Streaming Replication between PostGreSQL 9.2.2 on Red Hat and PostGreSQL 9.2.24 on Debian

On 05/21/2018 07:18 PM, Jonatan Evald Buus wrote:

Hi there,

I'm trying to configure streaming replication between a Red Hat server
running PostGreSQL 9.2.2 and a Debian server running PostGreSQL 9.2.24
with Hot Standby enabled.

While the base backup works fine using /pg_basebackup/, I get the following
errors with hot standby enabled on the Debian slave when starting PostGreSQL:

/WARNING: WAL was generated with wal_level=minimal, data may be missing/
/HINT: This happens if you temporarily set wal_level=minimal without taking a new base backup./
/FATAL: hot standby is not possible because wal_level was not set to "hot_standby" on the master server/
/HINT: Either set wal_level to "hot_standby" on the master, or turn off hot_standby here/

If I turn Hot Standby off on the Debian Slave I get the following errors:
/FATAL: database system identifier differs between the primary and standby/
/DETAIL: The primary's identifier is 5940475598986796885, the standby's identifier is 6557962695089036503./

The standby clearly hasn't been cloned from the primary, otherwise the
identifiers would be the same. Are you sure the PostgreSQL instance
running on the standby is the one you backed up with pg_basebackup?

Regards

Ian Barwick

--
Ian Barwick http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services

Thanks Ian, thank you for pointing out the obvious.
It appears that Debian's *pg_dropcluster* command had unexpected
consequences.... you live, you pull out your hair in frustration and you
learn.

I now have streaming replication working as we expected, can you confirm
that my *(somewhat unusual scenario?) *shouldn't cause any problems?
Specifically:
- Using Streaming Replication between two PostGreSQL instances with
different minor versions will work *(9.2.2 on RHEL and 9.2.24 on Debian)*
- Using Streaming Replication between two servers running different
operating systems *(RHEL 5.5 and Debian 8 / 9) *will work

Greatly appreciate your insight

Cheers
Jona

On 21 May 2018 at 13:27, Ian Barwick <ian.barwick@2ndquadrant.com> wrote:

On 05/21/2018 07:18 PM, Jonatan Evald Buus wrote:

Hi there,

I'm trying to configure streaming replication between a Red Hat server
running PostGreSQL 9.2.2 and a Debian server running PostGreSQL 9.2.24
with Hot Standby enabled.

While the base backup works fine using /pg_basebackup/, I get the

following

errors with hot standby enabled on the Debian slave when starting

PostGreSQL:

/WARNING: WAL was generated with wal_level=minimal, data may be missing/
/HINT: This happens if you temporarily set wal_level=minimal without

taking a new base backup./

/FATAL: hot standby is not possible because wal_level was not set to

"hot_standby" on the master server/

/HINT: Either set wal_level to "hot_standby" on the master, or turn off

hot_standby here/

If I turn Hot Standby off on the Debian Slave I get the following errors:
/FATAL: database system identifier differs between the primary and

standby/

/DETAIL: The primary's identifier is 5940475598986796885, the standby's

identifier is 6557962695089036503./

The standby clearly hasn't been cloned from the primary, otherwise the
identifiers would be the same. Are you sure the PostgreSQL instance
running on the standby is the one you backed up with pg_basebackup?

Regards

Ian Barwick

--
Ian Barwick http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services

--
Jonatan Evald Buus
CTO, CellPoint Mobile
www.cellpointmobile.com
*WE MAKE TRAVEL EASIER™*

O: +45 70211512 <+45%2070%2021%2015%2012> | M: +45 28882861
<+45%2028%2088%2028%2061>
E: jonatan.buus@cellpointmobile.com
*Copenhagen* | Dubai | London | Miami | Pune | Singapore

Hi,

- Doing Streaming Replication between different minor version of PG is
possible but not recommended [2]https://www.postgresql.org/docs/9.2/static/warm-standby.html (planning section)

- Doing Streaming Replication between different OSes is not recommended
pre ICU (pg10), please check you glibc versions. [1]/messages/by-id/BA6132ED-1F6B-4A0B-AC22-81278F5AB81E@tripadvisor.com

[1]: /messages/by-id/BA6132ED-1F6B-4A0B-AC22-81278F5AB81E@tripadvisor.com
/messages/by-id/BA6132ED-1F6B-4A0B-AC22-81278F5AB81E@tripadvisor.com
[2]: https://www.postgresql.org/docs/9.2/static/warm-standby.html (planning section)
section)

Hoep this helps.

Cheers
Ben

2018-05-22 10:13 GMT+02:00 Jonatan Evald Buus <
jonatan.buus@cellpointmobile.com>:

On Thu, May 24, 2018 at 10:21:33AM +0200, talk to ben wrote:

- Doing Streaming Replication between different minor version of PG is
possible but not recommended [2]

Standbys need to be updated first, hence be careful that the primary is
not updated before the standbys or WAL generated on the primary may not
be able to replay on its standbys. Note however that you won't get
support for such configurations on the community lists, so just make
sure that all nodes in a cluster are on the same version and that it is
the latest one.
--
Michael