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 version is available for Fluentd image. Debian version is recommended officially since it has jemalloc support. However, the Alpine image is smaller.

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
2021-03-16 09:11:32 +0000 [info]: parsing config file is succeeded path="/fluentd/etc/fluentd.conf"
2021-03-16 09:11:32 +0000 [info]: gem 'fluentd' version '1.11.5'
2021-03-16 09:11:32 +0000 [warn]: define <match fluent.**> to capture fluentd logs in top level is deprecated. Use <label @FLUENT_LOG> instead
2021-03-16 09:11:32 +0000 [info]: using configuration file: <ROOT>
  <source>
    @type http
    port 9880
    bind "0.0.0.0"
  </source>
  <match **>
    @type stdout
  </match>
</ROOT>
2021-03-16 09:11:32 +0000 [info]: starting fluentd-1.11.5 pid=7 ruby="2.6.6"
2021-03-16 09:11:32 +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", "-p", "/fluentd/plugins", "--under-supervisor"]
2021-03-16 09:11:33 +0000 [info]: adding match pattern="**" type="stdout"
2021-03-16 09:11:33 +0000 [info]: adding source type="http"
2021-03-16 09:11:33 +0000 [warn]: #0 define <match fluent.**> to capture fluentd logs in top level is deprecated. Use <label @FLUENT_LOG> instead
2021-03-16 09:11:33 +0000 [info]: #0 starting fluentd worker pid=16 ppid=7 worker=0
2021-03-16 09:11:33 +0000 [info]: #0 fluentd worker is now running worker=0
2021-03-16 09:11:33.025408358 +0000 fluent.info: {"pid":16,"ppid":7,"worker":0,"message":"starting fluentd worker pid=16 ppid=7 worker=0"}
2021-03-16 09:11:33.026503372 +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
775a8e192f2b        fluent/fluentd:edge-debian   "tini -- /bin/entryp…"   About a minute ago   Up About a minute   5140/tcp, 24224/tcp, 0.0.0.0:9880->9880/tcp   tender_leakey

$ docker logs 775a8e192f2b | tail -n 1
2021-03-16 09:12:15.257351750 +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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