Extend plugin/othttp handler to collect metrics as well as traces

[evantorrie]

The plugin/othttp middleware currently extracts trace ids and context from an incoming HTTP request, creates a new Otel span and augments it with attributes culled from the request and response.

Many systems, including the Opencensus http plugin, also produce corresponding metrics such as

• server requests
• server latency
• bytes read
• bytes written

tagged with very similar attributes as collected in our Otel http plugin.

As OpenTelemetry combines tracing and metrics, it would seem we should be able to optionally produce similar metrics in an automated fashion using plugin/othttp.

[evantorrie]

See some related discussion to this in open-telemetry/opentelemetry-specification#381

[rghetia]

It would be good to have standard metrics defined for http for plugins in the spec.

[AndrewGrachov]

Hi, we are adapting the opentelemetry now(our stack is both Golang and Nodejs), we did such functionality by ourserlves, but better it will be standard solution.
would like to contribute and take this