/
helpers.go
116 lines (106 loc) · 2.27 KB
/
helpers.go
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package pipe
import (
"fmt"
"log"
"math"
"time"
)
// ConsumerMiddleware func type to build consumers middleware
type ConsumerMiddleware func(fn ConsumerFunc) ConsumerFunc
func mergeMiddlewares(mws ...ConsumerMiddleware) ConsumerMiddleware {
return func(fn ConsumerFunc) ConsumerFunc {
for i := len(mws) - 1; i >= 0; i-- {
fn = mws[i](fn)
}
return fn
}
}
type errFatal struct{ err error }
func (e errFatal) Error() string { return e.err.Error() }
func (e errFatal) Unwrap() error { return e.err }
// RetryConsumer consumer middleware that will retry consumer up to 'tries' on
// error
func RetryConsumer(tries int) ConsumerMiddleware {
return func(fn ConsumerFunc) ConsumerFunc {
return func(m Message) error {
retry := 0
var err error
for ; retry <= tries; retry++ {
if retry > 0 {
log.Printf("retrying: %v", m.Value())
}
err = fn(m)
if err == nil {
break
}
if err, ok := err.(errFatal); ok {
return err
}
}
if err != nil {
return fmt.Errorf("%w (retries: %d) %T", err, retry, m.Value())
}
return nil
}
}
}
// BackoffConsumer consumer middleware that will retry at an exponential time
// until it reaches the maximum duration
func BackoffConsumer(max time.Duration, factor float64) ConsumerMiddleware {
b := &backoff{max: max, factor: factor}
return func(fn ConsumerFunc) ConsumerFunc {
return func(m Message) error {
err := fn(m)
if err == nil {
return nil
}
t := b.forAttempt(1)
for tries := 1; t < b.max; tries++ {
<-time.After(t)
err = fn(m)
if err == nil {
return nil
}
if err, ok := err.(errFatal); ok {
return err
}
t = b.forAttempt(tries)
}
return err
}
}
}
type backoff struct {
max time.Duration
factor float64
}
func (c backoff) forAttempt(n int) time.Duration {
attempt := float64(n)
min := 100 * time.Millisecond
max := c.max
if max <= 0 {
max = 10 * time.Second
}
if min >= max {
return max
}
factor := c.factor
if factor <= 0 {
factor = 2
}
minf := float64(min)
durf := minf * math.Pow(factor, attempt)
// durf = rand.Float64()*(durf-minf) + minf
if durf > math.MaxInt64 {
return max
}
dur := time.Duration(durf)
// keep within bounds
if dur < min {
return min
}
if dur > max {
return max
}
return dur
}