Feedback from a new charm author

[Charles Butler]

Greetings Dean,

First of all, great feedback. Thank you for posting this to the community
list so others can learn from your experience.

I'll attempt to address your concerns corresponding to the numbers they
were posted under.

1. Centos series charms, I haven't done a lot of work in this department,
but I do know that centos series charms do work, at least, under the
MAAS provider. This should be true for the other cloud providers but I'll
need to confirm with the core devs that this is the case, as centos support
was contributed by our partners over at Cloud Base Solutions.

2. This is a limitation of subordinates, that they must only co-locate with
the same series. You can define a multi-series charm, but once the
subordinate has been related to a series, i believe it will then be locked
to the series it was originally related to. I would need to run a
simulation to disprove that statement, as I haven't gotten my hands very
dirty with multi-series subordinates.

3.  It's expected that the subordinate itself would control the exposing of
the website, as its managing the workload. Any other scenario would need to
be coordinated with the principal charm and the principal charm would have
to perform those actions. It may be obtuse to do it this way, however, as
it's not obvious where the encapsulation begins/ends with this pattern. I'm
happy to take a look if you link the code in question.


4. Removing the entire application bundle does sound like an interesting
idea, but it's not something we've explored to date. I would highly
recommend filing a bug for this functionality so we can discuss it and get
it on the roadmap.

Thanks and all the best,

Charles



Charles Butler <charles.butler at canonical.com> - Juju Charmer
Come see the future of modeling your datacenter: http://jujucharms.com

On Mon, Dec 5, 2016 at 10:21 AM, Dean Maniatis <dean.maniatis at gmail.com>
wrote:

> Hello,
>
> I'm a new charm author trying to learn the basics and decided to start
> with a simple bash template. I'm working on porting netdata
> <https://github.com/firehol/netdata> as a subordinate charm which is a
> lightweight real-time performance and health monitoring tool. On my first charm
> revision <https://github.com/deanmaniatis/netdata-charm> i managed to
> deploy it and test it with Xenial and Trusty both on LXD and AWS. I have
> identified the following challenges/questions and since i couldn't find any
> information from docs i decided to post here. Some maybe more related to
> feature requests than actual questions so please treat the following as a
> mixed feedback from a newbie.
>
>
> 1. How to test centos7 series? The upstream developer has put a lot of
> effort to support all major Linux distributions but i can't seem to be able
> to find any information regarding "charming" in regards with Centos7. After
> some quick research it seems that currently centos7 image is not supported
> in either AWS or localhost provider
> <https://bugs.launchpad.net/juju/+bug/1495978>. In addition, it seems
> there are no centos7 charms to look into their code nor even a simple blank
> centos7 charm to be used as a sandbox (similar to the ubuntu charm).
>
> 2. When i first deployed my subordinate charm i couldn't figure why i was
> able to relate it to only to a few charms and not all available on the
> canvas. Later i understood that i have to deploy at least one for each
> series which somehow doesn't provide this really cool user experience of
> application modeling, i.e. deploy a single subordinate charm and during
> relation let the system/charm code handle the intricate details and provide
> meaningful message in case the relation is not feasible, e.g. this charm is
> not supported for this series. There is an informative message when using
> CLI but on the GUI it simply grays out the target charm and it is not
> really clear why that's not possible.
>
> 3. When a subordinate charm enables a new service on the principal charm
> shouldn't that service be listed under the `Expose application` GUI
> section? For example my charm enables a web UI dashboard on port 19999 so i
> would expect that to be added to whatever other service is listed under the
> principal charm. I've define this service on metadata.yaml with `provides:
> website: interface: http` and with `open-port 19999` on install hook but
> doesn't seem to be working. What am i doing wrong?
>
> 4.I can easily deploy an application bundle with one command but the
> opposite is not available except manually removing each service or
> destroying completely the model. Shouldn't `juju remove kubernetes-core`
> just work?
>
>
> Dean
>
>
>
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