Re: max_standby_delay considered harmful

On Wed, May 5, 2010 at 9:32 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Wed, May 5, 2010 at 11:50 PM, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
>> If someone wants to suggest that HS is useless if max_standby_delay
>> supports only boolean values, I am ready to suggest we remove HS as well
>> and head to 9.0 because that would suggest that HS itself is going to be
>> useless.
>
> I think HS is going to be a lot less useful than many people think, at
> least in 9.0.  But I think ripping out max_standby_delay will make it
> worse.
>
>> The code will not be thrown away;  we will bring it back for 9.1.
>
> If that's the case, then taking it out makes no sense.
>
<mysql dba troll>
I manage a bunch of different environments and I am pretty sure that
in any of them if the db started seemingly randomly killing queries I
would have application teams followed quickly by executives coming
after me with torches and pitchforks.

I can not imagine setting this value to anything other than a bool and
most of the time that bool would be -1. I would only be unleashing a
kill storm in utter desperation and I would probably need to explain
myself in detail after. Utter desperation means I am sure I am going
to have to do a impactful failover at any moment and need a slave
completely up to date NOW.

It is good to have the option to automatically cancel queries, but I
think it is a mistake to assume many people will use it.

What I would really need for instrumentation is the ability to
determine *easily* how much a slave is lagging in clock time.
</mysql dba troll>

--
Rob Wultsch
wultsch(at)gmail(dot)com