[Pgpool-hackers] removing backend_socket_dir parameter ?

[Tatsuo Ishii]

> Le 07/01/2011 01:55, Tatsuo Ishii a écrit :
>>> Le 06/01/2011 15:43, Jehan-Guillaume (ioguix) de Rorthais a écrit :
>>>> Le 05/01/2011 10:51, Jehan-Guillaume (ioguix) de Rorthais a écrit :
>>>>> Le 05/01/2011 10:22, Tatsuo Ishii a écrit :
>>>>>>> Le 04/01/2011 15:38, Jehan-Guillaume (ioguix) de Rorthais a écrit :
>>>>>>>> Le 04/01/2011 15:13, Guillaume Lelarge a écrit :
>>>>>>>>> Hi,
>>>>>>>>
>>>>>>>>> Le 04/01/2011 14:27, Jehan-Guillaume (ioguix) de Rorthais a écrit :
>>>>>>>>>> [...]
>>>>>>>>>> pgPool is currently using the parameter "backend_socket_dir" to define where it
>>>>>>>>>> can find the backend unix socket files.
>>>>>>>>>>
>>>>>>>>>> However, from the libpq world, we just use one parameter for both unix or inet
>>>>>>>>>> socket: host. If this parameter starts with '/', then this is a unix socket. All
>>>>>>>>>> other values are inet connections. See:
>>>>>>>>>>
>>>>>>>>>> http://www.postgresql.org/docs/9.0/static/libpq-connect.html#LIBPQ-CONNECT-HOST
>>>>>>>>>>
>>>>>>>>>> Back in pgPool world, the equivalent parameter is "backend_hostnameN". So, when
>>>>>>>>>> I was setting up a dev environment yesterday, I naturally set this parameter  to
>>>>>>>>>> my unix path (I'm using Debian) and end up with a hostname resolution error.
>>>>>>>>>>
>>>>>>>>>> So you'll find in attachment a patch to remove the "backend_socket_dir"
>>>>>>>>>> parameter and use the libpq policy. Moreover, on empty "backend_hostnameN"
>>>>>>>>>> value, the patch fall back to DEFAULT_SOCKET_DIR.
>>>>>>>>>>
>>>>>>>>
>>>>>>>>> This patch is really interesting. This is something I had on my todo
>>>>>>>>> list for quite some time.
>>>>>>>>
>>>>>>>> Glad to hear that :)
>>>>>>>> I wasn't the only one wondering about this then :)
>>>>>>>>
>>>>>>>>>> I realize it will break compatibility with older configuration file. But in a
>>>>>>>>>> first step, I prefer something clean and start discussing this issue with you if
>>>>>>>>>> you really mind this.
>>>>>>>>>>
>>>>>>>>
>>>>>>>>> On the configuration file, compatibility of configuration file is never
>>>>>>>>> garantied. So I don't think this is such an issue. We need to make it
>>>>>>>>> clear that the parameter has a new mail.
>>>>>>>>
>>>>>>>> s/new mail/new name/
>>>>>>>>
>>>>>>>> well, it's not a new name, we just drop one and promote an existing one to deal
>>>>>>>> with both unix and inet socket :)
>>>>>>>>
>>>>>>>>> If we really want to maintain the compatibility on this issue, we could
>>>>>>>>> still support the old parameter during two or three major releases. I
>>>>>>>>> guess we need to put a warning in the log to say "hey guy, you're still
>>>>>>>>> using that old obsolete configuration parameter, you should better
>>>>>>>>> change with this one".
>>>>>>>>
>>>>>>>> Yeah. What I have in mind is :
>>>>>>>>   if backend_hostnameN == ''
>>>>>>>>     if not backend_socket_dir
>>>>>>>>       backend_hostnameN = DEFAULT_SOCKET_DIR
>>>>>>>>     else
>>>>>>>>       log « please stop using that »
>>>>>>>>       backend_hostnameN = backend_socket_dir
>>>>>>>>
>>>>>>>> But really, I would prefer to drop backend_socket_dir and keep the code clean.
>>>>>>>>
>>>>>>>
>>>>>>> You can't have it both ways. Either you please your users, or you please
>>>>>>> your developpers. I think we should do the former.
>>>>
>>>>>> Agreed. I learned it in a hard way:-)
>>>>
>>>>>> Now I think the idea is great and am looking forward to accepting for
>>>>>> the next release.
>>>>
>>>>> Thank you !
>>>>
>>>> So here is the new patch including backward compatibility with backend_socket_dir.
>>>>
>>>
>>> Seems good to me. Could you also get rid of backend_socket_dir in the
>>> sample configuration files? this parameter won't be the prefered way to
>>> set the socket, so it shouldn't be in the sample conf files.
>> 
>> But according to the patches still backend_socket_dir remains and even
>> appears on show pool_status.
> 
> Yes, I kept it because cause you agree'd Guillaume statement:
> «
> You can't have it both ways. Either you please your users, or you please your
> developpers. I think we should do the former.
> »
> 
> My anderstanding is that "doing the former", so "please your users", means
> keeping backward compatibility for some time. Are we ok ?

Yup.

> So my last patch implement the logic I described above:
> 
>   if (backend_hostnameN == '' and backend_socket_dir != '')
>     log "this parameter is deprecated ! use backend_socket_dir instead."
>     backend_hostnameN = backend_socket_dir
> 
> 
> So yes, it appears in show pool_status :(
> 
>> Probably we should leave it in the
>> pgpool.conf.sample etc. with statting that "this directive is
>> obsoleted and used for only internal use." or something like that?
> 
> We don't use it internally.

Oh ok.

> In my opinion, we should
>   * remove it from the sample
>   * warn the user if he still use it in its configuration file
>   * add "DEPCRECATED use backend_hostname instead" as description for this
> parameter in "show pool_status"

If you and Guillaume agreed on this, I'm fine with removing it from
the sample conf.
--
Tatsuo Ishii
SRA OSS, Inc. Japan
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