聊聊nacos的ServerStatusManager

序

本文主要研究一下nacos的ServerStatusManager

ServerStatusManager

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

@Service
public class ServerStatusManager {

    @Resource(name = "consistencyDelegate")
    private ConsistencyService consistencyService;

    @Autowired
    private SwitchDomain switchDomain;

    private ServerStatus serverStatus = ServerStatus.STARTING;

    @PostConstruct
    public void init() {
        GlobalExecutor.registerServerStatusUpdater(new ServerStatusUpdater());
    }

    private void refreshServerStatus() {

        if (StringUtils.isNotBlank(switchDomain.getOverriddenServerStatus())) {
            serverStatus = ServerStatus.valueOf(switchDomain.getOverriddenServerStatus());
            return;
        }

        if (consistencyService.isAvailable()) {
            serverStatus = ServerStatus.UP;
        } else {
            serverStatus = ServerStatus.DOWN;
        }
    }

    public ServerStatus getServerStatus() {
        return serverStatus;
    }

    public class ServerStatusUpdater implements Runnable {

        @Override
        public void run() {
            refreshServerStatus();
        }
    }
}

• ServerStatusManager的init方法註冊了ServerStatusUpdater，它實現了Runnable接口，其run方法執行refreshServerStatus；refreshServerStatus會判斷consistencyService是不是available，若是是更新serverStatus爲ServerStatus.UP，不然爲ServerStatus.DOWN

ServerStatus

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

public enum ServerStatus {
    /**
     * server is up and ready for request
     */
    UP,
    /**
     * server is out of service, something abnormal happened
     */
    DOWN,
    /**
     * server is preparing itself for request, usually 'UP' is the next status
     */
    STARTING,
    /**
     * server is manually paused
     */
    PAUSED,
    /**
     * only write operation is permitted.
     */
    WRITE_ONLY,
    /**
     * only read operation is permitted.
     */
    READ_ONLY
}

• ServerStatus有UP、DOWN、STARTING、PAUSED、WRITE_ONLY、READ_ONLY這幾種狀態

TrafficReviseFilter

nacos-1.1.3/naming/src/main/java/com/alibaba/nacos/naming/web/TrafficReviseFilter.java

public class TrafficReviseFilter implements Filter {

    @Autowired
    private ServerStatusManager serverStatusManager;

    @Autowired
    private SwitchDomain switchDomain;

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain) throws IOException, ServletException {

        HttpServletRequest req = (HttpServletRequest) request;
        HttpServletResponse resp = (HttpServletResponse) response;

        // request limit if exist:
        String urlString = req.getRequestURI() + "?" + req.getQueryString();
        Map<String, Integer> limitedUrlMap = switchDomain.getLimitedUrlMap();

        if (limitedUrlMap != null && limitedUrlMap.size() > 0) {
            for (Map.Entry<String, Integer> entry : limitedUrlMap.entrySet()) {
                String limitedUrl = entry.getKey();
                if (StringUtils.startsWith(urlString, limitedUrl)) {
                    resp.setStatus(entry.getValue());
                    return;
                }
            }
        }

        // if server is UP:
        if (serverStatusManager.getServerStatus() == ServerStatus.UP) {
            filterChain.doFilter(req, resp);
            return;
        }

        // requests from peer server should be let pass:
        String agent = req.getHeader("Client-Version");
        if (StringUtils.isBlank(agent)) {
            agent = req.getHeader("User-Agent");
        }

        if (StringUtils.startsWith(agent, UtilsAndCommons.NACOS_SERVER_HEADER)) {
            filterChain.doFilter(req, resp);
            return;
        }

        // write operation should be let pass in WRITE_ONLY status:
        if (serverStatusManager.getServerStatus() == ServerStatus.WRITE_ONLY && !HttpMethod.GET.equals(req.getMethod())) {
            filterChain.doFilter(req, resp);
            return;
        }

        // read operation should be let pass in READ_ONLY status:
        if (serverStatusManager.getServerStatus() == ServerStatus.READ_ONLY && HttpMethod.GET.equals(req.getMethod())) {
            filterChain.doFilter(req, resp);
            return;
        }

        resp.getWriter().write("server is " + serverStatusManager.getServerStatus().name() + " now, please try again later!");
        resp.setStatus(HttpServletResponse.SC_SERVICE_UNAVAILABLE);
    }
}

• TrafficReviseFilter會根據status及httpMethod進行讀寫路由，路由的不到的返回HttpServletResponse.SC_SERVICE_UNAVAILABLE

小結

ServerStatusManager的init方法註冊了ServerStatusUpdater，它實現了Runnable接口，其run方法執行refreshServerStatus；refreshServerStatus會判斷consistencyService是不是available，若是是更新serverStatus爲ServerStatus.UP，不然爲ServerStatus.DOWN

doc

• ServerStatusManager