Docker Provider

Traefik can be configured to use Docker as a provider.

Docker

################################################################
# Docker Provider
################################################################
# Enable Docker Provider.
[docker]
# Docker server endpoint. Can be a tcp or a unix socket endpoint.
#
# Required
#
endpoint = "unix:///var/run/docker.sock"
# Default base domain used for the frontend rules.
# Can be overridden by setting the "traefik.domain" label on a container.
#
# Optional
#
domain = "docker.localhost"
# Enable watch docker changes.
#
# Optional
#
watch = true
# Override default configuration template.
# For advanced users :)
#
# Optional
#
# filename = "docker.tmpl"
# Override template version
# For advanced users :)
#
# Optional
# - "1": previous template version (must be used only with older custom templates, see "filename")
# - "2": current template version (must be used to force template version when "filename" is used)
#
# templateVersion = 2
# Expose containers by default in Traefik.
# If set to false, containers that don't have `traefik.enable=true` will be ignored.
#
# Optional
# Default: true
#
exposedByDefault = true
# Use the IP address from the binded port instead of the inner network one.
#
# In case no IP address is attached to the binded port (or in case 
# there is no bind), the inner network one will be used as a fallback.     
#
# Optional
# Default: false
#
usebindportip = true
# Use Swarm Mode services as data provider.
#
# Optional
# Default: false
#
swarmMode = false
# Polling interval (in seconds) for Swarm Mode.
#
# Optional
# Default: 15
#
swarmModeRefreshSeconds = 15
# Define a default docker network to use for connections to all containers.
# Can be overridden by the traefik.docker.network label.
#
# Optional
#
network = "web"
# Enable docker TLS connection.
#
# Optional
#
#  [docker.tls]
#  ca = "/etc/ssl/ca.crt"
#  cert = "/etc/ssl/docker.crt"
#  key = "/etc/ssl/docker.key"
#  insecureSkipVerify = true

To enable constraints see provider-specific constraints section.

Docker Swarm Mode

################################################################
# Docker Swarm Mode Provider
################################################################
# Enable Docker Provider.
[docker]
# Docker server endpoint.
# Can be a tcp or a unix socket endpoint.
#
# Required
# Default: "unix:///var/run/docker.sock"
#
# swarm classic (1.12-)
# endpoint = "tcp://127.0.0.1:2375"
# docker swarm mode (1.12+)
endpoint = "tcp://127.0.0.1:2377"
# Default base domain used for the frontend rules.
# Can be overridden by setting the "traefik.domain" label on a services.
#
# Optional
# Default: ""
#
domain = "docker.localhost"
# Enable watch docker changes.
#
# Optional
# Default: true
#
watch = true
# Use Docker Swarm Mode as data provider.
#
# Optional
# Default: false
#
swarmMode = true
# Define a default docker network to use for connections to all containers.
# Can be overridden by the traefik.docker.network label.
#
# Optional
#
network = "web"
# Override default configuration template.
# For advanced users :)
#
# Optional
#
# filename = "docker.tmpl"
# Override template version
# For advanced users :)
#
# Optional
# - "1": previous template version (must be used only with older custom templates, see "filename")
# - "2": current template version (must be used to force template version when "filename" is used)
#
# templateVersion = 2
# Expose services by default in Traefik.
#
# Optional
# Default: true
#
exposedByDefault = false
# Enable docker TLS connection.
#
# Optional
#
#  [docker.tls]
#  ca = "/etc/ssl/ca.crt"
#  cert = "/etc/ssl/docker.crt"
#  key = "/etc/ssl/docker.key"
#  insecureSkipVerify = true

To enable constraints see provider-specific constraints section.

Security Considerations

Security Challenge with the Docker Socket

Traefik requires access to the docker socket to get its dynamic configuration, by watching the Docker API through this socket.

Important

Depending on your context and your usage, accessing the Docker API without any restriction might be a security concern.

As explained on the Docker documentation: (Docker Daemon Attack Surface page):

[…] only **trusted** users should be allowed to control your Docker daemon […]

If the Traefik processes (handling requests from the outside world) is attacked, then the attacker can access the Docker (or Swarm Mode) backend.

Also, when using Swarm Mode, it is mandatory to schedule Traefik's containers on the Swarm manager nodes, to let Traefik accessing the Docker Socket of the Swarm manager node.

More information about Docker's security:

• KubeCon EU 2018 Keynote, Running with Scissors, from Liz Rice
• Don't expose the Docker socket (not even to a container)
• A thread on Stack Overflow about sharing the /var/run/docker.sock file
• To Dind or not to DinD

Workarounds

Improved Security

TraefikEE solves this problem by separating the control plane (connected to Docker) and the data plane (handling the requests).

Another possible workaround is to expose the Docker socket over TCP, instead of the default Unix socket file. It allows different implementation levels of the AAA (Authentication, Authorization, Accounting) concepts), depending on your security assessment:

• Authentication with Client Certificates as described in the "Protect the Docker daemon socket" page of Docker's documentation

• Authorization with the Docker Authorization Plugin Mechanism

• Accounting at networking level, by exposing the socket only inside a Docker private network, only available for Traefik.

• Accounting at container level, by exposing the socket on a another container than Traefik's. With Swarm mode, it allows scheduling of Traefik on worker nodes, with only the "socket exposer" container on the manager nodes.

• Accounting at kernel level, by enforcing kernel calls with mechanisms like SELinux, to only allows an identified set of actions for Traefik's process (or the "socket exposer" process).

Use the following ressources to get started:

• Traefik issue GH-4174 about security with Docker socket
• Inspecting Docker Activity with Socat
• Letting Traefik run on Worker Nodes
• Docker Socket Proxy from Tecnativa

Labels: overriding default behavior

Using Docker with Swarm Mode

If you use a compose file with the Swarm mode, labels should be defined in the deploy part of your service. This behavior is only enabled for docker-compose version 3+ (Compose file reference).

version: "3"
services:
  whoami:
    deploy:
      labels:
        traefik.docker.network: traefik

Required labels:

• traefik.frontend.rule
• traefik.port - Without this the debug logs will show this service is deliberately filtered out.
• traefik.docker.network - Without this a 504 may occur.

Troubleshooting

If service doesn't show up in the dashboard, check the debug logs to see if the port is missing: Filtering container without port, : port label is missing, …')

If 504 Gateway Timeout occurs and there are networks used, ensure that traefik.docker.network is defined. The complete name is required, meaning if the network is internal the name needs to be _.

Using Docker Compose

If you are intending to use only Docker Compose commands (e.g. docker-compose up --scale whoami=2 -d), labels should be under your service, otherwise they will be ignored.

version: "3"
services:
  whoami:
    labels:
      traefik.docker.network: traefik

On Containers

Labels can be used on containers to override default behavior.

[1] traefik.docker.network:

If a container is linked to several networks, be sure to set the proper network name (you can check with docker inspect ) otherwise it will randomly pick one (depending on how docker is returning them).

For instance when deploying docker stack from compose files, the compose defined networks will be prefixed with the stack name. Or if your service references external network use it's name instead.

[2] traefik.frontend.auth.basic.users=EXPR:

To create user:password pair, it's possible to use this command:

echo $(htpasswd -nb user password) | sed -e s/\$/\$\$/g.

The result will be user:apr19Cv/OMGj$$ZomWQzuQbL.3TRCS81A1g/, note additional symbol $ makes escaping.

[3] traefik.backend.loadbalancer.swarm:

If you enable this option, Traefik will use the virtual IP provided by docker swarm instead of the containers IPs. Which means that Traefik will not perform any kind of load balancing and will delegate this task to swarm.

It also means that Traefik will manipulate only one backend, not one backend per container.

Custom Headers

Security Headers

On containers with Multiple Ports (segment labels)

Segment labels are used to define routes to a container exposing multiple ports. A segment is a group of labels that apply to a port exposed by a container. You can define as many segments as ports exposed in a container.

Segment labels override the default behavior.

Custom Headers

Security Headers

Note

If a label is defined both as a container label and a segment label (for example traefik..port=PORT and traefik.port=PORT ), the segment label is used to defined the property (port in the example).

It's possible to mix container labels and segment labels, in this case container labels are used as default value for missing segment labels but no frontends are going to be created with the container labels.

More details in this example.

Warning

When running inside a container, Traefik will need network access through:

docker network connect

usebindportip

The default behavior of Traefik is to route requests to the IP/Port of the matching container. When setting usebindportip to true, you tell Traefik to use the IP/Port attached to the container's binding instead of the inner network IP/Port.

When used in conjunction with the traefik.port label (that tells Traefik to route requests to a specific port), Traefik tries to find a binding with traefik.port port to select the container. If it can't find such a binding, Traefik falls back on the internal network IP of the container, but still uses the traefik.port that is set in the label.

Below is a recap of the behavior of usebindportip in different situations.

Note

In the above table, ExtIp stands for "external IP found in the binding", IntIp stands for "internal network container's IP", ExtPort stands for "external Port found in the binding", and IntPort stands for "internal network container's port."