mirror of
https://github.com/diamondburned/arikawa.git
synced 2024-09-08 03:12:23 +00:00
233 lines
4.4 KiB
Go
233 lines
4.4 KiB
Go
package rate
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import (
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"context"
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"net/http"
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"strconv"
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"strings"
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"sync"
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"sync/atomic"
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"time"
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"github.com/pkg/errors"
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"github.com/sasha-s/go-csync"
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)
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// ExtraDelay because Discord is trash. I've seen this in both litcord and
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// discordgo, with dgo claiming from his experiments.
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// RE: Those who want others to fix it for them: release the source code then.
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const ExtraDelay = 250 * time.Millisecond
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// This makes me suicidal.
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// https://github.com/bwmarrin/discordgo/blob/master/ratelimit.go
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type Limiter struct {
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// Only 1 per bucket
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CustomLimits []*CustomRateLimit
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// These callbacks will only be called for valid buckets. They will also be
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// called right before locking. Returning false will not rate limit.
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OnAcquire func(path string) bool
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OnCancel func(path string) bool
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OnRelease func(path string) bool // false means not unlocking
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Prefix string
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global *int64 // atomic guarded, unixnano
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buckets sync.Map
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globalRate time.Duration
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}
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type CustomRateLimit struct {
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Contains string
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Reset time.Duration
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}
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type bucket struct {
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lock csync.Mutex
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custom *CustomRateLimit
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remaining uint64
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limit uint
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reset time.Time
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lastReset time.Time // only for custom
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}
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func returnTrue(string) bool {
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// time.Sleep(time.Nanosecond)
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return true
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}
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func NewLimiter(prefix string) *Limiter {
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return &Limiter{
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Prefix: prefix,
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global: new(int64),
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buckets: sync.Map{},
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CustomLimits: []*CustomRateLimit{},
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OnAcquire: returnTrue,
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OnCancel: returnTrue,
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OnRelease: returnTrue,
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}
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}
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func (l *Limiter) getBucket(path string, store bool) *bucket {
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path = ParseBucketKey(strings.TrimPrefix(path, l.Prefix))
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bc, ok := l.buckets.Load(path)
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if !ok && !store {
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return nil
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}
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if !ok {
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bc := &bucket{
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remaining: 1,
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}
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for _, limit := range l.CustomLimits {
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if strings.Contains(path, limit.Contains) {
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bc.custom = limit
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break
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}
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}
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l.buckets.Store(path, bc)
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return bc
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}
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return bc.(*bucket)
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}
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func (l *Limiter) Acquire(ctx context.Context, path string) error {
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b := l.getBucket(path, true)
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if !l.OnAcquire(path) {
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return nil
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}
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// Acquire lock with a timeout
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if err := b.lock.CLock(ctx); err != nil {
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return err
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}
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// Time to sleep
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var sleep time.Duration
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if b.remaining == 0 && b.reset.After(time.Now()) {
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// out of turns, gotta wait
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sleep = b.reset.Sub(time.Now())
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} else {
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// maybe global rate limit has it
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now := time.Now()
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until := time.Unix(0, atomic.LoadInt64(l.global))
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if until.After(now) {
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sleep = until.Sub(now)
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}
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}
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if sleep > 0 {
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select {
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case <-ctx.Done():
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b.lock.Unlock()
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return ctx.Err()
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case <-time.After(sleep):
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}
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}
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if b.remaining > 0 {
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b.remaining--
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}
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return nil
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}
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func (l *Limiter) Cancel(path string) error {
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b := l.getBucket(path, false)
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if b == nil {
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return nil
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}
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if !l.OnCancel(path) {
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return nil
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}
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// TryLock would either not lock because it's already locked, or lock
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// because it isn't.
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b.lock.TryLock()
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b.lock.Unlock()
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return nil
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}
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// Release releases the URL from the locks. This doesn't need a context for
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// timing out, it doesn't block that much.
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func (l *Limiter) Release(path string, headers http.Header) error {
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b := l.getBucket(path, false)
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if b == nil {
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return nil
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}
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defer func() {
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if l.OnRelease(path) {
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b.lock.Unlock()
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}
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}()
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// Check custom limiter
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if b.custom != nil {
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now := time.Now()
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if now.Sub(b.lastReset) >= b.custom.Reset {
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b.lastReset = now
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b.reset = now.Add(b.custom.Reset)
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}
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return nil
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}
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var (
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// boolean
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global = headers.Get("X-RateLimit-Global")
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// seconds
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remaining = headers.Get("X-RateLimit-Remaining")
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reset = headers.Get("X-RateLimit-Reset")
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retryAfter = headers.Get("Retry-After")
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)
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switch {
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case retryAfter != "":
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i, err := strconv.Atoi(retryAfter)
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if err != nil {
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return errors.Wrap(err, "Invalid retryAfter "+retryAfter)
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}
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at := time.Now().Add(time.Duration(i) * time.Millisecond)
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if global != "" { // probably true
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atomic.StoreInt64(l.global, at.UnixNano())
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} else {
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b.reset = at
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}
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case reset != "":
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unix, err := strconv.ParseFloat(reset, 64)
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if err != nil {
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return errors.Wrap(err, "Invalid reset "+reset)
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}
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b.reset = time.Unix(0, int64(unix*float64(time.Second))).
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Add(ExtraDelay)
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}
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if remaining != "" {
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u, err := strconv.ParseUint(remaining, 10, 64)
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if err != nil {
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return errors.Wrap(err, "Invalid remaining "+remaining)
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}
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b.remaining = u
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}
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return nil
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}
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