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package grpc
import (
"math/rand"
"time"
)
// DefaultBackoffConfig uses values specified for backoff in
// https://github.com/grpc/grpc/blob/master/doc/connection-backoff.md.
var (
DefaultBackoffConfig = BackoffConfig{
MaxDelay: 120 * time.Second,
baseDelay: 1.0 * time.Second,
factor: 1.6,
jitter: 0.2,
}
)
// backoffStrategy defines the methodology for backing off after a grpc
// connection failure.
//
// This is unexported until the gRPC project decides whether or not to allow
// alternative backoff strategies. Once a decision is made, this type and its
// method may be exported.
type backoffStrategy interface {
// backoff returns the amount of time to wait before the next retry given
// the number of consecutive failures.
backoff(retries int) time.Duration
}
// BackoffConfig defines the parameters for the default gRPC backoff strategy.
type BackoffConfig struct {
// MaxDelay is the upper bound of backoff delay.
MaxDelay time.Duration
// TODO(stevvooe): The following fields are not exported, as allowing
// changes would violate the current gRPC specification for backoff. If
// gRPC decides to allow more interesting backoff strategies, these fields
// may be opened up in the future.
// baseDelay is the amount of time to wait before retrying after the first
// failure.
baseDelay time.Duration
// factor is applied to the backoff after each retry.
factor float64
// jitter provides a range to randomize backoff delays.
jitter float64
}
func setDefaults(bc *BackoffConfig) {
md := bc.MaxDelay
*bc = DefaultBackoffConfig
if md > 0 {
bc.MaxDelay = md
}
}
func (bc BackoffConfig) backoff(retries int) (t time.Duration) {
if retries == 0 {
return bc.baseDelay
}
backoff, max := float64(bc.baseDelay), float64(bc.MaxDelay)
for backoff < max && retries > 0 {
backoff *= bc.factor
retries--
}
if backoff > max {
backoff = max
}
// Randomize backoff delays so that if a cluster of requests start at
// the same time, they won't operate in lockstep.
backoff *= 1 + bc.jitter*(rand.Float64()*2-1)
if backoff < 0 {
return 0
}
return time.Duration(backoff)
}
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