Selection Component

The Selector is the component appointed to collect the scores, verify the zero-knowledge proof thereto associated and to propagate the block hash associated with the highest score observed during a period of time denoted as timeLength. The block hash is then forwarded to the EventBus to be picked up by the Block Reducer

An abstract description of the Selection phase in the SBA* consensus protocol can be found here.

Values

Score Message

Architecture

The Selection component is implemented through the Phase struct. Internally, it carries a BlockGenerator in order to fully synchronize the creation of a candidate block and score, with the Selection phase. When the Selection component is called, the first thing it does is this block generation routine. Once finished (or if no block generator was actually initialized), queued events are flushed in order to catch up with any delays, and a listening loop is started. The selection component will listen on four channels:

• The internalScoreResult chan, on which it can receive a Score message from its own block generator - this message is then forwarded into the standard processing pipeline
• The evChan, which catches events coming from the network
• The timeOutChan, responsible for telling the Selection component when the time for the selection phase has ran out, and the component needs to wrap up its activites
• The ctx.Done chan, which notifies the Selection component of context cancellations, and allows for swift cleanup of the hanging goroutine

When an event comes through over the evChan, the following processing pipeline is followed:

1. Check if the event score is higher than the current bestEvent. If not, the flow ends here.
2. Verify the proof, included in the Score event. If the verification fails, the flow ends here.
3. The Score event is repropagated to the network.
4. The bestEvent field on the Selection component will now be set to the new Score event.

The purpose of this processing flow is to have the Score message with the highest score in memory when the timer expires. Once this timer expires, the message is returned and can be used to vote in the reduction step.