[FEATURE] Adjust monitoring metrics to latest OpenTelemetry semantic conventions

[cyrille-leclerc]

Requirements

Flagd uses the outdated OpenTelemetry Semantic Conventions 1.18 (here), producing outdated OTel metric that are not recognized by OpenTelemetry dashboards like the Lightweight APM for OpenTelemetry

HTTP Request Duration

# Current Flagd metric
http.server.duration {
 http.method: "POST",
 http.status_code: "200",
 http.url: "/flagd.evaluation.v1.Service/EventStream"
}


# Expected
http.server.request.duration {
  http.request.method: "POST"
  http.response.status_code: "200",
  http.route: "/flagd.evaluation.v1.Service/EventStream"
  url.scheme: "http"
}

Metric specs here.

Type	Current	Expected
Name	http.server.duration	http.server.request.duration (specs)
Attribute	http.method	http.request.method (specs)
Attribute	http.status_code	http.response.status_code (specs)
Attribute	http.url	http.route (specs) ⚠ http.url MUST NOT be used as it's a high cardinality attribute
Attribute		url.scheme (specs)

HTTP Response Size

# Current Flagd metric
http.server.response.size {
 http.method: "POST",
 http.status_code: "200",
 http.url: "/flagd.evaluation.v1.Service/EventStream"
}


# Expected
http.server.response.body.size {
  http.request.method: "POST"
  http.response.status_code: "200",
  http.route: "/flagd.evaluation.v1.Service/EventStream"
  url.scheme: "http"
}

Metric specs here.

Type	Current	Expected
Name	http.server.response.size	http.server.response.body.size (specs)
Attribute	http.method	http.request.method (specs)
Attribute	http.status_code	http.response.status_code (specs)
Attribute	http.url	http.route (specs) ⚠ http.url MUST NOT be used as it's a high cardinality attribute
Attribute		url.scheme (specs)

Source Code

• Imports of outdated semconv v1.18.0 or v1.13.0 here
• Outdated OTel metric names

  • flagd/core/pkg/telemetry/metrics.go

    Lines 22 to 23 in 07a45d9

    	httpRequestDurationMetric = "http.server.duration"
    	httpResponseSizeMetric = "http.server.response.size"

• Usage of outdated or undesired atributes:

  • flagd/core/pkg/telemetry/metrics.go

    Lines 74 to 76 in 07a45d9

    	semconv.HTTPURLKey.String(url),
    	semconv.HTTPMethodKey.String(method),
    	semconv.HTTPStatusCodeKey.String(code),

I'm sorry, I can't code in Go, I can't propose a PR.