[pgpool-hackers: 1190] Re: Problem with pcp's UNIX domain socket

[Tatsuo Ishii]

> Hi Ishii San
> 
> I don't think that PCP client side is required to recognize the
> *pcp_socket_dir*, one because *pcp_socket_dir* only sets the directory
> where the PCP server in pgpool-II would create the unix domain socket file.
> And to connect to PCP server using the unix domain socket, pcp_* clients
> needs to provide that path in hostname option of the command
> 
> For example, if pcp_socket_dir = '/tmp' the client can put this pcp_socket_dir
> path in -h command line argument of pcp_* commands
> 
> $ bin/pcp_watchdog_info -h  /tmp/ -U postgres -v 0

Ok, that makes sense.

> Secondly, pcp_* frontend clients have no dependency on and visibility
> of pgpool.conf file, so they have no idea about pcp_socket_dir value.

This is questionable if we think about how PostgreSQL's libpq clients
behaves. For example, on RHEL6 psql included in the official
PostgreSQL rpm connects to UNIX domain socket under /tmp/ by default.
However, on RHEL7, psql connects to UNIX domain socket under
/var/lib/pgsql by default. So surely PostgreSQL clients has an idea
about UNIX domain socket directory. Shouldn't we follow the
PostgreSQL's way?

> Thanks
> Best regards
> Muhammad Usama
> 
> 
> On Tue, Dec 8, 2015 at 9:40 AM, Tatsuo Ishii <ishii at postgresql.org> wrote:
> 
>> Usama,
>>
>> Does pcp recognize pcp_socket_dir? While searching libc/pcp.c, I could
>> not find any reference to pcp_socket_dir.
>>
>> Best regards,
>> --
>> Tatsuo Ishii
>> SRA OSS, Inc. Japan
>> English: http://www.sraoss.co.jp/index_en.php
>> Japanese:http://www.sraoss.co.jp
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