2f391fde80
- Support for exponential backoff on reconnect to be gentle on the server. - Clean up client by moving metrics and retry strategy to the connection manager. - Update echo_client to use client manager - Fix echo client XMPP message matching Fixes #21 Improvements for #8
102 lines
2.7 KiB
Go
102 lines
2.7 KiB
Go
/*
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Interesting reference on backoff:
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- Exponential Backoff And Jitter (AWS Blog):
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https://www.awsarchitectureblog.com/2015/03/backoff.html
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We use Jitter as a default for exponential backoff, as the goal of
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this module is not to provide precise 'ticks', but good behaviour to
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implement retries that are helping the server to recover faster in
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case of congestion.
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It can be used in several ways:
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- Using duration to get next sleep time.
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- Using ticker channel to trigger callback function on tick
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The functions for Backoff are not threadsafe, but you can:
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- Keep the attempt counter on your end and use DurationForAttempt(int)
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- Use lock in your own code to protect the Backoff structure.
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TODO: Implement Backoff Ticker channel
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TODO: Implement throttler interface. Throttler could be used to implement various reconnect strategies.
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*/
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package xmpp // import "gosrc.io/xmpp"
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import (
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"math"
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"math/rand"
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"time"
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)
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const (
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defaultBase int = 20 // Backoff base, in ms
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defaultFactor int = 2
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defaultCap int = 180000 // 3 minutes
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)
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// Backoff can provide increasing duration with the number of attempt
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// performed. The structure is used to support exponential backoff on
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// connection attempts to avoid hammering the server we are connecting
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// to.
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type Backoff struct {
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NoJitter bool
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Base int
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Factor int
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Cap int
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lastDuration int
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attempt int
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}
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// Duration returns the duration to apply to the current attempt.
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func (b *Backoff) Duration() time.Duration {
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d := b.DurationForAttempt(b.attempt)
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b.attempt++
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return d
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}
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// Wait sleeps for backoff duration for current attempt.
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func (b *Backoff) Wait() {
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time.Sleep(b.Duration())
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}
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// DurationForAttempt returns a duration for an attempt number, in a stateless way.
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func (b *Backoff) DurationForAttempt(attempt int) time.Duration {
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b.setDefault()
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expBackoff := math.Min(float64(b.Cap), float64(b.Base)*math.Pow(float64(b.Factor), float64(b.attempt)))
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d := int(math.Trunc(expBackoff))
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if !b.NoJitter {
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d = rand.Intn(d)
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}
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return time.Duration(d) * time.Millisecond
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}
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// Reset sets back the number of attempts to 0. This is to be called after a successfull operation has been performed,
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// to reset the exponential backoff interval.
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func (b *Backoff) Reset() {
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b.attempt = 0
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}
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func (b *Backoff) setDefault() {
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if b.Base == 0 {
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b.Base = defaultBase
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}
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if b.Cap == 0 {
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b.Cap = defaultCap
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}
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if b.Factor == 0 {
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b.Factor = defaultFactor
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}
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}
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/*
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We use full jitter as default for now as it seems to provide good behaviour for reconnect.
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Base is the default interval between attempts (if backoff Factor was equal to 1)
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Attempt is the number of retry for operation. If we start attempt at 0, first sleep equals base.
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Cap is the maximum sleep time duration we tolerate between attempts
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*/
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