Implements route backend timeout

* Adds `backendTimeout` filter to configure route backend timeout
* Proxy sets up request context with configured timeout and responds
with 504 status on timeout (note: if response streaming has already
started it will be terminated, client will receive backend status and
truncated response body).

See zalando#1041

Signed-off-by: Alexander Yastrebov <[email protected]>

docs/reference/filters.md

@@ -466,6 +466,23 @@ Example:
 * -> randomContent(42) -> <shunt>;
 ```
 
+## backendTimeout
+
+Configure backend timeout. Skipper responds with `504 Gateway Timeout` status if obtaining a connection,
+sending the request, and reading the backend response headers and body takes longer than the configured timeout.
+However, if response streaming has already started it will be terminated, i.e. client will receive backend response
+status and truncated response body.
+
+Parameters:
+
+* timeout [(duration string)](https://godoc.org/time#ParseDuration)
+
+Example:
+
+```
+* -> backendTimeout("10ms") -> "https://www.example.org";
+```
+
 ## latency
 
 Enable adding artificial latency

filters/builtin/builtin.go

@@ -72,6 +72,7 @@ const (
 	InlineContentIfStatusName = "inlineContentIfStatus"
 	HeaderToQueryName         = "headerToQuery"
 	QueryToHeaderName         = "queryToHeader"
+	BackendTimeoutName        = "backendTimeout"
 )
 
 // Returns a Registry object initialized with the default set of filter
@@ -120,6 +121,7 @@ func MakeRegistry() filters.Registry {
 		NewDecompress(),
 		NewHeaderToQuery(),
 		NewQueryToHeader(),
+		NewBackendTimeout(),
 		NewSetDynamicBackendHostFromHeader(),
 		NewSetDynamicBackendSchemeFromHeader(),
 		NewSetDynamicBackendUrlFromHeader(),

filters/builtin/timeout.go

@@ -0,0 +1,47 @@
+package builtin
+
+import (
+	"time"
+
+	"github.com/zalando/skipper/filters"
+)
+
+type timeout struct {
+	timeout time.Duration
+}
+
+func NewBackendTimeout() filters.Spec {
+	return &timeout{}
+}
+
+func (*timeout) Name() string { return BackendTimeoutName }
+
+func (*timeout) CreateFilter(args []interface{}) (filters.Filter, error) {
+	if len(args) != 1 {
+		return nil, filters.ErrInvalidFilterParameters
+	}
+
+	var tf timeout
+	switch v := args[0].(type) {
+	case string:
+		d, err := time.ParseDuration(v)
+		if err != nil {
+			return nil, err
+		}
+		tf.timeout = d
+	case time.Duration:
+		tf.timeout = v
+	default:
+		return nil, filters.ErrInvalidFilterParameters
+	}
+	return &tf, nil
+}
+
+func (t *timeout) Request(ctx filters.FilterContext) {
+	sb := ctx.StateBag()
+	if _, ok := sb[filters.BackendTimeout]; !ok { // once
+		sb[filters.BackendTimeout] = t.timeout
+	}
+}
+
+func (t *timeout) Response(filters.FilterContext) {}

filters/builtin/timeout_test.go

@@ -0,0 +1,37 @@
+package builtin
+
+import (
+	"net/http"
+	"testing"
+	"time"
+
+	"github.com/zalando/skipper/filters"
+	"github.com/zalando/skipper/filters/filtertest"
+)
+
+func TestBackendTimeout(t *testing.T) {
+	bt := NewBackendTimeout()
+	if bt.Name() != BackendTimeoutName {
+		t.Error("wrong name")
+	}
+
+	f, err := bt.CreateFilter([]interface{}{"2s"})
+	if err != nil {
+		t.Error("wrong id")
+	}
+
+	c := &filtertest.Context{FRequest: &http.Request{}, FStateBag: make(map[string]interface{})}
+	f.Request(c)
+
+	if c.FStateBag[filters.BackendTimeout] != 2*time.Second {
+		t.Error("wrong timeout")
+	}
+
+	// second filter
+	f, _ = bt.CreateFilter([]interface{}{"5s"})
+	f.Request(c)
+
+	if c.FStateBag[filters.BackendTimeout] != 2*time.Second {
+		t.Error("no change expected")
+	}
+}

filters/filters.go

@@ -20,6 +20,9 @@ const (
 
 	// BackendIsProxyKey is the key used in the state bag to notify proxy that the backend is also a proxy.
 	BackendIsProxyKey = "backend:isproxy"
+
+	// BackendTimeout is the key used in the state bag to configure backend timeout in proxy
+	BackendTimeout = "backend:timeout"
 )
 
 // Context object providing state and information that is unique to a request.

proxy/backendtimeout_test.go

@@ -0,0 +1,200 @@
+package proxy
+
+import (
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+)
+
+func TestSlowService(t *testing.T) {
+	service := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		time.Sleep(2 * time.Millisecond)
+	}))
+	defer service.Close()
+
+	doc := fmt.Sprintf(`* -> backendTimeout("1ms") -> "%s"`, service.URL)
+	tp, err := newTestProxy(doc, FlagsNone)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer tp.close()
+
+	ps := httptest.NewServer(tp.proxy)
+	defer ps.Close()
+
+	rsp, err := http.Get(ps.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if rsp.StatusCode != http.StatusGatewayTimeout {
+		t.Errorf("expected 504, got: %v", rsp)
+	}
+}
+
+func TestFastService(t *testing.T) {
+	service := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		time.Sleep(2 * time.Millisecond)
+	}))
+	defer service.Close()
+
+	doc := fmt.Sprintf(`* -> backendTimeout("10ms") -> "%s"`, service.URL)
+	tp, err := newTestProxy(doc, FlagsNone)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer tp.close()
+
+	ps := httptest.NewServer(tp.proxy)
+	defer ps.Close()
+
+	rsp, err := http.Get(ps.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if rsp.StatusCode != http.StatusOK {
+		t.Errorf("expected 200, got: %v", rsp)
+	}
+}
+
+func TestBackendTimeoutInTheMiddleOfServiceResponse(t *testing.T) {
+	service := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(200)
+		w.Write([]byte("Wish You"))
+
+		f := w.(http.Flusher)
+		f.Flush()
+
+		time.Sleep(20 * time.Millisecond)
+
+		w.Write([]byte(" Were Here"))
+	}))
+	defer service.Close()
+
+	doc := fmt.Sprintf(`* -> backendTimeout("10ms") -> "%s"`, service.URL)
+	tp, err := newTestProxy(doc, FlagsNone)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer tp.close()
+
+	ps := httptest.NewServer(tp.proxy)
+	defer ps.Close()
+
+	rsp, err := http.Get(ps.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if rsp.StatusCode != http.StatusOK {
+		t.Errorf("expected 200, got: %v", rsp)
+	}
+
+	body, err := ioutil.ReadAll(rsp.Body)
+	if err != nil {
+		t.Error(err)
+	}
+
+	content := string(body)
+	if content != "Wish You" {
+		t.Errorf("expected partial content, got %s", content)
+	}
+
+	const msg = "error while copying the response stream: context deadline exceeded"
+	if err = tp.log.WaitFor(msg, 10*time.Millisecond); err != nil {
+		t.Errorf("expected '%s' in logs", msg)
+	}
+}
+
+type unstableRoundTripper struct {
+	inner   http.RoundTripper
+	timeout time.Duration
+	attempt int
+}
+
+// Simulates dial timeout on every odd request
+func (r *unstableRoundTripper) RoundTrip(req *http.Request) (rsp *http.Response, err error) {
+	if r.attempt%2 == 0 {
+		time.Sleep(r.timeout)
+		rsp, err = nil, &proxyError{
+			code:          -1,   // omit 0 handling in proxy.Error()
+			dialingFailed: true, // indicate error happened before http
+		}
+	} else {
+		rsp, err = r.inner.RoundTrip(req)
+	}
+	r.attempt = r.attempt + 1
+	return
+}
+
+func newUnstable(timeout time.Duration) func(r http.RoundTripper) http.RoundTripper {
+	return func(r http.RoundTripper) http.RoundTripper {
+		return &unstableRoundTripper{inner: r, timeout: timeout}
+	}
+}
+
+// Retryable request, dial timeout on first attempt, load balanced backend
+// dial timeout (5ms) + service latency (5ms) > backendTimeout("9ms") => Gateway Timeout
+func TestRetryAndSlowService(t *testing.T) {
+	service := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		time.Sleep(5 * time.Millisecond)
+	}))
+	defer service.Close()
+
+	doc := fmt.Sprintf(`* -> backendTimeout("9ms") -> <"%s", "%s">`, service.URL, service.URL)
+	tp, err := newTestProxyWithParams(doc, Params{
+		CustomHttpRoundTripperWrap: newUnstable(5 * time.Millisecond),
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer tp.close()
+	tp.log.Unmute()
+
+	ps := httptest.NewServer(tp.proxy)
+	defer ps.Close()
+
+	rsp, err := http.Get(ps.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if rsp.StatusCode != http.StatusGatewayTimeout {
+		t.Errorf("expected 504, got: %v", rsp)
+	}
+}
+
+// Retryable request, dial timeout on first attempt, load balanced backend
+// dial timeout (5ms) + service latency (5ms) < backendTimeout("15ms") => OK
+func TestRetryAndFastService(t *testing.T) {
+	service := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		time.Sleep(5 * time.Millisecond)
+	}))
+	defer service.Close()
+
+	doc := fmt.Sprintf(`* -> backendTimeout("15ms") -> <"%s", "%s">`, service.URL, service.URL)
+	tp, err := newTestProxyWithParams(doc, Params{
+		CustomHttpRoundTripperWrap: newUnstable(5 * time.Millisecond),
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer tp.close()
+	tp.log.Unmute()
+
+	ps := httptest.NewServer(tp.proxy)
+	defer ps.Close()
+
+	rsp, err := http.Get(ps.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if rsp.StatusCode != http.StatusOK {
+		t.Errorf("expected 200, got: %v", rsp)
+	}
+}

proxy/context.go

@@ -2,6 +2,7 @@ package proxy
 
 import (
 	"bytes"
+	stdlibcontext "context"
 	"errors"
 	"io"
 	"io/ioutil"
@@ -45,6 +46,7 @@ type context struct {
 	parentSpan           opentracing.Span
 	proxy                *Proxy
 	routeLookup          *routing.RouteLookup
+	cancelBackendContext stdlibcontext.CancelFunc
 }
 
 type filterMetrics struct {