Re: [patch] demote

Mmm. Fat finger..

At Fri, 26 Jun 2020 16:14:38 +0900 (JST), Kyotaro Horiguchi <horikyota.ntt@gmail.com> wrote in 
> Hello.
> 
> If we are going to dive so close to server shutdown, we can just
> utilize the restart-after-crash path, which we can assume to work
> reliably. The attached is a quite rough sketch, hijacking smart
> shutdown path for a convenience, of that but seems working.  "pg_ctl
> -m s -W stop" lets server demote.
> 
> > I hadn't time to investigate Robert's concern about shared memory for snapshot
> > during recovery.
> 
> The patch does all required clenaup of resources including shared

The path does all required clenaup of..

> memory, I believe.  It's enough if we don't need to keep any resources
> alive?
> 
> > The patch doesn't deal with prepared xact yet. Testing "start->demote->promote"
> > raise an assert if some prepared xact exist. I suppose I will rollback them
> > during demote in next patch version.
> > 
> > I'm not sure how to divide this patch in multiple small independent steps. I
> > suppose I can split it like:
> > 
> > 1. add demote checkpoint
> > 2. support demote: mostly postmaster, startup/xlog and checkpointer related
> >    code
> > 3. cli using pg_ctl demote
> > 
> > ...But I'm not sure it worth it.

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center