47b74a63a8
The backoff function and parameters have been pulled up into an interface `backoffStrategy`. The default parameters are now part of a package variable `DefaultBackoffConfig`. The strategy is then plumbed through `dialOptions`. As a result of this PR, the maximum backoff delay can now be set using the `WithBackoffConfig` dial option. While the addition of strategy may seem premature, this allows one to simply export `BackoffStrategy` and `WithBackoff` to allow arbirarily configurable backoff strategies. Signed-off-by: Stephen J Day <stephen.day@docker.com>
69 lines
1.8 KiB
Go
69 lines
1.8 KiB
Go
package grpc
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import (
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"math/rand"
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"time"
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)
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// DefaultBackoffConfig uses values specified for backoff in
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// https://github.com/grpc/grpc/blob/master/doc/connection-backoff.md.
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var (
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DefaultBackoffConfig = &BackoffConfig{
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MaxDelay: 120 * time.Second,
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baseDelay: 1.0 * time.Second,
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factor: 1.6,
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jitter: 0.2,
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}
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)
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// backoffStrategy defines the methodology for backing off after a grpc
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// connection failure.
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//
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// This is unexported until the GRPC project decides whether or not to allow
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// alternative backoff strategies. Once a decision is made, this type and its
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// method may be exported.
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type backoffStrategy interface {
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// backoff returns the amount of time to wait before the next retry given
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// the number of consecutive failures.
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backoff(retries int) time.Duration
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}
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// BackoffConfig defines the parameters for the default GRPC backoff strategy.
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type BackoffConfig struct {
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// MaxDelay is the upper bound of backoff delay.
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MaxDelay time.Duration
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// TODO(stevvooe): The following fields are not exported, as allowing changes
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// baseDelay is the amount of time to wait before retrying after the first
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// failure.
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baseDelay time.Duration
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// factor is applied to the backoff after each retry.
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factor float64
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// jitter provides a range to randomize backoff delays.
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jitter float64
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}
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func (bc *BackoffConfig) backoff(retries int) (t time.Duration) {
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if retries == 0 {
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return bc.baseDelay
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}
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backoff, max := float64(bc.baseDelay), float64(bc.MaxDelay)
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for backoff < max && retries > 0 {
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backoff *= bc.factor
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retries--
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}
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if backoff > max {
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backoff = max
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}
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// Randomize backoff delays so that if a cluster of requests start at
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// the same time, they won't operate in lockstep.
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backoff *= 1 + bc.jitter*(rand.Float64()*2-1)
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if backoff < 0 {
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return 0
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}
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return time.Duration(backoff)
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}
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