motan提供了流量切换的功能，可以实现把一个group的流量切换到另一个group（一个或多个服务都可以）。大家可以使用tomcat部署motan的管理工具，并设置几个组，例如可以参考demo代码：motan_demo_server_commandRegistry.xml。分析源码时可以发现，流量切换是在客户端完成的，与服务端没什么关系，在实际的工作中，可以解决很多问题，例如：某个集群出了问题，可以马上将流量切换到其它集群；在系统升级的过程中，将带升级集群的流量切换到其它集群，实现了24小时随时升级等。
1.motan的流量切换是通过command来实现的，每次我们在motan管理器上进行设置的时候，其实是写入信息到注册中心的command节点，而motan又监听了这些command节点，下面是motan的客户端监听command相关的代码
protected void subscribeCommand(final URL url, final CommandListener commandListener) {
try {
clientLock.lock();//对clientLock进行上锁
ConcurrentHashMap<CommandListener, IZkDataListener> dataChangeListeners = commandListeners.get(url);//数据变更监听器
if (dataChangeListeners == null) {
commandListeners.putIfAbsent(url, new ConcurrentHashMap<CommandListener, IZkDataListener>());
dataChangeListeners = commandListeners.get(url);
}
IZkDataListener zkDataListener = dataChangeListeners.get(commandListener);
if (zkDataListener == null) {
dataChangeListeners.putIfAbsent(commandListener, new IZkDataListener() {//增加新的listener
@Override
public void handleDataChange(String dataPath, Object data) throws Exception {
commandListener.notifyCommand(url, (String) data);//调用commandListener的notifyCommand方法
LoggerUtil.info(String.format("[ZookeeperRegistry] command data change: path=%s, command=%s", dataPath, (String) data));
}
@Override
public void handleDataDeleted(String dataPath) throws Exception {
commandListener.notifyCommand(url, null);
LoggerUtil.info(String.format("[ZookeeperRegistry] command deleted: path=%s", dataPath));
}
});
zkDataListener = dataChangeListeners.get(commandListener);
}
String commandPath = ZkUtils.toCommandPath(url);
zkClient.subscribeDataChanges(commandPath, zkDataListener);//向zookeeper注册监听事件
LoggerUtil.info(String.format("[ZookeeperRegistry] subscribe command: path=%s, info=%s", commandPath, url.toFullStr()));
} catch (Throwable e) {
throw new MotanFrameworkException(String.format("Failed to subscribe %s to zookeeper(%s), cause: %s", url, getUrl(), e.getMessage()), e);
} finally {
clientLock.unlock();
}
}2.CommandServiceManager实现了上节中的commandListener
public void notifyCommand(URL serviceUrl, String commandString) {
LoggerUtil.info("CommandServiceManager notify command. service:" + serviceUrl.toSimpleString() + ", command:" + commandString);
if (!MotanSwitcherUtil.isOpen(MOTAN_COMMAND_SWITCHER) || commandString == null) {//判断命令开关是否打开
LoggerUtil.info("command reset empty since swither is close.");
commandString = "";
}
List<URL> finalResult = new ArrayList<URL>();
URL urlCopy = serviceUrl.createCopy();//serviceurl的副本
if (!StringUtils.equals(commandString, commandStringCache)) {
commandStringCache = commandString;
commandCache = RpcCommandUtil.stringToCommand(commandStringCache);//将字符串转换为命令
Map<String, Integer> weights = new HashMap<String, Integer>();
if (commandCache != null) {
commandCache.sort();
finalResult = discoverServiceWithCommand(refUrl, weights, commandCache);
} else {
// 如果是指令有异常时，应当按没有指令处理，防止错误指令导致服务异常
if (StringUtils.isNotBlank(commandString)) {
LoggerUtil.warn("command parse fail, ignored! command:" + commandString);
commandString = "";
}
// 没有命令时，只返回这个manager实际group对应的结果
finalResult.addAll(discoverOneGroup(refUrl));
}
// 指令变化时，删除不再有效的缓存，取消订阅不再有效的group
Set<String> groupKeys = groupServiceCache.keySet();
for (String gk : groupKeys) {
if (!weights.containsKey(gk)) {
groupServiceCache.remove(gk);
URL urlTemp = urlCopy.createCopy();
urlTemp.addParameter(URLParamType.group.getName(), gk);
registry.unsubscribeService(urlTemp, this);
}
}
} else {
LoggerUtil.info("command not change. url:" + serviceUrl.toSimpleString());
// 指令没有变化，什么也不做
return;
}
for (NotifyListener notifyListener : notifySet) {
notifyListener.notify(registry.getUrl(), finalResult);
}
// 当指令从有改到无时，会触发取消订阅所有的group，需要重新订阅本组的service
if ("".equals(commandString)) {
LoggerUtil.info("reSub service" + refUrl.toSimpleString());
registry.subscribeService(refUrl, this);
}
}
3.discoverServiceWithCommand的相关代码
public List<URL> discoverServiceWithCommand(URL serviceUrl, Map<String, Integer> weights, RpcCommand rpcCommand, String localIP) {
if (rpcCommand == null || CollectionUtil.isEmpty(rpcCommand.getClientCommandList())) {
return discoverOneGroup(serviceUrl);
}
List<URL> mergedResult = new LinkedList<URL>();
String path = serviceUrl.getPath();//获取路径
List<RpcCommand.ClientCommand> clientCommandList = rpcCommand.getClientCommandList();
boolean hit = false;
for (RpcCommand.ClientCommand command : clientCommandList) {
mergedResult = new LinkedList<URL>();
// 判断当前url是否符合过滤条件
boolean match = RpcCommandUtil.match(command.getPattern(), path);
if (match) {
hit = true;
if (!CollectionUtil.isEmpty(command.getMergeGroups())) {
// 计算出所有要合并的分组及权重
try {
buildWeightsMap(weights, command);
} catch (MotanFrameworkException e) {
LoggerUtil.warn("build weights map fail!" + e.getMessage());
continue;
}
// 根据计算结果，分别发现各个group的service，合并结果
mergedResult.addAll(mergeResult(serviceUrl, weights));
} else {
mergedResult.addAll(discoverOneGroup(serviceUrl));
}
LoggerUtil.info("mergedResult: size-" + mergedResult.size() + " --- " + mergedResult.toString());
if (!CollectionUtil.isEmpty(command.getRouteRules())) {
LoggerUtil.info("router: " + command.getRouteRules().toString());
for (String routeRule : command.getRouteRules()) {
String[] fromTo = routeRule.replaceAll("\\s+", "").split("to");
if (fromTo.length != 2) {
routeRuleConfigError();
continue;
}
String from = fromTo[0];
String to = fromTo[1];
if (from.length() < 1 || to.length() < 1 || !IP_PATTERN.matcher(from).find() || !IP_PATTERN.matcher(to).find()) {
routeRuleConfigError();
continue;
}
boolean oppositeFrom = from.startsWith("!");
boolean oppositeTo = to.startsWith("!");
if (oppositeFrom) {
from = from.substring(1);
}
if (oppositeTo) {
to = to.substring(1);
}
int idx = from.indexOf('*');
boolean matchFrom;
if (idx != -1) {
matchFrom = localIP.startsWith(from.substring(0, idx));
} else {
matchFrom = localIP.equals(from);
}
// 开头有!，取反
if (oppositeFrom) {
matchFrom = !matchFrom;
}
LoggerUtil.info("matchFrom: " + matchFrom + ", localip:" + localIP + ", from:" + from);
if (matchFrom) {
boolean matchTo;
Iterator<URL> iterator = mergedResult.iterator();
while (iterator.hasNext()) {
URL url = iterator.next();
if (url.getProtocol().equalsIgnoreCase("rule")) {
continue;
}
idx = to.indexOf('*');
if (idx != -1) {
matchTo = url.getHost().startsWith(to.substring(0, idx));
} else {
matchTo = url.getHost().equals(to);
}
if (oppositeTo) {
matchTo = !matchTo;
}
if (!matchTo) {
iterator.remove();
LoggerUtil.info("router To not match. url remove : " + url.toSimpleString());
}
}
}
}
}
// 只取第一个匹配的 TODO 考虑是否能满足绝大多数场景需求
break;
}
}
List<URL> finalResult = new ArrayList<URL>();
if (!hit) {
finalResult = discoverOneGroup(serviceUrl);
} else {
finalResult.addAll(mergedResult);
}
return finalResult;
}