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
|
package throttled
import (
"net/http"
"sync"
)
var (
// DefaultDeniedHandler handles the requests that were denied access because
// of a throttler. By default, returns a 429 status code with a
// generic message.
DefaultDeniedHandler = http.Handler(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
http.Error(w, "limit exceeded", 429)
}))
// Error is the function to call when an error occurs on a throttled handler.
// By default, returns a 500 status code with a generic message.
Error = ErrorFunc(func(w http.ResponseWriter, r *http.Request, err error) {
http.Error(w, "internal error", http.StatusInternalServerError)
})
)
// ErrorFunc defines the function type for the Error variable.
type ErrorFunc func(w http.ResponseWriter, r *http.Request, err error)
// The Limiter interface defines the methods required to control access to a
// throttled handler.
type Limiter interface {
Start()
Limit(http.ResponseWriter, *http.Request) (<-chan bool, error)
}
// Custom creates a Throttler using the provided Limiter implementation.
func Custom(l Limiter) *Throttler {
return &Throttler{
limiter: l,
}
}
// A Throttler controls access to HTTP handlers using a Limiter.
type Throttler struct {
// DeniedHandler is called if the request is disallowed. If it is nil,
// the DefaultDeniedHandler variable is used.
DeniedHandler http.Handler
limiter Limiter
// The mutex protects the started flag
mu sync.Mutex
started bool
}
// Throttle wraps a HTTP handler so that its access is controlled by
// the Throttler. It returns the Handler with the throttling logic.
func (t *Throttler) Throttle(h http.Handler) http.Handler {
dh := t.start()
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
ch, err := t.limiter.Limit(w, r)
if err != nil {
Error(w, r, err)
return
}
ok := <-ch
if ok {
h.ServeHTTP(w, r)
} else {
dh.ServeHTTP(w, r)
}
})
}
// start starts the throttling and returns the effective denied handler to
// use for requests that were denied access.
func (t *Throttler) start() http.Handler {
t.mu.Lock()
defer t.mu.Unlock()
// Get the effective denied handler
dh := t.DeniedHandler
if dh == nil {
dh = DefaultDeniedHandler
}
if !t.started {
t.limiter.Start()
t.started = true
}
return dh
}
|
