http: don't fail on accept hitting EMFILE

Fixes #1891

R=rsc
CC=golang-dev
https://golang.org/cl/4550112

src/pkg/http/serve_test.go

@@ -18,6 +18,7 @@ import (
 	"net"
 	"reflect"
 	"strings"
+	"syscall"
 	"testing"
 	"time"
 )
@@ -773,6 +774,42 @@ func TestHandlerPanic(t *testing.T) {
 	}
 }
 
+type errorListener struct {
+	errs []os.Error
+}
+
+func (l *errorListener) Accept() (c net.Conn, err os.Error) {
+	if len(l.errs) == 0 {
+		return nil, os.EOF
+	}
+	err = l.errs[0]
+	l.errs = l.errs[1:]
+	return
+}
+
+func (l *errorListener) Close() os.Error {
+	return nil
+}
+
+func (l *errorListener) Addr() net.Addr {
+	return dummyAddr("test-address")
+}
+
+func TestAcceptMaxFds(t *testing.T) {
+	log.SetOutput(ioutil.Discard) // is noisy otherwise
+	defer log.SetOutput(os.Stderr)
+
+	ln := &errorListener{[]os.Error{
+		&net.OpError{
+			Op:    "accept",
+			Error: os.Errno(syscall.EMFILE),
+		}}}
+	err := Serve(ln, HandlerFunc(HandlerFunc(func(ResponseWriter, *Request) {})))
+	if err != os.EOF {
+		t.Errorf("got error %v, want EOF", err)
+	}
+}
+
 func BenchmarkClientServer(b *testing.B) {
 	b.StopTimer()
 	ts := httptest.NewServer(HandlerFunc(func(rw ResponseWriter, r *Request) {

src/pkg/http/server.go

@@ -860,6 +860,10 @@ func (srv *Server) Serve(l net.Listener) os.Error {
 	for {
 		rw, e := l.Accept()
 		if e != nil {
+			if ne, ok := e.(net.Error); ok && ne.Temporary() {
+				log.Printf("http: Accept error: %v", e)
+				continue
+			}
 			return e
 		}
 		if srv.ReadTimeout != 0 {

src/pkg/os/error_posix.go

@@ -13,7 +13,7 @@ type Errno int64
 func (e Errno) String() string { return syscall.Errstr(int(e)) }
 
 func (e Errno) Temporary() bool {
-	return e == Errno(syscall.EINTR) || e.Timeout()
+	return e == Errno(syscall.EINTR) || e == Errno(syscall.EMFILE) || e.Timeout()
 }
 
 func (e Errno) Timeout() bool {