Re: Built-in connection pooling

On Fri, Jan 19, 2018 at 11:59 AM, Tomas Vondra
<tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
> Hmmm, that's unfortunate. I guess you'll have process the startup packet
> in the main process, before it gets forked. At least partially.

I'm not keen on a design that would involve doing more stuff in the
postmaster, because that would increase the chances of the postmaster
accidentally dying, which is really bad. I've been thinking about the
idea of having a separate "listener" process that receives
connections, and that the postmaster can restart if it fails. Or
there could even be multiple listeners if needed. When the listener
gets a connection, it hands it off to another process that then "owns"
that connection.

One problem with this is that the process that's going to take over
the connection needs to get started by the postmaster, not the
listener. The listener could signal the postmaster to start it, just
like we do for background workers, but that might add a bit of
latency. So what I'm thinking is that the postmaster could maintain
a small (and configurably-sized) pool of preforked workers. That
might be worth doing independently, as a way to reduce connection
startup latency, although somebody would have to test it to see
whether it really works... a lot of the startup work can't be done
until we know which database the user wants.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company