Traefik & Consul Catalog

Configuration Example

You can enable the Consul Catalog provider as detailed below:

File (YAML)

providers:
  consulCatalog: {}

File (TOML)

[providers.consulCatalog]

CLI

--providers.consulcatalog=true

Attaching tags to services:

- traefik.http.routers.my-router.rule=Host(`example.com`)

Configuration Options

requireConsistent

Forces the read to be fully consistent. Setting this option can be expensive due to an extra round-trip but prevents ever performing a stale read.

For more information, see the Consul documentation on consistency.

defaultRule

The default host rule for all services.

For a given service, if no routing rule was defined by a tag, it is defined by this defaultRule instead. The defaultRule must be set to a valid Go template, and can include sprig template functions. The service name can be accessed with the Name identifier, and the template has access to all the labels (i.e. tags beginning with the prefix) defined on this service.

The option can be overridden on an instance basis with the traefik.http.routers.{name-of-your-choice}.rule tag.

File (YAML)

providers:
  consulCatalog:
    defaultRule: "Host(`{{ .Name }}.{{ index .Labels \"customLabel\"}}`)"
    # ...

File (TOML)

[providers.consulCatalog]
  defaultRule = "Host(`{{ .Name }}.{{ index .Labels \"customLabel\"}}`)"
  # ...

CLI

--providers.consulcatalog.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.

constraints

The constraints option can be set to an expression that Traefik matches against the service tags to determine whether to create any route for that service. If none of the service tags match the expression, no route for that service is created. If the expression is empty, all detected services are included.

The expression syntax is based on the Tag(`tag`), and TagRegex(`tag`) functions, as well as the usual boolean logic, as shown in examples below.

Constraints Expression Examples

# Includes only services having the tag `a.tag.name=foo`
constraints = "Tag(`a.tag.name=foo`)"

# Excludes services having any tag `a.tag.name=foo`
constraints = "!Tag(`a.tag.name=foo`)"

# With logical AND.
constraints = "Tag(`a.tag.name`) && Tag(`another.tag.name`)"

# With logical OR.
constraints = "Tag(`a.tag.name`) || Tag(`another.tag.name`)"

# With logical AND and OR, with precedence set by parentheses.
constraints = "Tag(`a.tag.name`) && (Tag(`another.tag.name`) || Tag(`yet.another.tag.name`))"

# Includes only services having a tag matching the `a\.tag\.t.+` regular expression.
constraints = "TagRegex(`a\.tag\.t.+`)"

File (YAML)

providers:
  consulCatalog:
    constraints: "Tag(`a.tag.name`)"
    # ...

File (TOML)

[providers.consulCatalog]
  constraints = "Tag(`a.tag.name`)"
  # ...

CLI

--providers.consulcatalog.constraints="Tag(`a.tag.name`)"
# ...

For additional information, refer to Restrict the Scope of Service Discovery.

namespaces

The namespaces option defines the namespaces in which the consul catalog services will be discovered. When using the namespaces option, the discovered configuration object names will be suffixed as shown below:

<resource-name>@consulcatalog-<namespace>

Warning

• The namespaces option only works with Consul Enterprise, which provides the Namespaces feature.

• One should only define either the namespaces option or the namespace option.

File (YAML)

providers:
  consulCatalog:
    namespaces: 
      - "ns1"
      - "ns2"
    # ...

File (TOML)

[providers.consulCatalog]
  namespaces = ["ns1", "ns2"]
  # ...

CLI

--providers.consulcatalog.namespaces=ns1,ns2
# ...

Routing Configuration

See the dedicated section in routing.