grafana/pkg/infra/httpclient/httpclientprovider/tracing_middleware.go

package httpclientprovider

import (
	"fmt"
	"net/http"
	"strconv"

	"github.com/grafana/grafana-plugin-sdk-go/backend/httpclient"
	"github.com/grafana/grafana/pkg/infra/log"
	"github.com/grafana/grafana/pkg/infra/tracing"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/codes"
	"go.opentelemetry.io/otel/trace"
)

const (
	TracingMiddlewareName   = "tracing"
	httpContentLengthTagKey = "http.content_length"
)

func TracingMiddleware(logger log.Logger, tracer tracing.Tracer) httpclient.Middleware {
	return httpclient.NamedMiddlewareFunc(TracingMiddlewareName, func(opts httpclient.Options, next http.RoundTripper) http.RoundTripper {
		return httpclient.RoundTripperFunc(func(req *http.Request) (*http.Response, error) {
			ctx, span := tracer.Start(req.Context(), "HTTP Outgoing Request", trace.WithSpanKind(trace.SpanKindClient))
			defer span.End()

			req = req.WithContext(ctx)
			for k, v := range opts.Labels {
				span.SetAttributes(k, v, attribute.Key(k).String(v))
			}

			tracer.Inject(ctx, req.Header, span)
			res, err := next.RoundTrip(req)

			span.SetAttributes("http.url", req.URL.String(), attribute.String("http.url", req.URL.String()))
			span.SetAttributes("http.method", req.Method, attribute.String("http.method", req.Method))
			// ext.SpanKind.Set(span, ext.SpanKindRPCClientEnum)

			if err != nil {
				span.RecordError(err)
				return res, err
			}

			if res != nil {
				// we avoid measuring contentlength less than zero because it indicates
				// that the content size is unknown. https://godoc.org/github.com/badu/http#Response
				if res.ContentLength > 0 {
					span.SetAttributes(httpContentLengthTagKey, res.ContentLength, attribute.Key(httpContentLengthTagKey).Int64(res.ContentLength))
				}

				span.SetAttributes("http.status_code", res.StatusCode, attribute.Int("http.status_code", res.StatusCode))
				if res.StatusCode >= 400 {
					span.SetStatus(codes.Error, fmt.Sprintf("error with HTTP status code %s", strconv.Itoa(res.StatusCode)))
				}
			}

			return res, err
		})
	})
}