Fluentd
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
(Note: For Windows users, it is recommended to run this command in Command Prompt (cmd.exe). If using PowerShell, the JSON string may require different escaping rules to be parsed correctly.)
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:
- Fluentd official Docker image
- Fluentd official Docker image (Source)
- Docker Logging Driver and Fluentd
- Docker Logging via EFK (Elasticsearch + Fluentd + Kibana) Stack with Docker Compose
Also, refer to the following tutorials to learn how to collect data from various data sources:
- Basic Configuration
- Application Logs
- Examples