We've all encountered this scenario. PostgreSQL recently released version 9.6.1 and we need to upgrade to protect ourselves from potential data corruption. Or perhaps it isn't PostgreSQL that requires an upgrade, but the system kernel or another critical element of the operating system.
Regardless of the reason, we must accommodate the procedure somehow. Upgrading software while remaining online is the ultimate aspiration of maintaining a high availability stack. Let's see how we can reach that goal by leveraging Patroni's functionality.
This recipe depends on the presence of the entire stack. Please complete all recipes up to Installing and configuring HAProxy before continuing.