Consul-template: index on service

[bryanlarsen]

Suppose I would like to get the IP address of any consul agent. I would expect something like this to work:

 {{ index (service "consul") 0 }}

What am I doing wrong? Thanks.

[sethvargo]

@bryanlarsen what is the use case here? Any reason you couldn't do something like:

service("consul")[0].IP

You are definitely opening yourself up to a panic there though...

[bryanlarsen]

Use case: starting registrator (and similar apps), which take as their arguments a single consul URL.

I tried what you suggest (surrounded by {{}}) and I get: [ERR] template: out:1: unexpected "(" in operand; missing space?. Adding spaces judiciously will get me past that but I can't get past unexpected "[" in operand; missing space?

The reason I'm trying 'index' is because that's what is mentioned in the text/template package documentation, there's no mention of a [] operator.

In my vagrant test box there's only a single consul running, so http://{{ range service "consul-8500" }}{{ .Address }}:{{ .Port }}{{ end }} works fine. However, there will presumably be more than one consul running in a production environment, so I assume that would produce a very strange URL in that situation.

As far as the panic, this appears to work, and should prevent the panic.

{{ if gt ( len ( service "consul-8500" ) ) 0 }}

thanks for your help!

[sethvargo]

Awesome!

[bryanlarsen]

Sorry, the main issue hasn't been solved. I think I have a solution for the 'panic problem you raised', but I still cannot get the address or port of a single service.

[sethvargo]

{{range $index, $element := service "consul"}}
{{if $index == 0}}{{.IP}}{{end}}
{{end}}

There's also the index function:

index
    Returns the result of indexing its first argument by the
    following arguments. Thus "index x 1 2 3" is, in Go syntax,
    x[1][2][3]. Each indexed item must be a map, slice, or array.

[bryanlarsen]

That doesn't work, but this does:

{{range $index, $element := service "consul"}}
{{if eq $index 0}}{{.Address}}{{end}}
{{end}}

Thanks!

Also, the index function is what I was trying originally, that didn't work.

[blalor]

I also ran across this recently. I'd like to know why the index function (pipeline?) doesn't work…