Amazon CloudWatch vs Prometheus: What are the differences?

Amazon CloudWatch and Prometheus are both popular monitoring services used in the management of cloud infrastructure. Let's explore the key differences between them.

1. Data Collection: Amazon CloudWatch is designed to collect and monitor metrics from various AWS resources and services, providing a comprehensive view of the cloud environment. Prometheus, on the other hand, is a more flexible solution that can work with any system, allowing users to monitor custom application metrics and resources outside of AWS.

2. Metric Storage: CloudWatch stores metrics for a maximum of 15 months, providing long-term retention for historical data. Prometheus, however, utilizes a local time series database that retains data for a configurable amount of time, making it more suitable for short-term data storage and analysis.

3. Alerting and Notifications: CloudWatch includes a built-in alerting mechanism that triggers notifications based on defined thresholds. It can send notifications via email, SNS, or trigger automated actions through CloudWatch Alarms. Prometheus also supports alerting but relies on external integrations such as Alertmanager to handle alert notifications, making it more flexible in terms of notification customization.

4. Querying and Analysis: When it comes to querying and analysis, Prometheus offers a powerful and flexible query language called PromQL. It allows users to perform complex queries and provides advanced operator functions for metric selection and manipulation. CloudWatch, on the other hand, provides a simpler query interface with a limited set of query functions, making it less flexible in terms of data analysis capabilities.

5. Scalability and Cost: CloudWatch is a fully managed service provided by AWS, which means it automatically scales with the cloud environment. The pricing for CloudWatch varies based on the number of metrics ingested and API requests made. Prometheus, being an open-source project, requires manual setup and configuration to scale and can be run on-premises or in the cloud. While Prometheus itself is free to use, the overall cost may vary depending on the infrastructure and resources required for its deployment.

6. Integration Ecosystem: CloudWatch integrates seamlessly with other AWS services, allowing users to monitor and manage the entire AWS infrastructure from a single interface. It also provides built-in integrations with various third-party tools and platforms. Prometheus has a vast ecosystem of exporters and integrations, enabling users to collect metrics from a wide range of systems, services, and frameworks, providing more flexibility in terms of data collection.

In summary, Amazon CloudWatch is a managed service tightly integrated into AWS, providing a comprehensive monitoring solution for AWS resources. Prometheus, on the other hand, is a highly flexible and extensible solution suitable for monitoring custom metrics in both cloud and on-premises environments.