// TrackMessageAge is middleware that tracks the exponential moving average of message age, calling a callback function with the current average periodically
func TrackMessageAge(period time.Duration, f func(age float64)) MessageHandlerDecorator {
ema := movingaverage.New(period)
go func() {
for {
<-time.After(period)
f(ema.Value())
}
}()
return func(fn sqsconsumer.MessageHandlerFunc) sqsconsumer.MessageHandlerFunc {
return func(ctx context.Context, msg string) error {
age, err := computeMessageAge(ctx)
if err == nil {
ema.Update(age)
}
return fn(ctx, msg)
}
}
}
// TrackMetrics decorates a MessageHandler to collect metrics about successes, failures and runtime reports in ms*10.
func TrackMetrics(successes, failures *expvar.Int, timing *expvar.Float) MessageHandlerDecorator {
ema := movingaverage.New(5 * time.Second)
return func(fn sqsconsumer.MessageHandlerFunc) sqsconsumer.MessageHandlerFunc {
return func(ctx context.Context, msg string) error {
start := time.Now()
defer func() {
v := ema.Update(time.Since(start).Seconds() * 1000)
timing.Set(v)
}()
err := fn(ctx, msg)
if err != nil {
failures.Add(1)
} else {
successes.Add(1)
}
return err
}
}
}