Add context timeout middleware

middleware/context_timeout.go

@@ -0,0 +1,72 @@
+package middleware
+
+import (
+	"context"
+	"errors"
+	"time"
+
+	"github.com/labstack/echo/v4"
+)
+
+// ContextTimeoutConfig defines the config for ContextTimeout middleware.
+type ContextTimeoutConfig struct {
+	// Skipper defines a function to skip middleware.
+	Skipper Skipper
+
+	// ErrorHandler is a function when error aries in middeware execution.
+	ErrorHandler func(err error, c echo.Context) error
+
+	// Timeout configures a timeout for the middleware, defaults to 0 for no timeout
+	Timeout time.Duration
+}
+
+// ContextTimeout returns a middleware which returns error (503 Service Unavailable error) to client
+// when underlying method returns context.DeadlineExceeded error.
+func ContextTimeout(timeout time.Duration) echo.MiddlewareFunc {
+	return ContextTimeoutWithConfig(ContextTimeoutConfig{Timeout: timeout})
+}
+
+// ContextTimeoutWithConfig returns a Timeout middleware with config.
+func ContextTimeoutWithConfig(config ContextTimeoutConfig) echo.MiddlewareFunc {
+	mw, err := config.ToMiddleware()
+	if err != nil {
+		panic(err)
+	}
+	return mw
+}
+
+// ToMiddleware converts Config to middleware.
+func (config ContextTimeoutConfig) ToMiddleware() (echo.MiddlewareFunc, error) {
+	if config.Timeout == 0 {
+		return nil, errors.New("timeout must be set")
+	}
+	if config.Skipper == nil {
+		config.Skipper = DefaultSkipper
+	}
+	if config.ErrorHandler == nil {
+		config.ErrorHandler = func(err error, c echo.Context) error {
+			if err != nil && errors.Is(err, context.DeadlineExceeded) {
+				return echo.ErrServiceUnavailable.WithInternal(err)
+			}
+			return err
+		}
+	}
+
+	return func(next echo.HandlerFunc) echo.HandlerFunc {
+		return func(c echo.Context) error {
+			if config.Skipper(c) {
+				return next(c)
+			}
+
+			timeoutContext, cancel := context.WithTimeout(c.Request().Context(), config.Timeout)
+			defer cancel()
+
+			c.SetRequest(c.Request().WithContext(timeoutContext))
+
+			if err := next(c); err != nil {
+				return config.ErrorHandler(err, c)
+			}
+			return nil
+		}
+	}, nil
+}

middleware/context_timeout_test.go

@@ -0,0 +1,226 @@
+package middleware
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/labstack/echo/v4"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestContextTimeoutSkipper(t *testing.T) {
+	t.Parallel()
+	m := ContextTimeoutWithConfig(ContextTimeoutConfig{
+		Skipper: func(context echo.Context) bool {
+			return true
+		},
+		Timeout: 10 * time.Millisecond,
+	})
+
+	req := httptest.NewRequest(http.MethodGet, "/", nil)
+	rec := httptest.NewRecorder()
+
+	e := echo.New()
+	c := e.NewContext(req, rec)
+
+	err := m(func(c echo.Context) error {
+		if err := sleepWithContext(c.Request().Context(), time.Duration(20*time.Millisecond)); err != nil {
+			return err
+		}
+
+		return errors.New("response from handler")
+	})(c)
+
+	// if not skipped we would have not returned error due context timeout logic
+	assert.EqualError(t, err, "response from handler")
+}
+
+func TestContextTimeoutWithTimeout0(t *testing.T) {
+	t.Parallel()
+	assert.Panics(t, func() {
+		ContextTimeout(time.Duration(0))
+	})
+}
+
+func TestContextTimeoutErrorOutInHandler(t *testing.T) {
+	t.Parallel()
+	m := ContextTimeoutWithConfig(ContextTimeoutConfig{
+		// Timeout has to be defined or the whole flow for timeout middleware will be skipped
+		Timeout: 10 * time.Millisecond,
+	})
+
+	req := httptest.NewRequest(http.MethodGet, "/", nil)
+	rec := httptest.NewRecorder()
+
+	e := echo.New()
+	c := e.NewContext(req, rec)
+
+	rec.Code = 1 // we want to be sure that even 200 will not be sent
+	err := m(func(c echo.Context) error {
+		// this error must not be written to the client response. Middlewares upstream of timeout middleware must be able
+		// to handle returned error and this can be done only then handler has not yet committed (written status code)
+		// the response.
+		return echo.NewHTTPError(http.StatusTeapot, "err")
+	})(c)
+
+	assert.Error(t, err)
+	assert.EqualError(t, err, "code=418, message=err")
+	assert.Equal(t, 1, rec.Code)
+	assert.Equal(t, "", rec.Body.String())
+}
+
+func TestContextTimeoutSuccessfulRequest(t *testing.T) {
+	t.Parallel()
+	m := ContextTimeoutWithConfig(ContextTimeoutConfig{
+		// Timeout has to be defined or the whole flow for timeout middleware will be skipped
+		Timeout: 10 * time.Millisecond,
+	})
+
+	req := httptest.NewRequest(http.MethodGet, "/", nil)
+	rec := httptest.NewRecorder()
+
+	e := echo.New()
+	c := e.NewContext(req, rec)
+
+	err := m(func(c echo.Context) error {
+		return c.JSON(http.StatusCreated, map[string]string{"data": "ok"})
+	})(c)
+
+	assert.NoError(t, err)
+	assert.Equal(t, http.StatusCreated, rec.Code)
+	assert.Equal(t, "{\"data\":\"ok\"}\n", rec.Body.String())
+}
+
+func TestContextTimeoutTestRequestClone(t *testing.T) {
+	t.Parallel()
+	req := httptest.NewRequest(http.MethodPost, "/uri?query=value", strings.NewReader(url.Values{"form": {"value"}}.Encode()))
+	req.AddCookie(&http.Cookie{Name: "cookie", Value: "value"})
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	rec := httptest.NewRecorder()
+
+	m := ContextTimeoutWithConfig(ContextTimeoutConfig{
+		// Timeout has to be defined or the whole flow for timeout middleware will be skipped
+		Timeout: 1 * time.Second,
+	})
+
+	e := echo.New()
+	c := e.NewContext(req, rec)
+
+	err := m(func(c echo.Context) error {
+		// Cookie test
+		cookie, err := c.Request().Cookie("cookie")
+		if assert.NoError(t, err) {
+			assert.EqualValues(t, "cookie", cookie.Name)
+			assert.EqualValues(t, "value", cookie.Value)
+		}
+
+		// Form values
+		if assert.NoError(t, c.Request().ParseForm()) {
+			assert.EqualValues(t, "value", c.Request().FormValue("form"))
+		}
+
+		// Query string
+		assert.EqualValues(t, "value", c.Request().URL.Query()["query"][0])
+		return nil
+	})(c)
+
+	assert.NoError(t, err)
+}
+
+func TestContextTimeoutWithDefaultErrorMessage(t *testing.T) {
+	t.Parallel()
+
+	timeout := 10 * time.Millisecond
+	m := ContextTimeoutWithConfig(ContextTimeoutConfig{
+		Timeout: timeout,
+	})
+
+	req := httptest.NewRequest(http.MethodGet, "/", nil)
+	rec := httptest.NewRecorder()
+
+	e := echo.New()
+	c := e.NewContext(req, rec)
+
+	err := m(func(c echo.Context) error {
+		if err := sleepWithContext(c.Request().Context(), time.Duration(20*time.Millisecond)); err != nil {
+			return err
+		}
+		return c.String(http.StatusOK, "Hello, World!")
+	})(c)
+
+	assert.IsType(t, &echo.HTTPError{}, err)
+	assert.Error(t, err)
+	assert.Equal(t, http.StatusServiceUnavailable, err.(*echo.HTTPError).Code)
+	assert.Equal(t, "Service Unavailable", err.(*echo.HTTPError).Message)
+}
+
+func TestContextTimeoutCanHandleContextDeadlineOnNextHandler(t *testing.T) {
+	t.Parallel()
+
+	timeoutErrorHandler := func(err error, c echo.Context) error {
+		if err != nil {
+			if errors.Is(err, context.DeadlineExceeded) {
+				return &echo.HTTPError{
+					Code:    http.StatusServiceUnavailable,
+					Message: "Timeout! change me",
+				}
+			}
+			return err
+		}
+		return nil
+	}
+
+	timeout := 10 * time.Millisecond
+	m := ContextTimeoutWithConfig(ContextTimeoutConfig{
+		Timeout:      timeout,
+		ErrorHandler: timeoutErrorHandler,
+	})
+
+	req := httptest.NewRequest(http.MethodGet, "/", nil)
+	rec := httptest.NewRecorder()
+
+	e := echo.New()
+	c := e.NewContext(req, rec)
+
+	err := m(func(c echo.Context) error {
+		// NOTE: when difference between timeout duration and handler execution time is almost the same (in range of 100microseconds)
+		// the result of timeout does not seem to be reliable - could respond timeout, could respond handler output
+		// difference over 500microseconds (0.5millisecond) response seems to be reliable
+
+		if err := sleepWithContext(c.Request().Context(), time.Duration(20*time.Millisecond)); err != nil {
+			return err
+		}
+
+		// The Request Context should have a Deadline set by http.ContextTimeoutHandler
+		if _, ok := c.Request().Context().Deadline(); !ok {
+			assert.Fail(t, "No timeout set on Request Context")
+		}
+		return c.String(http.StatusOK, "Hello, World!")
+	})(c)
+
+	assert.IsType(t, &echo.HTTPError{}, err)
+	assert.Error(t, err)
+	assert.Equal(t, http.StatusServiceUnavailable, err.(*echo.HTTPError).Code)
+	assert.Equal(t, "Timeout! change me", err.(*echo.HTTPError).Message)
+}
+
+func sleepWithContext(ctx context.Context, d time.Duration) error {
+	timer := time.NewTimer(d)
+
+	defer func() {
+		_ = timer.Stop()
+	}()
+
+	select {
+	case <-ctx.Done():
+		return context.DeadlineExceeded
+	case <-timer.C:
+		return nil
+	}
+}