Traces provide a holistic view of an entire system, crossing application boundaries; you can zoom in on particular user requests and follow their entire completion across applications.
As outlined xref:integration/observability.adoc[at the beginning of this section], observations can generate timer Metrics and/or Traces depending on the configuration.
* `Observation` is the actual recording of something happening in your application. This is processed by `ObservationHandler` implementations to produce metrics or traces.
* Each observation has a corresponding `ObservationContext` implementation; this type holds all the relevant information for extracting metadata for it.
In the case of an HTTP server observation, the context implementation could hold the HTTP request, the HTTP response, any exception thrown during processing, and so forth.
* Each `Observation` holds `KeyValues` metadata. In the case of an HTTP server observation, this could be the HTTP request method, the HTTP response status, and so forth.
* `KeyValues` are said to be "low cardinality" if there is a low, bounded number of possible values for the `KeyValue` tuple (HTTP method is a good example).
This observation uses a `ServerRequestObservationConvention` with a `ServerRequestObservationContext`; custom conventions can be configured on the Servlet filter.
If you would like to customize the metadata produced with the observation, you can extend the `DefaultServerRequestObservationConvention` for your requirements:
It is using the `org.springframework.scheduling.support.DefaultScheduledTaskObservationConvention` by default, backed by the `ScheduledTaskObservationContext`.
You can configure a custom implementation on the `ObservationRegistry` directly.
During the execution of the scheduled method, the current observation is restored in the `ThreadLocal` context or the Reactor context (if the scheduled method returns a `Mono` or `Flux` type).
By default, the following `KeyValues` are created:
|`exception` _(required)_|Name of the exception thrown during the execution, or `"none"` if no exception happened.
|`outcome` _(required)_|Outcome of the method execution. Can be `"SUCCESS"`, `"ERROR"` or `"UNKNOWN"` (if for example the operation was cancelled during execution).
Spring Framework uses the Jakarta JMS instrumentation provided by Micrometer if the `io.micrometer:micrometer-core` dependency is on the classpath.
The `io.micrometer.core.instrument.binder.jms.JmsInstrumentation` instruments `jakarta.jms.Session` and records the relevant observations.
This instrumentation will create 2 types of observations:
* `"jms.message.publish"` when a JMS message is sent to the broker, typically with `JmsTemplate`.
* `"jms.message.process"` when a JMS message is processed by the application, typically with a `MessageListener` or a `@JmsListener` annotated method.
NOTE: currently there is no instrumentation for `"jms.message.receive"` observations as there is little value in measuring the time spent waiting for the reception of a message.
Such an integration would typically instrument `MessageConsumer#receive` method calls. But once those return, the processing time is not measured and the trace scope cannot be propagated to the application.
By default, both observations share the same set of possible `KeyValues`:
.Low cardinality Keys
[cols="a,a"]
|===
|Name | Description
|`exception` |Class name of the exception thrown during the messaging operation (or "none").
|`messaging.destination.temporary` _(required)_|Whether the destination is a `TemporaryQueue` or `TemporaryTopic` (values: `"true"` or `"false"`).
|`messaging.operation` _(required)_|Name of JMS operation being performed (values: `"publish"` or `"process"`).
|===
.High cardinality Keys
[cols="a,a"]
|===
|Name | Description
|`messaging.message.conversation_id` |The correlation ID of the JMS message.
|`messaging.destination.name` |The name of destination the current message was sent to.
|`messaging.message.id` |Value used by the messaging system as an identifier for the message.
|===
[[observability.jms.publish]]
=== JMS message Publication instrumentation
`"jms.message.publish"` observations are recorded when a JMS message is sent to the broker.
They measure the time spent sending the message and propagate the tracing information with outgoing JMS message headers.
You will need to configure the `ObservationRegistry` on the `JmsTemplate` to enable observations:
include-code::./JmsTemplatePublish[]
It uses the `io.micrometer.core.instrument.binder.jms.DefaultJmsPublishObservationConvention` by default, backed by the `io.micrometer.core.instrument.binder.jms.JmsPublishObservationContext`.
[[observability.jms.process]]
=== JMS message Processing instrumentation
`"jms.message.process"` observations are recorded when a JMS message is processed by the application.
They measure the time spent processing the message and propagate the tracing context with incoming JMS message headers.
Most applications will use the xref:integration/jms/annotated.adoc#jms-annotated[`@JmsListener` annotated methods] mechanism to process incoming messages.
You will need to ensure that the `ObservationRegistry` is configured on the dedicated `JmsListenerContainerFactory`:
include-code::./JmsConfiguration[]
A xref:integration/jms/annotated.adoc#jms-annotated-support[default container factory is required to enable the annotation support],
but note that `@JmsListener` annotations can refer to specific container factory beans for specific purposes.
In all cases, Observations are only recorded if the observation registry is configured on the container factory.
Similar observations are recorded with `JmsTemplate` when messages are processed by a `MessageListener`.
Such listeners are set on a `MessageConsumer` within a session callback (see `JmsTemplate.execute(SessionCallback<T>)`).
This observation uses the `io.micrometer.core.instrument.binder.jms.DefaultJmsProcessObservationConvention` by default, backed by the `io.micrometer.core.instrument.binder.jms.JmsProcessObservationContext`.
It uses the `org.springframework.http.server.observation.DefaultServerRequestObservationConvention` by default, backed by the `ServerRequestObservationContext`.
This will only record an observation as an error if the `Exception` has not been handled by the web framework and has bubbled up to the Servlet filter.
Typically, all exceptions handled by Spring MVC's `@ExceptionHandler` and xref:web/webmvc/mvc-ann-rest-exceptions.adoc[`ProblemDetail` support] will not be recorded with the observation.
NOTE: Because the instrumentation is done at the Servlet Filter level, the observation scope only covers the filters ordered after this one as well as the handling of the request.
For this use case, a container-specific implementation is required, such as a `org.apache.catalina.Valve` for Tomcat; this is outside of the scope of this project.
|`outcome` _(required)_|Outcome of the HTTP server exchange.
|`status` _(required)_|HTTP response raw status code, or `"UNKNOWN"` if no response was created.
|`uri` _(required)_|URI pattern for the matching handler if available, falling back to `REDIRECTION` for 3xx responses, `NOT_FOUND` for 404 responses, `root` for requests with no path info, and `UNKNOWN` for all other requests.
It is using the `org.springframework.http.server.reactive.observation.DefaultServerRequestObservationConvention` by default, backed by the `ServerRequestObservationContext`.
This will only record an observation as an error if the `Exception` has not been handled by an application Controller.
Typically, all exceptions handled by Spring WebFlux's `@ExceptionHandler` and <<web.adoc#webflux-ann-rest-exceptions,`ProblemDetail` support>> will not be recorded with the observation.
|`outcome` _(required)_|Outcome of the HTTP server exchange.
|`status` _(required)_|HTTP response raw status code, or `"UNKNOWN"` if no response was created.
|`uri` _(required)_|URI pattern for the matching handler if available, falling back to `REDIRECTION` for 3xx responses, `NOT_FOUND` for 404 responses, `root` for requests with no path info, and `UNKNOWN` for all other requests.
Unlike their server counterparts, the instrumentation is implemented directly in the client so the only required step is to configure an `ObservationRegistry` on the client.
Applications must configure an `ObservationRegistry` on `RestTemplate` instances to enable the instrumentation; without that, observations are "no-ops".
Spring Boot will auto-configure `RestTemplateBuilder` beans with the observation registry already set.
Instrumentation uses the `org.springframework.http.client.observation.ClientRequestObservationConvention` by default, backed by the `ClientRequestObservationContext`.
Applications must configure an `ObservationRegistry` on the `RestClient.Builder` to enable the instrumentation; without that, observations are "no-ops".
Instrumentation uses the `org.springframework.http.client.observation.ClientRequestObservationConvention` by default, backed by the `ClientRequestObservationContext`.
.Low cardinality Keys
[cols="a,a"]
|===
|Name | Description
|`method` _(required)_|Name of HTTP request method or `"none"` if the request could not be created.
|`uri` _(required)_|URI template used for HTTP request, or `"none"` if none was provided. Only the path part of the URI is considered.
|`client.name` _(required)_|Client name derived from the request URI host.
|`status` _(required)_|HTTP response raw status code, or `"IO_ERROR"` in case of `IOException`, or `"CLIENT_ERROR"` if no response was received.
|`outcome` _(required)_|Outcome of the HTTP client exchange.
|`exception` _(required)_|Name of the exception thrown during the exchange, or `"none"` if no exception happened.
Applications must configure an `ObservationRegistry` on the `WebClient` builder to enable the instrumentation; without that, observations are "no-ops".
Spring Boot will auto-configure `WebClient.Builder` beans with the observation registry already set.
Instrumentation uses the `org.springframework.web.reactive.function.client.ClientRequestObservationConvention` by default, backed by the `ClientRequestObservationContext`.
