Re: New trigger option of pg_standby

Fujii-san,

I like the new patch using the content of the file to determine the
mode. Much easier to use at failover time.

On Fri, 2009-04-10 at 12:47 +0900, Fujii Masao wrote:

> > One problem with this patch is that in smart mode, the trigger file is not
> > deleted. That's different from current pg_standby behavior, and makes
> > accidental failovers after one failover more likely.
> 
> Yes, it's because pg_standby cannot be sure when the trigger file
> can be removed in smart mode. If the trigger file is deleted as soon
> as it's found, just like in fast mode, pg_standby may keep waiting
> for WAL file again.

My understanding of smart mode is fairly simple: 
  if (triggered)  {if (smartMode && nextWALfile+1 exists)    exit(0);else{    delete trigger file    exit(1);}  }

If you perform a file lookahead (the +1) as shown above then you avoid
the problem Heikki observes.

-- Simon Riggs           www.2ndQuadrant.comPostgreSQL Training, Services and Support