloud/spring-cloud-commons/issues/737 for instance). The good news is that Spring Cloud 2020.0 has deprecated the bootstrap context in favour of a new mechnism introduced in Spring Boot 2.4 that makes this problem go away, see https://github.com/spring-cloud/spring-cloud-commons/issues/608#issuecomment-626340364.

[meltsufin]

@Dattish I think you’re right that this has something to do with using bootstrap dependencies. In your setup, when Spring invokes the CloudSqlEnvironmentPostProcessor it doesn’t see properties from application.properties. Of course, if you remove spring-cloud-gcp-starter-sql-postgresql from your pom.xml CloudSqlEnvironmentPostProcessor will be disabled because it won’t be on the classpath anymore.

cc/ @snicoll In case you have some insight on why an EnvironmentPostProcessor might not be able to see application.properties when boostrap.properties is in the picture.