The PostgreSQL charm, AWS and robustness

[Tim Penhey]

Hi folks,

I'm writing not as a canonical core developer, but as a user who is
occasionally stupid :-)

I have a new project that I'm wanting to deploy and it is a django
project backed with a postgresql database.  Pretty simple really.

I want to manage my deployment with Juju, but I want to manage it right.

To this effect, I want to make sure that the database that postgres is
managing is persistent even if the machine it is running on dies.  I
have taken a look at the config options for the postgres charm and I
find them a little overwhelming.

I have to say I was very much encouraged to see that there are automatic
backups taken of the database, but backups without a restore are little
value.  I know that there is work on "actions" and that restoring the
database is a wonderful use of an action with parameters, but I also
know that we are not there yet and I want to start using things now :-)

What I want to make myself comfortable with, initially at least, is the
robustness of my postgres database.

Let's assume that I'm going to deploy on AWS, how do I go about manually
configuring a machine so that the data directory for the postgres
database is a persistent mount?

How do I restore the database from a backup?

If the machine dies, which I will manually do in testing, how do I go
about bringing up a new machine, attaching the storage, deploying the
charm and have it use the existing database that is there?  I'm guessing
that there are orderings I need.

Do I have to deploy a new database with a new persistent mount point and
restore from a backup?  If I have to do that, what is the benefit of
having the database itself in a persistent mount?

Is there someone knowledgeable on the postgres charm and AWS that can
help me with these points?

BTW, I'm very happy to blog about this whole process once I have it all
figured out :-)

Cheers,
Tim