Having taken the inital hurdle of getting propellor running (cf. my last post in this forum), I am beginning to like propellor quite a lot. - This comes not too much as a surprise, as I am a Haskeller really. - I would love to use it for all my configuration needs, and to that end ditch ansible.

Propellor's biggest show stopper for me is this (maybe I am misunderstanding propellor?):

I can run

  propellor --spin myhost

from the command line, and all the tasks/properties that I have defined myhost to have beforehand will be executed/realized/configured.

Say eg. I haved defined (sorry for the bad formatting, seems I have to do it line by line to get the markdown look nice)

myhost :: Host
myhost = host "myhost"
         & os (System (Debian Testing) "amd64")
         & emacs
         & apt
emacs :: Property HasInfo
emacs = propertyList "install & configure emacs" $ props
        & Apt.installed ["emacs"
                        , "auto-complete-el"]
  apt :: Property HasInfo
apt = propertyList "apt update + upgrade" $ props
      & Apt.update
      & Apt.upgrade

Then running

  propellor --spin myhost

will make sure, that emacs is installed, and all my packages on myhost are up to date.

It does so every time I run propellor, but normally I install emacs only once (and I know it's installed), whereas the apt update+upgrade combo I would want to run every other day.

So what I would like is this: have just a minimal config for myhost, like this:

myhost :: Host
myhost = host "myhost"
         & os (System (Debian Testing) "amd64")

and then run a task (require a property ?) on myhost, somehow from the command line, like this

  propellor --spin myhost --task apt

Many other properties / installation steps I could run in this manner, like installing emacs initially

  propellor --spin myhost --task emacs

In ansible I can do this with playbooks:

  ansible-playbook -l myhost apt.yml

with some preconfigured playbook apt.yml that does just the apt update + upgrade task and nothing else. But I would have other tasks in other playbooks of course: I can install & configure emacs on myhost

  ansible-playbook -l myhost emacs.yml


Related to that (but maybe not strictly the same question):

I wouldn't mind writing my own haskell script that does the command line parsing (with optparse applicative eg): I could have options for

  --host (myhost/...)


  --task (emacs/apt/...)

and then just call into propellor. Unfortunately propellor's defaultMain does more than I want: gets the command line from processCmdLine.

So I tried to create my own otherMain (similar to defaultMain, but would let me do my own command line parsing):

  otherMain :: [Host] -> CmdLine -> IO ()

but then at some point just gave up: for one thing: things were getting complicated, because of all the indirection: the propellor command line tool recompiles itself (?), does all this git stuff etc.

And then: maybe I am approaching things in the wrong direction: maybe it's just not meant to be used that way (but ansible works fine for me in this regard)?

And I thought: I don't really want to start a major programming task just to get this thing working, the way that seems reasonable to me. Or maybe it's possible already, and I just don't know how to use it? (So I am stuck with ansible for the time being).

Still more or less related:

Say this otherMain function existed, that allowed me to to do my own command line parsing and just call propellor on some host with the one or the other task, I am not 100% what's the right way to ensure/require/execute such a task on a host:

above I am just using

   host & property

(from PropAccum), but maybe ensureProperty is better suited for that?

Also for the wish list: some CONFIG_FILE env variable that would allow me to keep my config.hs somewhere other than in ~/.propellor/config.hs

Anyway, thanks so far I would certainly want to switch to propellor completely.