127 lines
3.2 KiB
Go
127 lines
3.2 KiB
Go
// Package temperrcatcher provides a TempErrCatcher object,
|
|
// which implements simple error-retrying functionality.
|
|
package temperrcatcher
|
|
|
|
import (
|
|
"errors"
|
|
"time"
|
|
)
|
|
|
|
// InitialDelay governs how long to wait the first time.
|
|
// This is defaulted to time.Millisecond, which makes sense
|
|
// for network listener failures. You may want a much smaller
|
|
// delay. You can configure this package wide, or in each
|
|
// TempErrCatcher
|
|
var InitialDelay = time.Millisecond
|
|
|
|
// Temporary is an interface errors can implement to
|
|
// ensure they are correctly classified by the default
|
|
// TempErrCatcher classifier
|
|
type Temporary interface {
|
|
Temporary() bool
|
|
}
|
|
|
|
// ErrIsTemporary returns whether an error is Temporary(),
|
|
// iff it implements the Temporary interface.
|
|
func ErrIsTemporary(e error) bool {
|
|
var te Temporary
|
|
ok := errors.As(e, &te)
|
|
return ok && te.Temporary()
|
|
}
|
|
|
|
// TempErrCatcher catches temporary errors for you. It then sleeps
|
|
// for a bit before returning (you should then try again). This may
|
|
// seem odd, but it's exactly what net/http does:
|
|
// http://golang.org/src/net/http/server.go?s=51504:51550#L1728
|
|
//
|
|
// You can set a few options in TempErrCatcher. They all have defaults
|
|
// so a zero TempErrCatcher is ready to be used:
|
|
//
|
|
// var c tec.TempErrCatcher
|
|
// c.IsTemporary(tempErr)
|
|
//
|
|
type TempErrCatcher struct {
|
|
IsTemp func(error) bool // the classifier to use. default: ErrIsTemporary
|
|
Wait func(time.Duration) // the wait func to call. default: time.Sleep
|
|
Max time.Duration // the maximum time to wait. default: time.Second
|
|
Start time.Duration // the delay to start with. default: InitialDelay
|
|
delay time.Duration
|
|
last time.Time
|
|
}
|
|
|
|
func (tec *TempErrCatcher) init() {
|
|
if tec.Max == 0 {
|
|
tec.Max = time.Second
|
|
}
|
|
if tec.IsTemp == nil {
|
|
tec.IsTemp = ErrIsTemporary
|
|
}
|
|
if tec.Wait == nil {
|
|
tec.Wait = time.Sleep
|
|
}
|
|
if tec.Start == 0 {
|
|
tec.Start = InitialDelay
|
|
}
|
|
}
|
|
|
|
// IsTemporary checks whether an error is temporary. It will call
|
|
// tec.Wait before returning, with a delay. The delay is also
|
|
// doubled, so we do not constantly spin. This is the strategy
|
|
// net.Listener uses.
|
|
//
|
|
// Note: you will want to call Reset() if you get a success,
|
|
// so that the stored delay is brough back to 0.
|
|
func (tec *TempErrCatcher) IsTemporary(e error) bool {
|
|
tec.init()
|
|
if tec.IsTemp(e) {
|
|
now := time.Now()
|
|
if now.Sub(tec.last) > (tec.delay * 5) {
|
|
// this is a "new streak" of temp failures. reset.
|
|
tec.Reset()
|
|
}
|
|
|
|
if tec.delay == 0 { // init case.
|
|
tec.delay = tec.Start
|
|
} else {
|
|
tec.delay *= 2
|
|
}
|
|
|
|
if tec.delay > tec.Max {
|
|
tec.delay = tec.Max
|
|
}
|
|
tec.Wait(tec.delay)
|
|
tec.last = now
|
|
return true
|
|
}
|
|
tec.Reset() // different failure. call reset
|
|
return false
|
|
}
|
|
|
|
// Reset sets the internal delay counter to 0
|
|
func (tec *TempErrCatcher) Reset() {
|
|
tec.delay = 0
|
|
}
|
|
|
|
// ErrTemporary wraps any error and implements Temporary function.
|
|
//
|
|
// err := errors.New("beep boop")
|
|
// var c tec.TempErrCatcher
|
|
// c.IsTemporary(err) // false
|
|
// c.IsTemporary(tec.ErrTemp{err}) // true
|
|
//
|
|
type ErrTemporary struct {
|
|
Err error
|
|
}
|
|
|
|
func (e ErrTemporary) Temporary() bool {
|
|
return true
|
|
}
|
|
|
|
func (e ErrTemporary) Error() string {
|
|
return e.Err.Error()
|
|
}
|
|
|
|
func (e ErrTemporary) String() string {
|
|
return e.Error()
|
|
}
|