offtopic: ppg design decisions - encapsulation

offtopic: ppg design decisions - encapsulation

[Martin Langhoff]

[ Unashamedly offtopic... asking here because I like git design and
coding style, and ppg is drawing plenty of inspiration from the old
git shell scripts. Please kindly flame me privately... ]

ppg is a wrapper around git to maintain and distribute Puppet configs,
adding a few niceties.

Now, ppg will actuall manage two git repositories -- one for the
puppet configs, the second one for ferrying back the puppet run
results to the originating repo (were they get loaded in a puppet
dashboard server for cute webbased reporting). The puppet config repo
is a normally-behaved git repo. The "reports" repo is a bit of a hack
-- never used directly by the user, it will follow a store-and-forward
scheme, where I should trim old history or just use something other
than git.

So I see two possible repo layouts:

- "Transparent, nested"
 .git/ # holding puppet configs, allows direct use of git commands
 .git/reports.git # nested inside puppet configs repo

- "Mediated, parallel"
 .ppg/puppet.git # all git commands must be wrapped
 .ppg/reports.git

My laziness and laisses-faire take on things drives to to use the
transparent&nested approach. Let the user do anything in there
directly with git.

OTOH, the mediated approach allows for more complete support,
including sanity checks on commands that don't have hooks available. I
already have a /usr/bin/ppg wrapper, which I could use to wrap all git
commands, setting GIT_DIR=.ppg/puppet.git for all ops. It would force
ops to be from the top of the tree (unless I write explicit support)
and I would have to implement explicit. And it would break related
tools that are not mediated via /usr/bin/git (gitk!).

Written this way, it seems to be a minimal lazy approach vs DTRT.

Am I missing any important aspect or option? Thoughts?

cheers,



m
--
 martin.langhoff@gmail.com
 -  ask interesting questions
 - don't get distracted with shiny stuff  - working code first
 ~ http://docs.moodle.org/en/User:Martin_Langhoff

Re: offtopic: ppg design decisions - encapsulation

[John Keeping]

On Mon, May 06, 2013 at 11:34:28AM -0400, Martin Langhoff wrote:
> [ Unashamedly offtopic... asking here because I like git design and
> coding style, and ppg is drawing plenty of inspiration from the old
> git shell scripts. Please kindly flame me privately... ]
> 
> ppg is a wrapper around git to maintain and distribute Puppet configs,
> adding a few niceties.
> 
> Now, ppg will actuall manage two git repositories -- one for the
> puppet configs, the second one for ferrying back the puppet run
> results to the originating repo (were they get loaded in a puppet
> dashboard server for cute webbased reporting). The puppet config repo
> is a normally-behaved git repo. The "reports" repo is a bit of a hack
> -- never used directly by the user, it will follow a store-and-forward
> scheme, where I should trim old history or just use something other
> than git.

I'm not sure I fully understand what the reports are, but it sounds like
they are closely related to original configuration commits.  If that is
the case, have you considered using Git notes instead of a separate
repository?

Re: offtopic: ppg design decisions - encapsulation

[Martin Langhoff]

On Mon, May 6, 2013 at 11:53 AM, John Keeping <john@keeping.me.uk> wrote:
> I'm not sure I fully understand what the reports are, but it sounds like
> they are closely related to original configuration commits.  If that is
> the case, have you considered using Git notes instead of a separate
> repository?

Interesting suggestion! I read up on git-notes.

Yes, reports are closely related to a commit -- it's a lot of the
execution of puppet with that config on a client node. At the same
time, we have one report per change deployment, per client -- with
thousands of clients. So it will be a large dataset, and a transient
one -- I intend to use git as a store-and-forward mechanism for the
reports, and it is safe&sane to forget old reports.

I don't see much ease-of-expiry in the notes, so I guess I would have
to write that myself, which complicates things a bit :-)

cheers,


m
--
 martin.langhoff@gmail.com
 -  ask interesting questions
 - don't get distracted with shiny stuff  - working code first
 ~ http://docs.moodle.org/en/User:Martin_Langhoff