This commit moves the entire Metrics auto-configuration for Spring MVC
to the new `Observation` API and the instrumentation contributed in
Spring Framework.
Closes gh-32538
This commits adds a checkstyle rule to not use List.of(), Set.of()
and Map.of(), preferring Collections.emptyList(), emptySet(), and
emptyMap() respectively.
It replaces usages of these methods across the codebase.
See gh-32655
This commit updates the bean factory methods for beans that can be
instantiated at build-time to be static. Doing so makes sure that
the enclosing configuration class does not have to be resolved in
order to create the instance.
Closes gh-32570
As of spring-projects/spring-framework#28341, `WebClient` is
instrumented directly for `Observation`.
This commit removes the custom `ExchangeFilterFunction` that previously
instrumented the client for metrics.
As a result, the relevant tag providers are now deprecated and adapted
as `ObservationConvention` for the time being.
Closes gh-32518
Previously, RestTemplateBuilder and WebClient.Builder beans were used
to create the HTTP client for sending out spans. Those same beans are
also instrumented for observability which results in a cycle.
This commit breaks the cycle by not using the application-web
builders to create the RestTemplate and WebClient's used by the Zipkin
senders. Instead, builders are created inline, with new callbacks
being introduced to allow the user to customize these Zipkin-specific
builders.
See gh-32528
Previously, a Webclient-based sender was only for reactive web
applications, falling back to a RestTemplate-based sender in all
other cases.
With this commit we now prefer to use WebClient if it is available,
irrespective of the web application type. The assumption is that
if the user has WebClient on the classpath, it's either a reactive
web application, or it's a servlet web application or non-web
application but WebClient is preferred.
See gh-32529
Prior to this commit, Spring Boot would auto-configure a customizer that
instruments `RestTemplate` through a `RestTemplateBuilder`. This would
install a request interceptor that instrumented client exchanges for
producing metrics.
As of spring-projects/spring-framework#28341, the instrumentation is
done at the `RestTemplate` level directly using the `Observation` API.
The `Tag` (now `KeyValue`) extraction, observation name and
instrumentation behavior now lives in the Spring Framework project.
This commit updates the auto-configuration to switch from Boot-specific
Metrics instrumentation to a generic Observation instrumentation.
As a migration path, some configuration properties are deprecated in
favor of the new `management.observations.*` namespace.
Closes gh-32484
