Re: dividing privileges for replication role.

Hi, Tom

Thank you for comments.

> Tomonari Katsumata <t(dot)katsumata1122(at)gmail(dot)com> writes:
> >> Why is it better to do this with a privilege, rather than just using
> >> pg_hba.conf?
>
>
> > You are right.
> > Handling with pg_hba.conf is an easy way.
>
> > But I think many users think about switch over, so
> > the pg_hba.conf is same on master and standby.
> > it's not convinient that we have to rewrite pg_hba.conf
> > whenever switch over occurs.
>
> > In the other hand, using a privilege, although we have to prepare
> > each roles before, we don't need to rewrite pg_hba.conf.
>
>
> That sounds good, but if the behavior is controlled by a privilege
> (ie, it's stored in system catalogs) then it's impossible to have
> different settings on different slave servers --- or indeed to change
> the settings locally on a slave at all. You can only change settings
> on the master and let the change replicate to all the slaves.
>
Yes, I'm thinking changing settings on the master and the settings are
propagating to all slaves.

> Quite aside from whether you want to manage things like that, what
happens if
> your master has crashed and you find you need to change the settings on
> the way to getting a slave to take over?
>
> The crash-recovery worry is one of the main reasons that things like
> pg_hba.conf aren't stored in system catalogs already. It's not always
> convenient to need a running server before you can change the settings.
>
I understand that the approach in my patch(using pribileges for controlling
its behavior) does not match the policy.

But I'm still thinking I should put a something to controle
the behavior.

Then, how about to add a new option "standby_mode" to Database Connection
Control Functions like application_name.

ex:
primary_conninfo = 'port=5432 standby_mode=master-cascade'
primary_conninfo = 'port=5432 standby_mode=master-only'
primary_conninfo = 'port=5432 standby_mode=cascade-only'

I think it will be able to do same control with privilege controlling.
And it won't be contrary to the policy(no data is stored in system
catalogs).

Because it is corner-case, I should not do anything about this?
(Am I concerning too much?)

regards,
--------
NTT Software Corporation
Tomonari Katsumata