Monitoring and observability have become essential aspects of modern-day cloud-native architectures. As companies scale their systems, they need reliable and efficient tools for metrics collection and monitoring. Two of the most popular solutions in the ecosystem today are Prometheus and Thanos. While they are related, they cater to different needs, and understanding their differences and use cases can help teams make an informed decision on which tool is best suited for their infrastructure.
In this blog, we’ll dive into the Prometheus vs Thanos debate and explore their features, strengths, and ideal use cases.
What is Prometheus?
Prometheus is an open-source monitoring and alerting toolkit developed by SoundCloud and later contributed to the Cloud Native Computing Foundation (CNCF). It is designed for gathering, storing, and querying time-series data, especially for cloud-native environments. Prometheus is widely used in Kubernetes-based infrastructures and is a core component of the Cloud-Native Stack.
Key Features of Prometheus:
- Time-Series Data Collection: Prometheus collects metrics data in a time-series format, making it ideal for monitoring system performance over time.
- Pull-based Model: Prometheus uses a pull-based model for gathering metrics from endpoints, which means it periodically scrapes HTTP endpoints exposed by targets (such as application services).
- Powerful Query Language (PromQL): Prometheus offers PromQL, a powerful query language that allows users to aggregate, filter, and manipulate metrics.
- Alerting and Notification: Prometheus has built-in alerting mechanisms, allowing users to define alert rules based on the metrics being scraped.
- Short-term Storage: Prometheus stores data on disk for a short duration (usually a few weeks), designed for quick querying but not ideal for long-term storage.
Prometheus Use Case:
- On-demand Monitoring: Prometheus works great for short-term monitoring and alerting for small to medium-sized infrastructures.
- Local Storage: If you don’t need to store data for extended periods, Prometheus offers efficient storage for a limited retention period (typically 15-30 days).
- Cloud-Native Environments: Prometheus is highly suitable for Kubernetes environments, microservices, and other container-based systems.
What is Thanos?
Thanos is an open-source project that builds on top of Prometheus to provide a scalable, long-term storage solution for metrics. It was developed by Cortex creators and aims to solve several of Prometheus’ limitations, specifically around scalability, high availability, and long-term storage.
Thanos works by integrating seamlessly with Prometheus, enhancing it with global query capabilities, long-term storage, and better scalability across multiple Prometheus instances. If you’re already using Prometheus but need a more robust solution to handle metrics at scale, Thanos is often the go-to choice.
Key Features of Thanos:
- Global Querying: Thanos aggregates data from multiple Prometheus instances, providing a global query layer for metrics, enabling cross-cluster and multi-region queries.
- Long-Term Storage: Thanos allows users to store data in cheap, long-term object storage (e.g., AWS S3, Google Cloud Storage, etc.), solving Prometheus’ short retention period by offloading historical data.
- High Availability: Thanos introduces a high-availability architecture by ensuring that metrics are always accessible, even if individual Prometheus instances fail.
- Data Deduplication: Thanos handles deduplication of data from multiple Prometheus instances, ensuring that metrics aren’t double-counted when aggregating across many Prometheus servers.
- Prometheus Compatibility: Thanos is designed to be fully compatible with Prometheus, which means you can continue using your existing Prometheus setup while taking advantage of Thanos’ additional features.
Thanos Use Case:
- Long-Term Metrics Storage: If you need to store metrics for months or years, Thanos provides a solution by offloading Prometheus data to external object storage.
- Cross-Prometheus Querying: Thanos excels in large-scale environments with multiple Prometheus instances, allowing for global querying across clusters, regions, and even clouds.
- Scalable Monitoring: Thanos is ideal for enterprises and organizations that require horizontal scalability for their monitoring infrastructure.
Prometheus vs Thanos: Key Differences
- Storage Duration:
- Prometheus: Typically retains data for a short duration (usually up to 30 days).
- Thanos: Enables long-term storage by offloading data to object storage systems like S3, Google Cloud Storage, and others.
- Scalability:
- Prometheus: While it is highly efficient for small to medium-scale environments, it may face challenges with horizontal scalability in large distributed systems.
- Thanos: Designed for scalability, Thanos can aggregate data from multiple Prometheus instances across different clusters, making it suitable for large-scale environments.
- High Availability:
- Prometheus: A single Prometheus instance may become a point of failure if it crashes or loses data.
- Thanos: Ensures high availability by providing redundancy and access to historical data, even in the event of Prometheus failures.
- Querying:
- Prometheus: Prometheus only supports querying data from the local instance, making cross-instance queries difficult.
- Thanos: With Thanos, users can query data from all Prometheus instances globally, making it more suitable for large and distributed environments.
- Deployment Complexity:
- Prometheus: Relatively simple to deploy and use, particularly for smaller environments.
- Thanos: Adds a layer of complexity to the setup but provides significant benefits for large-scale deployments.
- Cost:
- Prometheus: Requires less infrastructure for local storage and can be more cost-effective for small to medium-sized environments.
- Thanos: Involves additional storage costs (for object storage), and the complexity of deployment could lead to higher operational costs.
When to Use Prometheus vs Thanos?
- Use Prometheus if:
- You are running a small to medium-sized infrastructure with relatively simple monitoring needs.
- You are focused on short-term monitoring and alerting.
- You do not need to store metrics for long periods.
- Use Thanos if:
- You need to scale your monitoring solution horizontally to support multiple Prometheus instances.
- You want to store metrics data for long durations and need to offload data to object storage.
- You need high availability and redundancy for your monitoring setup.
- You are dealing with a multi-cluster or multi-region environment that requires global query capabilities.
Conclusion
In summary, Prometheus is an excellent choice for short-term, localized monitoring, especially for small to medium-sized deployments. However, when your infrastructure grows, and you need features like long-term storage, high availability, and global querying, Thanos provides the necessary extensions to Prometheus, making it a robust and scalable solution for large-scale environments.
The choice between Prometheus and Thanos ultimately depends on your organization’s size, infrastructure complexity, and monitoring requirements. For smaller setups, Prometheus might be enough, but for enterprise-level needs, Thanos is a natural progression, allowing you to scale your monitoring solution effectively.
