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|
package middleware
import (
"context"
"net/http"
"time"
"github.com/labstack/echo/v4"
)
type (
// TimeoutConfig defines the config for Timeout middleware.
TimeoutConfig struct {
// Skipper defines a function to skip middleware.
Skipper Skipper
// ErrorMessage is written to response on timeout in addition to http.StatusServiceUnavailable (503) status code
// It can be used to define a custom timeout error message
ErrorMessage string
// OnTimeoutRouteErrorHandler is an error handler that is executed for error that was returned from wrapped route after
// request timeouted and we already had sent the error code (503) and message response to the client.
// NB: do not write headers/body inside this handler. The response has already been sent to the client and response writer
// will not accept anything no more. If you want to know what actual route middleware timeouted use `c.Path()`
OnTimeoutRouteErrorHandler func(err error, c echo.Context)
// Timeout configures a timeout for the middleware, defaults to 0 for no timeout
// 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
Timeout time.Duration
}
)
var (
// DefaultTimeoutConfig is the default Timeout middleware config.
DefaultTimeoutConfig = TimeoutConfig{
Skipper: DefaultSkipper,
Timeout: 0,
ErrorMessage: "",
}
)
// Timeout returns a middleware which returns error (503 Service Unavailable error) to client immediately when handler
// call runs for longer than its time limit. NB: timeout does not stop handler execution.
func Timeout() echo.MiddlewareFunc {
return TimeoutWithConfig(DefaultTimeoutConfig)
}
// TimeoutWithConfig returns a Timeout middleware with config.
// See: `Timeout()`.
func TimeoutWithConfig(config TimeoutConfig) echo.MiddlewareFunc {
// Defaults
if config.Skipper == nil {
config.Skipper = DefaultTimeoutConfig.Skipper
}
return func(next echo.HandlerFunc) echo.HandlerFunc {
return func(c echo.Context) error {
if config.Skipper(c) || config.Timeout == 0 {
return next(c)
}
handlerWrapper := echoHandlerFuncWrapper{
ctx: c,
handler: next,
errChan: make(chan error, 1),
errHandler: config.OnTimeoutRouteErrorHandler,
}
handler := http.TimeoutHandler(handlerWrapper, config.Timeout, config.ErrorMessage)
handler.ServeHTTP(c.Response().Writer, c.Request())
select {
case err := <-handlerWrapper.errChan:
return err
default:
return nil
}
}
}
}
type echoHandlerFuncWrapper struct {
ctx echo.Context
handler echo.HandlerFunc
errHandler func(err error, c echo.Context)
errChan chan error
}
func (t echoHandlerFuncWrapper) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
// replace echo.Context Request with the one provided by TimeoutHandler to let later middlewares/handler on the chain
// handle properly it's cancellation
t.ctx.SetRequest(r)
// replace writer with TimeoutHandler custom one. This will guarantee that
// `writes by h to its ResponseWriter will return ErrHandlerTimeout.`
originalWriter := t.ctx.Response().Writer
t.ctx.Response().Writer = rw
// in case of panic we restore original writer and call panic again
// so it could be handled with global middleware Recover()
defer func() {
if err := recover(); err != nil {
t.ctx.Response().Writer = originalWriter
panic(err)
}
}()
err := t.handler(t.ctx)
if ctxErr := r.Context().Err(); ctxErr == context.DeadlineExceeded {
if err != nil && t.errHandler != nil {
t.errHandler(err, t.ctx)
}
return // on timeout we can not send handler error to client because `http.TimeoutHandler` has already sent headers
}
// we restore original writer only for cases we did not timeout. On timeout we have already sent response to client
// and should not anymore send additional headers/data
// so on timeout writer stays what http.TimeoutHandler uses and prevents writing headers/body
t.ctx.Response().Writer = originalWriter
if err != nil {
// call global error handler to write error to the client. This is needed or `http.TimeoutHandler` will send status code by itself
// and after that our tries to write status code will not work anymore
t.ctx.Error(err)
// we pass error from handler to middlewares up in handler chain to act on it if needed. But this means that
// global error handler is probably be called twice as `t.ctx.Error` already does that.
t.errChan <- err
}
}
|
