聊聊nacos-client的ServerListManager的start

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<String> newList) {if (null == newList || newList.isEmpty()) {LOGGER.warn("[update-serverlist] current serverlist from address server is empty!!!");
            return;
        }
 
        List<String> newServerAddrList = new ArrayList<String>();
        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<String>(newServerAddrList);
        iterator = iterator();
        currentServerAddr = iterator.next();
 
        EventDispatcher.fireEvent(new ServerlistChangeEvent());
        LOGGER.info("[{}] [update-serverlist] serverlist updated to {}", name, serverUrls);
    }
 
    private List<String> 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<String> lines = IOUtils.readLines(new StringReader(httpResult.content));
                List<String> result = new ArrayList<String>(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

doc

• ServerListManager