[Bucardo-general] Bucardo zero downtime Postgres RDS upgrade

[Manoj Sahani]

Hello,
I am planning a zero downtime upgrade of Postgres RDS instance using Bucardo and appreciate if anyone has a better approach than the one below that they can share.

These are the high level steps…

1.Take snapshot of existing RDS instance
2.Create new RDS based on this snapshot
3.Upgrade new RDS instance
4.Create Bucardo master-slave group
5.Start sync from old to new RDS
6.Point apps to new RDS instance

While on step#5, I noticed that there was no way to start a bucardo sync and apply delta changes starting from the time step#1 was done. Is it possible for Bucardo to even do that?
As a workaround , I had to do step#5 with an initial OneTimeCopy=1. Is there a better way of doing this?
​​​​​
For rollback purposes, we need to have two options…

  1.  Rollback to original RDS (This seems easy)
  2.  Rollback to original RDS and apply delta (only if needed) after step#6. To achieve this, it seems a multi-master replication in step4 would be a better choice.
How safe is the multi-master replication in terms of causing an unintended reverse sync.

Thanks!
Manoj

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