What it does. 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. Part of mukul975/Anthropic-Cybersecurity-Skills (817 security skills) (mukul975/Anthropic-Cybersecurity-Skills).

Install

• npx skills add mukul975/Anthropic-Cybersecurity-Skills --skill implementing-log-forwarding-with-fluentd, or copy the skill folder into ~/.claude/skills/implementing-log-forwarding-with-fluentd/.
• Raw file: curl -sL https://raw.githubusercontent.com/mukul975/Anthropic-Cybersecurity-Skills/HEAD/skills/implementing-log-forwarding-with-fluentd/SKILL.md

SKILL.md (verbatim)

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

Other files in this skill

• LICENSE
• references/api-reference.md
• scripts/agent.py

references/api-reference.md (verbatim)

Fluentd / Fluent Bit Log Forwarding API Reference

Fluent Bit CLI

# Run Fluent Bit with config file
fluent-bit -c /etc/fluent-bit/fluent-bit.conf

# Validate configuration syntax
fluent-bit -c /etc/fluent-bit/fluent-bit.conf --dry-run

# Run with specific input and output (no config file)
fluent-bit -i cpu -o stdout -f 1

# Tail a log file and forward to Fluentd
fluent-bit -i tail -p path=/var/log/syslog -o forward -p host=fluentd.local -p port=24224

Fluentd CLI

# Start Fluentd with config
fluentd -c /etc/fluentd/fluent.conf

# Validate config file
fluentd --dry-run -c /etc/fluentd/fluent.conf

# Install output plugin
fluent-gem install fluent-plugin-elasticsearch
fluent-gem install fluent-plugin-s3
fluent-gem install fluent-plugin-splunk-hec

Fluent Bit Configuration Sections

[SERVICE]
    Flush        5
    Daemon       Off
    Log_Level    info

[INPUT]
    Name         tail
    Tag          app.logs
    Path         /var/log/app/*.log
    Parser       json
    DB           /var/log/flb_app.db

[FILTER]
    Name         record_modifier
    Match        *
    Record       hostname ${HOSTNAME}

[OUTPUT]
    Name         forward
    Match        *
    Host         aggregator.local
    Port         24224

Fluentd Configuration Directives

<source>
  @type forward
  port 24224
  bind 0.0.0.0
</source>

<filter **>
  @type record_transformer
  <record>
    hostname "#{Socket.gethostname}"
  </record>
</filter>

<match **>
  @type elasticsearch
  host es.local
  port 9200
  logstash_format true
</match>

Python fluent-logger

from fluent import sender
from fluent import event

# Create sender (default: localhost:24224)
sender.setup('app', host='fluentd.local', port=24224)
event.Event('access', {'user': 'admin', 'action': 'login'})

# Direct sender usage
logger = sender.FluentSender('myapp', host='fluentd.local', port=24224)
logger.emit('follow', {'from': 'userA', 'to': 'userB'})
logger.close()

Forward Protocol (TCP Port 24224)

Messages use MessagePack encoding: [tag, timestamp, record]

# Test connectivity
nc -zv fluentd.local 24224

# Monitor Fluentd buffer status
curl http://localhost:24220/api/plugins.json

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