How to get metrics from outgoing requests per route whe using ochttp.Transpor?

[lbeier]

Please answer these questions before submitting a bug report.

What version of OpenCensus are you using?

0.18.0

What version of Go are you using?

1.12.5

What did you do?

Created an HTTP client using ochttp.Transport:

&http.Client{
    Transport: &ochttp.Transport{
        Propagation: &b3.HTTPFormat{},
    },
}

What did you expect to see?

Stats about outgoing requests per route, such as:

opencensus_io_http_client_roundtrip_latency_bucket{http_client_method="GET",http_client_status="200",le="500", ---> http_server_route="/users/{UsersID}" <--- } 265
opencensus_io_http_client_roundtrip_latency_sum{http_client_method="GET",http_client_status="200", ---> http_server_route="/users/{UsersID}" <--- } 39628.590544999955
opencensus_io_http_client_roundtrip_latency_count{http_client_method="GET",http_client_status="200", ---> http_server_route="/users/{UsersID}" <--- } 278

What did you see instead?

The stats for the roundtrip (which I'm assuming are coming from ochttp.Transport:

opencensus_io_http_client_roundtrip_latency_bucket{http_client_method="GET",http_client_status="200",le="500"} 265
opencensus_io_http_client_roundtrip_latency_sum{http_client_method="GET",http_client_status="200"} 39628.590544999955
opencensus_io_http_client_roundtrip_latency_count{http_client_method="GET",http_client_status="200"} 278

[BradErz]

Right now the ochttp.DefaultClientViews don't export the path in the metric view. You can add it by doing something similar to this.

var (
	ClientRoundtripLatencyDistribution = &view.View{
		Name:        "opencensus.io/http/client/roundtrip_latency",
		Measure:     ochttp.ClientRoundtripLatency,
		Aggregation: ochttp.DefaultLatencyDistribution,
		Description: "End-to-end latency, by HTTP method and response status",
		TagKeys:     []tag.Key{ochttp.KeyClientMethod, ochttp.KeyClientHost, ochttp.KeyClientPath, ochttp.KeyClientStatus},
	}

	ClientCompletedCount = &view.View{
		Name:        "opencensus.io/net/http/client/completed_count",
		Measure:     ochttp.ClientRoundtripLatency,
		Aggregation: view.Count(),
		Description: "Count of completed requests, by HTTP method and response status",
		TagKeys:     []tag.Key{ochttp.KeyClientMethod, ochttp.KeyClientHost, ochttp.KeyClientPath, ochttp.KeyClientStatus},
	}

	DefaultHttpClientViews = []*view.View{ClientCompletedCount, ClientRoundtripLatencyDistribution}
)

What im trying to investigate right now is how to understand if req.URL.Path then replace it somehow... has anyone else found a solution to not having the metrics be super granular?

opencensus_io_http_client_completed_count{http_client_method="GET",http_client_status="200",, http_client_path="/users/42112f64-b2b0-4188-a429-2c292bc2d916"} 265

[basvanbeek]

If you use something like Gorilla mux for your client routes you can use named routes logic.

An example adjusting OC span names to these routes can be found here:
https://github.com/basvanbeek/opencensus-gorilla_mux-example/blob/master/client/main.go

You can probably use this as basis for metrics tagging.