Re: pending patch: Re: HS/SR and smart shutdown

On Wed, 2010-03-31 at 17:48 +0900, Fujii Masao wrote:
> On Wed, Mar 31, 2010 at 5:00 PM, Simon Riggs <simon@2ndquadrant.com> wrote:
> > Please add some docs that a) explains what the patch does and b) notes
> > any changes from behaviour in previous releases. ISTM this is a major
> > change in behaviour.
> 
> How about adding the following description into "17.5. Shutting Down
> the Server"?
> 
>     If the server is in recovery, it waits for all of the read only
>     connections to be closed.

You need to explain which mode you're talking about. Adding minimal
comments isn't my objective. We need good, useful documentation on every
aspect that you add or change.

> And, where should the note be put in? AFAIK, the previous behavior
> has not been documented anywhere.

> > >From what I have seen, the comment about PM_WAIT_BACKENDS is incorrect.
> > "backends might be waiting for the WAL record that conflicts with their
> > queries to be replayed". Recovery sometimes waits for backends, but
> > backends never wait for recovery.
> 
> Really? As Heikki explained before, backends might wait for the lock
> taken by the startup process.
> http://archives.postgresql.org/pgsql-hackers/2010-01/msg02984.php

Backends wait for locks, yes, but they could be waiting for user locks
also. That is not "waiting for the WAL record", that concept does not
exist.

-- Simon Riggs           www.2ndQuadrant.com