114 lines
5.5 KiB
Plaintext
114 lines
5.5 KiB
Plaintext
[[actuator.micrometer-tracing]]
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== Tracing
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Spring Boot Actuator provides dependency management and auto-configuration for https://micrometer.io/docs/tracing[Micrometer Tracing], a facade for popular tracer libraries.
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Micrometer Tracing hooks into Micrometer's `ObservationHandler`, which means a https://micrometer.io/docs/tracing#_glossary[span] is reported for every completed observation.
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TIP: To learn more about Micrometer Tracing capabilities, see its https://micrometer.io/docs/tracing[reference documentation].
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[[actuator.micrometer-tracing.tracers]]
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=== Supported tracers
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Spring Boot ships auto-configuration for the following tracers:
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* https://opentelemetry.io/[OpenTelemetry] with https://zipkin.io/[Zipkin] or https://docs.wavefront.com/[Wavefront]
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* https://github.com/openzipkin/brave[OpenZipkin Brave] with https://zipkin.io/[Zipkin] or https://docs.wavefront.com/[Wavefront]
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[[actuator.micrometer-tracing.getting-started]]
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=== Getting Started
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We need an example application that we can use to getting started with tracing.
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For our purposes, the simple "`Hello World!`" web application that's covered in the "`<<getting-started#getting-started.first-application>>`" section will suffice.
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We're going to use the OpenTelemetry tracer with Zipkin as trace backend.
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To recap, our main application code looks like this:
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include::code:MyApplication[]
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NOTE: There's an added logger statement in the `home()` method, which will be important later.
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Now we have to add the following dependencies:
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* `org.springframework.boot:spring-boot-starter-actuator`
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* `io.micrometer:micrometer-tracing-bridge-otel` - which is needed to bridge the Micrometer Observation API to OpenTelemetry.
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* `io.opentelemetry:opentelemetry-exporter-zipkin` - which is needed to report https://micrometer.io/docs/tracing#_glossary[traces] to Zipkin.
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Add the following application properties:
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[source,yaml,indent=0,subs="verbatim",configprops,configblocks]
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----
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management.tracing.sampling.probability: 1.0
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----
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By default, Spring Boot samples only 10% of requests to prevent overwhelming the trace backend.
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This property switches it to 100% so that every request is sent to the trace backend.
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To collect and visualize the traces, we need a running trace backend.
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We use Zipkin as our trace backend here.
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The https://zipkin.io/pages/quickstart[Zipkin Quickstart guide] provides instructions how to start Zipkin locally.
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After Zipkin is running, you can start your application.
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If you open a web browser to `http://localhost:8080`, you should see the following output:
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[indent=0]
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----
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Hello World!
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----
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Behind the scenes, an observation has been created for the HTTP request, which in turn gets bridged to OpenTelemetry, which reports a new trace to Zipkin.
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Now open the Zipkin UI at `http://localhost:9411` and press the "Run Query" button to list all collected traces.
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You should see one trace.
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Press the "Show" button to see the details of that trace.
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TIP: You can include the current trace and span id in the logs by setting the `logging.pattern.level` property to `%5p [${spring.application.name:},%X{traceId:-},%X{spanId:-}]`
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[[actuator.micrometer-tracing.tracer-implementations]]
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=== Tracer implementations
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As Micrometer Tracer supports multiple tracer implementations, there are multiple dependency combinations possible with Spring Boot.
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All tracer implementations need the `org.springframework.boot:spring-boot-starter-actuator` dependency.
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[[actuator.micrometer-tracing.tracer-implementations.otel-zipkin]]
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==== OpenTelemetry with Zipkin
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* `io.micrometer:micrometer-tracing-bridge-otel` - which is needed to bride the Micrometer Observation API to OpenTelemetry.
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* `io.opentelemetry:opentelemetry-exporter-zipkin` - which is needed to report traces to Zipkin.
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[[actuator.micrometer-tracing.tracer-implementations.otel-wavefront]]
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==== OpenTelemetry with Wavefront
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* `io.micrometer:micrometer-tracing-bridge-otel` - which is needed to bride the Micrometer Observation API to OpenTelemetry.
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* `io.micrometer:micrometer-tracing-reporter-wavefront` - which is needed to report traces to Wavefront.
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[[actuator.micrometer-tracing.tracer-implementations.brave-zipkin]]
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==== OpenZipkin Brave with Zipkin
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* `io.micrometer:micrometer-tracing-bridge-brave` - which is needed to bridge the Micrometer Observation API to Brave.
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* `io.zipkin.reporter2:zipkin-reporter-brave` - which is needed to report traces to Zipkin.
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NOTE: If your project doesn't use Spring MVC or Spring WebFlux, the `io.zipkin.reporter2:zipkin-sender-urlconnection` dependency is needed, too.
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[[actuator.micrometer-tracing.tracer-implementations.brave-wavefront]]
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==== OpenZipkin Brave with Wavefront
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* `io.micrometer:micrometer-tracing-bridge-brave` - which is needed to bridge the Micrometer Observation API to Brave.
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* `io.micrometer:micrometer-tracing-reporter-wavefront` - which is needed to report traces to Wavefront.
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[[actuator.micrometer-tracing.creating-spans]]
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=== Creating custom spans
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You can create your own spans by starting an observation.
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For this, inject `ObservationRegistry` into your component:
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include::code:CustomObservation[]
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This will create an observation named "some-operation" with the tag "some-tag=some-value".
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Completing an observation will create a metric and a span.
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NOTE: Low cardinality tags will be added to metrics and traces, while high cardinality tags will only be added to traces.
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TIP: If you want to create a span without creating a metric, you need to use the https://micrometer.io/docs/tracing#_using_micrometer_tracing_directly[lower-level `Tracer` API] from Micrometer.
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