Implementing Log Forwarding With Fluentd

---
name: implementing-log-forwarding-with-fluentd
description: >-
  Configures Fluent Bit as an endpoint log forwarder and Fluentd as the central
  aggregator for centralized log collection, routing, filtering, and enrichment,
  covering input plugins for syslog/file-tailing/application logs and output
  routing to Elasticsearch, S3, and Splunk. Use when setting up centralized log
  aggregation across distributed infrastructure or generating Fluent Bit/Fluentd
  configuration files for a new log pipeline.
domain: cybersecurity
subdomain: security-operations
tags:
- fluentd
- fluent-bit
- log-aggregation
- log-forwarding
- siem
- centralized-logging
- observability
version: '1.0'
author: mahipal
license: Apache-2.0
nist_csf:
- DE.CM-01
- RS.MA-01
- GV.OV-01
- DE.AE-02
mitre_attack:
- T1078
- T1190
- T1059
- T1685.002
- T1685.005
---

# Implementing Log Forwarding with Fluentd

## Overview

This skill covers configuring Fluentd and Fluent Bit for centralized log collection, routing, and enrichment. Fluent Bit acts as a lightweight log forwarder on endpoints, while Fluentd serves as the central aggregator and processor. The configuration covers input plugins for syslog, file tailing, and application logs, with output routing to Elasticsearch, S3, and Splunk.


## When to Use

- When deploying or configuring implementing log forwarding with fluentd capabilities in your environment
- When establishing security controls aligned to compliance requirements
- When building or improving security architecture for this domain
- When conducting security assessments that require this implementation

## Prerequisites

- Fluentd (td-agent) v1.16+ or Fluent Bit v3.0+
- Python 3.8+ with fluent-logger library
- Elasticsearch or Splunk for log destination
- Network access on port 24224 (Fluentd forward protocol)
- Ruby 2.7+ (for Fluentd plugin development)

## Steps

1. **Generate Fluent Bit Configuration** — Create input, filter, and output configuration for endpoint log collection
2. **Generate Fluentd Aggregator Configuration** — Configure the central Fluentd instance with forward input, parsing, and multi-output routing
3. **Configure Log Filtering and Enrichment** — Add record_transformer and grep filters for log enrichment and noise reduction
4. **Validate Configuration Syntax** — Parse and validate Fluentd/Fluent Bit configuration files for syntax errors
5. **Test Log Forwarding** — Send test events via fluent-logger Python library and verify delivery
6. **Generate Deployment Report** — Produce configuration summary with routing topology and health metrics

## Expected Output

- Fluent Bit and Fluentd configuration files (INI/YAML format)
- Configuration validation report
- Log routing topology diagram (text-based)
- Test event delivery confirmation