# Docker Agent

The Docker agent executes flow runs in individual Docker containers. This provides more isolation and control than the Local Agent, while still working well on a single machine.

# Requirements

The Docker agent requires a valid Prefect installation, as well as an active and accessible Docker Daemon. Before starting the Docker agent, you should check that you have Docker installed and running. The minimum supported Docker engine version is v20.10.0.

# Flow Configuration

The Docker Agent will deploy flows using either a UniversalRun (the default) or DockerRun run_config. Using a DockerRun object lets you customize the deployment environment for a flow (exposing env, image, etc...):

from prefect.run_configs import DockerRun

# Configure extra environment variables for this flow,
# and set a custom image
flow.run_config = DockerRun(
    env={"SOME_VAR": "VALUE"},
    image="example/image-name:with-tag"
)

See the DockerRun documentation for more information.

# Agent Configuration

The Docker agent can be started from the Prefect CLI as

prefect agent docker start

API Keys Cloud

When using Prefect Cloud, this will require a service account API key, see here for more information.

Below we cover a few common configuration options, see the CLI docs for a full list of options.

# Streaming Flow Run Logs

The Docker agent includes an option to stream logs from its running flows to the console, rather than relying on Prefect Cloud/Server to access these logs. This can be useful for debugging flow runs locally. To enable, use the --show-flow-logs flag:

prefect agent docker start --show-flow-logs

# Configuring Networking

To add all flow run containers to an existing docker network, you can use the --network flag.

prefect agent docker start --network my-network

# Mounting Volumes

To mount volumes in all flow run containers, you can use the --volume flag. This matches the docker CLI --volume flag for using Docker bind mounts. The flag can be provided multiple times to pass multiple volumes.

prefect agent docker start --volume /host/path:/container/path --volume /another/volume

# Disabling Image Pulling

The docker agent includes a --no-pull flag which disables its ability to pull non-local images. This can be useful in debugging scenarios (where you don't want to accidentally pull a remote image) or for extra security where you want to ensure only local images are used.

prefect agent docker start --no-pull

# Docker Daemon Address

The Docker agent will use the default Docker daemon address for your system ( npipe:////./pipe/docker_engine on Windows, unix://var/run/docker.sock on everything else). If you need to configure this manually, you can use the --base-url option:

prefect agent docker start --base-url unix://some/other/docker.sock