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10.6K Stars 1.2K Forks Apache License 2.0 6.1K Commits 101 Opened issues


Fluentd: Unified Logging Layer (project under CNCF)

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Fluentd: Open-Source Log Collector

GitHub Actions:

Testing on Ubuntu Testing on Windows Testing on macOS Code Climate CII Best Practices FOSSA Status

Drone CI for Arm64:

pipeline status

Fluentd collects events from various data sources and writes them to files, RDBMS, NoSQL, IaaS, SaaS, Hadoop and so on. Fluentd helps you unify your logging infrastructure (Learn more about the Unified Logging Layer).

An event consists of tag, time and record. Tag is a string separated with '.' (e.g. myapp.access). It is used to categorize events. Time is a UNIX time recorded at occurrence of an event. Record is a JSON object.

Example Use Cases

Use Case

Description Diagram
Centralizing Apache/Nginx Server Logs Fluentd can be used to tail access/error logs and transport them reliably to remote systems.
Syslog Alerting Fluentd can "grep" for events and send out alerts.
Mobile/Web Application Logging Fluentd can function as middleware to enable asynchronous, scalable logging for user action events.

Quick Start

$ gem install fluentd
$ fluentd -s conf
$ fluentd -c conf/fluent.conf &
$ echo '{"json":"message"}' | fluent-cat debug.test



  • master: For v1 development.
  • v0.12: For v0.12. This is deprecated version. we already stopped supporting (See


  • Ruby 2.4 or later
  • git

should be in
. On Windows, you can use
Github for Windows
for easy setup.

Install dependent gems

Use bundler:

$ gem install bundler
$ bundle install --path vendor/bundle

Run test

$ bundle exec rake test

You can run specified test via

environment variable:
$ bundle exec rake test TEST=test/test_specified_path.rb
$ bundle exec rake test TEST=test/test_*.rb

Fluentd UI: Admin GUI

Fluentd UI is a graphical user interface to start/stop/configure Fluentd.

More Information

  • Website:
  • Documentation:
  • Project repository:
  • Discussion:
  • Slack / Community:
  • Newsletters:
  • Author: Sadayuki Furuhashi
  • Copyright: 2011-2021 Fluentd Authors
  • License: Apache License, Version 2.0


A third party security audit was performed by Cure53, you can see the full report here.


Patches contributed by great developers.

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