📘 Introduction
When it comes to logging in Amazon EKS, two of the most popular tools are Fluent Bit and Fluentd. Both are powerful log forwarders that can collect, filter, and route logs from your Kubernetes workloads to various destinations, such as CloudWatch, S3, Elasticsearch, or third-party observability platforms.
This guide provides a visual comparison of Fluent Bit vs Fluentd and offers best practices for using them in your EKS cluster.
🔍 Fluent Bit vs Fluentd: Key Differences
| Feature | Fluent Bit | Fluentd |
|---|---|---|
| Resource Usage | Lightweight, ideal for edge/devices | Heavier, more flexible |
| Performance | High throughput, low memory | Lower throughput, higher memory |
| Plugin Ecosystem | Smaller but growing | Large and mature |
| Configuration | Simpler | More powerful |
| CloudWatch Support | Official AWS EKS add-on | Manual setup required |
| Container Image Size | ~5MB | ~40MB+ |
🤔 Choosing the Right Tool
| Use Fluent Bit if... | Use Fluentd if... |
|---|---|
| ✅ You're using Fargate | ✅ You're on EC2-based nodes and need flexibility |
| ✅ You want lightweight and fast logging | ✅ You need advanced filtering or routing |
| ✅ You prefer AWS-managed add-ons | ✅ You're already using Fluentd elsewhere in your stack |
🚀 Deployment Models
Fluent Bit (EKS Add-on or Helm)
Fluent Bit can be deployed via the official AWS EKS add-on for minimal setup or manually using a Helm chart for more control over configuration.
Fluentd (DaemonSet Deployment)
Fluentd is typically deployed as a DaemonSet using a generic Kubernetes manifest. You’ll need to select a suitable image and provide your own configuration files to define input sources and output destinations.
✅ Best Practices
- 🧩 Use structured logging (e.g., JSON)
- 🔐 Assign least-privilege IAM roles to logging agents
- 🧼 Keep logging agents separate from app containers
- 🚦 Filter noisy logs to reduce CloudWatch costs
- 📤 Route logs based on namespace or label
🧾 Summary
Both Fluent Bit and Fluentd are great options for EKS logging, depending on your needs:
- Fluent Bit is fast, lightweight, and works seamlessly with AWS-native solutions — ideal for most users.
- Fluentd is a full-featured logging router with deep plugin support — great for advanced pipelines.
Choose the tool that fits your workload, and don’t hesitate to mix both in multi-node-type environments.
Happy logging! 📁
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