messages: add forward compatibility for gossiped messages - #91
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Previously, unknown fields received while gossiping would be silently dropped. This can happen if an older version of ckit receives a message from a newer version of ckit (where a new field has been added). This can lead to temporary convergence issues during a rollout: messages will continue to be refuted until all nodes are running the same version. While the State message has not changed since the original version of ckit, not having any support for forwards compatibility prevents us from being able to cleanly extend messages with new fields (see #89). This commit enforces all messages to handle and propagate unknown fields to permit forwards compatibility. Closes #90.
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Previously, unknown fields received while gossiping would be silently dropped. This can happen if an older version of ckit receives a message from a newer version of ckit (where a new field has been added).
This can lead to temporary convergence issues during a rollout: messages will continue to be refuted until all nodes are running the same version.
While the State message has not changed since the original version of ckit, not having any support for forwards compatibility prevents us from being able to cleanly extend messages with new fields (see #89).
This commit enforces all messages to handle and propagate unknown fields to permit forwards compatibility.
Unfortunately, the codec package requires the type being decoded into to explicitly handle unrecognized fields. This means that each message type must handle forwards compatibility, with no easy way to handle it at the package level generically.
Closes #90.