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 方法注册了 ServerStatusUpdater，它实现了 Runnable 接口，其 run 方法执行 refreshServerStatus；refreshServerStatus 会判断 consistencyService 是否是 available，如果是更新 serverStatus 为 ServerStatus.UP，否则为 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 这几种状态

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 会根据 status 及 httpMethod 进行读写路由，路由的不到的返回 HttpServletResponse.SC_SERVICE_UNAVAILABLE

小结

ServerStatusManager 的 init 方法注册了 ServerStatusUpdater，它实现了 Runnable 接口，其 run 方法执行 refreshServerStatus；refreshServerStatus 会判断 consistencyService 是否是 available，如果是更新 serverStatus 为 ServerStatus.UP，否则为 ServerStatus.DOWN

doc

• ServerStatusManager