func()

in receiver/loadgenreceiver/metrics.go [107:157]
44 lines of code
8 McCabe index (conditional complexity)

func (ar *metricsGenerator) Start(ctx context.Context, _ component.Host) error {
	startCtx, cancelFn := context.WithCancel(ctx)
	ar.cancelFn = cancelFn

	for i := 0; i < ar.cfg.Concurrency; i++ {
		ar.inflightConcurrency.Add(1)
		go func() {
			defer ar.inflightConcurrency.Done()
			next := pmetric.NewMetrics() // per-worker temporary container to avoid allocs
			for {
				select {
				case <-startCtx.Done():
					return
				default:
				}
				if next.IsReadOnly() {
					// As the optimization to reuse pdata is not compatible with fanoutconsumer,
					// i.e. in pipelines where there are more than 1 consumer,
					// as fanoutconsumer will mark the pdata struct as read only and cannot be reused.
					// See https://github.com/open-telemetry/opentelemetry-collector/blob/461a3558086a03ab13ea121d12e28e185a1c79b0/internal/fanoutconsumer/logs.go#L70
					next = pmetric.NewMetrics()
				}
				err := ar.nextMetrics(next)
				if errors.Is(err, list.ErrLoopLimitReached) {
					return
				}
				// For graceful shutdown, use ctx instead of startCtx to shield Consume* from context canceled
				// In other words, Consume* will finish at its own pace, which may take indefinitely long.
				if err := ar.consumer.ConsumeMetrics(ctx, next); err != nil {
					ar.logger.Error(err.Error())
					ar.statsMu.Lock()
					ar.stats.FailedRequests++
					ar.stats.FailedMetricDataPoints += next.DataPointCount()
					ar.statsMu.Unlock()
				} else {
					ar.statsMu.Lock()
					ar.stats.Requests++
					ar.stats.MetricDataPoints += next.DataPointCount()
					ar.statsMu.Unlock()
				}
			}
		}()
	}
	go func() {
		ar.inflightConcurrency.Wait()
		if ar.cfg.Metrics.doneCh != nil {
			ar.cfg.Metrics.doneCh <- ar.stats
		}
	}()
	return nil
}