Write article on how to do zero downtime upgrades with the operator

[alberttwong]

Upgrade BE nodes Run the following command to specify a new BE image file, such as starrocks/be-ubuntu:latest:

kubectl -n starrocks patch starrockscluster starrockscluster-sample --type='merge' -p '{"spec":{"starRocksBeSpec":{"image":"starrocks/be-ubuntu:latest"}}}'

Upgrade FE nodes Run the following command to specify a new FE image file, such as starrocks/fe-ubuntu:latest:

kubectl -n starrocks patch starrockscluster starrockscluster-sample --type='merge' -p '{"spec":{"starRocksFeSpec":{"image":"starrocks/fe-ubuntu:latest"}}}'

[!NOTE]
The upgrade process lasts for a while. You can run the command kubectl -n starrocks get pods to view the upgrade progress.

[!NOTE]
In flight SQL statements may need to be re-submitted to StarRocks due to bouncing the containers during the upgrade process.