Strange behavior when used with some nomad interpolation calling filesystem function

[nlko]

Hello,

I'm not fluent at all in go and go template and the worst of all I'm quite new to nomad but I found the following behavior strange.

I have a .nomad.tpl file for nomad pack with the following:

job "hello_pack" {
  … 
  group "app" {
    …
    task "server" {
      driver = "docker"
      …
      config {
        …
        volumes = ["${abspath(".")}/packs/hello_pack:/app"]
      }
    }
  }
}

The aim is to mount a relative folder. (I took my inspiration from there hashicorp/nomad#9369 (comment))

Result:

• nomad-pack complains when I try to do a nomad-pack run

! Failed To Parse Job Specification

	Error:   input.hcl:122,23-31: Error in function call; Call to function "abspath" failed: filesystem function disabled., and 1 other diagnostic(s)

• but when I render the final hcl file with nomad-pack render, the result is valid for nomad and so, the rendered job can be run with the nomad job run command.

The behavior seems odd to me (why in one case it's allowed and disallowed in the other?). I would expect the same result (both running).

Version numbers:

• Nomad v1.2.6 (a6c6b475db5073e33885377b4a5c733e1161020c)
• Nomad Pack v0.0.1-techpreview3 (568ac5e)

[jeteve]

I have a very similar question, but about including config file templates with the 'file' function.

My nomad pack template contains:

 template{
                destination = "local/some_conf.txt"
                data        = file("configs/some_conf.txt.tmpl")
            }

nomad-pack render renders that just fine, basically unchanged.

But when I want to deploy it:

nomad-pack plan --var=firstname=bob  .
! Failed To Parse Job Specification

    Error:   Unexpected response code: 400 (Failed to parse job: input.hcl:14,31-36: Error in function call; Call to function
"file" failed: filesystem function disabled.
input.hcl:14,31-36: Unsuitable value type; Unsuitable value: value must be known)

I guess something is missing here. Is there a way to send config files templates along with the job definition, so inclusions can work? Or is there a more idiomatic way of doing it?

[sofixa]

@jeteve to your question, you can do the following:

        data = <<EOP
        [[ fileContents (var "grafana_agent_configuration" .) ]]
        EOP

(fileContents puts in the contents of a file, and you need the heredoc(EOP) in case it's a multi-line file; I chose EOP for the heredoc to avoid conflicts with the more popular EOH/EOF/etc. which would conflict).

[josegonzalez]

Seems this is related to where the filesystem commands are processed. They now happen server-side, so are disabled because the extra files are not submitted. See this comment for more details.

That said, the fileContents template function isn't an exact replacement as it needs an absolute path to the files it is loading, and generally speaking there isn't a way to load a file relative to the pack file. I think thats probably the more common task here, shipping a large-ish config file with a nomad-pack for use in templating.

[josegonzalez]

@nlko I implemented a PR that provides functionality that might be useful in your case in #574.