Thread

1. BUG #18945: Standby synchronization problem

   PG Bug reporting form <noreply@postgresql.org> — 2025-06-02T12:18:58Z

   The following bug has been logged on the website:
   
   Bug reference:      18945
   Logged by:          lucas marola
   Email address:      lucasmarola@hotmail.com
   PostgreSQL version: 16.8
   Operating system:   Red Hat Enterprise Linux release 9.5 (Plow)
   Description:        
   
   Sometimes, the WAL application on the standby environment takes a long time
   to complete. However, after restarting the application process, it returns
   to normal.
   
   

2. Re: BUG #18945: Standby synchronization problem

   Dilip Kumar <dilipbalaut@gmail.com> — 2025-06-02T13:12:08Z

   On Mon, Jun 2, 2025 at 5:56 PM PG Bug reporting form
   <noreply@postgresql.org> wrote:
   >
   > The following bug has been logged on the website:
   >
   > Bug reference:      18945
   > Logged by:          lucas marola
   > Email address:      lucasmarola@hotmail.com
   > PostgreSQL version: 16.8
   > Operating system:   Red Hat Enterprise Linux release 9.5 (Plow)
   > Description:
   >
   > Sometimes, the WAL application on the standby environment takes a long time
   > to complete. However, after restarting the application process, it returns
   > to normal.
   
   it's difficult to pinpoint the exact problem with the information
   provided. However, a common scenario involves read-only queries on a
   standby database conflicting with the WAL apply process.  And as a
   result of restarting the application it will terminate all the backend
   so you are not facing issues of conflict any more.  You can check the
   value of 'max_standby_streaming_delay' as this will control how long
   the WAL apply process should wait in case of a conflict with the
   snapshot of the local queries.  If you have steps to reproduce/or more
   details on the exact scenario, then that would be helpful.
   
   
   -- 
   Regards,
   Dilip Kumar
   Google
   
   
   
   

3. Re: BUG #18945: Standby synchronization problem

   Michael Paquier <michael@paquier.xyz> — 2025-06-03T06:13:59Z

   On Mon, Jun 02, 2025 at 06:42:08PM +0530, Dilip Kumar wrote:
   > it's difficult to pinpoint the exact problem with the information
   > provided. However, a common scenario involves read-only queries on a
   > standby database conflicting with the WAL apply process.  And as a
   > result of restarting the application it will terminate all the backend
   > so you are not facing issues of conflict any more.  You can check the
   > value of 'max_standby_streaming_delay' as this will control how long
   > the WAL apply process should wait in case of a conflict with the
   > snapshot of the local queries.
   
   Indeed, there could be a lot going on.
   
   A sequence of commands to pinpoint an issue, with a precise
   description of what has been done, would help.  Their may be some
   tools you are using, that help in the reproducibility.  If you are
   seeing a process being stuck, attaching gdb to the process that
   matters, be it a WAL sender or the startup process, or something else,
   can also provide useful hints that could help in determining if you
   have hit an actual bug or not.  Log contents could provide useful
   hints, just be sure to trim any sensitive contents they may include
   before posting or attaching anything here.
   
   Three lines to describe your problem is not enough for one to
   potentially understand what's going on in your system.
   
   > If you have steps to reproduce/or more
   > details on the exact scenario, then that would be helpful.
   
   Right.
   --
   Michael