Configuring the Docker Driver

    The command can be configured to use a different logging driverthan the Docker daemon’s default with the --log-driver flag. Any options thatthe 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 GrafanaCloud, using a batch size of 400 entries and no more than 5 retries if a sendfails.

    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 setthe value of log-driver to loki:

    1. {
    2.   "log-driver": "loki"
    3. }

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

    After changing daemon.json, restart the Docker daemon for the changes to takeeffect. All containers from that host will then send logs to Loki.

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

    1. version: "3.7"
    2. services:
    3.   logger:
    4.     image: grafana/grafana
    5.     logging:
    6.       options:
    7.         loki-url: "https://<user_id>:<password>@logs-us-west1.grafana.net/loki/api/v1/push"

    You can then deploy your stack using:

    Or with docker-compose:

    1. docker-compose -f docker-compose.yaml up

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

    Labels

    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
    • container_name: the name of the container generating logs
    • swarm_stack, swarm_service: added when deploying from Docker Swarm.

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

    The following are all supported options that the Loki logging driver supports:

    Troubleshooting

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

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

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