While working on #75745 I accidentally broke the wire serialization of SearchRequest on 7.x and was suprised to find that not all hell broke lose when e.g. running the mixed cluster rest tests. I created an experimental PR that adds a new boolean flag to the SearchRequest serialization on 8.0 #77889, which without a bwc layer should break communication with older 7.x nodes. It appears the only thing that failed was a CCS rolling upgrade test (SearchStatesIT) which I find to be a poot indicator of such a big break.
I'd like to understand better why the mixed cluster tests don't seem to be too sensitive to this kind of change and potentially modify them or add additional test that would surface these situations better.
While working on #75745 I accidentally broke the wire serialization of SearchRequest on 7.x and was suprised to find that not all hell broke lose when e.g. running the mixed cluster rest tests. I created an experimental PR that adds a new boolean flag to the SearchRequest serialization on 8.0 #77889, which without a bwc layer should break communication with older 7.x nodes. It appears the only thing that failed was a CCS rolling upgrade test (SearchStatesIT) which I find to be a poot indicator of such a big break.
I'd like to understand better why the mixed cluster tests don't seem to be too sensitive to this kind of change and potentially modify them or add additional test that would surface these situations better.