Re: pg_rewind and log messages

On Wed, Apr 8, 2015 at 5:53 AM, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> wrote:
> Heikki Linnakangas wrote:
>> On 04/07/2015 05:59 AM, Michael Paquier wrote:
>
>> >Fix inconsistent handling of logs in pg_rewind
>> >
>> >pg_rewind was handling a couple of things differently compared to the
>> >other src/bin utilities:
>> >- Logging output needs to be flushed on stderr, not stdout
>>
>> Agreed in general. But there's also precedent in printing some stuff to
>> stdout: pg_ctl does that for the status message, like "server starting". As
>> does initdb.
>>
>> I'm pretty unclear on what the rule here is.
>
> One principle that sometimes helps is to consider what happens if you
> use the command as part of a larger pipeline; progress messages can be
> read by some other command further down (and perhaps report them in a
> dialog box, if you embed the program in a GUI, say), but error messages
> should probably be processed differently; normally the pipeline would be
> aborted as a whole.

Make sense.

Regards,

--
Fujii Masao