niki/vendor/github.com/labstack/echo/v4/middleware/timeout.go

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// SPDX-License-Identifier: MIT
// SPDX-FileCopyrightText: © 2015 LabStack LLC and Echo contributors
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package middleware
import (
"context"
"net/http"
"sync"
"time"
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"github.com/labstack/echo/v4"
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)
// ---------------------------------------------------------------------------------------------------------------
// WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING
// WARNING: Timeout middleware causes more problems than it solves.
// WARNING: This middleware should be first middleware as it messes with request Writer and could cause data race if
// it is in other position
//
// Depending on out requirements you could be better of setting timeout to context and
// check its deadline from handler.
//
// For example: create middleware to set timeout to context
// func RequestTimeout(timeout time.Duration) echo.MiddlewareFunc {
// return func(next echo.HandlerFunc) echo.HandlerFunc {
// return func(c echo.Context) error {
// timeoutCtx, cancel := context.WithTimeout(c.Request().Context(), timeout)
// c.SetRequest(c.Request().WithContext(timeoutCtx))
// defer cancel()
// return next(c)
// }
// }
//}
//
// Create handler that checks for context deadline and runs actual task in separate coroutine
// Note: separate coroutine may not be even if you do not want to process continue executing and
// just want to stop long-running handler to stop and you are using "context aware" methods (ala db queries with ctx)
// e.GET("/", func(c echo.Context) error {
//
// doneCh := make(chan error)
// go func(ctx context.Context) {
// doneCh <- myPossiblyLongRunningBackgroundTaskWithCtx(ctx)
// }(c.Request().Context())
//
// select { // wait for task to finish or context to timeout/cancelled
// case err := <-doneCh:
// if err != nil {
// return err
// }
// return c.String(http.StatusOK, "OK")
// case <-c.Request().Context().Done():
// if c.Request().Context().Err() == context.DeadlineExceeded {
// return c.String(http.StatusServiceUnavailable, "timeout")
// }
// return c.Request().Context().Err()
// }
//
// })
//
// TimeoutConfig defines the config for Timeout middleware.
type 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
}
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// DefaultTimeoutConfig is the default Timeout middleware config.
var DefaultTimeoutConfig = TimeoutConfig{
Skipper: DefaultSkipper,
Timeout: 0,
ErrorMessage: "",
}
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// 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 or panics on invalid configuration.
func TimeoutWithConfig(config TimeoutConfig) echo.MiddlewareFunc {
mw, err := config.ToMiddleware()
if err != nil {
panic(err)
}
return mw
}
// ToMiddleware converts Config to middleware or returns an error for invalid configuration
func (config TimeoutConfig) ToMiddleware() (echo.MiddlewareFunc, error) {
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)
}
errChan := make(chan error, 1)
handlerWrapper := echoHandlerFuncWrapper{
writer: &ignorableWriter{ResponseWriter: c.Response().Writer},
ctx: c,
handler: next,
errChan: errChan,
errHandler: config.OnTimeoutRouteErrorHandler,
}
handler := http.TimeoutHandler(handlerWrapper, config.Timeout, config.ErrorMessage)
handler.ServeHTTP(handlerWrapper.writer, c.Request())
select {
case err := <-errChan:
return err
default:
return nil
}
}
}, nil
}
type echoHandlerFuncWrapper struct {
writer *ignorableWriter
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
}
if err != nil {
// This is needed as `http.TimeoutHandler` will write status code by itself on error and after that our tries to write
// status code will not work anymore as Echo.Response thinks it has been already "committed" and further writes
// create errors in log about `superfluous response.WriteHeader call from`
t.writer.Ignore(true)
t.ctx.Response().Writer = originalWriter // make sure we restore writer before we signal original coroutine about the error
// we pass error from handler to middlewares up in handler chain to act on it if needed.
t.errChan <- err
return
}
// 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
}
// ignorableWriter is ResponseWriter implementations that allows us to mark writer to ignore further write calls. This
// is handy in cases when you do not have direct control of code being executed (3rd party middleware) but want to make
// sure that external code will not be able to write response to the client.
// Writer is coroutine safe for writes.
type ignorableWriter struct {
http.ResponseWriter
lock sync.Mutex
ignoreWrites bool
}
func (w *ignorableWriter) Ignore(ignore bool) {
w.lock.Lock()
w.ignoreWrites = ignore
w.lock.Unlock()
}
func (w *ignorableWriter) WriteHeader(code int) {
w.lock.Lock()
defer w.lock.Unlock()
if w.ignoreWrites {
return
}
w.ResponseWriter.WriteHeader(code)
}
func (w *ignorableWriter) Write(b []byte) (int, error) {
w.lock.Lock()
defer w.lock.Unlock()
if w.ignoreWrites {
return len(b), nil
}
return w.ResponseWriter.Write(b)
}