67 lines
2.2 KiB
Go
67 lines
2.2 KiB
Go
package httputil // import "gopkg.in/DataDog/dd-trace-go.v1/contrib/internal/httputil"
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//go:generate sh -c "go run make_responsewriter.go | gofmt > trace_gen.go"
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import (
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"fmt"
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"net/http"
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"strconv"
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"gopkg.in/DataDog/dd-trace-go.v1/ddtrace"
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"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/ext"
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"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer"
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)
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// TraceAndServe will apply tracing to the given http.Handler using the passed tracer under the given service and resource.
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func TraceAndServe(h http.Handler, w http.ResponseWriter, r *http.Request, service, resource string, spanopts ...ddtrace.StartSpanOption) {
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opts := append([]ddtrace.StartSpanOption{
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tracer.SpanType(ext.SpanTypeWeb),
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tracer.ServiceName(service),
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tracer.ResourceName(resource),
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tracer.Tag(ext.HTTPMethod, r.Method),
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tracer.Tag(ext.HTTPURL, r.URL.Path),
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}, spanopts...)
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if spanctx, err := tracer.Extract(tracer.HTTPHeadersCarrier(r.Header)); err == nil {
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opts = append(opts, tracer.ChildOf(spanctx))
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}
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span, ctx := tracer.StartSpanFromContext(r.Context(), "http.request", opts...)
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defer span.Finish()
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w = wrapResponseWriter(w, span)
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h.ServeHTTP(w, r.WithContext(ctx))
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}
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// responseWriter is a small wrapper around an http response writer that will
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// intercept and store the status of a request.
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type responseWriter struct {
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http.ResponseWriter
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span ddtrace.Span
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status int
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}
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func newResponseWriter(w http.ResponseWriter, span ddtrace.Span) *responseWriter {
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return &responseWriter{w, span, 0}
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}
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// Write writes the data to the connection as part of an HTTP reply.
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// We explicitely call WriteHeader with the 200 status code
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// in order to get it reported into the span.
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func (w *responseWriter) Write(b []byte) (int, error) {
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if w.status == 0 {
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w.WriteHeader(http.StatusOK)
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}
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return w.ResponseWriter.Write(b)
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}
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// WriteHeader sends an HTTP response header with status code.
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// It also sets the status code to the span.
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func (w *responseWriter) WriteHeader(status int) {
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w.ResponseWriter.WriteHeader(status)
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w.status = status
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w.span.SetTag(ext.HTTPCode, strconv.Itoa(status))
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if status >= 500 && status < 600 {
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w.span.SetTag(ext.Error, fmt.Errorf("%d: %s", status, http.StatusText(status)))
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}
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}
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