Clarification on stateful workloads

[mr-karan]

Hi!

I am looking to send a PR for a Listmonk pack. It requires to run a PostgreSQL database as a dependency. What would be the best way to create volume/mount config blocks here? Should we assume a CSI plugin is used and create a volume resource in the pack? Or keep it simple and provide an example with host_volumes (Note: That also requires the user to enable them)

[RickyGrassmuck]

I think the best approach here would be to let the user configure this through variables and just set it up with the templating.

Something like this would probably be a good start. I personally think a CSI type would be a sane default for the variable declaration portion but I could be wrong.

Note: Threw this together on the fly so adjustments will probably be needed to get it to behave properly

Job Template

  group "example" {    
    volume "pg_data" {
      type      = [[ .listmonk.pg_volume.type | quote ]]
      source    = [[ .listmonk.pg_volume.source | quote ]]
      read_only   = false
      [[- if eq .listmonk.pg_volume.type "csi" -]]
      attachment_mode = [[ .listmonk.pg_volume.attachment_mode | quote ]]
      access_mode        = [[ .listmonk.pg_volume.access_mode | quote ]]
      mount_options {
        fs_type     = [[ .listmonk.pg_volume.mount_options.fs_type | quote ]]
        mount_flags = [[ .listmonk.pg_volume.mount_options.mount_flags | toPrettyJson ]]
      }
      [[- end -]]
    }
    task "example" {
      volume_mount {
        volume      = "pg_data"
        destination = [[ .listmonk.pg_volume.destination | quote ]]
      } 
    }
  }

variables.hcl

variable "pg_volume" {
  description = "Postgres Data Volume"
  type = object({
    type     = string
    source   = string
    destination   = string
    attachment_mode
    access_mode
    mount_options = object({
      fs_type  = string
      mount_flags = list(string)
    })
  })
  default =  {
      type                       = "host"
      source                   = "pg_data"
      read_only               = false
      attachment_mode = "file-system"
      access_mode        = "single-node-writer"
      mount_options {
        fs_type     = "ext4"
        mount_flags = ["rw"]
      }
    }
}