Re: [PATCH] pg_isready (was: [WIP] pg_ping utility)

2013/1/26 Phil Sorber <phil(at)omniti(dot)com>:
> On Sat, Jan 26, 2013 at 12:39 PM, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote:
>> 2013/1/26 Phil Sorber <phil(at)omniti(dot)com>:
>>> On Sat, Jan 26, 2013 at 11:53 AM, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote:
>>>> 2013/1/26 Phil Sorber <phil(at)omniti(dot)com>:
>>>>> On Sat, Jan 26, 2013 at 4:02 AM, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote:
>>>>>> Hello
>>>>>>
>>>>>> We now haw to solve small puppet issue, because our puppets try to
>>>>>> start server too early, when old instance live still.
>>>>>>
>>>>>> Maybe some new parameter - is_done can be useful.
>>>>>>
>>>>>
>>>>> What about something like:
>>>>> pg_isready; while [ $? -ne 2 ]; do sleep 1; pg_isready; done
>>>>
>>>> it is not enough - server is done in a moment, where can be started
>>>> again - or when we can do safe copy of database data directory.
>>>>
>>>
>>> I guess i am not completely understanding the case you are trying to
>>> solve. Can you explain a bit further?
>>
>> We use puppets and due some simplification we cannot to use reload
>> when configuration is changed. Our puppets has not enough intelligence
>> to understand when is reload enough and when is restart necessary. So
>> any change to configuration require restarting postgres. I don't know
>> why "service restart" are not used. I believe so our puppet guru know
>> it. It just do sequence STOP:START Now puppets are "smart" and able
>> to wait for time, when server is ready. But there are missing simple
>> test if server is really done and I see a error messages related to
>> too early try to start. So some important feature can be verification
>> so server is really done.
>>
>> We can do it with test on pid file now - and probably we will use it.
>> But I see so this is similar use case (in opposite direction)
>>
>
> I guess I am still not clear why you can't do:
>
> stop_pg_via_puppet
> pg_isready
> while [ $? -ne 2 ]
> do
> sleep 1
> pg_isready
> done
> do_post_stop_things
> start_pg_via_puppet
>

because ! pg_isready <> pg_isdone

>> Regards
>>
>> Pavel
>>
>>>
>>>> Regards
>>>>
>>>> Pavel
>>>>
>>>>
>>>>
>>>>>
>>>>> Perhaps with a counter to break out of the loop after some number of attempts.
>>>>>
>>>>>> Regards
>>>>>>
>>>>>> Pavel
>>>>>>