net/http: add Server.Close & Server.Shutdown for forced & graceful shutdown

Also updates x/net/http2 to git rev 541150 for:

   http2: add support for graceful shutdown of Server
   https://golang.org/cl/32412

   http2: make http2.Server access http1's Server via an interface check
   https://golang.org/cl/32417

Fixes #4674
Fixes #9478

Change-Id: I8021a18dee0ef2fe3946ac1776d2b10d3d429052
Reviewed-on: https://go-review.googlesource.com/32329
Run-TryBot: Brad Fitzpatrick <[email protected]>
Reviewed-by: Brad Fitzpatrick <[email protected]>

Author: bradfitz

src/net/http/export_test.go

@@ -87,6 +87,12 @@ func (t *Transport) IdleConnKeysForTesting() (keys []string) {
 	return
 }
 
+func (t *Transport) IdleConnKeyCountForTesting() int {
+	t.idleMu.Lock()
+	defer t.idleMu.Unlock()
+	return len(t.idleConn)
+}
+
 func (t *Transport) IdleConnStrsForTesting() []string {
 	var ret []string
 	t.idleMu.Lock()

src/net/http/h2_bundle.go

@@ -12,8 +12,13 @@ import (
 	"os/exec"
 	"reflect"
 	"testing"
+	"time"
 )
 
+func init() {
+	shutdownPollInterval = 5 * time.Millisecond
+}
+
 func TestForeachHeaderElement(t *testing.T) {
 	tests := []struct {
 		in   string

src/net/http/http_test.go

@@ -4832,3 +4832,96 @@ func TestServerIdleTimeout(t *testing.T) {
 		t.Fatal("copy byte succeeded; want err")
 	}
 }
+
+func get(t *testing.T, c *Client, url string) string {
+	res, err := c.Get(url)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer res.Body.Close()
+	slurp, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return string(slurp)
+}
+
+// Tests that calls to Server.SetKeepAlivesEnabled(false) closes any
+// currently-open connections.
+func TestServerSetKeepAlivesEnabledClosesConns(t *testing.T) {
+	if runtime.GOOS == "nacl" {
+		t.Skip("skipping on nacl; see golang.org/issue/17695")
+	}
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		io.WriteString(w, r.RemoteAddr)
+	}))
+	defer ts.Close()
+
+	tr := &Transport{}
+	defer tr.CloseIdleConnections()
+	c := &Client{Transport: tr}
+
+	get := func() string { return get(t, c, ts.URL) }
+
+	a1, a2 := get(), get()
+	if a1 != a2 {
+		t.Fatal("expected first two requests on same connection")
+	}
+	var idle0 int
+	if !waitCondition(2*time.Second, 10*time.Millisecond, func() bool {
+		idle0 = tr.IdleConnKeyCountForTesting()
+		return idle0 == 1
+	}) {
+		t.Fatalf("idle count before SetKeepAlivesEnabled called = %v; want 1", idle0)
+	}
+
+	ts.Config.SetKeepAlivesEnabled(false)
+
+	var idle1 int
+	if !waitCondition(2*time.Second, 10*time.Millisecond, func() bool {
+		idle1 = tr.IdleConnKeyCountForTesting()
+		return idle1 == 0
+	}) {
+		t.Fatalf("idle count after SetKeepAlivesEnabled called = %v; want 0", idle1)
+	}
+
+	a3 := get()
+	if a3 == a2 {
+		t.Fatal("expected third request on new connection")
+	}
+}
+
+func TestServerShutdown_h1(t *testing.T) { testServerShutdown(t, h1Mode) }
+func TestServerShutdown_h2(t *testing.T) { testServerShutdown(t, h2Mode) }
+
+func testServerShutdown(t *testing.T, h2 bool) {
+	defer afterTest(t)
+	var doShutdown func() // set later
+	var shutdownRes = make(chan error, 1)
+	cst := newClientServerTest(t, h2, HandlerFunc(func(w ResponseWriter, r *Request) {
+		go doShutdown()
+		// Shutdown is graceful, so it should not interrupt
+		// this in-flight response. Add a tiny sleep here to
+		// increase the odds of a failure if shutdown has
+		// bugs.
+		time.Sleep(20 * time.Millisecond)
+		io.WriteString(w, r.RemoteAddr)
+	}))
+	defer cst.close()
+
+	doShutdown = func() {
+		shutdownRes <- cst.ts.Config.Shutdown(context.Background())
+	}
+	get(t, cst.c, cst.ts.URL) // calls t.Fail on failure
+
+	if err := <-shutdownRes; err != nil {
+		t.Fatalf("Shutdown: %v", err)
+	}
+
+	res, err := cst.c.Get(cst.ts.URL)
+	if err == nil {
+		res.Body.Close()
+		t.Fatal("second request should fail. server should be shut down")
+	}
+}