Add R2DBC observation auto-configuration

[ttddyy]

Currently, the code exists in the spring experimental repository.
https://github.com/spring-projects-experimental/r2dbc-micrometer-spring-boot

This project provides Spring Boot auto configuration for Micrometer Tracing for R2DBC.
This ticket aims to move the code into Spring Boot.

[travispeloton]

any updates on this?

[mhalbritter]

To set the remote service, the ObservationProxyExecutionListener wants the R2DBC url. Reconstructing the R2DBC url when given a ConnectionFactory is hard, i've opened r2dbc/r2dbc-proxy#135 for an improvement. When r2dbc/r2dbc-proxy#135 is done, we can refactor the code in org.springframework.boot.actuate.autoconfigure.r2dbc.R2dbcObservationAutoConfiguration#extractUrl.

[syz51]

hey there. I see this is closed and this feature is included in 3.2.0-M2 release. Is there any pointers to how to enable this auto-configuration now? When I use r2dbc and actuator, it doesn't seem to auto configure the tracing components automatically. Much appriatiated.

[bclozel]

@syz51 you'll need the "io.r2dbc:r2dbc-proxy" dependency on your classpath.

[syz51]

@bclozel thanks!