Exclude some frontends in consul catalog

[minhdanh]

There are some services in consul such as nomad, nomad-client, etc. that I want to exclude from the auto discovered frontends by consul catalog backend. Currently is there a way to prohibit those frontends (and theirs corresponding backends) from being included by consul catalog?

[keis]

You can add a traefik.enable=false tag to a service to exclude it

[minhdanh]

Unfortunately Nomad, (and maybe some other services) registers itself with Consul without an option to specify a tag/label. So I think this is not a preferable way to exclude some system services from traefik.

[emilevauge]

I do see tags in Nomad : https://www.nomadproject.io/docs/jobspec/servicediscovery.html#tags

[minhdanh]

That's not what I'm talking about. I can assign the tag with a nomad job, but not with Nomad itself. As when bootstrapping a Nomad cluster, Nomad register itself with Consul, so that other Nomad agents can refer to this Nomad service by using nomad.service.consul:4747. I want to exclude the Nomad service, not Nomad jobs' services.

[emilevauge]

OK I see. Hum, then I don't see any way for traefik to filter those services... Any idea?

[minhdanh]

I'm thinking of something like this in consul catalog backend configuration:

exclude_services = "nomad,redis"

Which will exclude the specified services. It'll be nice if exclude_services also supports regex. But I'm not sure this is the best way possible.

[emilevauge]

In fact, there is already a way to do that, but it is not documented for now #479, we are waiting this issue #451 to be fixed to add documentation on constraints ;)

[minhdanh]

I see. That looks cool. So I would be able to use a constraints directive to specify which frontends should be included and excluded, right?

[emilevauge]

Yep, and it already works, but the toml config have to be refined.
You can use it with traefik --consulcatalog --consulcatalog.constraints="tag==traefik" and then add a traefik tag on all the services you want to expose in traefik.

[minhdanh]

Thank you.

[emilevauge]

Can we close this one?

[minhdanh]

Ok. Never mind. Closing.

[nhaumont]

Hi

I tried the solution you provided:

You can use it with traefik --consulcatalog --consulcatalog.constraints="tag==traefik" and then add a traefik tag on all the services you want to expose in traefik.

And I cannot make it work, every time I set the constraints, it excludes all the services even if I have some in consul which have the traefik label like:

  "ServiceTags":[
     "traefik"
  ],

I'm starting traefik with the docker image (docker run -t traefik -c /dev/null --web --consul --consulcatalog.constraints=tag==traefik --logLevel=DEBUG)

Thanks

[nhaumont]

Ok, I got it working, my mistake.
In consul, it has to be something like: "ServiceTags":["traefik.tags=traefik"]

[billykwooten]

@nhaumont That works perfectly in consul. Thanks!!

[bilke]

@nhaumont 's solutions works but I would like to use Consuls default tags such as http as a constraint. I think the syntax for defining the Traefik tag is a bit weird in contrast to just plain tags such as http

service {
        tags = ["traefik.tags=traefik", "http"]
        ...
}

@emilevauge Can I somehow configure consulCatalog to use simple tags? I played with the prefix-parameter but this did not help... Thanks!

[dduportal]

Hi @bilke , as Traefik v2.0 is currently worked on (alpha state), the behavior of the KV stores (as Consul Backends) might be subject to change, so stay tuned! You can track the work on the Kanban board on this repository (tab "Projects").