OpenCost — Real-Time Kubernetes Cost Monitoring

Introduction

OpenCost is a CNCF sandbox project that provides real-time cost monitoring for Kubernetes clusters. It allocates infrastructure spend to namespaces, deployments, pods, and labels so engineering and finance teams can see exactly where cloud dollars go.

What OpenCost Does

• Tracks CPU, memory, storage, and network costs per Kubernetes workload
• Allocates shared costs like control plane and load balancers across tenants
• Integrates with cloud billing APIs from AWS, GCP, and Azure for accurate pricing
• Exposes a REST API and Prometheus metrics for cost data consumption
• Provides a built-in web dashboard for quick cost exploration

Architecture Overview

OpenCost runs as a single Go pod that queries the Kubernetes API for resource usage and correlates it with cloud provider pricing data. It pulls on-demand and spot pricing from AWS Cost and Usage Reports, GCP BigQuery billing exports, or Azure rate cards. The cost model is exposed as Prometheus metrics and a JSON API, making it easy to build Grafana dashboards or feed data into FinOps platforms.

Self-Hosting & Configuration

• Deploy via Helm chart into any Kubernetes cluster running Prometheus
• Configure cloud provider integrations by setting billing API credentials
• Set custom CPU and memory pricing for on-prem or bare-metal clusters
• Adjust shared cost allocation weights via the cost model configuration
• Expose the API externally or scrape metrics with an existing Prometheus stack

Key Features

• CNCF-backed open standard for Kubernetes cost monitoring
• Real-time cost allocation by namespace, label, controller, and pod
• Native Prometheus metrics integration for alerting and dashboards
• Multi-cloud pricing support including spot and reserved instances
• Lightweight single-pod deployment with no external database required

Comparison with Similar Tools

• Kubecost — Commercial product built on top of OpenCost; OpenCost is the free open-source engine
• Infracost — Estimates IaC costs before deploy; OpenCost monitors live runtime spend
• Cloud provider cost dashboards — Aggregate billing only; OpenCost maps costs to Kubernetes objects
• Prometheus + custom queries — Requires building cost models manually; OpenCost provides them out of the box

FAQ

Q: Is OpenCost the same as Kubecost? A: OpenCost is the open-source cost allocation engine that Kubecost originally created and donated to the CNCF. Kubecost adds a commercial UI and advanced features on top.

Q: Does it work with on-prem Kubernetes clusters? A: Yes. You can configure custom CPU, memory, and storage rates for clusters without cloud billing APIs.

Q: What Prometheus setup is needed? A: OpenCost works with any Prometheus-compatible stack. It can run its own bundled Prometheus or connect to an existing one.

Q: Can I see costs per team or product? A: Yes. Use Kubernetes labels and namespaces to group costs, then query by those dimensions via the API or dashboard.

Sources

• https://github.com/opencost/opencost
• https://www.opencost.io/docs