func pullImage()

in sources/host-ctr/cmd/host-ctr/main.go [819:878]
53 lines of code
10 McCabe index (conditional complexity)

func pullImage(ctx context.Context, source string, client *containerd.Client, registryConfigPath string) (containerd.Image, error) {
	// Handle registry config
	var registryConfig *RegistryConfig
	if registryConfigPath != "" {
		var err error
		registryConfig, err = NewRegistryConfig(registryConfigPath)
		if err != nil {
			log.G(ctx).
				WithError(err).
				WithField("registry-config", registryConfigPath).
				Error("failed to read registry config")
			return nil, err
		}
	}

	// Pull the image
	// Retry with exponential backoff when failures occur, maximum retry duration will not exceed 31 seconds
	const maxRetryAttempts = 5
	const intervalMultiplier = 2
	const maxRetryInterval = 30 * time.Second
	const jitterPeakAmplitude = 4000
	const jitterLowerBound = 2000
	var retryInterval = 1 * time.Second
	var retryAttempts = 0
	var img containerd.Image
	for {
		var err error
		img, err = client.Pull(ctx, source,
			withDynamicResolver(ctx, source, registryConfig),
			containerd.WithSchema1Conversion)
		if err == nil {
			log.G(ctx).WithField("img", img.Name()).Info("pulled image successfully")
			break
		}
		if retryAttempts >= maxRetryAttempts {
			return nil, errors.Wrap(err, "retries exhausted")
		}
		// Add a random jitter between 2 - 6 seconds to the retry interval
		retryIntervalWithJitter := retryInterval + time.Duration(rand.Int31n(jitterPeakAmplitude))*time.Millisecond + jitterLowerBound*time.Millisecond
		log.G(ctx).WithError(err).Warnf("failed to pull image. waiting %s before retrying...", retryIntervalWithJitter)
		timer := time.NewTimer(retryIntervalWithJitter)
		select {
		case <-timer.C:
			retryInterval *= intervalMultiplier
			if retryInterval > maxRetryInterval {
				retryInterval = maxRetryInterval
			}
			retryAttempts++
		case <-ctx.Done():
			return nil, errors.Wrap(err, "context ended while retrying")
		}
	}

	log.G(ctx).WithField("img", img.Name()).Info("unpacking image...")
	if err := img.Unpack(ctx, containerd.DefaultSnapshotter); err != nil {
		return nil, errors.Wrap(err, "failed to unpack image")
	}

	return img, nil
}