71 lines
1.8 KiB
Go
71 lines
1.8 KiB
Go
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// Copyright 2016 The Chihaya Authors. All rights reserved.
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// Use of this source code is governed by the BSD 2-Clause license,
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// which can be found in the LICENSE file.
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package varinterval
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import (
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"errors"
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"math/rand"
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"time"
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"github.com/chihaya/chihaya"
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"github.com/chihaya/chihaya/tracker"
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)
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func init() {
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tracker.RegisterAnnounceMiddlewareConstructor("varinterval", constructor)
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}
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type varintervalMiddleware struct {
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cfg *Config
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r *rand.Rand
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}
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// constructor provides a middleware constructor that returns a middleware to
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// insert a variation into announce intervals.
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//
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// It returns an error if the config provided is either syntactically or
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// semantically incorrect.
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func constructor(c chihaya.MiddlewareConfig) (tracker.AnnounceMiddleware, error) {
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cfg, err := newConfig(c)
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if err != nil {
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return nil, err
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}
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if cfg.ModifyResponseProbability <= 0 || cfg.ModifyResponseProbability > 1 {
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return nil, errors.New("modify_response_probability must be in [0,1)")
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}
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if cfg.MaxIncreaseDelta <= 0 {
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return nil, errors.New("max_increase_delta must be > 0")
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}
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mw := varintervalMiddleware{
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cfg: cfg,
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r: rand.New(rand.NewSource(time.Now().UnixNano())),
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}
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return mw.modifyResponse, nil
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}
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func (mw *varintervalMiddleware) modifyResponse(next tracker.AnnounceHandler) tracker.AnnounceHandler {
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return func(cfg *chihaya.TrackerConfig, req *chihaya.AnnounceRequest, resp *chihaya.AnnounceResponse) error {
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err := next(cfg, req, resp)
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if err != nil {
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return err
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}
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if mw.cfg.ModifyResponseProbability == 1 || mw.r.Float32() < mw.cfg.ModifyResponseProbability {
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addSeconds := time.Duration(mw.r.Intn(mw.cfg.MaxIncreaseDelta)+1) * time.Second
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resp.Interval += addSeconds
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if mw.cfg.ModifyMinInterval {
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resp.MinInterval += addSeconds
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}
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}
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return nil
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}
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}
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