Re: Re: Proposal for Allow postgresql.conf values to be changed via SQL [review]

On Wed, Jan 23, 2013 at 12:24 PM, Amit Kapila <amit.kapila@huawei.com> wrote:
> On Tuesday, January 22, 2013 8:25 PM Fujii Masao wrote:
>> On Tue, Jan 22, 2013 at 11:07 PM, Amit Kapila <amit.kapila@huawei.com>
>> wrote:
>> > On Tuesday, January 22, 2013 7:10 PM Zoltán Böszörményi wrote:
>> >> 2013-01-22 13:32 keltezéssel, Amit kapila írta:
>> >> > On Saturday, January 19, 2013 2:37 AM Boszormenyi Zoltan wrote:
>> >> > 2013-01-18 21:48 keltezéssel, Boszormenyi Zoltan írta:
>> >> >> 2013-01-18 21:32 keltezéssel, Tom Lane írta:
>> >> >>> Boszormenyi Zoltan <zb@cybertec.at> writes:
>> >> >>>> 2013-01-18 11:05 keltezéssel, Amit kapila írta:
>> >> >>>>>> On using mktemp, linux compilation gives below warning
>> >> >>>>>> warning: the use of `mktemp' is dangerous, better use
>> `mkstemp'
>> >> >
>> >> >>>> Everywhere else that we need to do something like this, we just
>> >> use our
>> >> >>>> own PID to disambiguate, ie
>> >> >>>>      sprintf(tempfilename, "/path/to/file.%d", (int) getpid());
>> >> >>>> There is no need to deviate from that pattern or introduce
>> >> portability
>> >> >>>> issues, since we can reasonably assume that no non-Postgres
>> >> programs are
>> >> >>>> creating files in this directory.
>> >> >>> Thanks for the enlightenment, I will post a new version soon.
>> >> >> Here it is.
>> >> > The patch sent by you works fine.
>> >> > It needs small modification as below:
>> >> >
>> >> > The "auto.conf.d" directory should follow the postgresql.conf file
>> >> directory not the data_directory.
>> >> > The same is validated while parsing the postgresql.conf
>> configuration
>> >> file.
>> >> >
>> >> > Patch is changed to use the postgresql.conf file directory as
>> below.
>> >> >
>> >> > StrNCpy(ConfigFileDir, ConfigFileName, sizeof(ConfigFileDir));
>> >> > get_parent_directory(ConfigFileDir);
>> >> > /* Frame auto conf name and auto conf sample temp file name */
>> >> > snprintf(AutoConfFileName, sizeof(AutoConfFileName), "%s/%s/%s",
>> >> >                                          ConfigFileDir,
>> >> >                                          PG_AUTOCONF_DIR,
>> >> >                                          PG_AUTOCONF_FILENAME);
>> >>
>> >> Maybe it's just me but I prefer to have identical
>> >> settings across all replicated servers. But I agree
>> >> that there can be use cases with different setups.
>> >>
>> >> All in all, this change makes it necessary to run the
>> >> same SET PERSISTENT statements on all slave servers,
>> >> too, to make them identical again if the configuration
>> >> is separated from the data directory (like on Debian
>> >> or Ubuntu using the default packages). This needs to be
>> >> documented explicitly.
>> >
>> > SET PERSISTENT command needs to run on all slave servers even if the
>> path we
>> > take w.r.t data directory
>> > unless user takes backup after command.
>>
>> Is it safe to write something in the directory other than data
>> directory
>> via SQL?
>>
>> postgres user usually has the write permission for the configuration
>> directory like /etc/postgresql?
>
> As postgresql.conf will also be in same path and if user can change that,
> then what's the problem with postgresql.auto.conf

If the configuration directory like /etc is owned by root and only root has
a write permission for it, the user running PostgreSQL server would not
be able to update postgresql.auto.conf there. OTOH, even in that case,
a user can switch to root and update the configuration file there. I'm not
sure whether the configuration directory is usually writable by the user
running PostgreSQL server in Debian or Ubuntu, though.

> Do you see any security risk?

I have no idea. I just wondered that because some functions like pg_file_write()
in adminpack are restricted to write something in the directory other
than $PGDATA.

>> >> > This closes all comments raised till now for this patch.
>> >> > Kindly let me know if you feel something is missing?
>> >>
>> >> I can't think of anything else.
>>
>> For removing
>> +   a configuration entry from
>> <filename>postgresql.auto.conf</filename> file,
>> +   use <command>RESET PERSISTENT</command>. The values will be
>> effective
>> +   after reload of server configuration (SIGHUP) or server startup.
>>
>> The description of RESET PERSISTENT is in the document, but it
>> seems not to be implemented.
>
> This command support has been removed from patch due to parser issues, so it
> should be removed from documentation as well. I shall fix this along with
> other issues raised by you.

Okay.

Regards,

--
Fujii Masao