Zab协议（9）-数据恢复源码分析（4）

Zab协议（9）-数据恢复源码分析（4）

2021SC@SDUSC

目录

• 回顾
• 源码分析

回顾

上一篇分析到了

 queuedPackets.add(new QuorumPacket(Leader.UPTODATE, -1, null, null));

继续分析

源码分析

           while (true) {
                qp = new QuorumPacket();
                ia.readRecord(qp, "packet");

                long traceMask = ZooTrace.SERVER_PACKET_TRACE_MASK;
                if (qp.getType() == Leader.PING) {
                    traceMask = ZooTrace.SERVER_PING_TRACE_MASK;
                }
                if (LOG.isTraceEnabled()) {
                    ZooTrace.logQuorumPacket(LOG, traceMask, 'i', qp);
                }
                tickOfNextAckDeadline = leader.self.tick.get() + leader.self.syncLimit;


                ByteBuffer bb;
                long sessionId;
                int cxid;
                int type;

                switch (qp.getType()) {
                case Leader.ACK:
                    if (this.learnerType == LearnerType.OBSERVER) {
                        if (LOG.isDebugEnabled()) {
                            LOG.debug("Received ACK from Observer  " + this.sid);
                        }
                    }
                    syncLimitCheck.updateAck(qp.getZxid());
                    leader.processAck(this.sid, qp.getZxid(), sock.getLocalSocketAddress());
                    break;

Leader获得ack后包装成proposal，交由LearnerHandler来发送。

        Proposal p = outstandingProposals.get(zxid);
        if (p == null) {
            LOG.warn("Trying to commit future proposal: zxid 0x{} from {}",
                    Long.toHexString(zxid), followerAddr);
            return;
        }
        
        p.ackSet.add(sid);
        if (LOG.isDebugEnabled()) {
            LOG.debug("Count for zxid: 0x{} is {}",
                    Long.toHexString(zxid), p.ackSet.size());
        }
        if (self.getQuorumVerifier().containsQuorum(p.ackSet)){             
            if (zxid != lastCommitted+1) {
                LOG.warn("Commiting zxid 0x{} from {} not first!",
                        Long.toHexString(zxid), followerAddr);
                LOG.warn("First is 0x{}", Long.toHexString(lastCommitted + 1));
            }
            outstandingProposals.remove(zxid);
            if (p.request != null) {
                toBeApplied.add(p);
            }

            if (p.request == null) {
                LOG.warn("Going to commmit null request for proposal: {}", p);
            }
            commit(zxid);
            inform(p);
            zk.commitProcessor.commit(p.request);
            if(pendingSyncs.containsKey(zxid)){
                for(LearnerSyncRequest r: pendingSyncs.remove(zxid)) {
                    sendSync(r);
                }
            }
        }
    }

leader收集follower关于本次proposal的投票

        if (zk instanceof FollowerZooKeeperServer) {
            FollowerZooKeeperServer fzk = (FollowerZooKeeperServer)zk;
            for(PacketInFlight p: packetsNotCommitted) {
                fzk.logRequest(p.hdr, p.rec);
            }
            for(Long zxid: packetsCommitted) {
                fzk.commit(zxid);
            }
        } else if (zk instanceof ObserverZooKeeperServer) {
            // Similar to follower, we need to log requests between the snapshot
            // and UPTODATE
            ObserverZooKeeperServer ozk = (ObserverZooKeeperServer) zk;
            for (PacketInFlight p : packetsNotCommitted) {
                Long zxid = packetsCommitted.peekFirst();
                if (p.hdr.getZxid() != zxid) {
                    // log warning message if there is no matching commit
                    // old leader send outstanding proposal to observer
                    LOG.warn("Committing " + Long.toHexString(zxid)
                            + ", but next proposal is "
                            + Long.toHexString(p.hdr.getZxid()));
                    continue;
                }
                packetsCommitted.remove();
                Request request = new Request(null, p.hdr.getClientId(),
                        p.hdr.getCxid(), p.hdr.getType(), null, null);
                request.txn = p.rec;
                request.hdr = p.hdr;
                ozk.commitRequest(request);
            }
        } else {
            // New server type need to handle in-flight packets
            throw new UnsupportedOperationException("Unknown server type");
        }
    }

判断当前是follower 还是 observer ，处理数据

syncWithLeader(newEpochZxid);                
QuorumPacket qp = new QuorumPacket();
while (self.isRunning()) {
    readPacket(qp);
    processPacket(qp);
}

读取leader发来的数据，处理后保存

    protected Leader makeLeader(FileTxnSnapLog logFactory) throws IOException {
        return new Leader(this, new LeaderZooKeeperServer(logFactory,
                this,new ZooKeeperServer.BasicDataTreeBuilder(), this.zkDb));
    }

初始化一个leader对象，表示leader 节点的请求处理服务。