1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
|
package middleware
import (
"context"
"net/http"
"time"
"github.com/labstack/echo/v4"
)
// ---------------------------------------------------------------------------------------------------------------
// 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()
// }
//
// })
//
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
if err != nil {
// Error must be written into Writer created in `http.TimeoutHandler` so to get Response into `commited` state.
// So 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 and/or create errors in
// log about `superfluous response.WriteHeader call from`
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.
// NB: later call of the global error handler or middlewares will not take any effect, as echo.Response will be
// already marked as `committed` because we called global error handler above.
t.ctx.Response().Writer = originalWriter // make sure we restore before we signal original coroutine about the error
t.errChan <- err
return
}
t.ctx.Response().Writer = originalWriter
}
|
