Consul-template - Service tag interpolation in key lookup

[Nick Wales]

I'm trying to iterate over a service with multiple tagged versions, grabbing a load balanced weight value from the key value store based on the tag and  putting that in the key request path but having no luck. 

The key/value path is "test_service/1.x/lb_weight" and so far the snippet looks like this, it returns what looks like a working template but I get the string rather than the K/V response in my haproxy config file.

 {{range $test_service := service "test_service"}}
      {{range $tags := .Tags}}
      {{$weight := print "{{key \"test_service/" $tags "/lb_weight\"}}"}}
        server {{$test_service.Name}} {{$test_service.Address}}:{{$test_service.Port}} weight {{$weight}}
      {{end}}
 {{end}}

Response:

    server test_service 172.28.11.165:45000 weight {{key "test_service/1.0/lb_weight"}}

    server test_service 172.28.11.165:45001 weight {{key "test_service/1.1/lb_weight"}}

I'm running consul-template 0.6.0, any help much appreciated!

[Seth Vargo]

Hi Nick,

Go's tempplating language does not permit nested evaluation like that. I think you want something like this instead:

 {{range $test_service := service "test_service"}}

  {{range $tags := .Tags}}

    {{$weight := key ($tag | printf "test_service/%s/lb_weight")}}

    server {{$test_service.Name}} {{$test_service.Address}}:{{$test_service.Port}} weight {{$weight}}

  {{end}}

 {{end}}

You still need to make a raw call to `key` in the top-level evaluation.

Best,

Seth

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[Nick Wales]

Excellent, that totally works.

Thanks for your help!