AWS metric EMF exporter fails to report http.route for Cloudwatch metrics

[Ryang20718]

Describe the bug
AWS metric EMF exporter fails to report http.route for Cloudwatch metrics when otelhttp is used as middleware

Steps to reproduce
Spin up the otel collector via docker,

instrument some code with otelhttp

import(
	"go.opentelemetry.io/contrib/instrumentation/github.com/gin-gonic/gin/otelgin"
   "go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
)


       // tracing setup here for otel
       
       // tracing middleware
       
	router := gin.New()
   router.Use(otelgin.Middleware(config.OtelServiceName))

	mux := http.NewServeMux()
	mux.Handle("/api/", router)

	otelHTTPHandler := otelhttp.NewHandler(mux, "")

       httpServer := &http.Server{
           ReadHeaderTimeout: 1 * time.Minute,
           Addr:              ":8080",
           Handler:           otelHTTPHandler,
       }
       return httpServer.ListenAndServe()

What did you expect to see?
http.route as part of the metrics getting sent

What did you see instead?
no http.route was getting sent

{
    "OTelLib": "go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp",
    "Version": "1",
    "_aws": {
        "CloudWatchMetrics": [
            {
                "Namespace": "testing",
                "Dimensions": [
                    [
                        "OTelLib",
                        "http.scheme",
                        "http.status_code",
                        "net.sock.peer.port",
                        "net.host.name",
                        "net.host.port",
                        "net.sock.peer.addr",
                        "http.flavor",
                        "http.method",
                        "http.user_agent"
                    ],
                    [
                        "OTelLib"
                    ],
                    [
                        "OTelLib",
                        "http.status_code"
                    ],
                    [
                        "OTelLib",
                        "net.sock.peer.port"
                    ],
                    [
                        "OTelLib",
                        "http.scheme"
                    ],
                    [
                        "OTelLib",
                        "http.method"
                    ],
                    [
                        "OTelLib",
                        "http.user_agent"
                    ],
                    [
                        "OTelLib",
                        "net.host.name"
                    ],
                    [
                        "OTelLib",
                        "net.host.port"
                    ],
                    [
                        "OTelLib",
                        "net.sock.peer.addr"
                    ],
                    [
                        "OTelLib",
                        "http.flavor"
                    ]
                ],
                "Metrics": [
                    {
                        "Name": "http.server.duration"
                    }
                ]
            }
        ],
        "Timestamp": 1686603548366
    },
    "http.flavor": "1.1",
    "http.method": "GET",
    "http.scheme": "http",
    "http.server.duration": {
        "Max": 1.26,
        "Min": 0.14,
        "Count": 3,
        "Sum": 2.43
    },
    "http.status_code": "304",
    "http.user_agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/114.0.0.0 Safari/537.36",
    "net.host.name": "localhost",
    "net.host.port": "8080",
    "net.sock.peer.addr": "172.19.0.1",
    "net.sock.peer.port": "55952"
}

Environment
Collector config file

extensions:
  health_check:
  pprof:
    endpoint: 0.0.0.0:1777

receivers:
  otlp:
    protocols:
      grpc:
        endpoint: 0.0.0.0:4317

processors:
  batch:

exporters:
  logging:
    loglevel: debug
  awsemf:
    region: 'us-west-2'

service:
  pipelines:
    metrics:
      receivers: [otlp]
      exporters: [awsemf]

  extensions: [pprof]
  telemetry:
    logs:
      level: debug

Additional context
Exact command used to spin up collector was using the example in this repo

     docker run --rm -p 4317:4317 -p 55680:55680 -p 8889:8888 \
       -e AWS_REGION=us-west-2 \
       -e AWS_PROFILE=default \
       -v ~/.aws:/root/.aws \
       -v "${PWD}/examples/docker/config-test.yaml":/otel-local-config.yaml \
       --name awscollector public.ecr.aws/aws-observability/aws-otel-collector:latest \
       --config otel-local-config.yaml;
    ```

[Ryang20718]

related ticket : open-telemetry/opentelemetry-collector-contrib#23331

[rapphil]

The issue is that http.route is not being populated by the instrumentation: https://github.com/open-telemetry/opentelemetry-go-contrib/blob/main/instrumentation/net/http/otelhttp/internal/semconvutil/httpconv.go#L269

It is not being populated because net/http does not have the notion of route. It only deals with the path, which has high cardinality.

Please see note [1] about http.route in the semantic conventions: https://github.com/open-telemetry/semantic-conventions/blob/main/specification/metrics/semantic_conventions/http-metrics.md?plain=1#L75

Related ticket: open-telemetry/opentelemetry-go-contrib#3743

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[github-actions]

This issue was closed because it has been marked as stale for 30 days with no activity.