[pgpool-hackers: 2403] Re: Problems with the relative paths in daemon mode

[Tatsuo Ishii]

Usama,

Thanks for the patch.

I think this is good since we didn't define the behavior when a
relative path is specified for pid_file_name anyway. Now it's defined,
which is good.

Just out of curiosity, is there any use case to define the path of
pid_file_name relative to the path of pgpool.conf? Since most users
(and Linux systems) want to put pid_file_name under /var while they
want to put pgpool.conf under /etc.

Best regards,
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese:http://www.sraoss.co.jp

> Hi Ishii-San
> 
> Can you please have a look at the attached patch.
> The reason I want your consent before committing it is because apart from
> using the absolute paths for pgpool.conf, pcp.conf and pool_hba.conf files,
> I have also modified the behaviour of pid_file_name configuration parameter.
> Now when the relative path is specified for the pid file in pgpool.conf
> file that relative path is calculated with reference to the location of
> pgpool.conf file.
> 
> For example:
> 
> if pgpool.conf file sets pid_file_name parameter as
> 
> pid_file_name = 'somedir/pgpool.pid'
> 
> And pgpool.conf file is located in the "/etc/configurations/" directory
> than the Pgpool-II will create the pgpool.pid file
> in "/etc/configurations/somedir" directory
> 
> While if absolute path is specified than it will work as it works before
> 
> pid_file_name = '/etc/mydir/pgpool.pid' # this will create the pgpool.pid
> in /etc/mydir/ directory
> 
> 
> I have done this change because I think it will make the configuration of
> pid_file_name more intuitive and less confusing.
> P.S  The documentation changes are also part of the patch.
> 
> Thoughts and comments?
> 
> 
> Thanks
> Best regards
> Muhammad Usama
> 
> 
> 
> On Wed, Jun 14, 2017 at 3:27 AM, Tatsuo Ishii <ishii at sraoss.co.jp> wrote:
> 
>> Good catch! Please go ahead.
>>
>> Best regards,
>> --
>> Tatsuo Ishii
>> SRA OSS, Inc. Japan
>> English: http://www.sraoss.co.jp/index_en.php
>> Japanese:http://www.sraoss.co.jp
>>
>> > Hi
>> >
>> > Pgpool-II does not properly handle the relative paths especially when the
>> > pgpool.conf file is explicitly specified using the command line (-f
>> switch)
>> > while its patch is given relative to the current directory.
>> >
>> > For example:
>> >
>> > Suppose we invoke pgpool-II from "/home/work/installed/pgpool/bin"
>> directory
>> >
>> > $ pwd
>> > /home/work//installed/pgpool/bin
>> > $ ./pgpool -f simple_conf/pgpool.conf
>> >
>> > Now we are expecting here is that the Pgpool-II will look for pgpool.conf
>> > file in the
>> > /home/work/installed/pgpool/bin/simple_conf/ directory, which it does
>> > correctly :-), and also latter in the startup phase when it will require
>> > the pool_passwd file it will look in the same (
>> > /home/work/installed/pgpool/bin/simple_conf/)directory.
>> > So in the code what Pgpool-II does is, it take out the directory portion
>> > from the command line option provided to it for specifying the
>> pgpool.conf
>> > file and look for the pool_passwd file in that directory. which in this
>> > case is just simple_conf/
>> >
>> > Now the problem here is since the pgpool.conf path used in the command
>> line
>> > option was a relative path, so it will only be able to go to the correct
>> > directory location if the current directory of Pgpool-II remains the same
>> > from where it was invoked from.
>> >
>> > And since we do not change the current directory when Pgpool-II is
>> started
>> > with "-n" switch ( non daemon mode) so everything works as expected in
>> that
>> > mode.
>> > But when the Pgpool-II is started in the daemon mode the daemonize()
>> > function changes the current directory to "/"
>> >
>> > main.c:380 if(chdir("/"))
>> >
>> > and after that all relative path becomes invalid and Pgpool-II will start
>> > looking for files in invalid or non-existent location. which as per our
>> > example in daemon mode it will try to find the pool_passwd file in
>> >
>> > /simple_conf/pool_passed
>> >
>> > instead of
>> >
>> > /home/work//installed/pgpool/bin/simple_conf/pool_passwd
>> > The solution to this is to convert the relative path of the pgpool.conf
>> to
>> > the absolute path at the startup and later use that absolute path for all
>> > other path calculations.
>> >
>> > If you do not have any reservation, than I will start working on the fix.
>> >
>> > Thanks
>> > Best Regards
>> > Muhammad Usama
>>