BEEFY voter should have "non-authority light mode"

[acatangiu]

These would not vote themselves, but could/should gossip votes and provide on-demand justifications.

[seunlanlege]

Wait so, Beefy justifications either via block justifications or through beefy_subscribeJustifications aren't available on non-authority nodes?

[acatangiu]

Right now the beefy worker code does not have an explicit switch between authority and non-authority. As such all nodes are gossiping votes, all nodes handle votes, and all nodes also try to vote (with non-auth ones failing to vote because no auth key available in keystore).

This translates to:

• all nodes handle BEEFY votes so all nodes append block justifications and publish justifications to subscribers,
• non-auth nodes waste a bit of CPU trying to vote before they realize they can't - this should be improved

[acatangiu]

With the new BEEFY justification import logic, BEEFY justifications are stripped at block import and passed to the voter for validation before being included in the chain backend.

If the beefy voter isn't running on the node then it doesn't include beefy justifications anymore. If we start the voter on non-auth nodes, we end up wasting a some cpu cycles trying to vote and failing (because node is not validator).

Maybe we can add extra logic to voter to explicitly skip voting for sessions it knows it's not a validator. Non-auth voter should still follow and process justifications and finality notifications and switch between auth/non-auth states at session boundaries (when validator set changes).