Measuring Image Pull Latency in Kubernetes Clusters with Prometheus and Exporters

Maintaining a high-performing container orchestration environment requires constant monitoring of various metrics. One aspect that’n often overlooked is the image pull latency within your Kubernetes (K8s) cluster, which can significantly impact pod startup times when pulling images from repositories like Docker Hub or Google Cloud Registry (GCR).

To address this and build a dashboard for visualizing these metrics in real-time, leveraging Prometheus alongside specific exporters is an effective approach. Here’s how you might go about measuring image pull latency using your Kubernetes cluster:

Integration with Kubelet Exporter

With Kubernetes 1.30 and above, the kubelet now exposes a histogram that can be used to monitor image_pull_duration, providing insight into how long it takes for an image pull operation within your cluster:

• The key metric here is <code>image_pull_duration_seconds</code> which gives you detailed information about the time spent pulling each container.

For further details on this exporter, please refer to Kubernetes Issue #121719. This pulls through historical data into Prometheus’ powerful monitoring capabilities allowing for precise visualization and analysis of your image pulling latencies in a dashboard setting.

By capturing this metric, you will gain visibility over which images are causing delays during pod startup phases or if certain repositories consistently outperform others with respect to speed — all contributing factors crucial when optimizing the performance metrics for efficiency and reliability of your containerized applications in Kubernetes environments.