Add http instruments

pkg/opentelemetry/plugins/othttp/instruments.go

@@ -0,0 +1,69 @@
+package othttp
+
+import (
+	"go.opentelemetry.io/otel/api/key"
+	"go.opentelemetry.io/otel/api/metric"
+	"go.opentelemetry.io/otel/api/unit"
+)
+
+// The following labels are applied to metrics recorded by this package. Host, Path
+// and Method are applied to all measures.
+var (
+	// Host is the value of the HTTP Host header.
+	//
+	// The value of this label can be controlled by the HTTP client, so you need
+	// to watch out for potentially generating high-cardinality labels in your
+	// metrics backend if you use this tag in views.
+	Host = key.New("http.host")
+
+	// StatusCode is the numeric HTTP response status code,
+	// or "error" if a transport error occurred and no status code was read.
+	StatusCode = key.New("http.status")
+
+	// Path is the URL path (not including query string) in the request.
+	//
+	// The value of this tag can be controlled by the HTTP client, so you need
+	// to watch out for potentially generating high-cardinality labels in your
+	// metrics backend if you use this tag in views.
+	Path = key.New("http.path")
+
+	// Method is the HTTP method of the request, capitalized (GET, POST, etc.).
+	Method = key.New("http.method")
+
+	// KeyServerRoute is a low cardinality string representing the logical
+	// handler of the request. This is usually the pattern registered on the a
+	// ServeMux (or similar string).
+	KeyServerRoute = key.New("http_server_route")
+)
+
+type instruments struct {
+	serverRequestCount  metric.Int64Counter
+	serverRequestBytes  metric.Int64Measure
+	serverResponseBytes metric.Int64Measure
+	serverLatency       metric.Float64Measure
+}
+
+func newInstruments(meter metric.Meter) instruments {
+	return instruments{
+		serverRequestCount: metric.Must(meter).NewInt64Counter(
+			"opentelemetry.io/http/server/request_count",
+			metric.WithDescription("Count of HTTP requests started"),
+			metric.WithUnit(unit.Dimensionless),
+		),
+		serverRequestBytes: metric.Must(meter).NewInt64Measure(
+			"opencensus.io/http/server/request_bytes",
+			metric.WithDescription("HTTP request body size if set as ContentLength (uncompressed)"),
+			metric.WithUnit(unit.Bytes),
+		),
+		serverResponseBytes: metric.Must(meter).NewInt64Measure(
+			"opencensus.io/http/server/response_bytes",
+			metric.WithDescription("HTTP response body size (uncompressed)"),
+			metric.WithUnit(unit.Bytes),
+		),
+		serverLatency: metric.Must(meter).NewFloat64Measure(
+			"opencensus.io/http/server/latency",
+			metric.WithDescription("End-to-end latency"),
+			metric.WithUnit(unit.Milliseconds),
+		),
+	}
+}