Docker Image

This article explains how to use the official Fluentd Docker image, maintained by Treasure Data, Inc.

Step 0: Install Docker

Please download and install Docker from here:

Step 1: Pull Fluentd Docker Image

Then, download Fluentd edge-debian's (edge-debian means latest version of Fluentd) image by docker pull command:

$ docker pull fluent/fluentd:edge-debian

Debian and Alpine Linux versions are available for Fluentd image. Debian version is recommended officially since it has jemalloc support. However, the Alpine image is smaller. And, Windows server version is also available.

Step 2: Launch Fluentd Container

To make the test simple, create the example config below at $(pwd)/tmp/fluentd.conf. This example accepts records from http, and outputs to stdout.

# $(pwd)/tmp/fluentd.conf

<source>
  @type http
  port 9880
  bind 0.0.0.0
</source>

<match **>
  @type stdout
</match>

Finally, you can run Fluentd with docker run command:

$ docker run -p 9880:9880 -v $(pwd)/tmp:/fluentd/etc fluent/fluentd:edge-debian -c /fluentd/etc/fluentd.conf
2025-02-04 01:57:09 +0000 [info]: init supervisor logger path=nil rotate_age=nil rotate_size=nil
2025-02-04 01:57:09 +0000 [info]: parsing config file is succeeded path="/fluentd/etc/fluentd.conf"
2025-02-04 01:57:09 +0000 [info]: gem 'fluentd' version '1.16.7'
2025-02-04 01:57:09 +0000 [warn]: define <match fluent.**> to capture fluentd logs in top level is deprecated. Use <label @FLUENT_LOG> instead
2025-02-04 01:57:09 +0000 [info]: using configuration file: <ROOT>
  <source>
    @type http
    port 9880
    bind "0.0.0.0"
  </source>
  <match **>
    @type stdout
  </match>
</ROOT>
2025-02-04 01:57:09 +0000 [info]: starting fluentd-1.16.7 pid=7 ruby="3.2.6"
2025-02-04 01:57:09 +0000 [info]: spawn command to main:  cmdline=["/usr/local/bin/ruby", "-Eascii-8bit:ascii-8bit", "/usr/local/bundle/bin/fluentd", "-c", "/fluentd/etc/fluentd.conf", "--plugin", "/fluentd/plugins", "--under-supervisor"]
2025-02-04 01:57:10 +0000 [info]: #0 init worker0 logger path=nil rotate_age=nil rotate_size=nil
2025-02-04 01:57:10 +0000 [info]: adding match pattern="**" type="stdout"
2025-02-04 01:57:10 +0000 [info]: adding source type="http"
2025-02-04 01:57:10 +0000 [warn]: #0 define <match fluent.**> to capture fluentd logs in top level is deprecated. Use <label @FLUENT_LOG> instead
2025-02-04 01:57:10 +0000 [info]: #0 starting fluentd worker pid=16 ppid=7 worker=0
2025-02-04 01:57:10 +0000 [info]: #0 fluentd worker is now running worker=0
2025-02-04 01:57:10.255688431 +0000 fluent.info: {"pid":16,"ppid":7,"worker":0,"message":"starting fluentd worker pid=16 ppid=7 worker=0"}
2025-02-04 01:57:10.266084977 +0000 fluent.info: {"worker":0,"message":"fluentd worker is now running worker=0"}

Step 3: Post Sample Logs via HTTP

Use curl command to post sample logs via HTTP like this:

$ curl -X POST -d 'json={"json":"message"}' http://127.0.0.1:9880/sample.test

Use docker ps command to retrieve container ID and use docker logs command to check the specific container's log like this:

$ docker ps -a
CONTAINER ID   IMAGE                        COMMAND                   CREATED         STATUS         PORTS                                                            NAMES
5f0ac46c5b35   fluent/fluentd:edge-debian   "tini -- /bin/entryp…"   5 minutes ago   Up 5 minutes   5140/tcp, 24224/tcp, 0.0.0.0:9880->9880/tcp, :::9880->9880/tcp   great_mcclintock

$ docker logs 5f0ac46c5b35 | tail -n 1
2025-02-04 02:00:53.842179032 +0000 sample.test: {"json":"message"}

Next Steps

Now, you know how to use Fluentd via Docker.

Here are some Docker related resources for Fluentd:

Also, refer to the following tutorials to learn how to collect data from various data sources:

If this article is incorrect or outdated, or omits critical information, please let us know. Fluentd is an open-source project under Cloud Native Computing Foundation (CNCF). All components are available under the Apache 2 License.

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