這篇博客我們通過示例來了解學習一下 Nacos 的客戶端獲取配置以及服務端發送配置的相關流程。
服務端創建配置
在 Nacos 的管理頁面我們可以創建如下配置信息
1、在默認命名空間下新建配置
2、編輯配置併發布
客戶端獲取配置
1、客戶端主動獲取配置
（1）客戶端創建 ConfigService 服務根據 dataId 和 group 來獲取配置信息
示例：根據dataId 和 group 獲取相關配置
package com.alibaba.nacos.example;
import java.util.Properties;
import java.util.concurrent.Executor;
import com.alibaba.nacos.api.NacosFactory;
import com.alibaba.nacos.api.config.ConfigService;
import com.alibaba.nacos.api.config.listener.Listener;
import com.alibaba.nacos.api.exception.NacosException;
/**
* Config service example
*
* @author Nacos
*
*/
public class ConfigExample {
public static void main(String[] args) throws NacosException, InterruptedException {
String serverAddr = "localhost";
String dataId = "mysql";
String group = "DEFAULT_GROUP";
Properties properties = new Properties();
properties.put(PropertyKeyConst.SERVER_ADDR, serverAddr);
ConfigService configService = NacosFactory.createConfigService(properties);
String content = configService.getConfig(dataId, group, 5000);
System.out.println(content);
}
}
（2）nacos 服務端在 ConfigController 中提供接口 getConfig 來提供相關配置查詢接口
@RequestMapping(method = RequestMethod.GET)
public void getConfig(HttpServletRequest request, HttpServletResponse response,
@RequestParam("dataId") String dataId, @RequestParam("group") String group,
@RequestParam(value = "tenant", required = false, defaultValue = StringUtils.EMPTY)
String tenant,
@RequestParam(value = "tag", required = false) String tag)
throws IOException, ServletException, NacosException {
// check params
ParamUtils.checkParam(dataId, group, "datumId", "content");
ParamUtils.checkParam(tag);
final String clientIp = RequestUtil.getRemoteIp(request);
inner.doGetConfig(request, response, dataId, group, tenant, tag, clientIp);
}
在 ConfigServletInner 的 doGetConfig 方法中會根據 dataId、group、tenant、tag 等進行查詢
public String doGetConfig(HttpServletRequest request, HttpServletResponse response, String dataId, String group,
String tenant, String tag, String clientIp) throws IOException, ServletException {
//省略部分代碼
ConfigInfoBase configInfoBase = null;
//省略部分代碼
configInfoBase = persistService.findConfigInfo4Beta(dataId, group, tenant);
//省略部分代碼
}
在 PersistService 的findConfigInfo4Beta 方法中會執行 SQL 從庫中查找相關配置信息
/**
* 根據dataId和group查詢配置信息
*/
public ConfigInfo4Beta findConfigInfo4Beta(final String dataId, final String group, final String tenant) {
String tenantTmp = StringUtils.isBlank(tenant) ? StringUtils.EMPTY : tenant;
try {
return this.jt.queryForObject(
"SELECT ID,data_id,group_id,tenant_id,app_name,content,beta_ips FROM config_info_beta WHERE data_id=?"
+ " AND group_id=? AND tenant_id=?",
new Object[] {dataId, group, tenantTmp}, CONFIG_INFO4BETA_ROW_MAPPER);
} catch (EmptyResultDataAccessException e) { // 表明數據不存在, 返回null
return null;
} catch (CannotGetJdbcConnectionException e) {
fatalLog.error("[db-error] " + e.toString(), e);
throw e;
}
}
2、客戶端監聽配置
客戶端在啓動時候從註冊中心獲取配置外，也可以主動監聽配置中心相關的配置變化
示例代碼：
package com.alibaba.nacos.example;
import java.util.Properties;
import java.util.concurrent.Executor;
import com.alibaba.nacos.api.NacosFactory;
import com.alibaba.nacos.api.config.ConfigService;
import com.alibaba.nacos.api.config.listener.Listener;
import com.alibaba.nacos.api.exception.NacosException;
/**
* Config service example
*
* @author Nacos
*
*/
public class ConfigExample {
public static void main(String[] args) throws NacosException, InterruptedException {
String serverAddr = "localhost";
String dataId = "mysql";
String group = "DEFAULT_GROUP";
Properties properties = new Properties();
properties.put(PropertyKeyConst.SERVER_ADDR, serverAddr);
ConfigService configService = NacosFactory.createConfigService(properties);
String content = configService.getConfig(dataId, group, 5000);
System.out.println(content);
//註冊監聽
configService.addListener(dataId, group, new Listener() {
@Override
public void receiveConfigInfo(String configInfo) {
System.out.println("recieve:" + configInfo);
}
@Override
public Executor getExecutor() {
return null;
}
});
boolean isPublishOk = configService.publishConfig(dataId, group, "content");
System.out.println(isPublishOk);
Thread.sleep(3000);
content = configService.getConfig(dataId, group, 5000);
System.out.println(content);
boolean isRemoveOk = configService.removeConfig(dataId, group);
System.out.println(isRemoveOk);
Thread.sleep(3000);
content = configService.getConfig(dataId, group, 5000);
System.out.println(content);
Thread.sleep(300000);
}
}
1、客戶端調用 ConfigController 的 listener 的監聽接口，與服務端通過 http 建立長連接來監聽配置變更
configService.addListener(dataId, group, new Listener() {
@Override
public void receiveConfigInfo(String configInfo) {
System.out.println("recieve:" + configInfo);
}
@Override
public Executor getExecutor() {
return null;
}
});
2、Nacos 服務提供接口 listener 用於客戶端註冊監聽服務（還是基於web 容器的長連接技術）
/**
* 比較MD5
*/
@RequestMapping(value = "/listener", method = RequestMethod.POST)
public void listener(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setAttribute("org.apache.catalina.ASYNC_SUPPORTED", true);
String probeModify = request.getParameter("Listening-Configs");
if (StringUtils.isBlank(probeModify)) {
throw new IllegalArgumentException("invalid probeModify");
}
probeModify = URLDecoder.decode(probeModify, Constants.ENCODE);
Map<String, String> clientMd5Map;
try {
clientMd5Map = MD5Util.getClientMd5Map(probeModify);
} catch (Throwable e) {
throw new IllegalArgumentException("invalid probeModify");
}
// do long-polling
inner.doPollingConfig(request, response, clientMd5Map, probeModify.length());
}
在 ConfigServletInner 的 doPollingConfig 會根據客戶端請求獲取 AsyncContext，然後異步建立長連接
/**
* 輪詢接口
*/
public String doPollingConfig(HttpServletRequest request, HttpServletResponse response,
Map<String, String> clientMd5Map, int probeRequestSize)
throws IOException, ServletException {
// 長輪詢
if (LongPollingService.isSupportLongPolling(request)) {
longPollingService.addLongPollingClient(request, response, clientMd5Map, probeRequestSize);
return HttpServletResponse.SC_OK + "";
}
// else 兼容短輪詢邏輯
List<String> changedGroups = MD5Util.compareMd5(request, response, clientMd5Map);
// 兼容短輪詢result
String oldResult = MD5Util.compareMd5OldResult(changedGroups);
String newResult = MD5Util.compareMd5ResultString(changedGroups);
String version = request.getHeader(Constants.CLIENT_VERSION_HEADER);
if (version == null) {
version = "2.0.0";
}
int versionNum = Protocol.getVersionNumber(version);
/**
* 2.0.4版本以前, 返回值放入header中
*/
if (versionNum < START_LONGPOLLING_VERSION_NUM) {
response.addHeader(Constants.PROBE_MODIFY_RESPONSE, oldResult);
response.addHeader(Constants.PROBE_MODIFY_RESPONSE_NEW, newResult);
} else {
request.setAttribute("content", newResult);
}
// 禁用緩存
response.setHeader("Pragma", "no-cache");
response.setDateHeader("Expires", 0);
response.setHeader("Cache-Control", "no-cache,no-store");
response.setStatus(HttpServletResponse.SC_OK);
return HttpServletResponse.SC_OK + "";
}
在 LongPollingService 的 addLongPollingClient 中從請求中獲取 AsyncContext，然後異步建立長連接
public void addLongPollingClient(HttpServletRequest req, HttpServletResponse rsp, Map<String, String> clientMd5Map,
int probeRequestSize) {
String str = req.getHeader(LongPollingService.LONG_POLLING_HEADER);
String noHangUpFlag = req.getHeader(LongPollingService.LONG_POLLING_NO_HANG_UP_HEADER);
String appName = req.getHeader(RequestUtil.CLIENT_APPNAME_HEADER);
String tag = req.getHeader("Vipserver-Tag");
int delayTime = SwitchService.getSwitchInteger(SwitchService.FIXED_DELAY_TIME, 500);
/**
* 提前500ms返回響應，爲避免客戶端超時 @qiaoyi.dingqy 2013.10.22改動 add delay time for LoadBalance
*/
long timeout = Math.max(10000, Long.parseLong(str) - delayTime);
if (isFixedPolling()) {
timeout = Math.max(10000, getFixedPollingInterval());
// do nothing but set fix polling timeout
} else {
long start = System.currentTimeMillis();
List<String> changedGroups = MD5Util.compareMd5(req, rsp, clientMd5Map);
if (changedGroups.size() > 0) {
generateResponse(req, rsp, changedGroups);
LogUtil.clientLog.info("{}|{}|{}|{}|{}|{}|{}",
System.currentTimeMillis() - start, "instant", RequestUtil.getRemoteIp(req), "polling",
clientMd5Map.size(), probeRequestSize, changedGroups.size());
return;
} else if (noHangUpFlag != null && noHangUpFlag.equalsIgnoreCase(TRUE_STR)) {
LogUtil.clientLog.info("{}|{}|{}|{}|{}|{}|{}", System.currentTimeMillis() - start, "nohangup",
RequestUtil.getRemoteIp(req), "polling", clientMd5Map.size(), probeRequestSize,
changedGroups.size());
return;
}
}
String ip = RequestUtil.getRemoteIp(req);
// 一定要由HTTP線程調用，否則離開後容器會立即發送響應
final AsyncContext asyncContext = req.startAsync();
// AsyncContext.setTimeout()的超時時間不準，所以只能自己控制
asyncContext.setTimeout(0L);
scheduler.execute(
new ClientLongPolling(asyncContext, clientMd5Map, ip, probeRequestSize, timeout, appName, tag));
}
在ClientLongPolling 中會將客戶端信息添加到 長輪詢訂閱關係隊列 中
/**
* 長輪詢訂閱關係
*/
final Queue<ClientLongPolling> allSubs;
在 ClientLongPolling 執行時添加客戶端長連接到 allSubs 中
class ClientLongPolling implements Runnable {
@Override
public void run() {
asyncTimeoutFuture = scheduler.schedule(new Runnable() {
public void run() {
try {
getRetainIps().put(ClientLongPolling.this.ip, System.currentTimeMillis());
/**
* 刪除訂閱關係
*/
allSubs.remove(ClientLongPolling.this);
if (isFixedPolling()) {
LogUtil.clientLog.info("{}|{}|{}|{}|{}|{}",
(System.currentTimeMillis() - createTime),
"fix", RequestUtil.getRemoteIp((HttpServletRequest)asyncContext.getRequest()),
"polling",
clientMd5Map.size(), probeRequestSize);
List<String> changedGroups = MD5Util.compareMd5(
(HttpServletRequest)asyncContext.getRequest(),
(HttpServletResponse)asyncContext.getResponse(), clientMd5Map);
if (changedGroups.size() > 0) {
sendResponse(changedGroups);
} else {
sendResponse(null);
}
} else {
LogUtil.clientLog.info("{}|{}|{}|{}|{}|{}",
(System.currentTimeMillis() - createTime),
"timeout", RequestUtil.getRemoteIp((HttpServletRequest)asyncContext.getRequest()),
"polling",
clientMd5Map.size(), probeRequestSize);
sendResponse(null);
}
} catch (Throwable t) {
LogUtil.defaultLog.error("long polling error:" + t.getMessage(), t.getCause());
}
}
}, timeoutTime, TimeUnit.MILLISECONDS);
allSubs.add(this);
}
void sendResponse(List<String> changedGroups) {
/**
* 取消超時任務
*/
if (null != asyncTimeoutFuture) {
asyncTimeoutFuture.cancel(false);
}
generateResponse(changedGroups);
}
void generateResponse(List<String> changedGroups) {
if (null == changedGroups) {
/**
* 告訴容器發送HTTP響應
*/
asyncContext.complete();
return;
}
HttpServletResponse response = (HttpServletResponse)asyncContext.getResponse();
try {
String respString = MD5Util.compareMd5ResultString(changedGroups);
// 禁用緩存
response.setHeader("Pragma", "no-cache");
response.setDateHeader("Expires", 0);
response.setHeader("Cache-Control", "no-cache,no-store");
response.setStatus(HttpServletResponse.SC_OK);
response.getWriter().println(respString);
asyncContext.complete();
} catch (Exception se) {
pullLog.error(se.toString(), se);
asyncContext.complete();
}
}
ClientLongPolling(AsyncContext ac, Map<String, String> clientMd5Map, String ip, int probeRequestSize,
long timeoutTime, String appName, String tag) {
this.asyncContext = ac;
this.clientMd5Map = clientMd5Map;
this.probeRequestSize = probeRequestSize;
this.createTime = System.currentTimeMillis();
this.ip = ip;
this.timeoutTime = timeoutTime;
this.appName = appName;
this.tag = tag;
}
// =================
final AsyncContext asyncContext;
final Map<String, String> clientMd5Map;
final long createTime;
final String ip;
final String appName;
final String tag;
final int probeRequestSize;
final long timeoutTime;
Future<?> asyncTimeoutFuture;
}
3、配置修改發佈時調用 ConfigController 的 publishConfig 接口給監聽者發送消息
當用戶修改配置併發布時會調用 ConfigController 的 publishConfig 方法，將配置信息入庫並轉發發佈事件，通知建立長連接的客戶端。
/**
* 增加或更新非聚合數據。
*
* @throws NacosException
*/
@RequestMapping(method = RequestMethod.POST)
@ResponseBody
public Boolean publishConfig(HttpServletRequest request, HttpServletResponse response,
@RequestParam("dataId") String dataId, @RequestParam("group") String group,
@RequestParam(value = "tenant", required = false, defaultValue = StringUtils.EMPTY)
String tenant,
@RequestParam("content") String content,
@RequestParam(value = "tag", required = false) String tag,
@RequestParam(value = "appName", required = false) String appName,
@RequestParam(value = "src_user", required = false) String srcUser,
@RequestParam(value = "config_tags", required = false) String configTags,
@RequestParam(value = "desc", required = false) String desc,
@RequestParam(value = "use", required = false) String use,
@RequestParam(value = "effect", required = false) String effect,
@RequestParam(value = "type", required = false) String type,
@RequestParam(value = "schema", required = false) String schema)
throws NacosException {
final String srcIp = RequestUtil.getRemoteIp(request);
String requestIpApp = RequestUtil.getAppName(request);
ParamUtils.checkParam(dataId, group, "datumId", content);
ParamUtils.checkParam(tag);
Map<String, Object> configAdvanceInfo = new HashMap<String, Object>(10);
if (configTags != null) {
configAdvanceInfo.put("config_tags", configTags);
}
if (desc != null) {
configAdvanceInfo.put("desc", desc);
}
if (use != null) {
configAdvanceInfo.put("use", use);
}
if (effect != null) {
configAdvanceInfo.put("effect", effect);
}
if (type != null) {
configAdvanceInfo.put("type", type);
}
if (schema != null) {
configAdvanceInfo.put("schema", schema);
}
ParamUtils.checkParam(configAdvanceInfo);
if (AggrWhitelist.isAggrDataId(dataId)) {
log.warn("[aggr-conflict] {} attemp to publish single data, {}, {}",
RequestUtil.getRemoteIp(request), dataId, group);
throw new NacosException(NacosException.NO_RIGHT, "dataId:" + dataId + " is aggr");
}
final Timestamp time = TimeUtils.getCurrentTime();
String betaIps = request.getHeader("betaIps");
ConfigInfo configInfo = new ConfigInfo(dataId, group, tenant, appName, content);
if (StringUtils.isBlank(betaIps)) {
if (StringUtils.isBlank(tag)) {
persistService.insertOrUpdate(srcIp, srcUser, configInfo, time, configAdvanceInfo, false);
EventDispatcher.fireEvent(new ConfigDataChangeEvent(false, dataId, group, tenant, time.getTime()));
} else {
persistService.insertOrUpdateTag(configInfo, tag, srcIp, srcUser, time, false);
EventDispatcher.fireEvent(new ConfigDataChangeEvent(false, dataId, group, tenant, tag, time.getTime()));
}
} else { // beta publish
persistService.insertOrUpdateBeta(configInfo, betaIps, srcIp, srcUser, time, false);
EventDispatcher.fireEvent(new ConfigDataChangeEvent(true, dataId, group, tenant, time.getTime()));
}
ConfigTraceService.logPersistenceEvent(dataId, group, tenant, requestIpApp, time.getTime(),
LOCAL_IP, ConfigTraceService.PERSISTENCE_EVENT_PUB, content);
return true;
}
在 EventDispatcher的 fireEvent 方法中會根據 根據事件類型獲取所有的監聽器，然後調用監聽器的通知方法 onEvent
static public void fireEvent(Event event) {
if (null == event) {
throw new IllegalArgumentException();
}
for (AbstractEventListener listener : getEntry(event.getClass()).listeners) {
try {
listener.onEvent(event);
} catch (Exception e) {
log.error(e.toString(), e);
}
}
}
在 最終調用AbstractEventListener 的實現類LongPollingService 的 onEvent 方法
@Override
public void onEvent(Event event) {
if (isFixedPolling()) {
// ignore
} else {
if (event instanceof LocalDataChangeEvent) {
LocalDataChangeEvent evt = (LocalDataChangeEvent)event;
scheduler.execute(new DataChangeTask(evt.groupKey, evt.isBeta, evt.betaIps));
}
}
}
在 DataChangeTask 中會從 allSubs中獲取所有的長連接客戶端，然後通知客戶端配置變更
class DataChangeTask implements Runnable {
@Override
public void run() {
try {
ConfigService.getContentBetaMd5(groupKey);
for (Iterator<ClientLongPolling> iter = allSubs.iterator(); iter.hasNext(); ) {
ClientLongPolling clientSub = iter.next();
if (clientSub.clientMd5Map.containsKey(groupKey)) {
// 如果beta發佈且不在beta列表直接跳過
if (isBeta && !betaIps.contains(clientSub.ip)) {
continue;
}
// 如果tag發佈且不在tag列表直接跳過
if (StringUtils.isNotBlank(tag) && !tag.equals(clientSub.tag)) {
continue;
}
getRetainIps().put(clientSub.ip, System.currentTimeMillis());
iter.remove(); // 刪除訂閱關係
LogUtil.clientLog.info("{}|{}|{}|{}|{}|{}|{}",
(System.currentTimeMillis() - changeTime),
"in-advance",
RequestUtil.getRemoteIp((HttpServletRequest)clientSub.asyncContext.getRequest()),
"polling",
clientSub.clientMd5Map.size(), clientSub.probeRequestSize, groupKey);
clientSub.sendResponse(Arrays.asList(groupKey));
}
}
} catch (Throwable t) {
LogUtil.defaultLog.error("data change error:" + t.getMessage(), t.getCause());
}
}
DataChangeTask(String groupKey) {
this(groupKey, false, null);
}
DataChangeTask(String groupKey, boolean isBeta, List<String> betaIps) {
this(groupKey, isBeta, betaIps, null);
}
總結：
（1）客戶端可以在啓動時第一次拉取配置信息
（2）客戶端可以利用 web 容器的長連接機制與服務端建立長連接，服務端將訂閱輪詢存放在 allSubs 隊列中
（3）用戶修改配置發佈時會從 allSubs 中取出相關長連接客戶端今天配置變更通知。