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153 lines
3.2 KiB
Go
153 lines
3.2 KiB
Go
package limiter
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import (
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"context"
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"io"
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"net/http"
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"golang.org/x/time/rate"
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)
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type staticLimiter struct {
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upstream *rate.Limiter
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downstream *rate.Limiter
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}
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// Limits represents static upload and download limits.
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// For both, zero means unlimited.
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type Limits struct {
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UploadKb int
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DownloadKb int
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}
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// NewStaticLimiter constructs a Limiter with a fixed (static) upload and
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// download rate cap
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func NewStaticLimiter(l Limits) Limiter {
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var (
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upstreamBucket *rate.Limiter
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downstreamBucket *rate.Limiter
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)
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if l.UploadKb > 0 {
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upstreamBucket = rate.NewLimiter(rate.Limit(toByteRate(l.UploadKb)), int(toByteRate(l.UploadKb)))
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}
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if l.DownloadKb > 0 {
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downstreamBucket = rate.NewLimiter(rate.Limit(toByteRate(l.DownloadKb)), int(toByteRate(l.DownloadKb)))
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}
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return staticLimiter{
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upstream: upstreamBucket,
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downstream: downstreamBucket,
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}
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}
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func (l staticLimiter) Upstream(r io.Reader) io.Reader {
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return l.limitReader(r, l.upstream)
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}
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func (l staticLimiter) UpstreamWriter(w io.Writer) io.Writer {
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return l.limitWriter(w, l.upstream)
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}
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func (l staticLimiter) Downstream(r io.Reader) io.Reader {
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return l.limitReader(r, l.downstream)
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}
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func (l staticLimiter) DownstreamWriter(w io.Writer) io.Writer {
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return l.limitWriter(w, l.downstream)
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}
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type roundTripper func(*http.Request) (*http.Response, error)
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func (rt roundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
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return rt(req)
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}
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func (l staticLimiter) roundTripper(rt http.RoundTripper, req *http.Request) (*http.Response, error) {
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type readCloser struct {
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io.Reader
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io.Closer
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}
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if req.Body != nil {
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req.Body = &readCloser{
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Reader: l.Upstream(req.Body),
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Closer: req.Body,
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}
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}
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res, err := rt.RoundTrip(req)
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if res != nil && res.Body != nil {
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res.Body = &readCloser{
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Reader: l.Downstream(res.Body),
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Closer: res.Body,
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}
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}
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return res, err
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}
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// Transport returns an HTTP transport limited with the limiter l.
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func (l staticLimiter) Transport(rt http.RoundTripper) http.RoundTripper {
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return roundTripper(func(req *http.Request) (*http.Response, error) {
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return l.roundTripper(rt, req)
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})
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}
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func (l staticLimiter) limitReader(r io.Reader, b *rate.Limiter) io.Reader {
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if b == nil {
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return r
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}
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return &rateLimitedReader{r, b}
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}
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type rateLimitedReader struct {
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reader io.Reader
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bucket *rate.Limiter
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}
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func (r *rateLimitedReader) Read(p []byte) (int, error) {
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n, err := r.reader.Read(p)
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if err := consumeTokens(n, r.bucket); err != nil {
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return n, err
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}
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return n, err
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}
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func (l staticLimiter) limitWriter(w io.Writer, b *rate.Limiter) io.Writer {
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if b == nil {
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return w
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}
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return &rateLimitedWriter{w, b}
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}
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type rateLimitedWriter struct {
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writer io.Writer
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bucket *rate.Limiter
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}
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func (w *rateLimitedWriter) Write(buf []byte) (int, error) {
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if err := consumeTokens(len(buf), w.bucket); err != nil {
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return 0, err
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}
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return w.writer.Write(buf)
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}
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func consumeTokens(tokens int, bucket *rate.Limiter) error {
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// bucket allows waiting for at most Burst() tokens at once
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maxWait := bucket.Burst()
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for tokens > maxWait {
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if err := bucket.WaitN(context.Background(), maxWait); err != nil {
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return err
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}
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tokens -= maxWait
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}
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return bucket.WaitN(context.Background(), tokens)
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}
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func toByteRate(val int) float64 {
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return float64(val) * 1024.
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}
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