Prior to this commit, the Observation instrumentation for Reactive
server applications was implemented with a `WebFilter`. This allowed to
record observations and set up a tracing context for the controller
handlers.
The limitation of this approach is that all processing happening at a
lower level is not aware of any observation. Here, the
`HttpWebHandlerAdapter` handles several interesting aspects:
* logging of HTTP requests and responses at the TRACE level
* logging of client disconnect errors
* handling of unresolved errors
With the current instrumentation, these logging statements will miss the
tracing context information. As a result, this commit deprecates the
`ServerHttpObservationFilter` in favor of a more direct instrumentation
of the `HttpWebHandlerAdapter`. This enables a more precise
instrumentattion and allows to set up the current observation earlier in
the reactor context: log statements will now contain the relevant
information.
Fixes gh-30013
The `ServerHttpObservationFilter` implementations record observations
for processed HTTP exchanges. The `Observation.Context` contains various
metadata contributed by the observation convention. The instrumentation
can also mark the observation as an error by setting any `Throwable` on
the context.
Because the instrumentation is done as filters, only exceptions reaching
the filter can be considered. Any error handled at a lower level by the
Framework can, or cannot be considered as an error for an observation.
This commit documents how a web application should opt-in for
considering a handled exception as an error for the current observation.
Closes gh-29848
This commit documents how Observation instrumentation should be
activated for `RestTemplate` and `WebClient`: they both need an
`ObservationRegistry` configured to create and record actual
observations.
This is being done automatically in Spring Boot if auto-configured
builders (`RestTemplateBuilder`, `WebClient.Builder`) are used.
Closes gh-29904
Prior to this commit, the "uri" KeyValue for low cardinality metadata
would contain the entire uri template given to the HTTP client when
creating the request. This was a breaking change for existing metrics
dashboards, as previous support was removing the protocol, host and port
parts of the URI.
Indeed, this information is available in the "client.name" and
"http.uri" KayValue.
This commit parses and removes the protocol+host+port information from
the uri template for the "uri" KeyValue.
Fixes gh-29885
Prior to this commit, the `"client.name"` key value for the
`"http.client.requests"` client HTTP observations would be considered as
high cardinality, as the URI host is technically unbounded.
In practice, the number of hosts used by a client in a given application
can be considered as low cardinality. This commit moves this keyvalue to
low cardinality so that it's present for both metrics and traces.
Closes gh-29839
rstoyanchev
Brian Clozel
Rob Winch
Johnny Lim
Yanming Zhou