【Soul閘道器探祕】http資料同步-變更通知機制
引言
上一篇,梳理除了 soul-admin
在發出資料變更通知前的處理脈絡,本篇開始探究 http 同步策略的變更通知機制,
不同資料變更的通知機制應當是一致的,故本篇以 selector 配置變更通知為切入點進行深入。
配置操作入口
找到 ConfigController,這是配置操作的入口
其持有一個 HttpLongPollingDataChangedListener 引用,通過 HttpLongPollingDataChangedListener 實現配置變更通知訂閱和配置獲取。
通知訂閱:
@PostMapping(value = "/listener")
public void listener(final HttpServletRequest request, final HttpServletResponse response) {
longPollingListener.doLongPolling(request, response);
}
配置獲取:
@GetMapping("/fetch")
public SoulAdminResult fetchConfigs(@NotNull final String[] groupKeys) {
Map<String, ConfigData<?>> result = Maps.newHashMap();
for (String groupKey : groupKeys) {
ConfigData<?> data = longPollingListener.fetchConfig(ConfigGroupEnum.valueOf(groupKey));
result.put(groupKey, data);
}
return SoulAdminResult.success(SoulResultMessage.SUCCESS, result) ;
}
通知訂閱實現
使用 HttpLongPollingDataChangedListener#doLongPolling 實現通知訂閱
public void doLongPolling(final HttpServletRequest request, final HttpServletResponse response) {
// 比較配置組md5
List<ConfigGroupEnum> changedGroup = compareChangedGroup(request);
String clientIp = getRemoteIp(request);
// 發現配置組變化則立即響應
if (CollectionUtils.isNotEmpty(changedGroup)) {
this.generateResponse(response, changedGroup);
log.info("send response with the changed group, ip={}, group={}", clientIp, changedGroup);
return;
}
// 監聽配置變化
final AsyncContext asyncContext = request.startAsync();
asyncContext.setTimeout(0L);
// 阻塞客戶端執行緒
scheduler.execute(new LongPollingClient(asyncContext, clientIp, HttpConstants.SERVER_MAX_HOLD_TIMEOUT));
}
通過比較 MD5 檢查配置組是否發生變更,若配置組發生變更則立即響應,否則阻塞客戶端執行緒。
此處 compareChangedGroup 實現不做深究,繼續看LongPollingClient 具體處理:
@Override
public void run() {
this.asyncTimeoutFuture = scheduler.schedule(() -> {
clients.remove(LongPollingClient.this);
List<ConfigGroupEnum> changedGroups = compareChangedGroup((HttpServletRequest) asyncContext.getRequest());
sendResponse(changedGroups);
}, timeoutTime, TimeUnit.MILLISECONDS);
clients.add(this);
}
這裡將 client 加入 clients 的同時,開啟了一個定時任務,負責超時移除 client 並返回發生變化的配置組資訊。
超時時間為構造時傳入的 HttpConstants.SERVER_MAX_HOLD_TIMEOUT = 60s
配置獲取實現
使用 AbstractDataChangedListener#fetchConfig 實現配置獲取
public ConfigData<?> fetchConfig(final ConfigGroupEnum groupKey) {
ConfigDataCache config = CACHE.get(groupKey.name());
switch (groupKey) {
case APP_AUTH:
...
case PLUGIN:
...
case RULE:
...
case SELECTOR:
List<SelectorData> selectorList = GsonUtils.getGson().fromJson(config.getJson(), new TypeToken<List<SelectorData>>() {
}.getType());
return new ConfigData<>(config.getMd5(), config.getLastModifyTime(), selectorList);
case META_DATA:
...
default:
throw new IllegalStateException("Unexpected groupKey: " + groupKey);
}
}
這裡從 CACHE 快取獲取對應配置組資訊,包裝成 ConfigData 並返回。
建立訂閱關係
soul-web
端通過 HttpSyncDataConfiguration 初始化 HttpSyncDataService 並注入 spring容器。
HttpSyncDataService#start 方法在初始化時完成配置獲取和訂閱:
private void start() {
// It could be initialized multiple times, so you need to control that.
if (RUNNING.compareAndSet(false, true)) {
// fetch all group configs.
this.fetchGroupConfig(ConfigGroupEnum.values());
int threadSize = serverList.size();
this.executor = new ThreadPoolExecutor(threadSize, threadSize, 60L, TimeUnit.SECONDS,
new LinkedBlockingQueue<>(),
SoulThreadFactory.create("http-long-polling", true));
// start long polling, each server creates a thread to listen for changes.
this.serverList.forEach(server -> this.executor.execute(new HttpLongPollingTask(server)));
} else {
log.info("soul http long polling was started, executor=[{}]", executor);
}
}
1)配置獲取
private void fetchGroupConfig(final ConfigGroupEnum... groups) throws SoulException {
for (int index = 0; index < this.serverList.size(); index++) {
String server = serverList.get(index);
try {
this.doFetchGroupConfig(server, groups);
break;
} catch (SoulException e) {
// no available server, throw exception.
if (index >= serverList.size() - 1) {
throw e;
}
log.warn("fetch config fail, try another one: {}", serverList.get(index + 1));
}
}
}
doFetchGroupConfig 內部發起配置獲取請求並更新本地快取
private void doFetchGroupConfig(final String server, final ConfigGroupEnum... groups) {
...
String url = server + "/configs/fetch?" + StringUtils.removeEnd(params.toString(), "&");
...
try {
json = this.httpClient.getForObject(url, String.class);
} catch (RestClientException e) {
...
}
// update local cache
boolean updated = this.updateCacheWithJson(json);
...
}
2)配置訂閱
藉助 HttpLongPollingTask 完成
@Override
public void run() {
while (RUNNING.get()) {
for (int time = 1; time <= retryTimes; time++) {
try {
doLongPolling(server);
} catch (Exception e) {
...
}
}
}
log.warn("Stop http long polling.");
}
HttpLongPollingTask 不斷迴圈 doLongPolling,此處有 retry 操作
private void doLongPolling(final String server) {
...
String listenerUrl = server + "/configs/listener";
...
try {
String json = this.httpClient.postForEntity(listenerUrl, httpEntity, String.class).getBody();
log.debug("listener result: [{}]", json);
groupJson = GSON.fromJson(json, JsonObject.class).getAsJsonArray("data");
} catch (RestClientException e) {
...
}
if (groupJson != null) {
// fetch group configuration async.
ConfigGroupEnum[] changedGroups = GSON.fromJson(groupJson, ConfigGroupEnum[].class);
if (ArrayUtils.isNotEmpty(changedGroups)) {
log.info("Group config changed: {}", Arrays.toString(changedGroups));
this.doFetchGroupConfig(server, changedGroups);
}
}
}
doLongPolling 內部發起 post 請求訂閱配置變更,若發生變更則重新獲取配置。
至此,通知訂閱處理脈絡已清晰:
soul-web
端通過 http 發起訂閱請求
soul-admin
端收到請求,通過比較 MD5 檢查配置組是否存在變更
- 若存在變更,則立即響應變更組資訊
- 若無變更,則阻塞客戶端執行緒,並開啟定時任務 60s 後重新比較配置組變更並返回響應
soul-web
端收到響應,判斷配置組是否存在變更
- 若存在變更,則發起獲取配置請求獲取最新配置資訊
soul-web
重新發起訂閱請求
配置變更
上回我們說到AbstractDataChangedListener 的 onSelectorChanged 實現:
public void onSelectorChanged(final List<SelectorData> changed, final DataEventTypeEnum eventType) {
if (CollectionUtils.isEmpty(changed)) {
return;
}
// 更新 selector 快取
this.updateSelectorCache();
// selector 變更後處理,實現具體的變更通知
this.afterSelectorChanged(changed, eventType);
}
這裡 selector 變更處理是先更快取後發通知,繼續看 afterSelectorChanged 實現。
HttpLongPollingDataChangedListener 真正實現了 AbstractDataChangedListener 的 afterSelectorChanged:
@Override
protected void afterSelectorChanged(final List<SelectorData> changed, final DataEventTypeEnum eventType) {
scheduler.execute(new DataChangeTask(ConfigGroupEnum.SELECTOR));
}
由定時任務重複執行 DataChangeTask,DataChangeTask 具體處理如下:
@Override
public void run() {
for (Iterator<LongPollingClient> iter = clients.iterator(); iter.hasNext();) {
LongPollingClient client = iter.next();
iter.remove();
client.sendResponse(Collections.singletonList(groupKey));
log.info("send response with the changed group,ip={}, group={}, changeTime={}", client.ip, groupKey, changeTime);
}
}
DataChangeTask 負責從 clients 依次移除 LongPollingClient 並將 groupKey 作為響應返回,sendResponse 內部處理如下:
void sendResponse(final List<ConfigGroupEnum> changedGroups) {
// cancel scheduler
if (null != asyncTimeoutFuture) {
asyncTimeoutFuture.cancel(false);
}
generateResponse((HttpServletResponse) asyncContext.getResponse(), changedGroups);
asyncContext.complete();
}
負責生成響應報文並非同步響應客戶端,注意有個 asyncTimeoutFuture.cancel 操作,取消之前的 60s 超時響應。
總結
本篇梳理和分析了 soul-web
端到 soul-admin
端的配置變更通知訂閱關係建立過程,配合上配置獲取介面,完成了整個 http 資料同步策略的變更通知機制。
下篇,將探究 http 同步策略的web端處理變更通知,期待驚喜。