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package services | ||
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import ( | ||
"time" | ||
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"github.com/smartcontractkit/chainlink-common/pkg/timeutil" | ||
) | ||
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// NewTicker returns a new timeutil.Ticker configured to: | ||
// - fire the first tick immediately | ||
// - apply +/- 10% jitter to each period | ||
func NewTicker(d time.Duration) *timeutil.Ticker { | ||
return TickerConfig{Period: d, JitterPct: 0.1}.NewTicker() | ||
} | ||
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type TickerConfig struct { | ||
// Initial delay before the first tick. | ||
Initial time.Duration | ||
// Delay between each subsequent tick. | ||
Period time.Duration | ||
//TODO doc | ||
JitterPct timeutil.JitterPct | ||
} | ||
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func (c TickerConfig) NewTicker() *timeutil.Ticker { | ||
first := true | ||
return timeutil.NewTicker(func() time.Duration { | ||
if first { | ||
first = false | ||
return c.Initial | ||
} | ||
p := c.Period | ||
if c.JitterPct != 0.0 { | ||
p = c.JitterPct.Apply(p) | ||
} | ||
return p | ||
}) | ||
} |
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package timeutil | ||
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import ( | ||
mrand "math/rand" | ||
"time" | ||
) | ||
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// JitterPct is a percent by which to scale a duration up or down. | ||
// For example, 0.1 will result in +/- 10%. | ||
type JitterPct float64 | ||
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func (p JitterPct) Apply(d time.Duration) time.Duration { | ||
// #nosec | ||
if d == 0 { | ||
return 0 | ||
} | ||
// ensure non-zero arg to Intn to avoid panic | ||
ub := max(1, int(float64(d.Abs())*float64(p))) | ||
// #nosec - non critical randomness | ||
jitter := mrand.Intn(2*ub) - ub | ||
return time.Duration(int(d) + jitter) | ||
} |
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package timeutil | ||
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import ( | ||
"testing" | ||
"time" | ||
) | ||
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func TestJitterPct(t *testing.T) { | ||
for _, tt := range []struct { | ||
pct JitterPct | ||
dur time.Duration | ||
from, to time.Duration | ||
}{ | ||
{0.1, 0, 0, 0}, | ||
{0.1, time.Second, 900 * time.Millisecond, 1100 * time.Millisecond}, | ||
{0.1, time.Minute, 54 * time.Second, 66 * time.Second}, | ||
{0.1, 24 * time.Hour, 21*time.Hour + 36*time.Minute, 26*time.Hour + 24*time.Minute}, | ||
} { | ||
t.Run(tt.dur.String(), func(t *testing.T) { | ||
for i := 0; i < 100; i++ { | ||
got := tt.pct.Apply(tt.dur) | ||
t.Logf("%d: %s", i, got) | ||
if got < tt.from || got > tt.to { | ||
t.Errorf("expected duration %s with jitter to be between (%s, %s) but got: %s", tt.dur, tt.from, tt.to, got) | ||
} | ||
} | ||
}) | ||
} | ||
} |
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package timeutil | ||
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import ( | ||
"time" | ||
) | ||
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// Ticker is like time.Ticker, but with a variable period. | ||
type Ticker struct { | ||
C <-chan time.Time | ||
stop chan struct{} | ||
reset chan struct{} | ||
} | ||
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// NewTicker returns a started Ticker which calls nextDur for each period. | ||
func NewTicker(nextDur func() time.Duration) *Ticker { | ||
c := make(chan time.Time) // unbuffered so we block and delay if not being handled | ||
t := Ticker{C: c, stop: make(chan struct{}), reset: make(chan struct{})} | ||
go t.run(c, nextDur) | ||
return &t | ||
} | ||
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func (t *Ticker) run(c chan<- time.Time, nextDur func() time.Duration) { | ||
for { | ||
timer := time.NewTimer(nextDur()) | ||
select { | ||
case <-t.stop: | ||
timer.Stop() | ||
return | ||
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case <-t.reset: | ||
timer.Stop() | ||
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case <-timer.C: | ||
timer.Stop() | ||
select { | ||
case <-t.stop: | ||
return | ||
case c <- time.Now(): | ||
} | ||
} | ||
} | ||
} | ||
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func (t *Ticker) Stop() { close(t.stop) } | ||
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func (t *Ticker) Reset() { | ||
select { | ||
case <-t.stop: | ||
case <-t.reset: | ||
default: | ||
// unecessary | ||
return | ||
} | ||
} |
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