[Consensus] Leader Election - Productionize the sortition algorithm

[jessicadaugherty]

Objective

Implement random leader election proportional to the Validator's total stake that is not susceptible to grinding attacks, while also productionizing the leader election process.

Origin Document

The algorithm for HotPOKT leader election algorithm can be found in the consensus specification. It is based on Section 5.1 in the Algorand whitepaper.

The leader election package in this repository implements most of the core business logic as a separate library to enable this.

The current leader election algorithm uses round robin defined in consensus/helpers.go:

func (m *consensusModule) electNextLeader(message *typesCons.HotstuffMessage) error {
	leaderId, err := m.leaderElectionMod.ElectNextLeader(message)
	if err != nil || leaderId == 0 {
    // ...
}

Goals

• Enable node flow to use VRF/CDF functions in leader election
• Ensure Validator selection probability is proportional to stake_tokens/total_stake_tokens
• Identify next steps for leader election TODOs

Deliverable

• Integrate the leader_election library in place of the current "round robin" leader election process
• Ensure the node can assign a proper leader and monitor the leader election
• Review the existing VRF & CDF functions to verify that there are no implementation gaps
• Add logging and monitoring so the current leader can be easily tracked
• Business logic to fallback to round-robin leader election if one is not found using the sortition algorithm
• Identify all TODOs in the leader election package via grep -rl "TODO" ./consensus/leader_election and:
  • Delete impertinent TODOs
  • Document which TODOs require new issues

Non-goals / Non-deliverables

• Tending to every TODO in the leader election package

General issue deliverables

• Update the appropriate CHANGELOG
• Update any relevant READMEs (local and/or global)
• Update any relevant global documentation & references

Testing Methodology

• Required: add new tests for the changes added here
• VRF Tests: make test_vrf # Update if needed
• Sortition Tests: make test_sortition # Update if needed
• All tests: make test_all
• LocalNet: verify a LocalNet is still functioning correctly by following the instructions at docs/development/README.md

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Creator: @jessicadaugherty
Co-Owners: @Olshansk

[jessicadaugherty]

@Olshansk define ty

[jessicadaugherty]

@gokutheengineer updated AC for review. Ty!