Thread

1. pg_basebackup and pg_switch_wal()

   Fabrice Chapuis <fabrice636861@gmail.com> — 2025-07-29T07:48:59Z

   Hi,
   
   I read the doc concerning pg_basebackup
   
   pg_basebackup cannot force the standby to switch to a new WAL file at the
   end of backup.
   When you are using -X none, if write activity on the primary is low,
   pg_basebackup may need to wait a long time for the last WAL file required
   for the backup to be switched and archived.
   In this case, it may be useful to run pg_switch_wal on the primary in order
   to trigger an immediate WAL file switch.
   
   This is not the case also when the backup is made from the primary?
   
   I didn't find any pg_switch_wal() call in the source code of the
   pg_basebackup
   
   ~/GIT/postgres-18beta1/src/bin/pg_basebackup  (master)$ grep
   --include="*.c" "switch" *
   astreamer_inject.c:     switch (context)
   pg_basebackup.c:        switch (pg_check_dir(dirname))
   pg_basebackup.c:        switch (GetCopyDataByte(r, copybuf, &cursor))
   pg_basebackup.c:                switch (c)
   pg_createsubscriber.c:          pg_log_warning_hint("You can use
   --enable-two-phase switch to enable two_phase.");
   pg_createsubscriber.c:          switch (c)
   pg_createsubscriber.c:          char       *bad_switch = NULL;
   pg_createsubscriber.c:                  bad_switch = "--database";
   pg_createsubscriber.c:                  bad_switch = "--publication";
   pg_createsubscriber.c:                  bad_switch = "--replication-slot";
   pg_createsubscriber.c:                  bad_switch = "--subscription";
   pg_createsubscriber.c:          if (bad_switch)
   pg_createsubscriber.c:                  pg_log_error("%s cannot be used
   with -a/--all", bad_switch);
   pg_receivewal.c:         * timeline switch, xlogpos points to the beginning
   of the segment because
   pg_receivewal.c:                pg_log_info("switched to timeline %u at
   %X/%X",
   pg_receivewal.c:                switch (c)
   pg_recvlogical.c:               switch (c)
   pg_recvlogical.c:               switch (reason)
   
   Thanks for your comment
   
   Regards
   
   Fabrice
   

2. Re: pg_basebackup and pg_switch_wal()

   Sergei Kornilov <sk@zsrv.org> — 2025-07-29T10:15:30Z

   Hello
   
   > This is not the case also when the backup is made from the primary?
   
   On primary it is handled in do_pg_backup_stop function (called from perform_base_backup after basebackup was transferred), without explicitly called pg_switch_wal from pg_basebackup. pg_basebackup can change this behavior using options to the BASE_BACKUP replication command.
   
   regards, Sergei
   
   
   
   

3. Re: pg_basebackup and pg_switch_wal()

   Fabrice Chapuis <fabrice636861@gmail.com> — 2025-07-29T13:11:43Z

   Thanks for answering Sergei.
   
   ok in file postgres/src/backend/access/transam/xlog.c
   
   function
   void
   do_pg_backup_stop(BackupState *state, bool waitforarchive)
   
   there is
   /*
   * Force a switch to a new xlog segment file, so that the backup is
   * valid as soon as archiver moves out the current segment file.
   */
   RequestXLogSwitch(false);
   
   But I do not understand this error with the barman wrapper:
   
   Backup completed (start time: 2025-07-26 21:45:07.238223, elapsed time: 19
   seconds)
   Waiting for the WAL file 0000000300000B3F0000000C from server 'x_service'
   (max: 600 seconds)
   Processing xlog segments from streaming for x_service
   0000000300000B3F0000000A
   Processing xlog segments from streaming for x_service
   0000000300000B3F0000000B
   ERROR: The WAL file 0000000300000B3F0000000C has not been received in 600
   seconds
   
   Regards,
   
   Fabrice
   
   
   On Tue, Jul 29, 2025 at 12:15 PM Sergei Kornilov <sk@zsrv.org> wrote:
   
   > Hello
   >
   > > This is not the case also when the backup is made from the primary?
   >
   > On primary it is handled in do_pg_backup_stop function (called from
   > perform_base_backup after basebackup was transferred), without explicitly
   > called pg_switch_wal from pg_basebackup. pg_basebackup can change this
   > behavior using options to the BASE_BACKUP replication command.
   >
   > regards, Sergei
   >
   

4. Re: pg_basebackup and pg_switch_wal()

   Israel Barth Rubio <barthisrael@gmail.com> — 2025-07-29T22:47:31Z

   Hello Fabrice,
   
   > But I do not understand this error with the barman wrapper:
   >
   > Backup completed (start time: 2025-07-26 21:45:07.238223, elapsed time:
   19 seconds)
   > Waiting for the WAL file 0000000300000B3F0000000C from server 'x_service'
   (max: 600 seconds)
   > Processing xlog segments from streaming for x_service
   > 0000000300000B3F0000000A
   > Processing xlog segments from streaming for x_service
   > 0000000300000B3F0000000B
   > ERROR: The WAL file 0000000300000B3F0000000C has not been received in 600
   seconds
   
   Are you by chance running PostgreSQL 17?
   
   If you are using PostgreSQL 17, you are very likely encountering the issue
   tracked here: https://github.com/EnterpriseDB/barman/issues/1041. In that
   case,
   a fix has already been merged and will be included in an upcoming release of
   Barman.
   
   As a quick note for the future, the Barman GitHub issues page is the
   correct place
   to report problems like this directly to the development team. In any case,
   I understand
   that you raised it here given the context of the original question about
   pg_basebackup.
   
   Hope that helps you.
   
   Best regards,
   Israel.
   

5. Re: pg_basebackup and pg_switch_wal()

   Fabrice Chapuis <fabrice636861@gmail.com> — 2025-07-30T08:33:25Z

   Thanks Israel for these informations. In fact, I thought at first of a
   problem related to the version of pg_basebackup in version 17. I should
   have posted first on the barman github.
   
   Best regards,
   
   Fabrice
   
   On Wed, Jul 30, 2025 at 12:47 AM Israel Barth Rubio <barthisrael@gmail.com>
   wrote:
   
   > Hello Fabrice,
   >
   > > But I do not understand this error with the barman wrapper:
   > >
   > > Backup completed (start time: 2025-07-26 21:45:07.238223, elapsed time:
   > 19 seconds)
   > > Waiting for the WAL file 0000000300000B3F0000000C from server
   > 'x_service' (max: 600 seconds)
   > > Processing xlog segments from streaming for x_service
   > > 0000000300000B3F0000000A
   > > Processing xlog segments from streaming for x_service
   > > 0000000300000B3F0000000B
   > > ERROR: The WAL file 0000000300000B3F0000000C has not been received in
   > 600 seconds
   >
   > Are you by chance running PostgreSQL 17?
   >
   > If you are using PostgreSQL 17, you are very likely encountering the issue
   > tracked here: https://github.com/EnterpriseDB/barman/issues/1041. In that
   > case,
   > a fix has already been merged and will be included in an upcoming release
   > of
   > Barman.
   >
   > As a quick note for the future, the Barman GitHub issues page is the
   > correct place
   > to report problems like this directly to the development team. In any
   > case, I understand
   > that you raised it here given the context of the original question about
   > pg_basebackup.
   >
   > Hope that helps you.
   >
   > Best regards,
   > Israel.
   >
   

6. Re: pg_basebackup and pg_switch_wal()

   Fabrice Chapuis <fabrice636861@gmail.com> — 2025-07-30T11:09:21Z

   To note effectively that the problem comes from a fix in version 17
   
   PostgreSQL: Release Notes <https://www.postgresql.org/docs/release/17.0/>
   
   Change file boundary handling of two WAL file name functions (Kyotaro
   Horiguchi, Andres Freund, Bruce Momjian)
   
   Regards,
   
   Fabrice
   
   
   On Wed, Jul 30, 2025 at 10:33 AM Fabrice Chapuis <fabrice636861@gmail.com>
   wrote:
   
   > Thanks Israel for these informations. In fact, I thought at first of a
   > problem related to the version of pg_basebackup in version 17. I should
   > have posted first on the barman github.
   >
   > Best regards,
   >
   > Fabrice
   >
   > On Wed, Jul 30, 2025 at 12:47 AM Israel Barth Rubio <barthisrael@gmail.com>
   > wrote:
   >
   >> Hello Fabrice,
   >>
   >> > But I do not understand this error with the barman wrapper:
   >> >
   >> > Backup completed (start time: 2025-07-26 21:45:07.238223, elapsed time:
   >> 19 seconds)
   >> > Waiting for the WAL file 0000000300000B3F0000000C from server
   >> 'x_service' (max: 600 seconds)
   >> > Processing xlog segments from streaming for x_service
   >> > 0000000300000B3F0000000A
   >> > Processing xlog segments from streaming for x_service
   >> > 0000000300000B3F0000000B
   >> > ERROR: The WAL file 0000000300000B3F0000000C has not been received in
   >> 600 seconds
   >>
   >> Are you by chance running PostgreSQL 17?
   >>
   >> If you are using PostgreSQL 17, you are very likely encountering the issue
   >> tracked here: https://github.com/EnterpriseDB/barman/issues/1041. In
   >> that case,
   >> a fix has already been merged and will be included in an upcoming release
   >> of
   >> Barman.
   >>
   >> As a quick note for the future, the Barman GitHub issues page is the
   >> correct place
   >> to report problems like this directly to the development team. In any
   >> case, I understand
   >> that you raised it here given the context of the original question about
   >> pg_basebackup.
   >>
   >> Hope that helps you.
   >>
   >> Best regards,
   >> Israel.
   >>
   >