I want to deploy hybris builds with zero down time. Our technical architecture consist of two frontend servers, two backend servers, two master/slave solr clusters, but a single DB server (MS SQL 2012). A new build may require patch execution which changes the DB schema.
Would it be possible to achieve this in a single DB landscape?
If two DB's are required (blue and green), then what is the best practice for DB replication in case of hybris?
Hybris does provide a rolling update feature (when you're running it in a cluster environment). This is targeted to allow for zero downtime.
You can find more information on the hybris help pages, e.g. https://help.hybris.com/6.5.0/hcd/8c455268866910149b25f7b53d1af3e1.html
Looking at the first picture there it seems to be pretty much fitting for the architecture you describe.
(But to be honest I have no experience with it, so I can't tell you whether or or how well it works :) )
If you have risky changes or end up needing to rollback your rolled out update you will have to do quite a bit of db cleanup etc.
From that perspective a blue/green setup might sound better although with db replication you would end up with the same problem (as your updated schema would be replicated as well I assume).
Hybris only adding new columns to db, never change their type or remove them. So single DB can be OK. I didn't test this using store front while updating system. I think it will be OK. On the other hand you need development for empty/null check for new attributes in development.
