Re: SIGHUP during recovery

Simon Riggs wrote:
> On Thu, 2009-03-05 at 19:52 +0900, Fujii Masao wrote:
>> Hi,
>>
>> On Thu, Mar 5, 2009 at 6:28 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>>> Should we reload recovery.conf also?
>> I think no for now. At least the parameters which specify the recovery target
>> should not be changed during recovery.
>
> Why not?

I don't see either why it wouldn't work. As long as the new value is
greater than the current point in recovery.

BTW, we now have some extra safeguards (minRecoveryPoint) in place to
prevent you from corrupting your database by moving recovery target
backwards to a point earlier than an already recovery xlog record.
That's not really that relevant to reloading recovery.conf on the fly,
but it's worth noting. The documentation currently says about the
settings in recovery.conf that "They cannot be changed once recovery has
begun." That wording should probably be relaxed.

>> On the other hand, restore_command
>> maybe can be set safely, but I'm not sure if it's really useful at this time.
>
> Not sure changing those parameters would be a bad thing. Other
> parameters can be changed, why not those?

It seems safe to me. It doesn't seem very useful, though. The only
options left in recovery.conf are restore_command, and all the
target-related options. If you want to change those, you can always stop
the server, change the settings and restart; without hot standby there
isn't any other backends active yet that would get upset about the shutdown.

The main reason why reloading the main config file on SIGHUP is a good
idea is that otherwise you get an inconsistency between the background
writer and the startup process.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com