see:

* prometheus/client_rust#242
* prometheus/client_rust#241

for now, refactor this test so that it gates all use of the (proposed)
`sum()` and `count()` accessors behind a temporary feature gate.

Signed-off-by: katelyn martin <[email protected]>

see:

* prometheus/client_rust#242
* prometheus/client_rust#241

for now, refactor this test so that it gates all use of the (proposed)
`sum()` and `count()` accessors behind a temporary feature gate.

Signed-off-by: katelyn martin <[email protected]>

see:

* prometheus/client_rust#242
* prometheus/client_rust#241

for now, refactor this test so that it gates all use of the (proposed)
`sum()` and `count()` accessors behind a temporary feature gate.

Signed-off-by: katelyn martin <[email protected]>

* feat(app): Backend response frame count metrics

this introduces a new tower middleware for Prometheus metrics, used for
instrumenting HTTP and gRPC response bodies, and observing (a) the
number of frames yielded by a body, and (b) the number of bytes included
in body frames, and (c) the distribution of frame sizes.

this middleware allows operators to reason about how large or small the
packets being served in a backend's response bodies are.

a route-level middleware that instruments request bodies will be added
in a follow-on PR.

 ### 📝 changes

an overview of changes made here:

* the `linkerd-http-prom` has a new `body_data` submodule. it exposes
  `request` and `response` halves, to be explicit about which body is
  being instrumented on a `tower::Service`.

* the `linkerd-http-prom` crate now has a collection of new
  dependencies: `bytes` is added as a dependency in order to inspect the
  data chunk when the inner body yields a new frame. `futures-util` and
  `http-body` are added as dev-dependencies for the accompanying test
  coverage.

* body metrics are affixed to the `RouteBackendMetrics<L>` structure,
  and registered at startup.

Signed-off-by: katelyn martin <[email protected]>

* review: Inline attribute to service passthrough

Signed-off-by: katelyn martin <[email protected]>

* review: Inline attribute to body passthrough

continuing this theme of inlining, we inline the passthrough methods on
`Body` as well.

Signed-off-by: katelyn martin <[email protected]>

* review: Box `<RecordBodyData as Service>::Future` values

Signed-off-by: katelyn martin <[email protected]>

* review: rename `get()` to `metrics()`

Signed-off-by: katelyn martin <[email protected]>

* review: simplify `RecordBodyData<S>` response

Signed-off-by: katelyn martin <[email protected]>

* Update ResponseBody metrics to use a histogram

Signed-off-by: Oliver Gould <[email protected]>

* refactor(tests): feature gate frame size histogram assertions

see:

* prometheus/client_rust#242
* prometheus/client_rust#241

for now, refactor this test so that it gates all use of the (proposed)
`sum()` and `count()` accessors behind a temporary feature gate.

Signed-off-by: katelyn martin <[email protected]>

---------

Signed-off-by: katelyn martin <[email protected]>
Signed-off-by: Oliver Gould <[email protected]>
Co-authored-by: Oliver Gould <[email protected]>

 ### ⛅ overview

this introduces a new tower middleware for Prometheus metrics, used for
instrumenting HTTP and gRPC request bodies, and observing (a) the
number of frames yielded by a body, (b) the number of bytes included
in body frames, and (c) a distribution of the size of frames yielded.

this builds upon the backend-level metrics added in #3308. this
additionally uses the route label extractor, hoisted out of the retry
middleware's Prometheus telemetry in #3337.

 ### 📝 changes

* a `linkerd_http_prom::body_data::request::NewRecordBodyData::NewRecordBodyData`
  middleware is added, which complements the equivalent
  `linkerd_http_prom::body_data::response` middleware.

* this is added to policy routes' metrics layer.

see prometheus/client_rust#241 and prometheus/client_rust#242, which
track upstream proposals to add accessors to `Histogram` that will allow
us to make test assertions that metrics are working properly. for now,
these are feature gated as also done in #3308.

Signed-off-by: katelyn martin <[email protected]>

 ### ⛅ overview

this introduces a new tower middleware for Prometheus metrics, used for
instrumenting HTTP and gRPC request bodies, and observing (a) the
number of frames yielded by a body, (b) the number of bytes included
in body frames, and (c) a distribution of the size of frames yielded.

this builds upon the backend-level metrics added in #3308. this
additionally uses the route label extractor, hoisted out of the retry
middleware's Prometheus telemetry in #3337.

 ### 📝 changes

* a `linkerd_http_prom::body_data::request::NewRecordBodyData::NewRecordBodyData`
  middleware is added, which complements the equivalent
  `linkerd_http_prom::body_data::response` middleware.

* this is added to policy routes' metrics layer.

see prometheus/client_rust#241 and prometheus/client_rust#242, which
track upstream proposals to add accessors to `Histogram` that will allow
us to make test assertions that metrics are working properly. for now,
these are feature gated as also done in #3308.

Signed-off-by: katelyn martin <[email protected]>

### ⛅ overview

this introduces a new tower middleware for Prometheus metrics, used for
instrumenting HTTP and gRPC request bodies, and observing (a) the
number of frames yielded by a body, (b) the number of bytes included
in body frames, and (c) a distribution of the size of frames yielded.

this builds upon the backend-level metrics added in #3308. this
additionally uses the route label extractor, hoisted out of the retry
middleware's Prometheus telemetry in #3337.

 ### 📝 changes

* a `linkerd_http_prom::body_data::request::NewRecordBodyData::NewRecordBodyData`
  middleware is added, which complements the equivalent
  `linkerd_http_prom::body_data::response` middleware.

* this is added to policy routes' metrics layer.

see prometheus/client_rust#241 and prometheus/client_rust#242, which
track upstream proposals to add accessors to `Histogram` that will allow
us to make test assertions that metrics are working properly. for now,
these are feature gated as also done in #3308.

Signed-off-by: katelyn martin <[email protected]>