On Fri, Jun 18, 2021 at 4:26 PM Antony Stone
<[email protected]> wrote:
>
> On Friday 18 June 2021 at 23:10:46, jane p wrote:
>

> If you install a second time (with the same playbook) you want no further
> changes to be made, because what needed to be installed has already been
> instealled.
>
> If you update, you want the system to be updated (again, pretty obvious).
>

It is not trivial to distinguish between 'install a second time' and 'update'.
When the playbook starts, it is not known whether there are any
changes, and which specific changes have been made.

> If you update a second time (with the same playbook) you want no further
> changes to be made, because the system has already been updated, nothing
> further needs updating; the system should be left as it is.
>

Installing for the first time and updating-in-place may not be identical.
Consider a system that involves a web server.  On initial install the
server is started at the end, after all the apps are installed.
On subsequent update the server is already running.  Should the web
server be reloaded?  If apps are updated, then yes, if not, then not
necessarily.

Encoding the dependency for each app update to web server reload is
complexity of the system expressed in Ansible.
Not encoding the dependency for each update, and reloading the web
server in all cases is breaking the 'no state changes if nothing got
updated' requirement at least some of the time.

> What you would like to see, or what example can you give, as a "simple
> implementation" which does not leave the target system in the same state after
> every run?
>
I think leaving the target system in the same state after every run is
essential.
The question is about whether state changes within the run are allowed.

>
> Antony.
>
> --
> "Have you been drinking brake fluid again?  I think you're addicted to the
> stuff."
>
> "No, no, it's alright - I can stop any time I want to."
>
>                                                    Please reply to the list;
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