Performance based leader selection
Creating incentives for high performant validator nodes
Last updated
Creating incentives for high performant validator nodes
Last updated
Solana stands out because it was designed from the outset to operate without a mempool. Unlike traditional blockchains that use gossip protocols to randomly and broadly propagate transactions across the network, Solana forwards all transactions to a predetermined lead validator, known as the leader, for each slot. Once an RPC receives a transaction message to be included in a block, it must be forwarded to the leader.
A leader schedule is produced before every epoch (approximately every two days). The upcoming epoch is divided into slots, each fixed at 400 milliseconds, and a leader is chosen for each slot. The sequence of leaders is determined ahead of time, and validators know when they will become the leader. This rotation happens very quickly, with leaders changing every few hundred milliseconds.
Validators with a higher stake have a higher probability of being chosen as a leader within each epoch. During each slot, transaction messages are forwarded to the leader, who has the opportunity to produce a block. When it is a validator’s turn, they switch to "leader mode," begin actively processing transactions and broadcasting blocks to the rest of the network.
The Solana "skip rate"—the percentage of slots in which a block was not produced—varies from 2% to 10%. While forks are a primary reason for skipped slots, validator performance is another significant factor. Currently, the only selection criteria for becoming a leader is stake weight, which does not consider the performance of the validator.
If a validator is chosen as a leader but has poor performance due to network connection issues or hardware problems, they risk skipping slots they would have been rewarded for. This not only slows down the network but also increases the risk of transactions being dropped, which is detrimental to the chain's overall performance.
On Solana, there are nodes with significant stake weight that are regularly selected as leaders despite having poor historic performance. Some of these nodes exhibit skip rates exceeding 50%, yet they continue to be selected in the leader schedule. Solana currently does not reject poorly performing validators from the leader schedule, leading to inefficiencies in the network.
To optimize the system, it's clear that leader selection should be based on more than just stake weight. In addition to stake weight, the X1 Blockchain will introduce new criteria for eligibility in the leader schedule. The stake weight will be virtualized into a score, which can be adjusted based on a validator's historical performance. Should a validator's score drop due to poor performance, they will either be removed from the leader schedule or rejected from becoming a leader altogether.
This solution leverages existing economic incentives, encouraging validators to maintain high-functioning and high-performing nodes. By incorporating both relative stake and historical performance into the selection process, the X1 Blockchain aims to ensure that only the most capable validators are chosen as leaders, thereby improving the overall efficiency and reliability of the network.
