In the world of observability and monitoring, choosing the right tool can make or break your infrastructure management strategy. Whether you’re an SRE, DevOps engineer, or a cloud enthusiast, monitoring is a crucial part of your workflow. Two of the most widely adopted solutions in this space are Prometheus and AWS CloudWatch. Both tools excel in different areas, but the right choice depends on your use case, infrastructure setup, and scalability requirements.
In this article, I’ll share my experience working with both Prometheus and AWS CloudWatch and explore the key differences to help you make an informed decision.
1. Overview of Prometheus
Prometheus is an open-source monitoring and alerting toolkit designed for reliability and scalability, widely adopted for cloud-native applications. It was originally developed at SoundCloud and later became a part of the Cloud Native Computing Foundation (CNCF).
- Main Features: Time-series data collection, flexible querying language (PromQL), custom metrics support, and powerful alerting.
- Popular for: Kubernetes and microservices architectures, since it integrates seamlessly with containerized environments.
2. Overview of AWS CloudWatch
AWS CloudWatch is a fully managed monitoring and observability service provided by AWS. It allows you to monitor AWS resources, applications, and services in real-time.
- Main Features: Native integration with AWS services, metrics collection, logging, alarms, and automatic scaling.
- Popular for: Users within the AWS ecosystem who need simple, managed monitoring with minimal infrastructure setup.
3. Data Collection & Custom Metrics
- Prometheus:
- Data Collection: Prometheus scrapes metrics from endpoints exposed by applications or services. You can push metrics from applications or use exporters to gather system-level metrics.
- Custom Metrics: You can define and push custom metrics easily, making Prometheus highly flexible for monitoring almost anything.
- Data Retention: Prometheus stores its metrics locally, which means you need to manage the storage for long-term retention.
- AWS CloudWatch:
- Data Collection: CloudWatch seamlessly integrates with AWS services and collects metrics without requiring additional setup. It can also receive custom metrics, though AWS pricing is based on the number of custom metrics used.
- Custom Metrics: Custom metrics are supported but can incur additional costs, especially if you are pushing many metrics frequently.
- Data Retention: AWS handles metric storage automatically with long-term retention.
4. High Availability (HA) & Fault Tolerance
One of the major distinctions between Prometheus and CloudWatch is how they handle high availability and fault tolerance.
- Prometheus:
- Disadvantage in HA: Prometheus is a self-managed solution, so ensuring high availability (HA) is your responsibility. If the server hosting Prometheus goes down, monitoring, alerting, and metrics collection will stop. This is especially a risk in critical environments.
- Workarounds for HA: You can ensure HA by implementing multi-instance Prometheus setups (federation), or by integrating with Thanos or Cortex for global queries, redundancy, and long-term storage. However, these setups add complexity and additional infrastructure overhead.
- AWS CloudWatch:
- Built-in HA: Since CloudWatch is a managed service by AWS, it comes with built-in high availability. AWS takes care of redundancy and ensures that CloudWatch is always available. You don’t need to worry about infrastructure outages affecting your monitoring solution.
5. Alerting & Remediation
- Prometheus:
- Alerting: Prometheus uses Alertmanager for alerting, allowing you to create highly customizable alerts based on Prometheus queries (PromQL). You can route alerts to different receivers such as email, Slack, or PagerDuty.
- Remediation: Prometheus is primarily focused on monitoring and alerting. Remediation actions require external tools or manual interventions.
- AWS CloudWatch:
- Alerting: CloudWatch Alarms allow you to define thresholds for metrics and trigger actions (like notifications) when these thresholds are breached. Alarms integrate seamlessly with Amazon SNS, email, and other AWS services.
- Remediation: CloudWatch integrates directly with AWS EventBridge and AWS Systems Manager (SSM), allowing for automatic remediation actions such as restarting instances or scaling resources without manual intervention.
6. Cost Considerations
- Prometheus:
- Self-Hosted: Prometheus is free and open-source. However, you need to consider the costs of managing and maintaining the servers or infrastructure hosting Prometheus. There are no direct usage costs, but there are indirect costs associated with storage, HA, and scaling.
- Long-Term Storage Costs: If you require long-term storage, you need to integrate with external systems like Thanos or S3, which can introduce additional costs.
- AWS CloudWatch:
- Managed: CloudWatch charges based on the number of metrics, API requests, log storage, and alarms. This can become expensive if you have a large number of custom metrics or high-frequency log ingestion.
- Scaling Costs: While CloudWatch handles scaling for you, the costs can grow significantly for large-scale environments.
7. Ease of Setup & Maintenance
- Prometheus:
- Setup: Prometheus requires setting up and configuring scraping endpoints, storage management, and alerting rules. While it’s flexible and powerful, the learning curve is steeper.
- Maintenance: Requires constant oversight for upgrades, backups, scaling, and ensuring HA.
- AWS CloudWatch:
- Setup: CloudWatch is easy to set up, especially if you are already in the AWS ecosystem. AWS handles most of the setup and management.
- Maintenance: Since it’s a fully managed service, there’s little to no maintenance required from your side. AWS manages the backend, scaling, and updates.
8. Flexibility & Use Cases
- Prometheus:
- Flexibility: Prometheus shines in environments where you need flexibility and custom setups. It works well in hybrid cloud setups, Kubernetes, and microservices architectures where you need to monitor applications across various platforms.
- Best Use Case: Ideal for users who need to monitor diverse infrastructures and have custom monitoring needs, especially in containerized or cloud-native environments.
- AWS CloudWatch:
- Simplicity: CloudWatch excels in simplicity and integration. It’s perfect for AWS-native applications and infrastructures, where you need monitoring without worrying about the underlying infrastructure.
- Best Use Case: Ideal for users heavily invested in the AWS ecosystem who want a “hands-off” monitoring solution that handles scaling, HA, and management without additional work.
Conclusion
Both Prometheus and AWS CloudWatch are powerful monitoring solutions, but they cater to different needs.
- If you’re running a multi-cloud or on-prem infrastructure and need maximum flexibility, Prometheus with extensions like Thanos or Cortex provides an excellent, albeit more complex, solution.
- If you’re deep into the AWS ecosystem and want a fully managed service that handles everything from metrics to remediation, CloudWatch is the obvious choice.
Prometheus offers deep customization but requires more effort to manage, particularly when it comes to ensuring high availability. In contrast, CloudWatch’s fully managed service offers peace of mind with built-in high availability and seamless integration with AWS services.
In my next article, I’ll dive deeper into how to choose between Prometheus and CloudWatch, including more pros and cons, and how you can leverage each based on your needs. Stay tuned!