Implement HTTP Hijacker interface

http/sentryhttp.go

@@ -63,22 +63,6 @@ func New(options Options) *Handler {
 	}
 }
 
-// responseWriter is a wrapper around http.ResponseWriter that captures the status code.
-type responseWriter struct {
-	http.ResponseWriter
-	statusCode int
-}
-
-// WriteHeader captures the status code and calls the original WriteHeader method.
-func (rw *responseWriter) WriteHeader(code int) {
-	rw.statusCode = code
-	rw.ResponseWriter.WriteHeader(code)
-}
-
-func newResponseWriter(w http.ResponseWriter) *responseWriter {
-	return &responseWriter{ResponseWriter: w, statusCode: http.StatusOK}
-}
-
 // Handle works as a middleware that wraps an existing http.Handler. A wrapped
 // handler will recover from and report panics to Sentry, and provide access to
 // a request-specific hub to report messages and errors.
@@ -122,10 +106,10 @@ func (h *Handler) handle(handler http.Handler) http.HandlerFunc {
 		)
 		transaction.SetData("http.request.method", r.Method)
 
-		rw := newResponseWriter(w)
+		rw := NewWrapResponseWriter(w, r.ProtoMajor)
 
 		defer func() {
-			status := rw.statusCode
+			status := rw.Status()
 			transaction.Status = sentry.HTTPtoSpanStatus(status)
 			transaction.SetData("http.response.status_code", status)
 			transaction.Finish()

http/wrap_writer.go

@@ -0,0 +1,178 @@
+package sentryhttp
+
+import (
+	"bufio"
+	"io"
+	"net"
+	"net/http"
+)
+
+// This wrapper is derived from https://github.com/go-chi/chi/blob/master/middleware/wrap_writer.go
+
+// NewWrapResponseWriter wraps an http.ResponseWriter, returning a proxy that allows you to
+// hook into various parts of the response process.
+func NewWrapResponseWriter(w http.ResponseWriter, protoMajor int) WrapResponseWriter {
+	_, fl := w.(http.Flusher)
+
+	bw := basicWriter{ResponseWriter: w, code: http.StatusOK}
+
+	if protoMajor == 2 {
+		_, ps := w.(http.Pusher)
+		if fl && ps {
+			return &http2FancyWriter{bw}
+		}
+	} else {
+		_, hj := w.(http.Hijacker)
+		_, rf := w.(io.ReaderFrom)
+		if fl && hj && rf {
+			return &httpFancyWriter{bw}
+		}
+	}
+	if fl {
+		return &flushWriter{bw}
+	}
+
+	return &bw
+}
+
+// WrapResponseWriter is a proxy around an http.ResponseWriter that allows you to hook
+// into various parts of the response process.
+type WrapResponseWriter interface {
+	http.ResponseWriter
+	// Status returns the HTTP status of the request, or 200 if one has not
+	// yet been sent.
+	Status() int
+	// BytesWritten returns the total number of bytes sent to the client.
+	BytesWritten() int
+	// Tee causes the response body to be written to the given io.Writer in
+	// addition to proxying the writes through. Only one io.Writer can be
+	// tee'd to at once: setting a second one will overwrite the first.
+	// Writes will be sent to the proxy before being written to this
+	// io.Writer. It is illegal for the tee'd writer to be modified
+	// concurrently with writes.
+	Tee(io.Writer)
+	// Unwrap returns the original proxied target.
+	Unwrap() http.ResponseWriter
+}
+
+// basicWriter wraps a http.ResponseWriter that implements the minimal
+// http.ResponseWriter interface.
+type basicWriter struct {
+	http.ResponseWriter
+	tee         io.Writer
+	code        int
+	bytes       int
+	wroteHeader bool
+}
+
+func (b *basicWriter) WriteHeader(code int) {
+	if !b.wroteHeader {
+		b.code = code
+		b.wroteHeader = true
+	}
+	b.ResponseWriter.WriteHeader(code)
+}
+
+func (b *basicWriter) Write(buf []byte) (int, error) {
+	b.maybeWriteHeader()
+	n, err := b.ResponseWriter.Write(buf)
+	if b.tee != nil {
+		_, err2 := b.tee.Write(buf[:n])
+		// Prefer errors generated by the proxied writer.
+		if err == nil {
+			err = err2
+		}
+	}
+	b.bytes += n
+	return n, err
+}
+
+func (b *basicWriter) maybeWriteHeader() {
+	if !b.wroteHeader {
+		b.WriteHeader(http.StatusOK)
+	}
+}
+
+func (b *basicWriter) Status() int {
+	return b.code
+}
+
+func (b *basicWriter) BytesWritten() int {
+	return b.bytes
+}
+
+func (b *basicWriter) Tee(w io.Writer) {
+	b.tee = w
+}
+
+func (b *basicWriter) Unwrap() http.ResponseWriter {
+	return b.ResponseWriter
+}
+
+type flushWriter struct {
+	basicWriter
+}
+
+func (f *flushWriter) Flush() {
+	f.wroteHeader = true
+
+	fl := f.basicWriter.ResponseWriter.(http.Flusher)
+	fl.Flush()
+}
+
+var _ http.Flusher = &flushWriter{}
+
+// httpFancyWriter is a HTTP writer that additionally satisfies
+// http.Flusher, http.Hijacker, and io.ReaderFrom. It exists for the common case
+// of wrapping the http.ResponseWriter that package http gives you, in order to
+// make the proxied object support the full method set of the proxied object.
+type httpFancyWriter struct {
+	basicWriter
+}
+
+func (f *httpFancyWriter) Flush() {
+	f.wroteHeader = true
+	f.basicWriter.ResponseWriter.(http.Flusher).Flush()
+}
+
+func (f *httpFancyWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	return f.basicWriter.ResponseWriter.(http.Hijacker).Hijack()
+}
+
+func (f *http2FancyWriter) Push(target string, opts *http.PushOptions) error {
+	return f.basicWriter.ResponseWriter.(http.Pusher).Push(target, opts)
+}
+
+func (f *httpFancyWriter) ReadFrom(r io.Reader) (int64, error) {
+	if f.basicWriter.tee != nil {
+		n, err := io.Copy(&f.basicWriter, r)
+		f.basicWriter.bytes += int(n)
+		return n, err
+	}
+	rf := f.basicWriter.ResponseWriter.(io.ReaderFrom)
+	f.basicWriter.maybeWriteHeader()
+	n, err := rf.ReadFrom(r)
+	f.basicWriter.bytes += int(n)
+	return n, err
+}
+
+var _ http.Flusher = &httpFancyWriter{}
+var _ http.Hijacker = &httpFancyWriter{}
+var _ http.Pusher = &http2FancyWriter{}
+var _ io.ReaderFrom = &httpFancyWriter{}
+
+// http2FancyWriter is a HTTP2 writer that additionally satisfies
+// http.Flusher, and io.ReaderFrom. It exists for the common case
+// of wrapping the http.ResponseWriter that package http gives you, in order to
+// make the proxied object support the full method set of the proxied object.
+type http2FancyWriter struct {
+	basicWriter
+}
+
+func (f *http2FancyWriter) Flush() {
+	f.wroteHeader = true
+
+	f.basicWriter.ResponseWriter.(http.Flusher).Flush()
+}
+
+var _ http.Flusher = &http2FancyWriter{}