Horton

Re: [Patch] pg_rewind: options to use restore_command from recovery.conf or command line

Alexey Kondratov <a.kondratov@postgrespro.ru>

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From: Alexey Kondratov <a.kondratov@postgrespro.ru>
To: Michael Paquier <michael@paquier.xyz>
Cc: Alexander Korotkov <a.korotkov@postgrespro.ru>, Alvaro Herrera <alvherre@2ndquadrant.com>, Liudmila Mantrova <l.mantrova@postgrespro.ru>, Thomas Munro <thomas.munro@gmail.com>, Andrey Borodin <x4mmm@yandex-team.ru>, David Steele <david@pgmasters.net>, Andres Freund <andres@anarazel.de>, PostgreSQL-development <pgsql-hackers@postgresql.org>, Dmitry Dolgov <9erthalion6@gmail.com>, vladimirlesk@yandex-team.ru, dsarafan@yandex-team.ru
Date: 2020-03-02T17:59:49Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Move frontend-side archive APIs from src/common/ to src/fe_utils/

  2. Add -c/--restore-target-wal to pg_rewind

  3. Move routine definitions of xlogarchive.c to a new header file

  4. Move routine building restore_command to src/common/

  5. Integrate recovery.conf into postgresql.conf

On 2020-03-02 07:53, Michael Paquier wrote:

> 
>> + * For fixed-size files, the caller may pass the expected size as an
>> + * additional crosscheck on successful recovery.  If the file size is 
>> not
>> + * known, set expectedSize = 0.
>> + */
>> +int
>> +RestoreArchivedWALFile(const char *path, const char *xlogfname,
>> +					   off_t expectedSize, const char *restoreCommand)
> 
> Actually, expectedSize is IMO a bad idea, because any caller of this
> routine passing down zero could be trapped with an incorrect file
> size.  So let's remove the behavior where it is possible to bypass
> this sanity check.  We don't need it in pg_rewind either.
> 

OK, sounds reasonable, but just to be clear. I will remove only a 
possibility to bypass this sanity check (with 0), but leave expectedSize 
argument intact. We still need it, since pg_rewind takes WalSegSz from 
ControlFile and should pass it further, am I right?

> 
>> +		/* Remove trailing newline */
>> +		if (strchr(cmd_output, '\n') != NULL)
>> +			*strchr(cmd_output, '\n') = '\0';
> 
> It seems to me that what you are looking here is to use
> pg_strip_crlf().  Thinking harder, we have pipe_read_line() in
> src/common/exec.c which does the exact same job..
> 

pg_strip_crlf fits well, but would you mind if I also make 
pipe_read_line external in this patch?

> 
>> -	/*
>> -	 * construct the command to be executed
>> -	 */
> 
> Perhaps you meant "build" here.
> 

Actually, the verb 'construct' is used historically applied to 
archive/restore commands (see also xlogarchive.c and pgarch.c), but it 
should be 'build' in (fe_)archive.c, since we have BuildRestoreCommand 
there now.

All other remarks look clear for me, so I fix them in the next patch 
version, thanks.


Regards
--
Alexey Kondratov

Postgres Professional https://www.postgrespro.com
The Russian Postgres Company