ForwardCommand
data class ForwardCommand(val v: Int = VERSION, val command: CommandWire, val transport: Transport? = null, val deadline: Long)
The cluster channel's one message kind for now: a node forwards command to the owner of its partition and waits for the reply until deadline (epoch milliseconds). transport carries the command's wait context and the trace context it executes in, in the one form of a transport (TransportCodec); null when it has neither. The wait's origin stays the node the command arrived at, so later hops signal that node directly, never through the channel.
Every cluster message carries its format version v. A reader ignores the fields it does not know, so a node reads the messages of the next minor version.