Spring Cloud Sleuth currently is an autoconfiguration over Brave. It also consists of various instrumentation mechanisms for libraries that are not supported by Brave (e.g. Spring Cloud Circuitbreaker).
We would like to abstract Brave so that Spring Cloud Sleuth becomes an autoconfiguration for any tracer implementation that is compatible with Spring Cloud Sleuth. That way Spring Cloud Sleuth in its core module would consist of an API and various tracer implementations would implement that API which would also allow automatic instrumentation of libraries that are supported by Spring Cloud Sleuth.
## OpenTelemetry Support
Thanks to doing this abstraction we are able to support new tracer implementations, not only Brave. We've decided to add support for the OpenTelemetry SDK as the second one. If in the future if we decide to add new tracers then it will be just a matter of adding a new module that bridges to the Spring Cloud Sleuth one. Thanks to abstraction of tests as well we will be easily able to plug that tracer mechanism into our current suite of tests.
- adds Spring Cloud Function instrumentation
- adds Operators to manually provide instrumentation for Fluxes
- introduces Manual instrumentation mode for Reactor
TODO: Documentation (will add it soon)
related gh-1684
* Updates to latest Sampling infrastructure
Brave recently switched to an interface model for higher level sampling
like HTTP. So, `HttpSampler` -> `SamplingFunction<HttpRequest>`. Don't
worry because `HttpSampler` was retrofitted as a `SamplingFunction`.
This change moves to the higher interface, avoiding deprecated methods
and such. More interestingly, this weaves in support for `RpcTracing`,
which *finally* introduces RPC sampling the same way. Specifically, this
adds `SamplingFunction<RpcRequest>` under the same conventions as HTTP.
Most immediately, this can be used here in gRPC and Dubbo, as
autoconfiguration exists. It also works with any autoconfiguration that
isn't here, such as Armeria.
Ex. Here's a sampler that traces 100 "GetUserToken" requests per second. This
doesn't start new traces for requests to the health check service. Other
requests will use a global rate provided by the tracing component.
```java
import static brave.rpc.RpcRequestMatchers.methodEquals;
import static brave.rpc.RpcRequestMatchers.serviceEquals;
import static brave.sampler.Matchers.and;
--snip--
@Bean(name = ServerSampler.NAME)
SamplerFunction<RpcRequest> myRpcSampler() {
Matcher<RpcRequest> userAuth = and(
serviceEquals("users.UserService"),
methodEquals("GetUserToken")
);
return RpcRuleSampler.newBuilder()
.putRule(serviceEquals("grpc.health.v1.Health"), Sampler.NEVER_SAMPLE)
.putRule(userAuth, RateLimitingSampler.create(100)).build();
}
```
