Wrong HINT during database recovery when occur a minimal wal.

Sorry, I don't known why it showed in wrong format, and try to correct it.
-----

When I do PITR in a strange step, I get this FATAL:

2021-01-15 15:02:52.364 CST [14958] FATAL: hot standby is not possible because wal_level was not set to "replica" or higher on the primary server
2021-01-15 15:02:52.364 CST [14958] HINT: Either set wal_level to "replica" on the primary, or turn off hot_standby here.

The strange step is that I change wal_level to minimal after basebackup.

My question is that what's the mean of [set wal_level to "replica" on the primary] in
HINT describe, I can't think over a case to solve this FATAL by set wal_level, I can
solve it by turn off hot_standby only.

Do you think we can do this code change?
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -6300,7 +6300,7 @@ CheckRequiredParameterValues(void)
  if (ControlFile->wal_level < WAL_LEVEL_REPLICA)
  ereport(ERROR,
  (errmsg("hot standby is not possible because wal_level was not set to \"replica\" or higher on the primary server"),
-  errhint("Either set wal_level to \"replica\" on the primary, or turn off hot_standby here.")));
+  errhint("You should turn off hot_standby here.")));

Regards,
Highgo Software (Canada/China/Pakistan)
URL : www.highgo.ca
EMAIL: mailto:movead(dot)li(at)highgo(dot)ca

At Fri, 15 Jan 2021 15:32:58 +0800, "lchch1990@sina.cn" <lchch1990@sina.cn> wrote in

Sorry, I don't known why it showed in wrong format, and try to correct it.
-----

When I do PITR in a strange step, I get this FATAL:

2021-01-15 15:02:52.364 CST [14958] FATAL: hot standby is not possible because wal_level was not set to "replica" or higher on the primary server
2021-01-15 15:02:52.364 CST [14958] HINT: Either set wal_level to "replica" on the primary, or turn off hot_standby here.

The strange step is that I change wal_level to minimal after basebackup.

Mmm. Maybe something's missing. If you took the base-backup using
pg_basebackup, that means max_wal_senders > 0 on the primary. If you
lowered wal_level in the backup (or replica) then started it, You
would get something like this.

| FATAL: WAL streaming (max_wal_senders > 0) requires wal_level "replica" or "logical".

If you changed max_wal_senders to zero, you would get the following instead.

| FATAL: hot standby is not possible because max_wal_senders = 0 is a lower setting than on the primary server (its value was 2)

So I couldn't reproduce the situation.

Anyways..

My question is that what's the mean of [set wal_level to "replica" on the primary] in
HINT describe, I can't think over a case to solve this FATAL by set wal_level, I can
solve it by turn off hot_standby only.

Do you think we can do this code change?
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -6300,7 +6300,7 @@ CheckRequiredParameterValues(void)
if (ControlFile->wal_level < WAL_LEVEL_REPLICA)
ereport(ERROR,
(errmsg("hot standby is not possible because wal_level was not set to \"replica\" or higher on the primary server"),
-  errhint("Either set wal_level to \"replica\" on the primary, or turn off hot_standby here.")));
+  errhint("You should turn off hot_standby here.")));

Since it's obvious that the change in a primary cannot be propagted by
taking a backup or starting replication, the first sentence reads to
me as "you should retake a base-backup from a primary where wal_level
is replica or higher". So *I* don't think it needs a fix.

Any thoughts?

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center

Mmm. Maybe something's missing. If you took the base-backup using
pg_basebackup, that means max_wal_senders > 0 on the primary. If you
lowered wal_level in the backup (or replica) then started it, You
would get something like this.
| FATAL: WAL streaming (max_wal_senders > 0) requires wal_level "replica" or "logical".
If you changed max_wal_senders to zero, you would get the following instead.
| FATAL: hot standby is not possible because max_wal_senders = 0 is a lower setting than on the primary server (its value was 2)

Then mark hot_standby off and continue try lowered wal_level.
And do recovery from the basebackup, then you will see the FATAL.

So I couldn't reproduce the situation.
Anyways.

My question is that what's the mean of [set wal_level to "replica" on the primary] in
HINT describe, I can't think over a case to solve this FATAL by set wal_level, I can
solve it by turn off hot_standby only.

Do you think we can do this code change?
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -6300,7 +6300,7 @@ CheckRequiredParameterValues(void)
if (ControlFile->wal_level < WAL_LEVEL_REPLICA)
ereport(ERROR,
(errmsg("hot standby is not possible because wal_level was not set to \"replica\" or higher on the primary server"),
-  errhint("Either set wal_level to \"replica\" on the primary, or turn off hot_standby here.")));
+  errhint("You should turn off hot_standby here.")));

Since it's obvious that the change in a primary cannot be propagted by
taking a backup or starting replication, the first sentence reads to
me as "you should retake a base-backup from a primary where wal_level
is replica or higher". So *I* don't think it needs a fix.

I think this HINT is want to guide users to finish this recovery, and the first guide is
invalid in my opinion.

Regards,
Highgo Software (Canada/China/Pakistan)
URL : www.highgo.ca
EMAIL: mailto:movead(dot)li(at)highgo(dot)ca

At Fri, 15 Jan 2021 17:04:19 +0800, "lchch1990@sina.cn" <lchch1990@sina.cn> wrote in

Mmm. Maybe something's missing. If you took the base-backup using
pg_basebackup, that means max_wal_senders > 0 on the primary. If you
lowered wal_level in the backup (or replica) then started it, You
would get something like this.
| FATAL: WAL streaming (max_wal_senders > 0) requires wal_level "replica" or "logical".
If you changed max_wal_senders to zero, you would get the following instead.
| FATAL: hot standby is not possible because max_wal_senders = 0 is a lower setting than on the primary server (its value was 2)

Then mark hot_standby off and continue try lowered wal_level.
And do recovery from the basebackup, then you will see the FATAL.

So I couldn't reproduce the situation.
Anyways.

My question is that what's the mean of [set wal_level to "replica" on the primary] in
HINT describe, I can't think over a case to solve this FATAL by set wal_level, I can
solve it by turn off hot_standby only.

Do you think we can do this code change?
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -6300,7 +6300,7 @@ CheckRequiredParameterValues(void)
if (ControlFile->wal_level < WAL_LEVEL_REPLICA)
ereport(ERROR,
(errmsg("hot standby is not possible because wal_level was not set to \"replica\" or higher on the primary server"),
-  errhint("Either set wal_level to \"replica\" on the primary, or turn off hot_standby here.")));
+  errhint("You should turn off hot_standby here.")));

Since it's obvious that the change in a primary cannot be propagted by
taking a backup or starting replication, the first sentence reads to
me as "you should retake a base-backup from a primary where wal_level
is replica or higher". So *I* don't think it needs a fix.

I think this HINT is want to guide users to finish this recovery, and the first guide is
invalid in my opinion.

I think it's also important to suggest to the users how they can turn
on hot_standby on their standby. So, perhaps-a-bit-verbose hint would
be like this.

"Either start this standby from base backup taken after setting
wal_level to \"replica\" on the primary, or turn off hot_standby
here."

This this make sense?

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center

I think it's also important to suggest to the users how they can turn
on hot_standby on their standby. So, perhaps-a-bit-verbose hint would
be like this.
"Either start this standby from base backup taken after setting
wal_level to \"replica\" on the primary, or turn off hot_standby
here."
This this make sense?Can you help me understand what [setting wal_level to \"replica\"] helpfor this startup from basebackup?

Do you mean set wal_level on basebackup or on the database we dobasebackup?