Graylog Extended Format logging driver

Table of contents

The gelf logging driver is a convenient format that's understood by a number of tools such as Graylog, Logstash, and Fluentd. Many tools use this format.

In GELF, every log message is a dict with the following fields:

Version
Host (who sent the message in the first place)
Timestamp
Short and long version of the message
Any custom fields you configure yourself

Usage

To use the gelf driver as the default logging driver, set the log-driver and log-opt keys to appropriate values in the daemon.json file, which is located in /etc/docker/ on Linux hosts or C:\ProgramData\docker\config\daemon.json on Windows Server. For more about configuring Docker using daemon.json, see daemon.json.

The following example sets the log driver to gelf and sets the gelf-address option.

{
  "log-driver": "gelf",
  "log-opts": {
    "gelf-address": "udp://1.2.3.4:12201"
  }
}

Restart Docker for the changes to take effect.

Note
log-opts configuration options in the daemon.json configuration file must be provided as strings. Boolean and numeric values (such as the value for gelf-tcp-max-reconnect) must therefore be enclosed in quotes (").

You can set the logging driver for a specific container by setting the --log-driver flag when using docker container create or docker run:

$ docker run \
      --log-driver gelf --log-opt gelf-address=udp://1.2.3.4:12201 \
      alpine echo hello world

GELF options

The gelf logging driver supports the following options:

Option	Required	Description	Example value
`gelf-address`	required	The address of the GELF server. `tcp` and `udp` are the only supported URI specifier and you must specify the port.	`--log-opt gelf-address=udp://192.168.0.42:12201`
`gelf-compression-type`	optional	`UDP Only` The type of compression the GELF driver uses to compress each log message. Allowed values are `gzip`, `zlib` and `none`. The default is `gzip`. Note that enabled compression leads to excessive CPU usage, so it's highly recommended to set this to `none`.	`--log-opt gelf-compression-type=gzip`
`gelf-compression-level`	optional	`UDP Only` The level of compression when `gzip` or `zlib` is the `gelf-compression-type`. An integer in the range of `-1` to `9` (BestCompression). Default value is 1 (BestSpeed). Higher levels provide more compression at lower speed. Either `-1` or `0` disables compression.	`--log-opt gelf-compression-level=2`
`gelf-tcp-max-reconnect`	optional	`TCP Only` The maximum number of reconnection attempts when the connection drop. An positive integer. Default value is 3.	`--log-opt gelf-tcp-max-reconnect=3`
`gelf-tcp-reconnect-delay`	optional	`TCP Only` The number of seconds to wait between reconnection attempts. A positive integer. Default value is 1.	`--log-opt gelf-tcp-reconnect-delay=1`
`tag`	optional	A string that's appended to the `APP-NAME` in the `gelf` message. 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.	`--log-opt tag=mailer`
`labels`	optional	Applies when starting the Docker daemon. A comma-separated list of logging-related labels this daemon accepts. Adds additional key on the `extra` fields, prefixed by an underscore (`_`). Used for advanced log tag options.	`--log-opt labels=production_status,geo`
`labels-regex`	optional	Similar to and compatible with `labels`. A regular expression to match logging-related labels. Used for advanced log tag options.	`--log-opt labels-regex=^(production_status\|geo)`
`env`	optional	Applies when starting the Docker daemon. A comma-separated list of logging-related environment variables this daemon accepts. Adds additional key on the `extra` fields, prefixed by an underscore (`_`). Used for advanced log tag options.	`--log-opt env=os,customer`
`env-regex`	optional	Similar to and compatible with `env`. A regular expression to match logging-related environment variables. Used for advanced log tag options.	`--log-opt env-regex=^(os\|customer)`

Note
The gelf driver doesn't support TLS for TCP connections. Messages sent to TLS-protected inputs can silently fail.

Examples

This example configures the container to use the GELF server running at 192.168.0.42 on port 12201.

$ docker run -dit \
    --log-driver=gelf \
    --log-opt gelf-address=udp://192.168.0.42:12201 \
    alpine sh