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ratelimit.go
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ratelimit.go
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package ratelimit
import (
"bufio"
"net"
"net/http"
"strconv"
"time"
"github.com/moonrhythm/parapet/pkg/header"
)
// New creates new rate limiter
func New(strategy Strategy) *RateLimiter {
return &RateLimiter{
Key: ClientIP,
Strategy: strategy,
}
}
// RateLimiter middleware
type RateLimiter struct {
Key func(r *http.Request) string
ExceededHandler ExceededHandler
Strategy Strategy
ReleaseOnWriteHeader bool // release token when write response's header
ReleaseOnHijacked bool // release token when hijacked
}
// Strategy interface
type Strategy interface {
// Take returns true if success
Take(key string) bool
// Put calls after finished
Put(key string)
// After returns next time that can take again
After(key string) time.Duration
}
// ExceededHandler type
type ExceededHandler func(w http.ResponseWriter, r *http.Request, after time.Duration)
func defaultExceededHandler(w http.ResponseWriter, _ *http.Request, after time.Duration) {
if after > 0 {
header.Set(w.Header(), header.RetryAfter, strconv.FormatInt(int64(after/time.Second), 10))
}
http.Error(w, "Too Many Requests", http.StatusTooManyRequests)
}
func defaultKey(_ *http.Request) string {
return ""
}
// ClientIP returns client ip from request
func ClientIP(r *http.Request) string {
ipStr := header.Get(r.Header, header.XRealIP)
ip := net.ParseIP(ipStr)
if ip == nil {
return ipStr
}
return string(ip)
}
// ServeHandler implements middleware interface
func (m RateLimiter) ServeHandler(h http.Handler) http.Handler {
if m.Key == nil {
m.Key = defaultKey
}
if m.ExceededHandler == nil {
m.ExceededHandler = defaultExceededHandler
}
modifyRW := m.ReleaseOnWriteHeader || m.ReleaseOnHijacked
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
key := m.Key(r)
if !m.Strategy.Take(key) {
m.ExceededHandler(w, r, m.Strategy.After(key))
return
}
released := false
release := func() {
if released {
return
}
released = true
m.Strategy.Put(key)
}
defer release() // use defer to always put token back when panic
if modifyRW {
nw := responseWriter{
ResponseWriter: w,
}
if m.ReleaseOnWriteHeader {
nw.OnWriteHeader = release
}
if m.ReleaseOnHijacked {
nw.OnHijack = release
}
w = &nw
}
h.ServeHTTP(w, r)
})
}
type responseWriter struct {
http.ResponseWriter
OnWriteHeader func()
OnHijack func()
wroteHeader bool
}
func (w *responseWriter) WriteHeader(statusCode int) {
if w.wroteHeader {
return
}
w.wroteHeader = true
if w.OnWriteHeader != nil {
w.OnWriteHeader()
}
w.ResponseWriter.WriteHeader(statusCode)
}
func (w *responseWriter) Write(p []byte) (int, error) {
if !w.wroteHeader {
w.WriteHeader(http.StatusOK)
}
return w.ResponseWriter.Write(p)
}
func (w *responseWriter) Unwrap() http.ResponseWriter {
return w.ResponseWriter
}
// Push implements Pusher interface
func (w *responseWriter) Push(target string, opts *http.PushOptions) error {
if w, ok := w.ResponseWriter.(http.Pusher); ok {
return w.Push(target, opts)
}
return http.ErrNotSupported
}
// Flush implements Flusher interface
func (w *responseWriter) Flush() {
if w, ok := w.ResponseWriter.(http.Flusher); ok {
w.Flush()
}
}
// Hijack implements Hijacker interface
func (w *responseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
if nw, ok := w.ResponseWriter.(http.Hijacker); ok {
if w.OnHijack != nil {
w.OnHijack()
}
return nw.Hijack()
}
return nil, nil, http.ErrNotSupported
}