Mostly I just wanted to ack that at least someone read the doc (somewhat superficially sure, but some parts with thought...)
One pre-feature that we would include in the preceding minor release is a > node level switch to disable all operations that modify cluster metadata > state. This would include schema changes as well as topology-altering > events like move, decommission or (gossip-based) bootstrap and would be > activated on all nodes for the duration of the *major* upgrade. If this > switch were accessible via internode messaging, activating it for an > upgrade could be automated. When an upgraded node starts up, it could send > a request to disable metadata changes to any peer still running the old > version. This would cost a few redundant messages, but simplify things > operationally. > > Although this approach would necessitate an additional minor version > upgrade, this is not without precedent and we believe that the benefits > outweigh the costs of additional operational overhead. > Sounds like a great idea, and probably necessary in practice? > If this part of the proposal is accepted, we could also include further > messaging protocol changes in the minor release, as these would largely > constitute additional verbs which would be implemented with no-op verb > handlers initially. This would simplify the major version code, as it would > not need to gate the sending of asynchronous replication messages on the > receiver's release version. During the migration, it may be useful to have > a way to directly inject gossip messages into the cluster, in case the > states of the yet-to-be upgraded nodes become inconsistent. This isn't > intended, so such a tool may never be required, but we have seen that > gossip propagation can be difficult to reason about at times. > Others will know the code better and I understand that adding new no-op verbs can be considered safe... But instinctively a bit hesitant on this one. Surely adding a few if statements to the upgraded version isn't that big of a deal? Also, it should make sense to minimize the dependencies from the previous major version (without CEP-21) to the new major version (with CEP-21). If a bug is found, it's much easier to fix code in the new major version than the old and supposedly stable one. henrik -- Henrik Ingo +358 40 569 7354 <358405697354> [image: Visit us online.] <https://www.datastax.com/> [image: Visit us on Twitter.] <https://twitter.com/DataStaxEng> [image: Visit us on YouTube.] <https://urldefense.proofpoint.com/v2/url?u=https-3A__www.youtube.com_channel_UCqA6zOSMpQ55vvguq4Y0jAg&d=DwMFaQ&c=adz96Xi0w1RHqtPMowiL2g&r=IFj3MdIKYLLXIUhYdUGB0cTzTlxyCb7_VUmICBaYilU&m=bmIfaie9O3fWJAu6lESvWj3HajV4VFwgwgVuKmxKZmE&s=16sY48_kvIb7sRQORknZrr3V8iLTfemFKbMVNZhdwgw&e=> [image: Visit my LinkedIn profile.] <https://www.linkedin.com/in/heingo/>
