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package throttled
import (
"errors"
"math"
"net/http"
"strconv"
)
var (
// DefaultDeniedHandler is the default DeniedHandler for an
// HTTPRateLimiter. It 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)
}))
// DefaultError is the default Error function for an HTTPRateLimiter.
// It returns a 500 status code with a generic message.
DefaultError = func(w http.ResponseWriter, r *http.Request, err error) {
http.Error(w, "internal error", http.StatusInternalServerError)
}
)
// HTTPRateLimiter faciliates using a Limiter to limit HTTP requests.
type HTTPRateLimiter struct {
// DeniedHandler is called if the request is disallowed. If it is
// nil, the DefaultDeniedHandler variable is used.
DeniedHandler http.Handler
// Error is called if the RateLimiter returns an error. If it is
// nil, the DefaultErrorFunc is used.
Error func(w http.ResponseWriter, r *http.Request, err error)
// Limiter is call for each request to determine whether the
// request is permitted and update internal state. It must be set.
RateLimiter RateLimiter
// VaryBy is called for each request to generate a key for the
// limiter. If it is nil, all requests use an empty string key.
VaryBy interface {
Key(*http.Request) string
}
}
// RateLimit wraps an http.Handler to limit incoming requests.
// Requests that are not limited will be passed to the handler
// unchanged. Limited requests will be passed to the DeniedHandler.
// X-RateLimit-Limit, X-RateLimit-Remaining, X-RateLimit-Reset and
// Retry-After headers will be written to the response based on the
// values in the RateLimitResult.
func (t *HTTPRateLimiter) RateLimit(h http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
if t.RateLimiter == nil {
t.error(w, r, errors.New("You must set a RateLimiter on HTTPRateLimiter"))
}
var k string
if t.VaryBy != nil {
k = t.VaryBy.Key(r)
}
limited, context, err := t.RateLimiter.RateLimit(k, 1)
if err != nil {
t.error(w, r, err)
return
}
setRateLimitHeaders(w, context)
if !limited {
h.ServeHTTP(w, r)
} else {
dh := t.DeniedHandler
if dh == nil {
dh = DefaultDeniedHandler
}
dh.ServeHTTP(w, r)
}
})
}
func (t *HTTPRateLimiter) error(w http.ResponseWriter, r *http.Request, err error) {
e := t.Error
if e == nil {
e = DefaultError
}
e(w, r, err)
}
func setRateLimitHeaders(w http.ResponseWriter, context RateLimitResult) {
if v := context.Limit; v >= 0 {
w.Header().Add("X-RateLimit-Limit", strconv.Itoa(v))
}
if v := context.Remaining; v >= 0 {
w.Header().Add("X-RateLimit-Remaining", strconv.Itoa(v))
}
if v := context.ResetAfter; v >= 0 {
vi := int(math.Ceil(v.Seconds()))
w.Header().Add("X-RateLimit-Reset", strconv.Itoa(vi))
}
if v := context.RetryAfter; v >= 0 {
vi := int(math.Ceil(v.Seconds()))
w.Header().Add("Retry-After", strconv.Itoa(vi))
}
}
|
