Re: pgbouncer increase pool_size, reload does not work

On Thu, 2 Feb 2017 04:27:45 -0700 (MST)
alexanderfelipewo <alexanderfelipewo(at)gmail(dot)com> wrote:

> hello!
>
> i have a question for pgbouncer in case someone has faced this and there is
> a solution available.
>
> i have a db with pgbouncer where the pool_size is set to 50 (i ve noticed
> this using both session/transaction modes). Sometimes there are waiting
> sessions b/c more than 50 want to execute sth at once and usually each query
> is not so fast. So let's say i want to increase the pool_size from 50 to 70.
> I change the config file and then login to pgbouncer where i run a
> 'reload;'. Now when i check the 'show config' i see the new value in the
> 'default_pool_size' parameter.
>
> BUT
>
> the problem is that the amount of servers is still 50 and does not go up to
> 70. At the same time there are clients in a 'waiting' state. If i do a
> restart then it will work and the servers will be able to go up to 70.
>
> I ve tried these in different databases and it doesnt happen all the time
> but it does happen pretty often.
> Has anyone else seen this? if so, is there a solution (except restarting) or
> explanation?

That's because internally, it seems each pool (pair of role/db) is set up when
it is created, eg. during the very first connexion.

Even if the default pool_size can be changed with a simple reload,
you will have to wait for your pool to be fully deallocated before it
can be recreated with the new pool_size value.

I didn't dig too much in the code, maybe a core hacker of pgbouncer can provide
some better details and tips about this.