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hashicorp
HCL2: Support user defined blocks and importing other files
For compliance and consistency across jobs in a company, it's very useful to have a library of tasks/configuration that job submitters can invoke. Terraform has module system to enable such capability, though it may be an overkill for Nomad. Consider using Terraform approach or introduce a lightweight alternative.
Straw-man Proposal
Support include keyword that imports an external HCL file and embed a parsed version in-place. We can support passing variables and local (scoped to the file).
For example, if an organization standardized on nginx sidecar, then they can declare a template file like:
variable "image" {
default = "nginx:1.19"
}
task "nginx-sidecar" {
driver = "docker"
config { .... }
}
Then, to include that task, one can just add include "path/to/sidecar-nginx.hcl" {} with an option to set the image default: include "path/to/sidecar-nginx.hcl" { image = "nginx:1.18" }
More sophisticated module
A more complicated proposal may allow for defining a user defined block, allowing for multiple defined blocks in a file. For example, the above task can be declared
module "nginx_sidecar" {
variable "image" { default = "nginx:1.19" }
content {
task "nginx-sidecar" {
driver = "driver"
config { ... }
}
}
}
User can then invoke these modules and have the parser embed the content in-place, e.g. nginx_sidecar { image = "..." } to achieve the same effect as above. The CLI can search for these modules in files in current paths, or in a specific environment variables, or through import statements in file, or another mechanism.
and linking to prior art: https://pkg.go.dev/github.com/hashicorp/hcl2/ext/include
This would be highly appreceated. At the moment variable definitions are duplicated around multiple job-specifications. Having the possibility to declare them once and then include-them would simplify the maintenance of a bunch of job-specifications. See also https://github.com/angrycub/nomad_example_jobs/tree/main/HCL2/variable_jobs/env-vars
Folks, please use :+1: emojis rather than spamming notifications by adding comments. I promise we do consider them when prioritizing features.
