Traefik & Docker¶
A Story of Labels & Containers
Attach labels to your containers and let Traefik do the rest!
This provider works with Docker (standalone) Engine.
The Quick Start Uses Docker
If you have not already read it, maybe you would like to go through the quick start guide that uses the Docker provider.
Configuration Examples¶
Configuring Docker & Deploying / Exposing one Service
Enabling the docker provider
providers:
docker: {}
[providers.docker]
--providers.docker=true
Attaching labels to containers (in your docker compose file)
version: "3"
services:
my-container:
# ...
labels:
- traefik.http.routers.my-container.rule=Host(`example.com`)
Routing Configuration¶
When using Docker as a provider, Traefik uses container labels to retrieve its routing configuration.
See the list of labels in the dedicated routing section.
Routing Configuration with Labels¶
By default, Traefik watches for container level labels on a standalone Docker Engine.
When using Docker Compose, labels are specified by the directive
labels
from the
"services" objects.
Not Only Docker
Please note that any tool like Nomad, Terraform, Ansible, etc. that is able to define a Docker container with labels can work with Traefik and the Docker provider.
Port Detection¶
Traefik retrieves the private IP and port of containers from the Docker API.
Port detection for private communication works as follows:
- If a container exposes a single port, then Traefik uses this port.
- If a container exposes multiple ports,
then Traefik uses the lowest port. E.g. if
80
and8080
are exposed, Traefik will use80
. - If a container does not expose any port, or the selection from multiple ports does not fit,
then you must manually specify which port Traefik should use for communication
by using the label
traefik.http.services.<service_name>.loadbalancer.server.port
(Read more on this label in the dedicated section in routing).
Host networking¶
When exposing containers that are configured with host networking, the IP address of the host is resolved as follows:
- try a lookup of
host.docker.internal
- if the lookup was unsuccessful, try a lookup of
host.containers.internal
, (Podman equivalent ofhost.docker.internal
) - if that lookup was also unsuccessful, fall back to
127.0.0.1
On Linux, for versions of Docker older than 20.10.0, for host.docker.internal
to be defined, it should be provided
as an extra_host
to the Traefik container, using the --add-host
flag. For example, to set it to the IP address of
the bridge interface (docker0
by default): --add-host=host.docker.internal:172.17.0.1
IPv4 && IPv6¶
When using a docker stack that uses IPv6, Traefik will use the IPv4 container IP before its IPv6 counterpart. Therefore, on an IPv6 Docker stack, Traefik will use the IPv6 container IP.
Docker API Access¶
Traefik requires access to the docker socket to get its dynamic configuration.
You can specify which Docker API Endpoint to use with the directive endpoint
.
Security Note
Accessing the Docker API without any restriction is a security concern: If Traefik is attacked, then the attacker might get access to the underlying host.
As explained in the Docker Daemon Attack Surface documentation:
Quote
[...] only trusted users should be allowed to control your Docker daemon [...]
Solutions
Expose the Docker socket over TCP or SSH, 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 "Protect the Docker daemon socket."
- Authorize and filter requests to restrict possible actions with the TecnativaDocker Socket Proxy.
- 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.
- 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).
- SSH public key authentication (SSH is supported with Docker > 18.09)
More Resources and Examples
- "Paranoid about mounting /var/run/docker.sock?"
- Traefik and Docker: A Discussion with Docker Captain, Bret Fisher
- 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
- 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
Provider Configuration¶
endpoint
¶
Required, Default="unix:///var/run/docker.sock"
See the Docker API Access section for more information.
Using the docker.sock
The docker-compose file shares the docker sock with the Traefik container
version: '3'
services:
traefik:
image: traefik:v3.1 # The official v3 Traefik docker image
ports:
- "80:80"
volumes:
- /var/run/docker.sock:/var/run/docker.sock
We specify the docker.sock in traefik's configuration file.
providers:
docker:
endpoint: "unix:///var/run/docker.sock"
# ...
[providers.docker]
endpoint = "unix:///var/run/docker.sock"
# ...
--providers.docker.endpoint=unix:///var/run/docker.sock
# ...
Using SSH
Using Docker 18.09+ you can connect Traefik to daemon using SSH. We specify the SSH host and user in Traefik's configuration file. Note that if the server requires public keys for authentication, you must have them accessible for the user running Traefik.
providers:
docker:
endpoint: "ssh://[email protected]:2022"
# ...
[providers.docker]
endpoint = "ssh://[email protected]:2022"
# ...
--providers.docker.endpoint=ssh://[email protected]:2022
# ...
providers:
docker:
endpoint: "unix:///var/run/docker.sock"
[providers.docker]
endpoint = "unix:///var/run/docker.sock"
--providers.docker.endpoint=unix:///var/run/docker.sock
useBindPortIP
¶
Optional, Default=false
Traefik routes requests to the IP/port of the matching container.
When setting useBindPortIP=true
, you tell Traefik to use the IP/Port attached to the container's binding instead of its inner network IP/Port.
When used in conjunction with the traefik.http.services.<name>.loadbalancer.server.port
label (that tells Traefik to route requests to a specific port),
Traefik tries to find a binding on port traefik.http.services.<name>.loadbalancer.server.port
.
If it cannot find such a binding, Traefik falls back on the internal network IP of the container,
but still uses the traefik.http.services.<name>.loadbalancer.server.port
that is set in the label.
Examples of usebindportip
in different situations.
port label | Container's binding | Routes to |
---|---|---|
- | - | IntIP:IntPort |
- | ExtPort:IntPort | IntIP:IntPort |
- | ExtIp:ExtPort:IntPort | ExtIp:ExtPort |
LblPort | - | IntIp:LblPort |
LblPort | ExtIp:ExtPort:LblPort | ExtIp:ExtPort |
LblPort | ExtIp:ExtPort:OtherPort | IntIp:LblPort |
LblPort | ExtIp1:ExtPort1:IntPort1 & ExtIp2:LblPort:IntPort2 | ExtIp2:LblPort |
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"IntPort
stands for "internal network container's port."
providers:
docker:
useBindPortIP: true
# ...
[providers.docker]
useBindPortIP = true
# ...
--providers.docker.useBindPortIP=true
# ...
exposedByDefault
¶
Optional, Default=true
Expose containers by default through Traefik.
If set to false
, containers that do not have a traefik.enable=true
label are ignored from the resulting routing configuration.
For additional information, refer to Restrict the Scope of Service Discovery.
providers:
docker:
exposedByDefault: false
# ...
[providers.docker]
exposedByDefault = false
# ...
--providers.docker.exposedByDefault=false
# ...
network
¶
Optional, Default=""
Defines a default docker network to use for connections to all containers.
This option can be overridden on a per-container basis with the traefik.docker.network
label.
providers:
docker:
network: test
# ...
[providers.docker]
network = "test"
# ...
--providers.docker.network=test
# ...
defaultRule
¶
Optional, Default=Host(`{{ normalize .Name }}`)
The defaultRule
option defines what routing rule to apply to a container if no rule is defined by a label.
It must be a valid Go template,
and can use sprig template functions.
The container name can be accessed with the ContainerName
identifier.
The service name can be accessed with the Name
identifier.
The template has access to all the labels defined on this container with the Labels
identifier.
providers:
docker:
defaultRule: "Host(`{{ .Name }}.{{ index .Labels \"customLabel\"}}`)"
# ...
[providers.docker]
defaultRule = "Host(`{{ .Name }}.{{ index .Labels \"customLabel\"}}`)"
# ...
--providers.docker.defaultRule=Host(`{{ .Name }}.{{ index .Labels \"customLabel\"}}`)
# ...
Default rule and Traefik service
The exposure of the Traefik container, combined with the default rule mechanism, can lead to create a router targeting itself in a loop. In this case, to prevent an infinite loop, Traefik adds an internal middleware to refuse the request if it comes from the same router.
httpClientTimeout
¶
Optional, Default=0
Defines the client timeout (in seconds) for HTTP connections. If its value is 0
, no timeout is set.
providers:
docker:
httpClientTimeout: 300
# ...
[providers.docker]
httpClientTimeout = 300
# ...
--providers.docker.httpClientTimeout=300
# ...
watch
¶
Optional, Default=true
Watch Docker events.
providers:
docker:
watch: false
# ...
[providers.docker]
watch = false
# ...
--providers.docker.watch=false
# ...
constraints
¶
Optional, Default=""
The constraints
option can be set to an expression that Traefik matches against the container labels to determine whether
to create any route for that container. If none of the container labels match the expression, no route for that container is
created. If the expression is empty, all detected containers are included.
The expression syntax is based on the Label("key", "value")
, and LabelRegex("key", "value")
functions,
as well as the usual boolean logic, as shown in examples below.
Constraints Expression Examples
# Includes only containers having a label with key `a.label.name` and value `foo`
constraints = "Label(`a.label.name`, `foo`)"
# Excludes containers having any label with key `a.label.name` and value `foo`
constraints = "!Label(`a.label.name`, `value`)"
# With logical AND.
constraints = "Label(`a.label.name`, `valueA`) && Label(`another.label.name`, `valueB`)"
# With logical OR.
constraints = "Label(`a.label.name`, `valueA`) || Label(`another.label.name`, `valueB`)"
# With logical AND and OR, with precedence set by parentheses.
constraints = "Label(`a.label.name`, `valueA`) && (Label(`another.label.name`, `valueB`) || Label(`yet.another.label.name`, `valueC`))"
# Includes only containers having a label with key `a.label.name` and a value matching the `a.+` regular expression.
constraints = "LabelRegex(`a.label.name`, `a.+`)"
For additional information, refer to Restrict the Scope of Service Discovery.
providers:
docker:
constraints: "Label(`a.label.name`,`foo`)"
# ...
[providers.docker]
constraints = "Label(`a.label.name`,`foo`)"
# ...
--providers.docker.constraints=Label(`a.label.name`,`foo`)
# ...
tls
¶
Optional
Defines the TLS configuration used for the secure connection to Docker.
ca
¶
Optional
ca
is the path to the certificate authority used for the secure connection to Docker,
it defaults to the system bundle.
providers:
docker:
tls:
ca: path/to/ca.crt
[providers.docker.tls]
ca = "path/to/ca.crt"
--providers.docker.tls.ca=path/to/ca.crt
cert
¶
cert
is the path to the public certificate used for the secure connection to Docker.
When using this option, setting the key
option is required.
providers:
docker:
tls:
cert: path/to/foo.cert
key: path/to/foo.key
[providers.docker.tls]
cert = "path/to/foo.cert"
key = "path/to/foo.key"
--providers.docker.tls.cert=path/to/foo.cert
--providers.docker.tls.key=path/to/foo.key
key
¶
Optional
key
is the path to the private key used for the secure connection Docker.
When using this option, setting the cert
option is required.
providers:
docker:
tls:
cert: path/to/foo.cert
key: path/to/foo.key
[providers.docker.tls]
cert = "path/to/foo.cert"
key = "path/to/foo.key"
--providers.docker.tls.cert=path/to/foo.cert
--providers.docker.tls.key=path/to/foo.key
insecureSkipVerify
¶
Optional, Default=false
If insecureSkipVerify
is true
, the TLS connection to Docker accepts any certificate presented by the server regardless of the hostnames it covers.
providers:
docker:
tls:
insecureSkipVerify: true
[providers.docker.tls]
insecureSkipVerify = true
--providers.docker.tls.insecureSkipVerify=true
allowEmptyServices
¶
Optional, Default=false
If the parameter is set to true
,
any servers load balancer defined for Docker containers is created
regardless of the healthiness of the corresponding containers.
It also then stays alive and responsive even at times when it becomes empty,
i.e. when all its children containers become unhealthy.
This results in 503
HTTP responses instead of 404
ones,
in the above cases.
providers:
docker:
allowEmptyServices: true
[providers.docker]
allowEmptyServices = true
--providers.docker.allowEmptyServices=true
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