[pgpool-hackers: 4303] Re: Proposal: Add user_redirect_preference_list

[Bo Peng]

Hello,

> > I would like to add a new GUC parameter "user_redirect_preference_list" to 4.5
> > to allow routing queries to a specific backend node for a specific user connection.
> > 
> > Currently, we have database_redirect_preference_list and app_name_redirect_preference_list,
> > which allow routing queries to a specific backend node for a specific database connection or
> > a specific client application connection.
> > 
> > I think the use case, which uses a connection user based load balance, is also needed.
> > 
> > For example, an application has GUI management console and server daemon,
> > which connect to the same database. GUI management console mainly issues SELECT
> > and server daemon mainly issues INSERT.
> > In such case, users may want to route all queries issued by GUI management console
> > to standby servers to reduce the load on primary server.
> > 
> > To handle such case, normally we can use app_name_redirect_preference_list.
> > However, in some applications the application name may not be configurable.
> > 
> > That is the reason why I want to add this feature.
> > 
> > Any comments?
> 
> Sounds like a useful feature. However, if it's implemented, now we
> have
> database_redirect_preference_list. app_name_redirect_preference_list
> and user_redirect_preference_list. I feel a little bit redudant. I
> think we can unify all of them. For example:
> 
> redirect_preference_list = 'selector:user,user0:primary,user[1-4]:1,user[5-9]:standby'
> 
> where "selector" is one of "user", "app_name" and "database". In the
> example above, it means that:
> 
> - user0 is redirected to primary
> - user1 to user4 are redirected to db node 1
> - user5 to user9 are redirected to one of standby servers
> 
> What do you think?

Thank you!

Yes. I think it is a good idea to unify them.

If we add this new parameter like "redirect_preference_list",
I think we should also keep the backward compatibility to make sure
the old parameters can work with the new major version.

-- 
Bo Peng <pengbo at sraoss.co.jp>
SRA OSS LLC
https://www.sraoss.co.jp/