Re: database-relation-join not invoked

[James Page]

Hi Giuseppe

On Thu, 25 May 2017 at 18:00 Giuseppe Attardi 
wrote:

> I have written a charm for OpenStack Gnocchi.
>

Firstly its great that you've started work on a Gnocchi charm; this is on
the TODO list for the OpenStack Charms project for the current development
cycle and it would be great if we can converge your work with the plans we
already have!


> The service requires a postgresql database relation.
>
> The start hook fails, of course, because the relation is not set.
>
> I expected that, but I expected that when I issue
>
> juju add-relation gnocchi postgresql:db
>
> it will invoke the database-relation-joined hook, which does set the
> required parameter and then start would work.
> However the hook is not invoked: as a sanity check I set a juju-log
> message in it and it does not run at all.
>
> Is it correct to assume that add-relation will always trigger
> database-relation-join?
>

Yes that is correct; the addition of a unit to a relation will result in
its joined hook being executed.

A second question, I would like to avoid to start the service until the
> relation has been joined.
> What is the best way to test for the relation to be present?
>

I'm also guessing that you'll want to wait until the remote database
application has provided credentials, the database has been synced with a
schema and that you have a full storage backed for metric storage such as
ceph.

This all becomes a whole lot easier by using the reactive charms framework
[0], where each of the dependent sets of configuration (database, ceph,
keystone etc..) would be managed via states; once the state for all of the
datasets is available, its possible to fully configure the service and
start it up.

We also have some templates for 'charm create' which you can use to get you
started with an OpenStack style charm like Gnocchi [1] which will do alot
of the boilerplate installation and configuration for you using the
charms.openstack python module.

If you can I'd suggest you drop into #openstack-charms on Freenode IRC and
we can chat further!

Cheers

James

[0] https://jujucharms.com/docs/stable/developer-layers
[1] https://docs.openstack.org/developer/charm-guide/new-api-charm.html
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Re: database-relation-join not invoked

[John Meinel]

It depends if your hook goes into 'error' state or 'blocked'.
Error should generally be avoided because it is a signal to Juju that you
can no longer make forward progress (generally meant to mean there is a
logic bug/typo/etc in your charm). With Error Juju may retry the hook that
failed but it will not run other hooks until error is cleared (juju
resolved)

Using 'status-set blocked [message]' you can report to the user that you
are missing a relation, but Juju will continue to fire other hooks as
normal.

John
=:->

On May 25, 2017 21:00, "Giuseppe Attardi"  wrote:

> I have written a charm for OpenStack Gnocchi.
> The service requires a postgresql database relation.
>
> The start hook fails, of course, because the relation is not set.
>
> I expected that, but I expected that when I issue
>
> juju add-relation gnocchi postgresql:db
>
> it will invoke the database-relation-joined hook, which does set the
> required parameter and then start would work.
> However the hook is not invoked: as a sanity check I set a juju-log
> message in it and it does not run at all.
>
> Is it correct to assume that add-relation will always trigger
> database-relation-join?
>
> A second question, I would like to avoid to start the service until the
> relation has been joined.
> What is the best way to test for the relation to be present?
>
> I tried with
>
> db=`relation-get -r database host`
>
> but it fails with:
>
> INFO start error: invalid value "database" for flag -r: invalid
> relation id
>
> I am using juju-2.1.2
>
> Thanks for the help.
>
> — Beppe Attardi
> --
> Juju mailing list
> Juju@lists.ubuntu.com
> Modify settings or unsubscribe at: https://lists.ubuntu.com/
> mailman/listinfo/juju
>
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Re: database-relation-join not invoked

[Tim Van Steenburgh]

On Thu, May 25, 2017 at 12:59 PM, Giuseppe Attardi  wrote:

> I have written a charm for OpenStack Gnocchi.
> The service requires a postgresql database relation.
>
> The start hook fails, of course, because the relation is not set.
>
> I expected that, but I expected that when I issue
>
> juju add-relation gnocchi postgresql:db
>
> it will invoke the database-relation-joined hook, which does set the
> required parameter and then start would work.
> However the hook is not invoked: as a sanity check I set a juju-log
> message in it and it does not run at all.
>
> Is it correct to assume that add-relation will always trigger
> database-relation-join?
>

Yes it will. Assuming your relation is named 'database', then the
database-relation-joined will be triggered when that relation is
established. For more help debugging you may need to post a link to your
code.


> A second question, I would like to avoid to start the service until the
> relation has been joined.
> What is the best way to test for the relation to be present?
>

You should start the service in the database-relation-changed hook handler,
once you have received all necessary relation data.


>
> I tried with
>
> db=`relation-get -r database host`
>
> but it fails with:
>
> INFO start error: invalid value "database" for flag -r: invalid
> relation id
>
> I am using juju-2.1.2
>
> Thanks for the help.
>
> — Beppe Attardi
> --
> Juju mailing list
> Juju@lists.ubuntu.com
> Modify settings or unsubscribe at: https://lists.ubuntu.com/
> mailman/listinfo/juju
>
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database-relation-join not invoked

[Giuseppe Attardi]

I have written a charm for OpenStack Gnocchi.
The service requires a postgresql database relation.

The start hook fails, of course, because the relation is not set.

I expected that, but I expected that when I issue

juju add-relation gnocchi postgresql:db

it will invoke the database-relation-joined hook, which does set the required 
parameter and then start would work.
However the hook is not invoked: as a sanity check I set a juju-log message in 
it and it does not run at all.

Is it correct to assume that add-relation will always trigger 
database-relation-join?

A second question, I would like to avoid to start the service until the 
relation has been joined.
What is the best way to test for the relation to be present?

I tried with

db=`relation-get -r database host`

but it fails with:

INFO start error: invalid value "database" for flag -r: invalid 
relation id

I am using juju-2.1.2

Thanks for the help.

— Beppe Attardi
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