Documentation Grafana Loki Send data Docker driver

Docker driver client

Grafana Loki officially supports a Docker plugin that will read logs from Docker containers and ship them to Loki. The plugin can be configured to send the logs to a private Loki instance or Grafana Cloud.

Documentation on configuring the Loki Docker Driver can be found on the configuration page.

If you have any questions or issues using the Docker plugin, open an issue in the Loki repository.

Install the Docker driver client

The Docker plugin must be installed on each Docker host that will be running containers you want to collect logs from.

Run the following command to install the plugin, updating the release version if needed:

bash Copy

docker plugin install grafana/loki-docker-driver:2.9.2 --alias loki --grant-all-permissions

To check installed plugins, use the docker plugin ls command. Plugins that have started successfully are listed as enabled:

bash Copy

$ docker plugin ls

You should see output similar to the following:

bash Copy

ID                  NAME         DESCRIPTION           ENABLED
ac720b8fcfdb        loki         Loki Logging Driver   true

Once you have successfully installed the plugin you can configure it.

Upgrade the Docker driver client

The upgrade process involves disabling the existing plugin, upgrading, then re-enabling and restarting Docker:

bash Copy

docker plugin disable loki --force
docker plugin upgrade loki grafana/loki-docker-driver:2.9.2 --grant-all-permissions
docker plugin enable loki
systemctl restart docker

Uninstall the Docker driver client

To cleanly uninstall the plugin, disable and remove it:

bash Copy

docker plugin disable loki --force
docker plugin rm loki

Known Issue: Deadlocked Docker Daemon

The driver keeps all logs in memory and will drop log entries if Loki is not reachable and if the quantity of max_retries has been exceeded. To avoid the dropping of log entries, setting max_retries to zero allows unlimited retries; the driver will continue trying forever until Loki is again reachable. Trying forever may have undesired consequences, because the Docker daemon will wait for the Loki driver to process all logs of a container, until the container is removed. Thus, the Docker daemon might wait forever if the container is stuck.

The wait time can be lowered by setting loki-retries=2, loki-max-backoff=800ms, loki-timeout=1s and keep-file=true. This way the daemon will be locked only for a short time and the logs will be persisted locally when the Loki client is unable to re-connect.

To avoid this issue, use the Promtail Docker target or Docker service discovery.