nacos client中ServerListManager的start有什么作用

本篇内容主要讲解"nacos client中ServerListManager的start有什么作用"，感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷，实用性强。下面就让小编来带大家学习"nacos client中ServerListManager的start有什么作用"吧!

序

本文主要研究一下nacos client的ServerListManager的start

ServerListManager

nacos-1.1.3/client/src/main/java/com/alibaba/nacos/client/config/impl/ServerListManager.java

public class ServerListManager {    private static final Logger LOGGER = LogUtils.logger(ServerListManager.class);    private static final String HTTPS = "https://";    private static final String HTTP = "http://";    //......    public synchronized void start() throws NacosException {        if (isStarted || isFixed) {            return;        }        GetServerListTask getServersTask = new GetServerListTask(addressServerUrl);        for (int i = 0; i < initServerlistRetryTimes && serverUrls.isEmpty(); ++i) {            getServersTask.run();            try {                this.wait((i + 1) * 100L);            } catch (Exception e) {                LOGGER.warn("get serverlist fail,url: {}", addressServerUrl);            }        }        if (serverUrls.isEmpty()) {            LOGGER.error("[init-serverlist] fail to get NACOS-server serverlist! env: {}, url: {}", name,                addressServerUrl);            throw new NacosException(NacosException.SERVER_ERROR,                "fail to get NACOS-server serverlist! env:" + name + ", not connnect url:" + addressServerUrl);        }        TimerService.scheduleWithFixedDelay(getServersTask, 0L, 30L, TimeUnit.SECONDS);        isStarted = true;    }    //......}

• ServerListManager的start方法在非isStarted且非isFixed的条件下会执行GetServerListTask，失败重试次数为initServerlistRetryTimes，如果serverUrls为空则抛出NacosException；如果不为空则注册该getServersTask每隔30秒执行一次来刷新server list

GetServerListTask

nacos-1.1.3/client/src/main/java/com/alibaba/nacos/client/config/impl/ServerListManager.java

public class ServerListManager {        //......    class GetServerListTask implements Runnable {        final String url;        GetServerListTask(String url) {            this.url = url;        }        @Override        public void run() {            /**             * get serverlist from nameserver             */            try {                updateIfChanged(getApacheServerList(url, name));            } catch (Exception e) {                LOGGER.error("[" + name + "][update-serverlist] failed to update serverlist from address server!",                    e);            }        }    }    private void updateIfChanged(List newList) {        if (null == newList || newList.isEmpty()) {            LOGGER.warn("[update-serverlist] current serverlist from address server is empty!!!");            return;        }        List newServerAddrList = new ArrayList();        for (String server : newList) {            if (server.startsWith(HTTP) || server.startsWith(HTTPS)) {                newServerAddrList.add(server);            } else {                newServerAddrList.add(HTTP + server);            }        }        /**         * no change         */        if (newServerAddrList.equals(serverUrls)) {            return;        }        serverUrls = new ArrayList(newServerAddrList);        iterator = iterator();        currentServerAddr = iterator.next();        EventDispatcher.fireEvent(new ServerlistChangeEvent());        LOGGER.info("[{}] [update-serverlist] serverlist updated to {}", name, serverUrls);    }    private List getApacheServerList(String url, String name) {        try {            HttpResult httpResult = HttpSimpleClient.httpGet(url, null, null, null, 3000);            if (HttpURLConnection.HTTP_OK == httpResult.code) {                if (DEFAULT_NAME.equals(name)) {                    EnvUtil.setSelfEnv(httpResult.headers);                }                List lines = IOUtils.readLines(new StringReader(httpResult.content));                List result = new ArrayList(lines.size());                for (String serverAddr : lines) {                    if (org.apache.commons.lang3.StringUtils.isNotBlank(serverAddr)) {                        String[] ipPort = serverAddr.trim().split(":");                        String ip = ipPort[0].trim();                        if (ipPort.length == 1) {                            result.add(ip + ":" + ParamUtil.getDefaultServerPort());                        } else {                            result.add(serverAddr);                        }                    }                }                return result;            } else {                LOGGER.error("[check-serverlist] error. addressServerUrl: {}, code: {}", addressServerUrl,                    httpResult.code);                return null;            }        } catch (IOException e) {            LOGGER.error("[check-serverlist] exception. url: " + url, e);            return null;        }    }    //......}

• GetServerListTask实现了Runnable接口，其run方法会通过getApacheServerList请求addressServerUrl获取服务端地址列表，然后执行updateIfChanged方法；该方法会判断server list是否有变更，有变更则更新serverUrls，然后发布ServerlistChangeEvent

小结

ServerListManager的start方法在非isStarted且非isFixed的条件下会执行GetServerListTask，失败重试次数为initServerlistRetryTimes，如果serverUrls为空则抛出NacosException；如果不为空则注册该getServersTask每隔30秒执行一次来刷新server list

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