1 files changed, 40 insertions, 20 deletions

diff --git a/src/net/http/server.go b/src/net/http/server.go
index 25fab288f2..4776d960e5 100644
--- a/src/net/http/server.go
+++ b/src/net/http/server.go
@@ -14,8 +14,8 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"log"
+	"math/rand"
 	"net"
 	"net/textproto"
 	"net/url"
@@ -890,12 +890,12 @@ func (srv *Server) initialReadLimitSize() int64 {
 type expectContinueReader struct {
 	resp       *response
 	readCloser io.ReadCloser
-	closed     bool
+	closed     atomicBool
 	sawEOF     atomicBool
 }
 
 func (ecr *expectContinueReader) Read(p []byte) (n int, err error) {
-	if ecr.closed {
+	if ecr.closed.isSet() {
 		return 0, ErrBodyReadAfterClose
 	}
 	w := ecr.resp
@@ -917,7 +917,7 @@ func (ecr *expectContinueReader) Read(p []byte) (n int, err error) {
 }
 
 func (ecr *expectContinueReader) Close() error {
-	ecr.closed = true
+	ecr.closed.setTrue()
 	return ecr.readCloser.Close()
 }
 
@@ -992,7 +992,7 @@ func (c *conn) readRequest(ctx context.Context) (w *response, err error) {
 	}
 
 	if !http1ServerSupportsRequest(req) {
-		return nil, badRequestError("unsupported protocol version")
+		return nil, statusError{StatusHTTPVersionNotSupported, "unsupported protocol version"}
 	}
 
 	c.lastMethod = req.Method
@@ -1368,7 +1368,7 @@ func (cw *chunkWriter) writeHeader(p []byte) {
 		}
 
 		if discard {
-			_, err := io.CopyN(ioutil.Discard, w.reqBody, maxPostHandlerReadBytes+1)
+			_, err := io.CopyN(io.Discard, w.reqBody, maxPostHandlerReadBytes+1)
 			switch err {
 			case nil:
 				// There must be even more data left over.
@@ -1773,9 +1773,16 @@ func (c *conn) getState() (state ConnState, unixSec int64) {
 // badRequestError is a literal string (used by in the server in HTML,
 // unescaped) to tell the user why their request was bad. It should
 // be plain text without user info or other embedded errors.
-type badRequestError string
+func badRequestError(e string) error { return statusError{StatusBadRequest, e} }
 
-func (e badRequestError) Error() string { return "Bad Request: " + string(e) }
+// statusError is an error used to respond to a request with an HTTP status.
+// The text should be plain text without user info or other embedded errors.
+type statusError struct {
+	code int
+	text string
+}
+
+func (e statusError) Error() string { return StatusText(e.code) + ": " + e.text }
 
 // ErrAbortHandler is a sentinel panic value to abort a handler.
 // While any panic from ServeHTTP aborts the response to the client,
@@ -1898,11 +1905,11 @@ func (c *conn) serve(ctx context.Context) {
 				return // don't reply
 
 			default:
-				publicErr := "400 Bad Request"
-				if v, ok := err.(badRequestError); ok {
-					publicErr = publicErr + ": " + string(v)
+				if v, ok := err.(statusError); ok {
+					fmt.Fprintf(c.rwc, "HTTP/1.1 %d %s: %s%s%d %s: %s", v.code, StatusText(v.code), v.text, errorHeaders, v.code, StatusText(v.code), v.text)
+					return
 				}
-
+				publicErr := "400 Bad Request"
 				fmt.Fprintf(c.rwc, "HTTP/1.1 "+publicErr+errorHeaders+publicErr)
 				return
 			}
@@ -2685,14 +2692,14 @@ func (srv *Server) Close() error {
 	return err
 }
 
-// shutdownPollInterval is how often we poll for quiescence
-// during Server.Shutdown. This is lower during tests, to
-// speed up tests.
+// shutdownPollIntervalMax is the max polling interval when checking
+// quiescence during Server.Shutdown. Polling starts with a small
+// interval and backs off to the max.
 // Ideally we could find a solution that doesn't involve polling,
 // but which also doesn't have a high runtime cost (and doesn't
 // involve any contentious mutexes), but that is left as an
 // exercise for the reader.
-var shutdownPollInterval = 500 * time.Millisecond
+const shutdownPollIntervalMax = 500 * time.Millisecond
 
 // Shutdown gracefully shuts down the server without interrupting any
 // active connections. Shutdown works by first closing all open
@@ -2725,8 +2732,20 @@ func (srv *Server) Shutdown(ctx context.Context) error {
 	}
 	srv.mu.Unlock()
 
-	ticker := time.NewTicker(shutdownPollInterval)
-	defer ticker.Stop()
+	pollIntervalBase := time.Millisecond
+	nextPollInterval := func() time.Duration {
+		// Add 10% jitter.
+		interval := pollIntervalBase + time.Duration(rand.Intn(int(pollIntervalBase/10)))
+		// Double and clamp for next time.
+		pollIntervalBase *= 2
+		if pollIntervalBase > shutdownPollIntervalMax {
+			pollIntervalBase = shutdownPollIntervalMax
+		}
+		return interval
+	}
+
+	timer := time.NewTimer(nextPollInterval())
+	defer timer.Stop()
 	for {
 		if srv.closeIdleConns() && srv.numListeners() == 0 {
 			return lnerr
@@ -2734,7 +2753,8 @@ func (srv *Server) Shutdown(ctx context.Context) error {
 		select {
 		case <-ctx.Done():
 			return ctx.Err()
-		case <-ticker.C:
+		case <-timer.C:
+			timer.Reset(nextPollInterval())
 		}
 	}
 }
@@ -3400,7 +3420,7 @@ func (globalOptionsHandler) ServeHTTP(w ResponseWriter, r *Request) {
 		// (or an attack) and we abort and close the connection,
 		// courtesy of MaxBytesReader's EOF behavior.
 		mb := MaxBytesReader(w, r.Body, 4<<10)
-		io.Copy(ioutil.Discard, mb)
+		io.Copy(io.Discard, mb)
 	}
 }