Horton

Re: [PoC] pg_upgrade: allow to upgrade publisher node

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>
Cc: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>, Peter Smith <smithpb2250@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Bruce Momjian <bruce@momjian.us>, Julien Rouhaud <rjuju123@gmail.com>, vignesh C <vignesh21@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>
Date: 2023-09-13T09:49:24Z
Lists: pgsql-hackers 
On Tue, Sep 12, 2023 at 5:20 PM Hayato Kuroda (Fujitsu)
<kuroda.hayato@fujitsu.com> wrote:
>

Few comments:
=============
1. One thing to note is that if user checks whether the old cluster is
upgradable with --check option and then try to upgrade, that will also
fail. Because during the --check run there would at least one
additional shutdown checkpoint WAL and then in the next run the slots
position won't match. Note, I am saying this in context of using
--check option with not-running old cluster. Won't that be surprising
to users? One possibility is that we document such a behaviour and
other is that we go back to WAL reading design where we can ignore
known WAL records like shutdown checkpoint, XLOG_RUNNING_XACTS, etc.

2.
+ /*
+ * Store the names of output plugins as well. There is a possibility
+ * that duplicated plugins are set, but the consumer function
+ * check_loadable_libraries() will avoid checking the same library, so
+ * we do not have to consider their uniqueness here.
+ */
+ for (slotno = 0; slotno < slot_arr->nslots; slotno++)
+ {
+ os_info.libraries[totaltups].name = pg_strdup(slot_arr->slots[slotno].plugin);

Here, we should ignore invalid slots.

3.
+ if (!live_check && !slot->caught_up)
+ {
+ if (script == NULL &&
+ (script = fopen_priv(output_path, "w")) == NULL)
+ pg_fatal("could not open file \"%s\": %s",
+ output_path, strerror(errno));
+
+ fprintf(script,
+ "The slot \"%s\" has not consumed the WAL yet\n",
+ slot->slotname);

Is it possible to print the LSN locations of slot and last checkpoint?
I think that will aid in debugging the problems if any and could be
helpful to users as well.

-- 
With Regards,
Amit Kapila.

Commits

  1. Fix issues in binary_upgrade_logical_slot_has_caught_up().

  2. Fix a random failure in 003_logical_slots.pl.

  3. Fix a test in 003_logical_slots.

  4. Fix uninitialized slot array access during the upgrade.

  5. Fix the test 003_logical_slots.

  6. Commit b195e6d482 forgot to update meson.build.

  7. Use shorter file names in the upgrade logical slots test.

  8. Migrate logical slots to the new node during an upgrade.

  9. Flush logical slots to disk during a shutdown checkpoint if required.

  10. Prevent possibility of panics during shutdown checkpoint.