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本文主要研究一下nacos的ServerChangeListener

ServerChangeListener

nacos-1.1.3/naming/src/main/java/com/alibaba/nacos/naming/cluster/servers/ServerChangeListener.java

public interface ServerChangeListener {

    /**
     * If member list changed, this method is invoked.
     *
     * @param servers servers after change
     */
    void onChangeServerList(List<Server> servers);

    /**
     * If reachable member list changed, this method is invoked.
     *
     * @param healthyServer reachable servers after change
     */
    void onChangeHealthyServerList(List<Server> healthyServer);
}

• ServerChangeListener定义了onChangeServerList、onChangeHealthyServerList方法

DistroMapper

nacos-1.1.3/naming/src/main/java/com/alibaba/nacos/naming/core/DistroMapper.java

@Component("distroMapper")
public class DistroMapper implements ServerChangeListener {

    private List<String> healthyList = new ArrayList<>();

    //......

    @Override
    public void onChangeServerList(List<Server> latestMembers) {

    }

    @Override
    public void onChangeHealthyServerList(List<Server> latestReachableMembers) {

        List<String> newHealthyList = new ArrayList<>();
        for (Server server : latestReachableMembers) {
            newHealthyList.add(server.getKey());
        }
        healthyList = newHealthyList;
    }

    //......
}

• DistroMapper实现了ServerChangeListener接口，其onChangeHealthyServerList会更新自己的healthyList

RaftPeerSet

nacos-1.1.3/naming/src/main/java/com/alibaba/nacos/naming/consistency/persistent/raft/RaftPeerSet.java

@Component
@DependsOn("serverListManager")
public class RaftPeerSet implements ServerChangeListener, ApplicationContextAware {

    @Autowired
    private ServerListManager serverListManager;

    private ApplicationContext applicationContext;

    private AtomicLong localTerm = new AtomicLong(0L);

    private RaftPeer leader = null;

    private Map<String, RaftPeer> peers = new HashMap<>();

    private Set<String> sites = new HashSet<>();

    private boolean ready = false;

    //......

    @Override
    public void onChangeServerList(List<Server> latestMembers) {

        Map<String, RaftPeer> tmpPeers = new HashMap<>(8);
        for (Server member : latestMembers) {

            if (peers.containsKey(member.getKey())) {
                tmpPeers.put(member.getKey(), peers.get(member.getKey()));
                continue;
            }

            RaftPeer raftPeer = new RaftPeer();
            raftPeer.ip = member.getKey();

            // first time meet the local server:
            if (NetUtils.localServer().equals(member.getKey())) {
                raftPeer.term.set(localTerm.get());
            }

            tmpPeers.put(member.getKey(), raftPeer);
        }

        // replace raft peer set:
        peers = tmpPeers;

        if (RunningConfig.getServerPort() > 0) {
            ready = true;
        }

        Loggers.RAFT.info("raft peers changed: " + latestMembers);
    }

    @Override
    public void onChangeHealthyServerList(List<Server> latestReachableMembers) {

    }

    //......
}

• RaftPeerSet实现了ServerChangeListener接口，其onChangeServerList方法会更新peers及ready属性

小结

ServerChangeListener定义了onChangeServerList、onChangeHealthyServerList方法；DistroMapper实现了ServerChangeListener接口，其onChangeHealthyServerList会更新自己的healthyList；RaftPeerSet实现了ServerChangeListener接口，其onChangeServerList方法会更新peers及ready属性

doc

• ServerChangeListener