Observability changes for Quarkus 4

[brunobat]

Hi all,

We are planning to introduce several changes in Quarkus 4 that may impact users. I’d like to give everyone the opportunity to review these updates and provide feedback if needed.

Here are the main changes:

• Set OpenTelemetry trace sampling to 10% by default
  This aligns with production deployment practices, where trace sampling is typically set between 1% and 10%. Note that all tracing tests will need to be updated to sample at 100%, otherwise they may fail.
• Change default OpenTelemetry protocol to HTTP/protobuf
  This aligns with upstream defaults. The port will also change, along with route configurations.
• Require metric durations in seconds for quarkus-micrometer-opentelemetry
  This aligns with semantic conventions and will impact existing queries and dashboards.
• Upgrade Micrometer to use Prometheus client v1.x
  This has been planned for some time. For more details, please see:
  https://quarkus.io/blog/micrometer-prometheus-v1/
• Metric changes (ongoing evaluation)
  Some metrics will change; the full scope is still under evaluation. This will impact existing queries and dashboards.

You can find more details in the Observability.next working group resources:

• Discussion: https://github.com/quarkusio/quarkus/discussions/44423
• Board: https://github.com/orgs/quarkusio/projects/42/views/1

Cheers,
Bruno Baptista