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) 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) }