Fluentd logging driver
The fluentd
logging driver sends container logs to the Fluentd collector as structured log data. Then, users can use any of the various output plugins of Fluentd to write these logs to various destinations.
In addition to the log message itself, the fluentd
log driver sends the following metadata in the structured log message:
Field | Description |
---|---|
container_id | The full 64-character container ID. |
container_name | The container name at the time it was started. If you use docker rename to rename a container, the new name is not reflected in the journal entries. |
source |
stdout or stderr
|
The docker logs
command is not available for this logging driver.
Usage
Some options are supported by specifying --log-opt
as many times as needed:
-
fluentd-address
: specifyhost:port
to connectlocalhost:24224
-
tag
: specify tag for fluentd message, which interpret some markup, ex{{.ID}}
,{{.FullID}}
or{{.Name}}
docker.{{.ID}}
Configure the default logging driver by passing the --log-driver
option to the Docker daemon:
docker daemon --log-driver=fluentd
To set the logging driver for a specific container, pass the --log-driver
option to docker run
:
docker run --log-driver=fluentd ...
Before using this logging driver, launch a Fluentd daemon. The logging driver connects to this daemon through localhost:24224
by default. Use the fluentd-address
option to connect to a different address.
docker run --log-driver=fluentd --log-opt fluentd-address=myhost.local:24224
If container cannot connect to the Fluentd daemon, the container stops immediately unless the fluentd-async-connect
option is used.
Options
Users can use the --log-opt NAME=VALUE
flag to specify additional Fluentd logging driver options.
fluentd-address
By default, the logging driver connects to localhost:24224
. Supply the fluentd-address
option to connect to a different address.
docker run --log-driver=fluentd --log-opt fluentd-address=myhost.local:24224
tag
By default, Docker uses the first 12 characters of the container ID to tag log messages. Refer to the log tag option documentation for customizing the log tag format.
labels and env
The labels
and env
options each take a comma-separated list of keys. If there is collision between label
and env
keys, the value of the env
takes precedence. Both options add additional fields to the extra attributes of a logging message.
fluentd-async-connect
Docker connects to Fluentd in the background. Messages are buffered until the connection is established.
Fluentd daemon management with Docker
About Fluentd
itself, see the project webpage and its documents.
To use this logging driver, start the fluentd
daemon on a host. We recommend that you use the Fluentd docker image. This image is especially useful if you want to aggregate multiple container logs on each host then, later, transfer the logs to another Fluentd node to create an aggregate store.
Testing container loggers
-
Write a configuration file (
test.conf
) to dump input logs:<source> @type forward </source> <match docker.**> @type stdout </match>
-
Launch Fluentd container with this configuration file:
$ docker run -it -p 24224:24224 -v /path/to/conf/test.conf:/fluentd/etc -e FLUENTD_CONF=test.conf fluent/fluentd:latest
-
Start one or more containers with the
fluentd
logging driver:$ docker run --log-driver=fluentd your/application
Please login to continue.