Error message
In the message, %s marks a value that the engine fills in when it raises the error.
The story
Your node just removed itself from the distributed set, on purpose. Here is why. Nodes that share data agree on an order of events, and that agreement depends on their clocks staying close together. Rush measures the gap through heartbeats: the offset between the two clocks, plus half the delay. If that skew grows to about eighty percent of the coalescing quantum, rush acts before the limit is actually broken. It closes the wire, stops sending, and leaves the distributed set for the rest of the process. The node reports itself as not a member. This is not a crash and not a bug. It is the engine refusing to emit under an order it can no longer vouch for, because a wrong order, silently emitted, would corrupt data on every node. The first slot names the heartbeat, and the second shows the measurement. To get back in, fix the cause: a drifting clock, a slow network, or a heavily loaded machine. Synchronize the clocks, for instance with a time service, and start the node again.
Text from the Rush engine's error catalogue.