Hey all, In a recent discussion, we noticed that the 0.20.2 HDFS client will not be wire-compatible with 0.20.0 or 0.20.1 due to the inclusion of HDFS-793 (required for HDFS-101). This begs a few questions:
1) Although we certainly do not guarantee wire compatibility between minor versions (0.20 -> 0.21) have we previously implied wire compatibility between bugfix releases? 2) Is the above something we *should* be guaranteeing already? 3) If we haven't guaranteed the above, how many users think we have? (ie how do we correctly call out this fact in the 0.20.2 release notes in such a way that no one gets surprised). I can imagine plenty of organizations where a lockstep upgrade between client and server is difficult, and we should make sure that cluster operators know it will be necessary. Since it wasn't necessary between 0.20.0 and 0.20.1, or various 0.18 releases, people may have grown used to non-lockstep upgrades. 4) If the above are problems, would it be worth considering a patch for branch-20 that provides a client that is compatible with either, based on the datanode protocol version number of the server? It seems like a bit of scary complexity, but wanted to throw it out there. Thanks -Todd
