Leader Election Design

Abstract

Leader election is the idea of designating a node in a distributed system with special powers. A fair and deterministic election process is important to maintaining liveness and decentralization.

In Othentic Stack, the leader election algorithm decides which Operator node will execute the AVS Task. After an election algorithm has been run, each node in the network recognizes a particular node as the leader.

The selected Operator—also known as the Performer Node—receives rewards for their contributions. In a shared security environment, these rewards incentivize Operator participation. An Operator’s total rewards depend on two factors: the base reward per task and the frequency with which they are selected to perform tasks. As such, AVS developers must implement a robust leader election mechanism to fairly and deterministically control how often each Operator is selected.

Importance of Fair and Deterministic Leader Election

Liveness refers to the AVS’s ability to function, ensuring:

• Tasks are consistently executed, and don't remain in the queue indefinitely.
• When a Performer node fails to execute a task or becomes unavailable, another node can step in to replace it.
• Network service is not interrupted as Operators join or leave the network.

Decentralization prevents operator bias from impacting the network and mitigates manipulation by its participants:

• If some operators are selected more often than others (due to a biased, random or gameable selection process), it can lead to an unfair distribution of rewards and may discourage other Operators from participating.
• Leader election mechanisms serve as additional safeguards if operators attempt to manipulate or tamper with the system.

Fair leader election improves resilience, preserves neutrality by ensuring that no single Operator monopolizes tasks and rewards.

Selecting the right Leader Election Algorithm

In an AVS, leader election determines which Operator executes a Task—whether processing AI computation, validating a block, or triggering an off-chain workflow. The "right" election mechanism depends heavily on the type of Task and the design goals of the AVS. Key evaluation factors include Latency, Security, Scale, Incentives, and Fairness:

• Latency: If the Task is time-sensitive (e.g., real-time trading or block production), low-latency leader selection is important. In contrast, AVSs like indexers or batch processors may tolerate slower elections without impacting performance.
  ‍
• Security: Predictable leader selection is a risk—attackers can front-run or target known leaders. Secure election methods like VRF-based randomness or stake-weighted randomness reduce predictability and increase robustness in risk environments.
  ‍
• Scale: Mechanisms like Round Robin or RAFT may perform well in small, trusted sets but can break down at scale. AVSs with a large number of Operators need election strategies that remain performant and reliable as the system scales.
  ‍
• Incentives: AVSs often rely on economic alignment. Stake-weighted or auction-based systems ensure that those with skin in the game—through capital, compute, or reputation—are more likely to be selected, aligning performance with investment.
  ‍
• Fairness: In a fair system, every Operator should get an equal chance. However, full fairness promotes decentralization but may ignore differences in individual Opertaor contributions or capabilities. Some AVSs benefit by prioritizing fairness to avoid centralization, while others favor merit-based selection.
  ‍

Different Leader Election Algorithms

1. Round Robin: The "Task Performer" is chosen in a round-robin manner, where operators take turns performing tasks in a fixed sequence based on their IDs. The system cycles through the list of active Operators, ensuring an even distribution of tasks.‍
   ‍
2. Random Selection: The "Task Performer" is chosen randomly and deterministically from the pool of nodes. This method ensures that no Operator is favored over another, and it can prevent systematic bias in task distribution. A random number generator can be used to select a task performer from the pool of active operators.‍
   ‍
3. Stake-weighted: The "Task Performer" is selected based on a weighted probability. It ensures that operators with higher Voting Power (or other assigned weights) have a greater likelihood of being chosen while still maintaining an element of randomness.
   ‍‍
4. Priority-based : Operators are assigned different priority levels, and the highest priority operator is chosen to perform the task. This priority can be based on factors such as reputation, available resources, or past performance.‍
   ‍
5. Consensus-based (RAFT): In this approach, operators participate in a consensus mechanism, such as RAFT, to elect a leader to perform the task. This is commonly used in distributed systems, where the leader coordinates task execution and ensures system consistency.
   ‍
6. Leaderless Auction: In this model, Operators bid for the right to execute tasks. A two-phase commit ensures fairness: nodes first submit hashed bids (commit phase), then reveal them (reveal phase). The highest bidder wins task execution rights.
   ‍

Constructing the Rewards Function Based on a Leader Election Mechanism

The Othentic Stack supports any Leader Election mechanism implemented by the AVS developer. To generalize for any Leader Election algorithm, a probability function P(n) can be derived from the selected algorithm such that the aggregate probability of all electable leaders is equal to one:

We can then rewrite the formula to describe the expected reward for operator n as:

These are the components for the rewards function:

• P(n) — The probability of operator n to be elected for a task
• R — The base reward for each task
• C — The number of tasks the network produced overall.

P(n) is derived from the implemented Leader Election algorithm. Different algorithms could have different P functions. R is the base reward and is configurable via the AttestationCenter contract, while C is a factor of the demand for the services offered by the network.

Implement Leader election with the Othentic Stack

Othentic Stack allows you to customize the leader election algorithm based on the AVS use case.

Here are specific implementations that teams can use as per their needs:

• Custom Leader Election
• Round Robin implementation
• Random Selection implementation
• Stake Weighted implementation
• Leaderless Auction implementation

Summary

Leader election is a powerful tool used in distributed systems to help make fault-tolerant, fair, and scalable environments. Each design consideration comes with tradeoffs, the choice depends on task type, security model, and AVS design.

Further Reading

• Leader election in Othentic Stack
• Secret Leader election

‍