05-spring-coroutines-simple

05-spring-coroutines-simple

This project is testing observability APIs in a coroutines / reactive setup.

• build.gradle.kts
• spring-coroutines-simple.http
• ContextPropagationConfig.kt
• HelloControllerV1.kt
• AlohaCoRouterV1.kt
• UserAddingFilter.kt

How does it work?

io.micrometer:context-propagation

• defines io.micrometer.context.ThreadLocalAccessor interface
• io.projectreactor:reactor-core uses ThreadLocalAccessor and other abstractions defined in Micrometer to implement optional hooks that will be triggered for each time computation is switching threads

io.micrometer:micrometer-observation

• implements io.micrometer.observation.contextpropagation.ObservationThreadLocalAccessor to put and restore current Observation

io.micrometer:micrometer-tracing

• implements io.micrometer.tracing.contextpropagation.ObservationAwareSpanThreadLocalAccessor to put and restore current Span
• defines io.micrometer.tracing.handler.TracingObservationHandler which reacts to lifecycle events for Observation

HelloControllerV1

• Observation is created, started, and added to context under ObservationThreadLocalAccessor.KEY by org.springframework.web.server.adapter.HttpWebHandlerAdapter
• Span is then created, started, and made current by io.micrometer.tracing.handler.PropagatingReceiverTracingObservationHandler
• For the nested Observation, Span is handled by io.micrometer.tracing.handler.DefaultTracingObservationHandler