Solana中的投票流程

1. 引言

前序博客有：

• Solana代码解析
• Solana中的PoH

2. TPU中收集投票

		let (verified_vote_packets_sender, verified_vote_packets_receiver) = unbounded();
        let cluster_info_vote_listener = ClusterInfoVoteListener::new(
            exit,
            cluster_info.clone(),
            verified_vote_packets_sender,
            poh_recorder,
            vote_tracker,
            bank_forks.clone(),
            subscriptions.clone(),
            verified_vote_sender,
            gossip_verified_vote_hash_sender,
            replay_vote_receiver,
            blockstore.clone(),
            bank_notification_sender,
            cluster_confirmed_slot_sender,
        );

TPU中的监听投票流程与banking_stage是并行进行的。

投票的维度有2种，分别为：

• vote for label packets
• vote for transactions

		let (verified_vote_label_packets_sender, verified_vote_label_packets_receiver) =
            unbounded();
        let (verified_vote_transactions_sender, verified_vote_transactions_receiver) = unbounded();

并行处理的流程有：

• 1）recv_loop()：通过gossip协议收集投票信息 -》 验证投票中的交易和label信息-》分别发送transactions vote和label packets vote

let (labels, votes) = cluster_info.get_votes(&mut cursor);
.....
let (vote_txs, packets) = Self::verify_votes(votes, labels);
 verified_vote_transactions_sender.send(vote_txs)?;
verified_vote_label_packets_sender.send(packets)?;

• 2）bank_send_loop()： 2.1）借助receive_and_process_vote_packets()，若当前Validator为leader，则将相应的packets插入到VerifiedVotePackets中；若不是leader，则清空VerifiedVotePackets。 2.2）为leader时，借助get_latest_votes()，过滤VerifiedVotePackets中，version版本大于last_version的packets。 2.3）将过滤后的packets通过verified_packets_sender发出，并更新bank中记录的最新version。
• 3）process_votes_loop()： verify_for_unrooted_optimistic_slots()：Returns any optimistic slots that were not rooted log_unrooted_optimistic_slots()： progress_leader_schedule_epoch()：Update with any newly calculated epoch state about future epochs purge_stale_state()：Purge any outdated slot data listen_and_confirm_votes()： add_new_optimistic_confirmed_slots()：只对confirmed slots进行处理。

3. TVU在replay stage进行投票 4. Tower BFT

【重点看replay_stage，有is_partition_detected().】 Replay_stage::new()->handle_votable_bank->push_vote->generate_vote_tx。 Solana中有维护skipped slot：是指由于leader下线 或 the fork containing the slot was abandoned for a better alternative by cluster consensus 原因，导致的slot中未产块的情况，称为skipped slot。 A skipped slot： 不会作为an ancestor for blocks at subsequent slots 不会increment the block height 决定一个slot是否为skipped slot的标准是：其 becomes older than the latest rooted (thus not-skipped) slot。 root：A block or slot that has reached maximum lockout on a validator. The root is the highest block that is an ancestor of all active forks on a validator. All ancestor blocks of a root are also transitively a root. Blocks that are not an ancestor and not a descendant of the root are excluded from consideration for consensus and can be discarded. lockout：The duration of time for which a validator is unable to vote on another fork.

	// The number of slots for which this vote is locked
    pub fn lockout(&self) -> u64 {
        (INITIAL_LOCKOUT as u64).pow(self.confirmation_count)
    }

    // The last slot at which a vote is still locked out. Validators should not
    // vote on a slot in another fork which is less than or equal to this slot
    // to avoid having their stake slashed.
    pub fn last_locked_out_slot(&self) -> Slot {
        self.slot + self.lockout()
    }