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PIP-19: Availability Score for Validators


Authors B00f (@b00f)
Discussion View Discussion PIP-19
Created 01-01-2024

Abstract

This proposal suggests the introduction of an Availability Score for validators in the Pactus network to enhance network stability.

Motivation

Some users are running Pactus on extremely low-spec machines, potentially compromising the stability of the blockchain. For example, at the time of writing this proposal, only 50% of validators have signed more than 90% of blocks in a one-week period. Considering that validators have a 10-second window to validate the block and broadcast their votes, this level of performance is suboptimal Therefore, we need to take action to discourage users from dedicating very low-spec machines to run Pactus.

The chart below is extracted from the Testnet data over a one-week period:

Validators availability

This proposal recommends implementing an Availability Score System that evaluates validators based on their performance within the committee.

Specification

Availability Score Calculation

Each validator gives a score to other validators called the “Availability score.” To calculate this score, we look at the last 60,000 blocks, which covers almost a week (each block taking 10 seconds).

To calculate the score, we look at how many blocks a validator signed compared to how many times they were in the committee:

\[S_i = \frac{V_i}{N_i}\]

In this formula:

  • $S_i$ is the score for validator $i$.
  • $V_i$ is how many blocks validator $i$ signed.
  • $N_i$ is how many times validator $i$ was in the committee.

The score is a number between 0 and 1. If a validator wasn’t in the committee for the last 60,000 blocks, their score defaults to 1.

Penalties

When a validator within the committee receives a proposal from another validator, it first checks the availability score of the proposer. If the availability score is less than $0.9$, it rejects the proposal and enters the proposer-change phase 1. Since the majority of validators make the same decision, the proposal will be rejected, and the validator won’t receive any reward.

References


Copyright

Copyright and related rights waived via CC0.