Re: Standby server with cascade logical replication could not be properly stopped under load

On Fri, Dec 26, 2025 at 04:14:17PM +0500, G. Sl wrote:
> I've found the same behaviour in the 15.12 version. Any chances for
> backpatch for this version ?

As presented on this thread, the problem reported involves at least a
cluster configuration A -> B -> C, where:
- A is a primary.
- B is a physical standby, streaming changes from A.  In the test
setup, this node includes replication slots, that have been created
while the node is in standby mode.  This action can only happen in v16
and newer versions, where logical decoding on standbys has been added.
- C is a primary node, streaming logical changes from B.

Based on how the state of B required, this would not apply to v15
because it is not possible to create replication slots on a standby.
Also you may want to update to 15.15 first.

I am open to arguments or discussions if you have found a new or
different problem, of course, but there is nothing we can do without
knowing more about your setup.  An even better thing would be to have
a reproducible test case based on v15 to understand your problem, but
I can say for sure that we may be dealing with something different.
Please feel free to refer to the top of the thread, which offers an
excellent example of what a reproducible test case can be.  By that I
mean something that we can reuse and reproduce the issue.

Also note that the change committed is 5231ed8262c9, that relies on
the existence of am_cascading_walsender in XLogSendLogical() to not
use GetFlushRecPtr() in all cases.  Before the commit, we used
GetStandbyFlushRecPtr() for that in v16.  Again, v15 just uses
GetFlushRecPtr(), but it should not be possible to find yourself in a
position where XLogSendLogical() is called while on a standby, no?
--
Michael