busretry.go RawHistoryFolder

1// Package busretry keeps a D-Bus service running across bus restarts and
2// busy names: it runs an attempt again after a growing delay until the
3// context ends.
4package busretry
5
6import (
7	"context"
8	"errors"
9	"time"
10
11	"github.com/bnema/zerowrap"
12)
13
14// maxDelay bounds the delay between attempts.
15const maxDelay = time.Minute
16
17// Run calls attempt until ctx ends. When attempt returns, it waits retry,
18// doubling up to maxDelay on each failure, and calls it again. An attempt that
19// ran longer than maxDelay before failing starts the delay over: its failure is
20// new, not a retry streak. what names the feature in logs ("X ignored until
21// the next attempt"); a failure is warned once per distinct error, then
22// logged at debug level.
23func Run(ctx context.Context, retry time.Duration, what string, log zerowrap.Logger, attempt func(context.Context) error) {
24	delay := retry
25	var last string
26	for {
27		start := time.Now()
28		err := attempt(ctx)
29		if ctx.Err() != nil {
30			return
31		}
32		if err == nil {
33			err = errors.New(what + " stopped")
34		}
35		if time.Since(start) > maxDelay {
36			delay, last = retry, ""
37		}
38		if msg := err.Error(); msg != last {
39			last = msg
40			log.Warn().Err(err).Dur("retry", delay).Msg(what + " ignored until the next attempt")
41		} else {
42			log.Debug().Err(err).Dur("retry", delay).Msg(what + " still ignored")
43		}
44		select {
45		case <-ctx.Done():
46			return
47		case <-time.After(delay):
48		}
49		delay = min(2*delay, maxDelay)
50	}
51}