Re: [PATCH] Make pg_basebackup configure and start standby [Review] - Mailing list pgsql-hackers

2012-10-14 18:02 keltezéssel, Fujii Masao írta:
> Thanks for updating the patch!
>
> On Sun, Oct 14, 2012 at 8:41 PM, Boszormenyi Zoltan <zb@cybertec.at> wrote:
>> Backing up a standby server without -R preserves the original recovery.conf
>> of the
>> standby, it points to the standby's source server.
>>
>> Backing up a standby server with -R overwrites the original recovery.conf
>> with the new
>> one pointing to the standby instead of the standby's source server. Without
>> -Ft, it is
>> obvious. With -Ft, there are two recovery.conf files in the tar file and
>> upon extracting it,
>> the last written one (the one generated via -R) overwrites the original.
> The tar file is always extracted such way in all platform which PostgreSQL
> supports? I'm just concerned about that some tool in some platform might
> prefer the original recovery.conf when extracting tar file. If the spec of tar
> format specifies such behavior (i.e., the last written file of the same name
> is always preferred), it's OK.

Since tar is a sequential archive format, I think this is the behaviour of
every tar extractor. But I will look at adding code to skip the original
recovery.conf if it exists in the tar file.

> I found the bug that recovery.conf is included in the tar file of the tablespace
> instead of base.tar, when there are tablespaces in the server.

You are right, I am looking into this. But I don't know how it got there,
I check for (rownum == 0 && writerecoveryconf) and rownum == 0
supposedly means that it's the base.tar. Looking again.

> Maybe this is nitpicky problem,,,, but...
> If port number is not explicitly specified in pg_basebackup, the port
> number is not
> included to primary_conninfo in recovery.conf which is created during
> the backup.
> That is, the standby server using such recovery.conf tries to connect
> to the default
> port number because the port number is not supplied in primary_conninfo. This
> assumes that the default port number is the same between the master and standby.
> But this is not true. The default port number can be changed in --with-pgport
> configure option, so the default port number might be different
> between the master
> and standby. To avoid this uncertainty, pg_basebackup -R should always include
> the port number in primary_conninfo?

I think you are right. But, I wouldn't restrict it only to the port setting.
Any of the values that are set and equal to the compiled-in default,
it should be written into recovery.conf.

> When the password is required to connect to the server, pg_basebackup -R
> always writes the password setting into primary_conninfo in recovery.conf.
> But if the password is supplied from .pgpass, ISTM that the password setting
> doesn't need to be written into primary_conninfo. Right?

How can you deduce it from the PQconninfoOption structure?

Also, if the machine you take the base backup on is different
from the one where you actually use the backup on, it can be
different not only in the --with-pgport compilation option but
in the presence of .pgpass or the PGPASSWORD envvar, too.
The administrator is there for a reason or there is no .pgpass
or PGPASSWORD at all.

> +        The password written into recovery.conf is not escaped even if special
> +        characters appear in it. The administrator must review recovery.conf
> +        to ensure proper escaping.
>
> Is it difficult to make pg_basebackup escape the special characters in the
> password? It's better if we can remove this restriction.

It's not difficult. What other characters need to be escaped besides single quotes?

> I've not reviewed PQconninfo patch yet. Will review.

Thanks in advance.

Best regards,
Zoltán Böszörményi

--
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Zoltán Böszörményi
Cybertec Schönig & Schönig GmbH
Gröhrmühlgasse 26
A-2700 Wiener Neustadt, Austria
Web: http://www.postgresql-support.de     http://www.postgresql.at/