Docker driver client configuration

Thu, 09 Apr 2026 02:28:18 +0000

Docker driver client configuration

The Docker daemon on each machine has a default logging driver and each container will use the default driver unless configured otherwise.

Installation

Before configuring the plugin, install or upgrade the Grafana Loki Docker Driver Client

Change the logging driver for a container

The docker run command can be configured to use a different logging driver than the Docker daemon’s default with the --log-driver flag. Any options that the logging driver supports can be set using the --log-opt <NAME>=<VALUE> flag. --log-opt can be passed multiple times for each option to be set.

The following command will start Grafana in a container and send logs to Grafana Cloud, using a batch size of 400 entries and no more than 5 retries if a send fails.

docker run --log-driver=loki \
    --log-opt loki-url="https://<user_id>:<password>@logs-us-west1.grafana.net/loki/api/v1/push" \
    --log-opt loki-retries=5 \
    --log-opt loki-batch-size=400 \
    grafana/grafana

Note
The Loki logging driver still uses the json-log driver in combination with sending logs to Loki, this is mainly useful to keep the docker logs command working. You can adjust file size and rotation using the respective log option max-size and max-file. Keep in mind that default values for these options are not taken from json-log configuration. You can deactivate this behavior by setting the log option no-file to true.

Change the default logging driver

If you want the Loki logging driver to be the default for all containers, change Docker’s daemon.json file (located in /etc/docker on Linux) and set the value of log-driver to loki:

{
  "debug": true,
  "log-driver": "loki"
}

Options for the logging driver can also be configured with log-opts in the daemon.json:

{
  "debug": true,
  "log-driver": "loki",
  "log-opts": {
    "loki-url": "https://<user_id>:<password>@logs-us-west1.grafana.net/loki/api/v1/push",
    "loki-batch-size": "400"
  }
}

Note
log-opt configuration options in daemon.json must be provided as

strings. Boolean and numeric values (such as the value for loki-batch-size in the example above) must therefore be enclosed in quotes (").

After changing daemon.json, restart the Docker daemon for the changes to take effect. All newly created containers from that host will then send logs to Loki via the driver.

Configure the logging driver for a Swarm service or Compose

You can also configure the logging driver for a swarm service directly in your compose file. This also applies for docker-compose:

version: "3.7"
services:
  logger:
    image: grafana/grafana
    logging:
      driver: loki
      options:
        loki-url: "https://<user_id>:<password>@logs-prod-us-central1.grafana.net/loki/api/v1/push"

You can then deploy your stack using:

docker stack deploy my_stack_name --compose-file docker-compose.yaml

Or with docker-compose:

docker-compose -f docker-compose.yaml up

Once deployed, the Grafana service will send its logs to Loki.

Note
Stack name and service name for each swarm service and project name and service name for each compose service are automatically discovered and sent as Loki labels, this way you can filter by them in Grafana.

Labels

Loki can receive a set of labels along with log line. These labels are used to index log entries and query back logs using LogQL stream selector.

By default, the Docker driver will add the following labels to each log line:

filename: where the log is written to on disk
host: the hostname where the log has been generated
swarm_stack, swarm_service: added when deploying from Docker Swarm.
compose_project, compose_service: added when deploying with Docker Compose.

Custom labels can be added using the loki-external-labels, loki-pipeline-stages, loki-pipeline-stage-file, labels, env, and env-regex options. See the next section for all supported options.

loki-external-labels have the default value of container_name={{.Name}}. If you have custom value for loki-external-labels then that will replace the default value, meaning you won’t have container_name label unless you explcity add it (e.g: loki-external-labels: "job=docker,container_name={{.Name}}".

Pipeline stages

While you can provide loki-pipeline-stage-file it can be hard to mount the configuration file to the driver root filesystem. This is why another option loki-pipeline-stages is available allowing you to pass a list of stages inlined. Pipeline stages are run at last on every lines.

The example docker-compose below configures 2 stages, one to extract level values and one to set it as a label:

version: "3"
services:
  grafana:
    image: grafana/grafana
    logging:
      driver: loki
      options:
        loki-url: http://host.docker.internal:3100/loki/api/v1/push
        loki-pipeline-stages: |
          - regex:
              expression: '(level|lvl|severity)=(?P<level>\w+)'
          - labels:
              level:
    ports:
      - "3000:3000"

Note
Note the loki-pipeline-stages: | letting you keep the indentation correct.

When using docker run you can also pass the value via a string parameter like such:

read -d '' stages << EOF
- regex:
     expression: '(level|lvl|severity)=(?P<level>\\\w+)'
- labels:
    level:
EOF

docker run --log-driver=loki \
    --log-opt loki-url="http://host.docker.internal:3100/loki/api/v1/push" \
    --log-opt loki-pipeline-stages="$stages" \
    -p 3000:3000 grafana/grafana

This is a bit more difficult as you need to properly escape bash special characters. (note \\\w+ for \w+)

Providing both loki-pipeline-stage-file and loki-pipeline-stages will cause an error.

Relabeling

You can use Prometheus relabeling configuration to modify labels discovered by the driver. The configuration must be passed as a YAML string like the pipeline stages.

Relabeling phase will happen only once per container and it is applied on the container metadata when it starts. So you can for example rename the labels that are only available during the starting of the container, not the labels available on log lines. Use pipeline stages instead.

For example the configuration below will rename the label swarm_stack and swarm_service to respectively namespace and service.

version: "3"
services:
  grafana:
    image: grafana/grafana
    logging:
      driver: loki
      options:
        loki-url: http://host.docker.internal:3100/loki/api/v1/push
        loki-relabel-config: |
          - action: labelmap
            regex: swarm_stack
            replacement: namespace
          - action: labelmap
            regex: swarm_(service)
    ports:
      - "3000:3000"

Supported log-opt options

To specify additional logging driver options, you can use the –log-opt NAME=VALUE flag.

Option	Required?	Default Value	Description
`loki-url`	Yes		Loki HTTP push endpoint.
`loki-external-labels`	No	`container_name={{.Name}}`	Additional label value pair separated by `,` to send with logs. The value is expanded with the Docker tag template format. (eg: `container_name={{.ID}}.{{.Name}},cluster=prod`)
`loki-timeout`	No	`10s`	The timeout to use when sending logs to the Loki instance. Valid time units are “ns”, “us” (or “µs”), “ms”, “s”, “m”, “h”.
`loki-batch-wait`	No	`1s`	The amount of time to wait before sending a log batch complete or not. Valid time units are “ns”, “us” (or “µs”), “ms”, “s”, “m”, “h”.
`loki-batch-size`	No	`1048576`	The maximum size of a log batch to send.
`loki-min-backoff`	No	`500ms`	The minimum amount of time to wait before retrying a batch. Valid time units are “ns”, “us” (or “µs”), “ms”, “s”, “m”, “h”.
`loki-max-backoff`	No	`5m`	The maximum amount of time to wait before retrying a batch. Valid time units are “ns”, “us” (or “µs”), “ms”, “s”, “m”, “h”.
`loki-retries`	No	`10`	The maximum amount of retries for a log batch. Setting it to `0` will retry indefinitely.
`loki-pipeline-stage-file`	No		The location of a pipeline stage configuration file (example). Pipeline stages allows to parse log lines to extract more labels, see associated documentation.
`loki-pipeline-stages`	No		The pipeline stage configuration provided as a string see pipeline stages and associated documentation.
`loki-relabel-config`	No		A Prometheus relabeling configuration allowing you to rename labels see relabeling.
`loki-tenant-id`	No		Set the tenant id (http header`X-Scope-OrgID`) when sending logs to Loki. It can be overridden by a pipeline stage.
`loki-tls-ca-file`	No		Set the path to a custom certificate authority.
`loki-tls-cert-file`	No		Set the path to a client certificate file.
`loki-tls-key-file`	No		Set the path to a client key.
`loki-tls-server-name`	No		Name used to validate the server certificate.
`loki-tls-insecure-skip-verify`	No	`false`*	Allow to skip tls verification.
`loki-proxy-url`	No		Proxy URL use to connect to Loki.
`no-file`	No	`false`*	Default is “false” and log files are created. Set to “true” to tell driver not to ever create log files on disk. However, this means you won’t be able to use `docker logs` on the container anymore. Use this setting if you don’t need to use `docker logs` or run with limited disk space.
`keep-file`	No	`false`*	Default is “false” and log files are removed once a container is stopped. Set to “true” to tell driver to keep json log files once a container is stopped.
`max-size`	No	-1	The maximum size of the log before it is rolled. A positive integer plus a modifier representing the unit of measure (k, m, or g). Defaults to -1 (unlimited). This is used by json-log required to keep the `docker log` command working.
`max-file`	No	1	The maximum number of log files that can be present. If rolling the logs creates excess files, the oldest file is removed. Only effective when max-size is also set. A positive integer. Defaults to 1.
`labels`	No		Comma-separated list of keys of labels, which should be included in message, if these labels are specified for container.
`env`	No		Comma-separated list of keys of environment variables to be included in message if they specified for a container.
`env-regex`	No		A regular expression to match logging-related environment variables. Used for advanced log label options. If there is collision between the label and env keys, the value of the env takes precedence. Both options add additional fields to the labels of a logging message.

*note:

Boolean values in the configuration file only accept the following string type:

Value	Accepted Values
true	`"1", "t", "T", "true", "TRUE", "True"`
false	`"0", "f", "F", "false", "FALSE", "False"`

Troubleshooting

Plugin logs can be found as docker daemon log. To enable debug mode refer to the Docker daemon documentation.

The standard output (stdout) of a plugin is redirected to Docker logs. Such entries are prefixed with plugin=.

To find out the plugin ID of the Loki logging driver, use docker plugin ls and look for the loki entry.

Depending on your system, location of Docker daemon logging may vary. Refer to Docker documentation for Docker daemon log location for your specific platform.

Docker driver client on Grafana Labs

Docker driver client configuration

Docker driver client configuration

Installation

Change the logging driver for a container

Change the default logging driver

Configure the logging driver for a Swarm service or Compose

Labels

Pipeline stages

Relabeling

Supported log-opt options

*note:

Troubleshooting