What is the function of start of ServerListManager in nacos client

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This paper mainly studies the start of nacos client's ServerListManager.

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;} / /.}

The start method of ServerListManager executes GetServerListTask under the condition of non-isStarted and non-isFixed. The number of failed retries is initServerlistRetryTimes. If serverUrls is empty, NacosException; is thrown. If it is not empty, register the getServersTask and execute once every 30 seconds to refresh 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 emptiness!"); 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, 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 implements the Runnable interface, and its run method obtains the server address list through the getApacheServerList request addressServerUrl, and then executes the updateIfChanged method; this method determines whether the server list has changed, updates the serverUrls if there is a change, and then publishes the ServerlistChangeEvent

Summary

The start method of ServerListManager executes GetServerListTask under the condition of non-isStarted and non-isFixed. The number of failed retries is initServerlistRetryTimes. If serverUrls is empty, NacosException; is thrown. If it is not empty, register the getServersTask and execute once every 30 seconds to refresh server list.

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