Re: smart shutdown at end of transaction (was: Default mode for shutdown)

On Fri, Apr 27, 2012 at 3:00 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Fri, Apr 27, 2012 at 2:48 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> I'm not necessarily opposed to commandeering the name "smart" for the
>> new behavior, so that what we have to find a name for is the old "smart"
>> behavior.  How about
>>
>>        slow    - allow existing sessions to finish (old "smart")
>>        smart   - allow existing transactions to finish (new)
>>        fast    - kill active queries
>>        immediate - unclean shutdown
>
> I could live with that.  Really, I'd like to have fast just be the
> default.  But the above compromise would still be a big improvement
> over what we have now, assuming the new smart becomes the default.

So right now, we have a mapping from signals to shutdown types that
looks like this:

[Current] SIGTERM -> smart, SIGINT -> fast, SIGQUIT -> immediate

It seems we need another signal for the new mode, and the obvious
candidate is SIGUSR2. But what shall the mapping look like?

[Choice #1] SIGUSR2 -> slow, SIGTERM -> smart, SIGINT -> fast, SIGQUIT
-> immediate
[Choice #2] SIGTERM -> slow, SIGUSR2 -> smart, SIGINT -> fast, SIGQUIT
-> immediate

In other words, should we retain the existing behavior for SIGTERM and
make SIGUSR2 have the new behavior (choice #2)? Or shall we preserve
the invariant that SIGTERM invokes the default shutdown mode, and move
the current default behavior off into SIGUSR2 land (choice #1)?

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
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