status-go/vendor/github.com/jbenet/go-temp-err-catcher/temp_err_catcher.go

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// Package temperrcatcher provides a TempErrCatcher object,
// which implements simple error-retrying functionality.
package temperrcatcher
import (
"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 {
te, ok := e.(Temporary)
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()
}