Re: Server won't start with fallback setting by initdb.

On Sun, Mar 04, 2018 at 03:31:31PM -0500, Tom Lane wrote:
> Then, seeing that the factory defaults are ReservedBackends = 3 and
> max_wal_senders = 10, something's got to give; there's no way that
> max_connections = 10 can work with those. But what I would argue is that
> of those three choices, the least defensible one is max_wal_senders = 10.
> Where did that come from? What fraction of real-world installations will
> need that? We don't choose defaults that overprovision small
> installations by 5X or 10X anywhere else, so why here?

Those numbers are coming from f6d6d29, which points to this thread at
its root:
https://www.postgresql.org/message-id/CABUevEwfV7zDutescm2PHGvsJdYA0RWHFMTRGhwrJPGgSbzZDQ%40mail.gmail.com

The number of max_wal_senders came out as a consensus because those are
cheap to enable, now the number came out by itself. I am not seeing on
the thread any specific reason behind.

> My proposal is to default max_wal_senders to perhaps 3, and leave
> initdb's logic alone.

I agree with you here. That was actually my first counter proposal on
the matter, which is also conservative:
https://www.postgresql.org/message-id/CAB7nPqSFzsO6bEknEQ8yidwXOOUUeCc05NKsPQFhMWBFPv3Smg%40mail.gmail.com
--
Michael