On 2020/06/19 0:22, Robert Haas wrote:
On Thu, Jun 18, 2020 at 8:41 AM Fujii Masao <masao.fu...@oss.nttdata.com> wrote:ISTM that a clean switchover is possible without "ALTER SYSTEM READ ONLY". What about the following procedure? 1. Demote the primary to a standby. Then this demoted standby is read-only. 2. The orignal standby automatically establishes the cascading replication connection with the demoted standby. 3. Wait for all the WAL records available in the demoted standby to be streamed to the orignal standby. 4. Promote the original standby to new primary. 5. Change primary_conninfo in the demoted standby so that it establishes the replication connection with new primary. So it seems enough to implement "demote" feature for a clean switchover.There's something to that idea. I think it somewhat depends on how invasive the various operations are. For example, I'm not really sure how feasible it is to demote without a full server restart that kicks out all sessions. If that is required, it's a significant disadvantage compared to ASRO.
Even with ASRO, the server restart is necessary and RO sessions are kicked out when demoting RO primary to a standby, i.e., during a clean switchover? Regards, -- Fujii Masao Advanced Computing Technology Center Research and Development Headquarters NTT DATA CORPORATION
