# Traefik & Consul Catalog

A Story of Tags, Services & Instances
{: .subtitle }

![Consul Catalog](../assets/img/providers/consul.png)

Attach tags to your services and let Traefik do the rest!

## Configuration Examples

??? example "Configuring Consul Catalog & Deploying / Exposing Services"

    Enabling the consul catalog provider

    ```toml tab="File (TOML)"
    [providers.consulCatalog]
    ```

    ```yaml tab="File (YAML)"
    providers:
      consulCatalog: {}
    ```

    ```bash tab="CLI"
    --providers.consulcatalog=true
    ```

    Attaching tags to services

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

## Routing Configuration

See the dedicated section in [routing](../routing/providers/consul-catalog.md).

## Provider Configuration

### `refreshInterval`

_Optional, Default=15s_

Defines the polling interval.

```toml tab="File (TOML)"
[providers.consulCatalog]
  refreshInterval = "30s"
  # ...
```

```yaml tab="File (YAML)"
providers:
  consulCatalog:
    refreshInterval: 30s
    # ...
```

```bash tab="CLI"
--providers.consulcatalog.refreshInterval=30s
# ...
```

### `prefix`

_required, Default="traefik"_

The prefix for Consul Catalog tags defining Traefik labels.

```toml tab="File (TOML)"
[providers.consulCatalog]
  prefix = "test"
  # ...
```

```yaml tab="File (YAML)"
providers:
  consulCatalog:
    prefix: test
    # ...
```

```bash tab="CLI"
--providers.consulcatalog.prefix=test
# ...
```

### `requireConsistent`

_Optional, Default=false_

Forces the read to be fully consistent.

!!! note ""

    It is more expensive due to an extra round-trip but prevents ever performing a stale read.

    For more information, see the consul [documentation on consistency](https://www.consul.io/api-docs/features/consistency).

```toml tab="File (TOML)"
[providers.consulCatalog]
  requireConsistent = true
  # ...
```

```yaml tab="File (YAML)"
providers:
  consulCatalog:
    requireConsistent: true
    # ...
```

```bash tab="CLI"
--providers.consulcatalog.requireConsistent=true
# ...
```

### `stale`

_Optional, Default=false_

Use stale consistency for catalog reads.

!!! note ""

    This makes reads very fast and scalable at the cost of a higher likelihood of stale values.

    For more information, see the consul [documentation on consistency](https://www.consul.io/api-docs/features/consistency).

```toml tab="File (TOML)"
[providers.consulCatalog]
  stale = true
  # ...
```

```yaml tab="File (YAML)"
providers:
  consulCatalog:
    stale: true
    # ...
```

```bash tab="CLI"
--providers.consulcatalog.stale=true
# ...
```

### `cache`

_Optional, Default=false_

Use local agent caching for catalog reads.

```toml tab="File (TOML)"
[providers.consulCatalog]
  cache = true
  # ...
```

```yaml tab="File (YAML)"
providers:
  consulCatalog:
    cache: true
    # ...
```

```bash tab="CLI"
--providers.consulcatalog.cache=true
# ...
```

### `endpoint`

Defines the Consul server endpoint.

#### `address`

Defines the address of the Consul server.

_Optional, Default="127.0.0.1:8500"_

```toml tab="File (TOML)"
[providers.consulCatalog]
  [providers.consulCatalog.endpoint]
    address = "127.0.0.1:8500"
    # ...
```

```yaml tab="File (YAML)"
providers:
  consulCatalog:
    endpoint:
      address: 127.0.0.1:8500
    # ...
```

```bash tab="CLI"
--providers.consulcatalog.endpoint.address=127.0.0.1:8500
# ...
```

#### `scheme`

_Optional, Default=""_

Defines the URI scheme for the Consul server.

```toml tab="File (TOML)"
[providers.consulCatalog]
  [providers.consulCatalog.endpoint]
    scheme = "https"
    # ...
```

```yaml tab="File (YAML)"
providers:
  consulCatalog:
    endpoint:
      scheme: https
    # ...
```

```bash tab="CLI"
--providers.consulcatalog.endpoint.scheme=https
# ...
```

#### `datacenter`

_Optional, Default=""_

Defines the datacenter to use.
If not provided in Traefik, Consul uses the default agent datacenter.

```toml tab="File (TOML)"
[providers.consulCatalog]
  [providers.consulCatalog.endpoint]
    datacenter = "test"
    # ...
```

```yaml tab="File (YAML)"
providers:
  consulCatalog:
    endpoint:
      datacenter: test
    # ...
```

```bash tab="CLI"
--providers.consulcatalog.endpoint.datacenter=test
# ...
```

#### `token`

_Optional, Default=""_

Token is used to provide a per-request ACL token which overwrites the agent's default token.

```toml tab="File (TOML)"
[providers.consulCatalog]
  [providers.consulCatalog.endpoint]
    token = "test"
    # ...
```

```yaml tab="File (YAML)"
providers:
  consulCatalog:
    endpoint:
      token: test
    # ...
```

```bash tab="CLI"
--providers.consulcatalog.endpoint.token=test
# ...
```

#### `endpointWaitTime`

_Optional, Default=""_

Limits the duration for which a Watch can block.
If not provided, the agent default values will be used.

```toml tab="File (TOML)"
[providers.consulCatalog]
  [providers.consulCatalog.endpoint]
    endpointWaitTime = "15s"
    # ...
```

```yaml tab="File (YAML)"
providers:
  consulCatalog:
    endpoint:
      endpointWaitTime: 15s
    # ...
```

```bash tab="CLI"
--providers.consulcatalog.endpoint.endpointwaittime=15s
# ...
```

#### `httpAuth`

_Optional_

Used to authenticate the HTTP client using HTTP Basic Authentication.

##### `username`

_Optional, Default=""_

Username to use for HTTP Basic Authentication.

```toml tab="File (TOML)"
[providers.consulCatalog.endpoint.httpAuth]
  username = "test"
```

```yaml tab="File (YAML)"
providers:
  consulCatalog:
    endpoint:
      httpAuth:
        username: test
```

```bash tab="CLI"
--providers.consulcatalog.endpoint.httpauth.username=test
```

##### `password`

_Optional, Default=""_

Password to use for HTTP Basic Authentication.

```toml tab="File (TOML)"
[providers.consulCatalog.endpoint.httpAuth]
  password = "test"
```

```yaml tab="File (YAML)"
providers:
  consulCatalog:
    endpoint:
      httpAuth:
        password: test
```

```bash tab="CLI"
--providers.consulcatalog.endpoint.httpauth.password=test
```

#### `tls`

_Optional_

Defines TLS options for Consul server endpoint.

##### `ca`

_Optional_

`ca` is the path to the CA certificate used for Consul communication, defaults to the system bundle if not specified.

```toml tab="File (TOML)"
[providers.consulCatalog.endpoint.tls]
  ca = "path/to/ca.crt"
```

```yaml tab="File (YAML)"
providers:
  consulCatalog:
    endpoint:
      tls:
        ca: path/to/ca.crt
```

```bash tab="CLI"
--providers.consulcatalog.endpoint.tls.ca=path/to/ca.crt
```

##### `caOptional`

_Optional_

The value of `tls.caOptional` defines which policy should be used for the secure connection with TLS Client Authentication to Consul.

!!! warning ""

    If `tls.ca` is undefined, this option will be ignored, and no client certificate will be requested during the handshake. Any provided certificate will thus never be verified.

When this option is set to `true`, a client certificate is requested during the handshake but is not required. If a certificate is sent, it is required to be valid.

When this option is set to `false`, a client certificate is requested during the handshake, and at least one valid certificate should be sent by the client.

```toml tab="File (TOML)"
[providers.consulCatalog.endpoint.tls]
  caOptional = true
```

```yaml tab="File (YAML)"
providers:
  consulCatalog:
    endpoint:
      tls:
        caOptional: true
```

```bash tab="CLI"
--providers.consulcatalog.endpoint.tls.caoptional=true
```

##### `cert`

_Optional_

`cert` is the path to the public certificate to use for Consul communication.

When using this option, setting the `key` option is required.

```toml tab="File (TOML)"
[providers.consulCatalog.endpoint.tls]
  cert = "path/to/foo.cert"
  key = "path/to/foo.key"
```

```yaml tab="File (YAML)"
providers:
  consulCatalog:
    endpoint:
      tls:
        cert: path/to/foo.cert
        key: path/to/foo.key
```

```bash tab="CLI"
--providers.consulcatalog.endpoint.tls.cert=path/to/foo.cert
--providers.consulcatalog.endpoint.tls.key=path/to/foo.key
```

##### `key`

_Optional_

`key` is the path to the private key for Consul communication.

When using this option, setting the `cert` option is required.

```toml tab="File (TOML)"
[providers.consulCatalog.endpoint.tls]
  cert = "path/to/foo.cert"
  key = "path/to/foo.key"
```

```yaml tab="File (YAML)"
providers:
  consulCatalog:
    endpoint:
      tls:
        cert: path/to/foo.cert
        key: path/to/foo.key
```

```bash tab="CLI"
--providers.consulcatalog.endpoint.tls.cert=path/to/foo.cert
--providers.consulcatalog.endpoint.tls.key=path/to/foo.key
```

##### `insecureSkipVerify`

_Optional_

If `insecureSkipVerify` is `true`, the TLS connection to Consul accepts any certificate presented by the server regardless of the hostnames it covers.

```toml tab="File (TOML)"
[providers.consulCatalog.endpoint.tls]
  insecureSkipVerify = true
```

```yaml tab="File (YAML)"
providers:
  consulCatalog:
    endpoint:
      tls:
        insecureSkipVerify: true
```

```bash tab="CLI"
--providers.consulcatalog.endpoint.tls.insecureskipverify=true
```

### `exposedByDefault`

_Optional, Default=true_

Expose Consul Catalog services by default in Traefik.
If set to `false`, services that don't have a `traefik.enable=true` tag will be ignored from the resulting routing configuration.

For additional information, refer to [Restrict the Scope of Service Discovery](./overview.md#restrict-the-scope-of-service-discovery).

```toml tab="File (TOML)"
[providers.consulCatalog]
  exposedByDefault = false
  # ...
```

```yaml tab="File (YAML)"
providers:
  consulCatalog:
    exposedByDefault: false
    # ...
```

```bash tab="CLI"
--providers.consulcatalog.exposedByDefault=false
# ...
```

### `defaultRule`

_Optional, Default=```Host(`{{ normalize .Name }}`)```_

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](https://golang.org/pkg/text/template/),
and can include [sprig template functions](http://masterminds.github.io/sprig/).
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.

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

```yaml tab="File (YAML)"
providers:
  consulCatalog:
    defaultRule: "Host(`{{ .Name }}.{{ index .Labels \"customLabel\"}}`)"
    # ...
```

```bash tab="CLI"
--providers.consulcatalog.defaultRule="Host(`{{ .Name }}.{{ index .Labels \"customLabel\"}}`)"
# ...
```

### `constraints`

_Optional, Default=""_

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.

??? example "Constraints Expression Examples"

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

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

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

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

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

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

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

```yaml tab="File (YAML)"
providers:
  consulCatalog:
    constraints: "Tag(`a.tag.name`)"
    # ...
```

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

For additional information, refer to [Restrict the Scope of Service Discovery](./overview.md#restrict-the-scope-of-service-discovery).