We are planning to do an online 6->7 upgrade for our ES clusters, and we are looking into ways of rolling back safely from 7 to 6 in case something bad happens. The ES docs state that once the upgrade starts, the ES cluster will run into a backwards-compatible mode and will start using ES7 features after all nodes are fully upgraded. To get a better understanding of this, I have a few questions:
- Is this switch happening automatically? Would it be possible to prevent it? (via a code change, or a setting change)
- What would be the place in the code where this switch would happen?