/**
 * Watch Key 与 DeferredResultWrapper 的 Multimap
 *
 * Key:Watch Key
 * Value:DeferredResultWrapper 数组
 */
private final Multimap<String, DeferredResultWrapper> deferredResults = Multimaps.synchronizedSetMultimap(HashMultimap.create());

private static final Splitter STRING_SPLITTER = Splitter.on(ConfigConsts.CLUSTER_NAMESPACE_SEPARATOR).omitEmptyStrings();
private static final Type notificationsTypeReference = new TypeToken<List<ApolloConfigNotification>>() {}.getType();

/**
 * 通过 ReleaseMessage 的消息内容,获得对应 Namespace 的名字
 */
private static final Function<String, String> retrieveNamespaceFromReleaseMessage =
 releaseMessage -> {
 if (Strings.isNullOrEmpty(releaseMessage)) {
 return null;
 }
 List<String> keys = STRING_SPLITTER.splitToList(releaseMessage);
 //message should be appId+cluster+namespace
 if (keys.size() != 3) {
 logger.error("message format invalid - {}", releaseMessage);
 return null;
 }
 return keys.get(2);
 };

/**
 * 大量通知分批执行 ExecutorService
 */
private final ExecutorService largeNotificationBatchExecutorService;
@Autowired
private WatchKeysUtil watchKeysUtil;
@Autowired
private ReleaseMessageServiceWithCache releaseMessageService;
@Autowired
private EntityManagerUtil entityManagerUtil;
@Autowired
private NamespaceUtil namespaceUtil;
@Autowired
private Gson gson;
@Autowired
private BizConfig bizConfig;

public NotificationControllerV2() {
 largeNotificationBatchExecutorService = Executors.newSingleThreadExecutor(ApolloThreadFactory.create("NotificationControllerV2", true));
}

 1: @RequestMapping(method = RequestMethod.GET)
 2: public DeferredResult<ResponseEntity<List<ApolloConfigNotification>>> pollNotification(
 3: @RequestParam(value = "appId") String appId,
 4: @RequestParam(value = "cluster") String cluster,
 5: @RequestParam(value = "notifications") String notificationsAsString,
 6: @RequestParam(value = "dataCenter", required = false) String dataCenter,
 7: @RequestParam(value = "ip", required = false) String clientIp) {
 8: // 解析 notificationsAsString 参数,创建 ApolloConfigNotification 数组。
 9: List<ApolloConfigNotification> notifications = null;
10: try {
11: notifications = gson.fromJson(notificationsAsString, notificationsTypeReference);
12: } catch (Throwable ex) {
13: Tracer.logError(ex);
14: }
15: if (CollectionUtils.isEmpty(notifications)) {
16: throw new BadRequestException("Invalid format of notifications: " + notificationsAsString);
17: }
18:
19: // 创建 DeferredResultWrapper 对象
20: DeferredResultWrapper deferredResultWrapper = new DeferredResultWrapper();
21: // Namespace 集合
22: Set<String> namespaces = Sets.newHashSet();
23: // 客户端的通知 Map 。key 为 Namespace 名,value 为通知编号。
24: Map<String, Long> clientSideNotifications = Maps.newHashMap();
25: // 过滤并创建 ApolloConfigNotification Map
26: Map<String, ApolloConfigNotification> filteredNotifications = filterNotifications(appId, notifications);
27: // 循环 ApolloConfigNotification Map ,初始化上述变量。
28: for (Map.Entry<String, ApolloConfigNotification> notificationEntry : filteredNotifications.entrySet()) {
29: String normalizedNamespace = notificationEntry.getKey();
30: ApolloConfigNotification notification = notificationEntry.getValue();
31: // 添加到 `namespaces` 中。
32: namespaces.add(normalizedNamespace);
33: // 添加到 `clientSideNotifications` 中。
34: clientSideNotifications.put(normalizedNamespace, notification.getNotificationId());
35: // 记录名字被归一化的 Namespace 。因为,最终返回给客户端,使用原始的 Namespace 名字,否则客户端无法识别。
36: if (!Objects.equals(notification.getNamespaceName(), normalizedNamespace)) {
37: deferredResultWrapper.recordNamespaceNameNormalizedResult(notification.getNamespaceName(), normalizedNamespace);
38: }
39: }
40: if (CollectionUtils.isEmpty(namespaces)) {
41: throw new BadRequestException("Invalid format of notifications: " + notificationsAsString);
42: }
43:
44: // 组装 Watch Key Multimap
45: Multimap<String, String> watchedKeysMap = watchKeysUtil.assembleAllWatchKeys(appId, cluster, namespaces, dataCenter);
46: // 生成 Watch Key 集合
47: Set<String> watchedKeys = Sets.newHashSet(watchedKeysMap.values());
48: // 获得 Watch Key 集合中,每个 Watch Key 对应的 ReleaseMessage 记录。
49: List<ReleaseMessage> latestReleaseMessages = releaseMessageService.findLatestReleaseMessagesGroupByMessages(watchedKeys);
50:
51: /**
52: * Manually close the entity manager.
53: * Since for async request, Spring won't do so until the request is finished,
54: * which is unacceptable since we are doing long polling - means the db connection would be hold
55: * for a very long time
56: */
57: // 手动关闭 EntityManager
58: // 因为对于 async 请求,Spring 在请求完成之前不会这样做
59: // 这是不可接受的,因为我们正在做长轮询——意味着 db 连接将被保留很长时间。
60: // 实际上,下面的过程,我们已经不需要 db 连接,因此进行关闭。
61: entityManagerUtil.closeEntityManager();
62: // 获得新的 ApolloConfigNotification 通知数组
63: List<ApolloConfigNotification> newNotifications = getApolloConfigNotifications(namespaces, clientSideNotifications, watchedKeysMap, latestReleaseMessages);
64: // 若有新的通知,直接设置结果。
65: if (!CollectionUtils.isEmpty(newNotifications)) {
66: deferredResultWrapper.setResult(newNotifications);
67: // 若无新的通知,
68: } else {
69: // 注册超时事件
70: deferredResultWrapper.onTimeout(() -> logWatchedKeys(watchedKeys, "Apollo.LongPoll.TimeOutKeys")); // 【TODO 6001】Tracer 日志
71: // 注册结束事件
72: deferredResultWrapper.onCompletion(() -> {
73: // 移除 Watch Key + DeferredResultWrapper 出 `deferredResults`
74: // unregister all keys
75: for (String key : watchedKeys) {
76: deferredResults.remove(key, deferredResultWrapper);
77: }
78: // 【TODO 6001】Tracer 日志
79: logWatchedKeys(watchedKeys, "Apollo.LongPoll.CompletedKeys");
80: });
81:
82: // 注册 Watch Key + DeferredResultWrapper 到 `deferredResults` 中,等待配置发生变化后通知。详见 `#handleMessage(...)` 方法。
83: // register all keys
84: for (String key : watchedKeys) {
85: this.deferredResults.put(key, deferredResultWrapper);
86: }
87:
88: // 【TODO 6001】Tracer 日志
89: logWatchedKeys(watchedKeys, "Apollo.LongPoll.RegisteredKeys");
90: logger.debug("Listening {} from appId: {}, cluster: {}, namespace: {}, datacenter: {}", watchedKeys, appId, cluster, namespaces, dataCenter);
91: }
92:
93: return deferredResultWrapper.getResult();
94: }

 1: private Map<String, ApolloConfigNotification> filterNotifications(String appId, List<ApolloConfigNotification> notifications) {
 2: Map<String, ApolloConfigNotification> filteredNotifications = Maps.newHashMap();
 3: for (ApolloConfigNotification notification : notifications) {
 4: if (Strings.isNullOrEmpty(notification.getNamespaceName())) {
 5: continue;
 6: }
 7: // 若 Namespace 名以 .properties 结尾,移除该结尾,并设置到 ApolloConfigNotification 中。例如 application.properties => application 。
 8: // strip out .properties suffix
 9: String originalNamespace = namespaceUtil.filterNamespaceName(notification.getNamespaceName());
10: notification.setNamespaceName(originalNamespace);
11: // 获得归一化的 Namespace 名字。因为,客户端 Namespace 会填写错大小写。
12: // 例如,数据库中 Namespace 名为 Fx.Apollo ,而客户端 Namespace 名为 fx.Apollo
13: // 通过归一化后,统一为 Fx.Apollo
14: // fix the character case issue, such as FX.apollo <-> fx.apollo
15: String normalizedNamespace = namespaceUtil.normalizeNamespace(appId, originalNamespace);
16:
17: // in case client side namespace name has character case issue and has difference notification ids
18: // such as FX.apollo = 1 but fx.apollo = 2, we should let FX.apollo have the chance to update its notification id
19: // which means we should record FX.apollo = 1 here and ignore fx.apollo = 2
20: // 如果客户端 Namespace 的名字有大小写的问题,并且恰好有不同的通知编号。
21: // 例如 Namespace 名字为 FX.apollo 的通知编号是 1 ,但是 fx.apollo 的通知编号为 2 。
22: // 我们应该让 FX.apollo 可以更新它的通知编号,
23: // 所以,我们使用 FX.apollo 的 ApolloConfigNotification 对象,添加到结果,而忽略 fx.apollo 。
24: if (filteredNotifications.containsKey(normalizedNamespace) &&
25: filteredNotifications.get(normalizedNamespace).getNotificationId() < notification.getNotificationId()) {
26: continue;
27: }
28:
29: filteredNotifications.put(normalizedNamespace, notification);
30: }
31: return filteredNotifications;
32: }

 1: private List<ApolloConfigNotification> getApolloConfigNotifications(Set<String> namespaces,
 2: Map<String, Long> clientSideNotifications,
 3: Multimap<String, String> watchedKeysMap,
 4: List<ReleaseMessage> latestReleaseMessages) {
 5: // 创建 ApolloConfigNotification 数组
 6: List<ApolloConfigNotification> newNotifications = Lists.newArrayList();
 7: if (!CollectionUtils.isEmpty(latestReleaseMessages)) {
 8: // 创建最新通知的 Map 。其中 Key 为 Watch Key 。
 9: Map<String, Long> latestNotifications = Maps.newHashMap();
10: for (ReleaseMessage releaseMessage : latestReleaseMessages) {
11: latestNotifications.put(releaseMessage.getMessage(), releaseMessage.getId());
12: }
13: // 循环 Namespace 的名字的集合,判断是否有配置更新
14: for (String namespace : namespaces) {
15: long clientSideId = clientSideNotifications.get(namespace);
16: long latestId = ConfigConsts.NOTIFICATION_ID_PLACEHOLDER;
17: // 获得 Namespace 对应的 Watch Key 集合
18: Collection<String> namespaceWatchedKeys = watchedKeysMap.get(namespace);
19: // 获得最大的通知编号
20: for (String namespaceWatchedKey : namespaceWatchedKeys) {
21: long namespaceNotificationId = latestNotifications.getOrDefault(namespaceWatchedKey, ConfigConsts.NOTIFICATION_ID_PLACEHOLDER);
22: if (namespaceNotificationId > latestId) {
23: latestId = namespaceNotificationId;
24: }
25: }
26: // 若服务器的通知编号大于客户端的通知编号,意味着有配置更新
27: if (latestId > clientSideId) {
28: // 创建 ApolloConfigNotification 对象
29: ApolloConfigNotification notification = new ApolloConfigNotification(namespace, latestId);
30: // 循环添加通知编号到 ApolloConfigNotification 中。
31: namespaceWatchedKeys.stream().filter(latestNotifications::containsKey).forEach(namespaceWatchedKey ->
32: notification.addMessage(namespaceWatchedKey, latestNotifications.get(namespaceWatchedKey)));
33: // 添加 ApolloConfigNotification 对象到结果
34: newNotifications.add(notification);
35: }
36: }
37: }
38: return newNotifications;
39: }

 1: @Override
 2: public void handleMessage(ReleaseMessage message, String channel) {
 3: logger.info("message received - channel: {}, message: {}", channel, message);
 4: // 【TODO 6001】Tracer 日志
 5: String content = message.getMessage();
 6: Tracer.logEvent("Apollo.LongPoll.Messages", content);
 7:
 8: // 仅处理 APOLLO_RELEASE_TOPIC
 9: if (!Topics.APOLLO_RELEASE_TOPIC.equals(channel) || Strings.isNullOrEmpty(content)) {
10: return;
11: }
12:
13: // 获得对应的 Namespace 的名字
14: String changedNamespace = retrieveNamespaceFromReleaseMessage.apply(content);
15: if (Strings.isNullOrEmpty(changedNamespace)) {
16: logger.error("message format invalid - {}", content);
17: return;
18: }
19:
20: // `deferredResults` 存在对应的 Watch Key
21: if (!deferredResults.containsKey(content)) {
22: return;
23: }
24:
25: // create a new list to avoid ConcurrentModificationException
26: // 创建 DeferredResultWrapper 数组,避免并发问题。
27: List<DeferredResultWrapper> results = Lists.newArrayList(deferredResults.get(content));
28:
29: // 创建 ApolloConfigNotification 对象
30: ApolloConfigNotification configNotification = new ApolloConfigNotification(changedNamespace, message.getId());
31: configNotification.addMessage(content, message.getId());
32:
33: // do async notification if too many clients
34: // 若需要通知的客户端过多,使用 ExecutorService 异步通知,避免"惊群效应"
35: if (results.size() > bizConfig.releaseMessageNotificationBatch()) {
36: largeNotificationBatchExecutorService.submit(() -> {
37: logger.debug("Async notify {} clients for key {} with batch {}", results.size(), content,
38: bizConfig.releaseMessageNotificationBatch());
39: for (int i = 0; i < results.size(); i++) {
40: // 每 N 个客户端,sleep 一段时间。
41: if (i > 0 && i % bizConfig.releaseMessageNotificationBatch() == 0) {
42: try {
43: TimeUnit.MILLISECONDS.sleep(bizConfig.releaseMessageNotificationBatchIntervalInMilli());
44: } catch (InterruptedException e) {
45: //ignore
46: }
47: }
48: logger.debug("Async notify {}", results.get(i));
49: // 设置结果
50: results.get(i).setResult(configNotification);
51: }
52: });
53: return;
54: }
55:
56: logger.debug("Notify {} clients for key {}", results.size(), content);
57: // 设置结果
58: for (DeferredResultWrapper result : results) {
59: result.setResult(configNotification);
60: }
61: logger.debug("Notification completed");
62: }

public class ApolloConfigNotification {

 /**
 * Namespace 名字
 */
 private String namespaceName;
 /**
 * 最新通知编号
 *
 * 目前使用 `ReleaseMessage.id` 。
 */
 private long notificationId;
 /**
 * 通知消息集合
 */
 private volatile ApolloNotificationMessages messages;

 public ApolloConfigNotification(String namespaceName, long notificationId) {
 this.namespaceName = namespaceName;
 this.notificationId = notificationId;
 }

}

public class ApolloNotificationMessages {

 /**
 * 明细 Map
 *
 * KEY :{appId} "+" {clusterName} "+" {namespace} ,例如:100004458+default+application
 * VALUE :通知编号
 */
 private Map<String, Long> details;

 public ApolloNotificationMessages() {
 this(Maps.<String, Long>newHashMap());
 }

}

public void put(String key, long notificationId) {
 details.put(key, notificationId);
}

public void mergeFrom(ApolloNotificationMessages source) {
 if (source == null) {
 return;
 }
 for (Map.Entry<String, Long> entry : source.getDetails().entrySet()) {
 // to make sure the notification id always grows bigger
 // 只合并新的通知编号大于的情况
 if (this.has(entry.getKey()) && this.get(entry.getKey()) >= entry.getValue()) {
 continue;
 }
 this.put(entry.getKey(), entry.getValue());
 }
}

/**
 * 默认超时时间
 */
private static final long TIMEOUT = 60 * 1000; //60 seconds
/**
 * 未修改时的 ResponseEntity 响应,使用 302 状态码。
 */
private static final ResponseEntity<List<ApolloConfigNotification>> NOT_MODIFIED_RESPONSE_LIST = new ResponseEntity<>(HttpStatus.NOT_MODIFIED);

/**
 * 归一化和原始的 Namespace 的名字的 Map
 */
private Map<String, String> normalizedNamespaceNameToOriginalNamespaceName;
/**
 * 响应的 DeferredResult 对象
 */
private DeferredResult<ResponseEntity<List<ApolloConfigNotification>>> result;

public DeferredResultWrapper() {
 result = new DeferredResult<>(TIMEOUT, NOT_MODIFIED_RESPONSE_LIST);
}

public void onTimeout(Runnable timeoutCallback) {
 result.onTimeout(timeoutCallback);
}

public void setResult(ApolloConfigNotification notification) {
 setResult(Lists.newArrayList(notification));
}

public void setResult(ApolloConfigNotification notification) {
 setResult(Lists.newArrayList(notification));
}

public void setResult(List<ApolloConfigNotification> notifications) {
 // 恢复被归一化的 Namespace 的名字为原始的 Namespace 的名字
 if (normalizedNamespaceNameToOriginalNamespaceName != null) {
 notifications.stream().filter(notification -> normalizedNamespaceNameToOriginalNamespaceName.containsKey
 (notification.getNamespaceName())).forEach(notification -> notification.setNamespaceName(
 normalizedNamespaceNameToOriginalNamespaceName.get(notification.getNamespaceName())));
 }
 // 设置结果,并使用 200 状态码。
 result.setResult(new ResponseEntity<>(notifications, HttpStatus.OK));
}

private static final Joiner STRING_JOINER = Joiner.on(ConfigConsts.CLUSTER_NAMESPACE_SEPARATOR).skipNulls();

@Autowired
private AppNamespaceRepository appNamespaceRepository;
@Autowired
private BizConfig bizConfig;

/**
 * 增量初始化周期
 */
private int scanInterval;
/**
 * 增量初始化周期单位
 */
private TimeUnit scanIntervalTimeUnit;
/**
 * 重建周期
 */
private int rebuildInterval;
/**
 * 重建周期单位
 */
private TimeUnit rebuildIntervalTimeUnit;
/**
 * 定时任务 ExecutorService
 */
private ScheduledExecutorService scheduledExecutorService;
/**
 * 最后扫描到的 AppNamespace 的编号
 */
private long maxIdScanned;

/**
 * 公用类型的 AppNamespace 的缓存
 *
 * //store namespaceName -> AppNamespace
 */
private CaseInsensitiveMapWrapper<AppNamespace> publicAppNamespaceCache;
/**
 * App 下的 AppNamespace 的缓存
 *
 * store appId+namespaceName -> AppNamespace
 */
private CaseInsensitiveMapWrapper<AppNamespace> appNamespaceCache;
/**
 * AppNamespace 的缓存
 *
 * //store id -> AppNamespace
 */
private Map<Long, AppNamespace> appNamespaceIdCache;

public AppNamespaceServiceWithCache() {
 initialize();
}

private void initialize() {
 maxIdScanned = 0;
 // 创建缓存对象
 publicAppNamespaceCache = new CaseInsensitiveMapWrapper<>(Maps.newConcurrentMap());
 appNamespaceCache = new CaseInsensitiveMapWrapper<>(Maps.newConcurrentMap());
 appNamespaceIdCache = Maps.newConcurrentMap();
 // 创建 ScheduledExecutorService 对象,大小为 1 。
 scheduledExecutorService = Executors.newScheduledThreadPool(1, ApolloThreadFactory.create("AppNamespaceServiceWithCache", true));
}

 1: @Override
 2: public void afterPropertiesSet() throws Exception {
 3: // 从 ServerConfig 中,读取定时任务的周期配置
 4: populateDataBaseInterval();
 5: // 全量初始化 AppNamespace 缓存
 6: scanNewAppNamespaces(); // block the startup process until load finished
 7: // 创建定时任务,全量重构 AppNamespace 缓存
 8: scheduledExecutorService.scheduleAtFixedRate(() -> {
 9: // 【TODO 6001】Tracer 日志
10: Transaction transaction = Tracer.newTransaction("Apollo.AppNamespaceServiceWithCache", "rebuildCache");
11: try {
12: // 全量重建 AppNamespace 缓存
13: this.updateAndDeleteCache();
14: // 【TODO 6001】Tracer 日志
15: transaction.setStatus(Transaction.SUCCESS);
16: } catch (Throwable ex) {
17: // 【TODO 6001】Tracer 日志
18: transaction.setStatus(ex);
19: logger.error("Rebuild cache failed", ex);
20: } finally {
21: // 【TODO 6001】Tracer 日志
22: transaction.complete();
23: }
24: }, rebuildInterval, rebuildInterval, rebuildIntervalTimeUnit);
25: // 创建定时任务,增量初始化 AppNamespace 缓存
26: scheduledExecutorService.scheduleWithFixedDelay(this::scanNewAppNamespaces, scanInterval, scanInterval, scanIntervalTimeUnit);
27: }

private void scanNewAppNamespaces() {
 // 【TODO 6001】Tracer 日志
 Transaction transaction = Tracer.newTransaction("Apollo.AppNamespaceServiceWithCache", "scanNewAppNamespaces");
 try {
 // 加载新的 AppNamespace 们
 this.loadNewAppNamespaces();
 // 【TODO 6001】Tracer 日志
 transaction.setStatus(Transaction.SUCCESS);
 } catch (Throwable ex) {
 // 【TODO 6001】Tracer 日志
 transaction.setStatus(ex);
 logger.error("Load new app namespaces failed", ex);
 } finally {
 // 【TODO 6001】Tracer 日志
 transaction.complete();
 }
}

private void updateAndDeleteCache() {
 // 从缓存中,获得所有的 AppNamespace 编号集合
 List<Long> ids = Lists.newArrayList(appNamespaceIdCache.keySet());
 if (CollectionUtils.isEmpty(ids)) {
 return;
 }
 // 每 500 一批,从数据库中查询最新的 AppNamespace 信息
 List<List<Long>> partitionIds = Lists.partition(ids, 500);
 for (List<Long> toRebuild : partitionIds) {
 Iterable<AppNamespace> appNamespaces = appNamespaceRepository.findAll(toRebuild);
 if (appNamespaces == null) {
 continue;
 }
 // 处理更新的情况
 // handle updated
 Set<Long> foundIds = handleUpdatedAppNamespaces(appNamespaces);
 // 处理删除的情况
 // handle deleted
 handleDeletedAppNamespaces(Sets.difference(Sets.newHashSet(toRebuild), foundIds));
 }
}

/**
 * 获得 AppNamespace 对象
 *
 * @param appId App 编号
 * @param namespaceName Namespace 名字
 * @return AppNamespace
 */
public AppNamespace findByAppIdAndNamespace(String appId, String namespaceName) {
 Preconditions.checkArgument(!StringUtils.isContainEmpty(appId, namespaceName), "appId and namespaceName must not be empty");
 return appNamespaceCache.get(STRING_JOINER.join(appId, namespaceName));
}

/**
 * 获得 AppNamespace 对象数组
 *
 * @param appId App 编号
 * @param namespaceNames Namespace 名字的集合
 * @return AppNamespace 数组
 */
public List<AppNamespace> findByAppIdAndNamespaces(String appId, Set<String> namespaceNames) {
 Preconditions.checkArgument(!Strings.isNullOrEmpty(appId), "appId must not be null");
 if (namespaceNames == null || namespaceNames.isEmpty()) {
 return Collections.emptyList();
 }
 List<AppNamespace> result = Lists.newArrayList();
 // 循环获取
 for (String namespaceName : namespaceNames) {
 AppNamespace appNamespace = appNamespaceCache.get(STRING_JOINER.join(appId, namespaceName));
 if (appNamespace != null) {
 result.add(appNamespace);
 }
 }
 return result;
}

/**
 * 获得公用类型的 AppNamespace 对象
 *
 * @param namespaceName Namespace 名字
 * @return AppNamespace
 */
public AppNamespace findPublicNamespaceByName(String namespaceName) {
 Preconditions.checkArgument(!Strings.isNullOrEmpty(namespaceName), "namespaceName must not be empty");
 return publicAppNamespaceCache.get(namespaceName);
}

/**
 * 获得公用类型的 AppNamespace 对象数组
 *
 * @param namespaceNames Namespace 名字的集合
 * @return AppNamespace 数组
 */
public List<AppNamespace> findPublicNamespacesByNames(Set<String> namespaceNames) {
 if (namespaceNames == null || namespaceNames.isEmpty()) {
 return Collections.emptyList();
 }

 List<AppNamespace> result = Lists.newArrayList();
 // 循环获取
 for (String namespaceName : namespaceNames) {
 AppNamespace appNamespace = publicAppNamespaceCache.get(namespaceName);
 if (appNamespace != null) {
 result.add(appNamespace);
 }
 }
 return result;
}

@Autowired
private ReleaseMessageRepository releaseMessageRepository;
@Autowired
private BizConfig bizConfig;

/**
 * 扫描周期
 */
private int scanInterval;
/**
 * 扫描周期单位
 */
private TimeUnit scanIntervalTimeUnit;
/**
 * 最后扫描到的 ReleaseMessage 的编号
 */
private volatile long maxIdScanned;
/**
 * ReleaseMessage 缓存
 *
 * KEY:`ReleaseMessage.message`
 * VALUE:对应的最新的 ReleaseMessage 记录
 */
private ConcurrentMap<String, ReleaseMessage> releaseMessageCache;
/**
 * 是否执行扫描任务
 */
private AtomicBoolean doScan;
/**
 * ExecutorService 对象
 */
private ExecutorService executorService;

public ReleaseMessageServiceWithCache() {
 initialize();
}

private void initialize() {
 // 创建缓存对象
 releaseMessageCache = Maps.newConcurrentMap();
 // 设置 doScan 为 true
 doScan = new AtomicBoolean(true);
 // 创建 ScheduledExecutorService 对象,大小为 1 。
 executorService = Executors.newSingleThreadExecutor(ApolloThreadFactory.create("ReleaseMessageServiceWithCache", true));
}

 1: @Override
 2: public void afterPropertiesSet() throws Exception {
 3: // 从 ServerConfig 中,读取任务的周期配置
 4: populateDataBaseInterval();
 5: // 初始拉取 ReleaseMessage 到缓存
 6: //block the startup process until load finished
 7: //this should happen before ReleaseMessageScanner due to autowire
 8: loadReleaseMessages(0);
 9: // 创建定时任务,增量拉取 ReleaseMessage 到缓存,用以处理初始化期间,产生的 ReleaseMessage 遗漏的问题。
10: executorService.submit(() -> {
11: while (doScan.get() && !Thread.currentThread().isInterrupted()) {
12: // 【TODO 6001】Tracer 日志
13: Transaction transaction = Tracer.newTransaction("Apollo.ReleaseMessageServiceWithCache", "scanNewReleaseMessages");
14: try {
15: // 增量拉取 ReleaseMessage 到缓存
16: loadReleaseMessages(maxIdScanned);
17: // 【TODO 6001】Tracer 日志
18: transaction.setStatus(Transaction.SUCCESS);
19: } catch (Throwable ex) {
20: // 【TODO 6001】Tracer 日志
21: transaction.setStatus(ex);
22: logger.error("Scan new release messages failed", ex);
23: } finally {
24: transaction.complete();
25: }
26: try {
27: scanIntervalTimeUnit.sleep(scanInterval);
28: } catch (InterruptedException e) {
29: //ignore
30: }
31: }
32: });
33: }

private void loadReleaseMessages(long startId) {
 boolean hasMore = true;
 while (hasMore && !Thread.currentThread().isInterrupted()) {
 // current batch is 500
 // 获得大于 maxIdScanned 的 500 条 ReleaseMessage 记录,按照 id 升序
 List<ReleaseMessage> releaseMessages = releaseMessageRepository.findFirst500ByIdGreaterThanOrderByIdAsc(startId);
 if (CollectionUtils.isEmpty(releaseMessages)) {
 break;
 }
 // 合并到 ReleaseMessage 缓存
 releaseMessages.forEach(this::mergeReleaseMessage);
 // 获得新的 maxIdScanned ,取最后一条记录
 int scanned = releaseMessages.size();
 startId = releaseMessages.get(scanned - 1).getId();
 // 若拉取不足 500 条,说明无新消息了
 hasMore = scanned == 500;
 logger.info("Loaded {} release messages with startId {}", scanned, startId);
 }
}

 1: @Override
 2: public void handleMessage(ReleaseMessage message, String channel) {
 3: // Could stop once the ReleaseMessageScanner starts to work
 4: // 关闭增量拉取定时任务的执行
 5: doScan.set(false);
 6: logger.info("message received - channel: {}, message: {}", channel, message);
 7: 
 8: // 仅处理 APOLLO_RELEASE_TOPIC
 9: String content = message.getMessage();
10: Tracer.logEvent("Apollo.ReleaseMessageService.UpdateCache", String.valueOf(message.getId()));
11: if (!Topics.APOLLO_RELEASE_TOPIC.equals(channel) || Strings.isNullOrEmpty(content)) {
12: return;
13: }
14: 
15: // 计算 gap
16: long gap = message.getId() - maxIdScanned;
17: // 若无空缺 gap ,直接合并
18: if (gap == 1) {
19: mergeReleaseMessage(message);
20: // 如有空缺 gap ,增量拉取
21: } else if (gap > 1) {
22: // gap found!
23: loadReleaseMessages(maxIdScanned);
24: }
25: }

 1: /**
 2: * 组装所有的 Watch Key Multimap 。其中 Key 为 Namespace 的名字,Value 为 Watch Key 集合。
 3: *
 4: * @param appId App 编号
 5: * @param clusterName Cluster 名
 6: * @param namespaces Namespace 的名字的数组
 7: * @param dataCenter IDC 的 Cluster 名
 8: * @return Watch Key Multimap
 9: */
10: public Multimap<String, String> assembleAllWatchKeys(String appId, String clusterName,
11: Set<String> namespaces,
12: String dataCenter) {
13: // 组装 Watch Key Multimap
14: Multimap<String, String> watchedKeysMap = assembleWatchKeys(appId, clusterName, namespaces, dataCenter);
15:
16: // 如果不是仅监听 'application' Namespace ,处理其关联来的 Namespace 。
17: // Every app has an 'application' namespace
18: if (!(namespaces.size() == 1 && namespaces.contains(ConfigConsts.NAMESPACE_APPLICATION))) {
19: // 获得属于该 App 的 Namespace 的名字的集合
20: Set<String> namespacesBelongToAppId = namespacesBelongToAppId(appId, namespaces);
21: // 获得关联来的 Namespace 的名字的集合
22: Set<String> publicNamespaces = Sets.difference(namespaces, namespacesBelongToAppId);
23: // 添加到 Watch Key Multimap 中
24: // Listen on more namespaces if it's a public namespace
25: if (!publicNamespaces.isEmpty()) {
26: watchedKeysMap.putAll(findPublicConfigWatchKeys(appId, clusterName, publicNamespaces, dataCenter));
27: }
28: }
29:
30: return watchedKeysMap;
31: }

/**
 * 获得每条消息内容对应的最新的 ReleaseMessage 对象
 *
 * @param messages 消息内容的集合
 * @return 集合
 */
public List<ReleaseMessage> findLatestReleaseMessagesGroupByMessages(Set<String> messages) {
 if (CollectionUtils.isEmpty(messages)) {
 return Collections.emptyList();
 }
 List<ReleaseMessage> releaseMessages = Lists.newArrayList();
 // 获得每条消息内容对应的最新的 ReleaseMessage 对象
 for (String message : messages) {
 ReleaseMessage releaseMessage = releaseMessageCache.get(message);
 if (releaseMessage != null) {
 releaseMessages.add(releaseMessage);
 }
 }
 return releaseMessages;
}

/**
 * 组装 Watch Key Multimap
 *
 * @param appId App 编号
 * @param clusterName Cluster 名
 * @param namespaces Namespace 的名字的集合
 * @param dataCenter IDC 的 Cluster 名字
 * @return Watch Key Multimap
 */
private Multimap<String, String> assembleWatchKeys(String appId, String clusterName, Set<String> namespaces, String dataCenter) {
 Multimap<String, String> watchedKeysMap = HashMultimap.create();
 // 循环 Namespace 的名字的集合
 for (String namespace : namespaces) {
 watchedKeysMap.putAll(namespace, assembleWatchKeys(appId, clusterName, namespace, dataCenter));
 }
 return watchedKeysMap;
}

/**
 * 获得属于该 App 的 Namespace 的名字的集合
 *
 * @param appId App 编号
 * @param namespaces Namespace 名
 * @return 集合
 */
private Set<String> namespacesBelongToAppId(String appId, Set<String> namespaces) {
 if (ConfigConsts.NO_APPID_PLACEHOLDER.equalsIgnoreCase(appId)) {
 return Collections.emptySet();
 }
 // 获得属于该 App 的 AppNamespace 集合
 List<AppNamespace> appNamespaces = appNamespaceService.findByAppIdAndNamespaces(appId, namespaces);
 if (appNamespaces == null || appNamespaces.isEmpty()) {
 return Collections.emptySet();
 }
 // 返回 AppNamespace 的名字的集合
 return appNamespaces.stream().map(AppNamespace::getName).collect(Collectors.toSet());
}

@Autowired
private AppNamespaceServiceWithCache appNamespaceService;

/**
 * 获得 Namespace 类型为 public 对应的 Watch Key Multimap
 *
 * 重要:要求非当前 App 的 Namespace
 *
 * @param applicationId App 编号
 * @param clusterName Cluster 名
 * @param namespaces Namespace 的名字的集合
 * @param dataCenter IDC 的 Cluster 名
 * @return Watch Key Map
 */
private Multimap<String, String> findPublicConfigWatchKeys(String applicationId, String clusterName, Set<String> namespaces, String dataCenter) {
 Multimap<String, String> watchedKeysMap = HashMultimap.create();
 // 获得 Namespace 为 public 的 AppNamespace 数组
 List<AppNamespace> appNamespaces = appNamespaceService.findPublicNamespacesByNames(namespaces);
 // 组装 Watch Key Map
 for (AppNamespace appNamespace : appNamespaces) {
 // 排除非关联类型的 Namespace
 // check whether the namespace's appId equals to current one
 if (Objects.equals(applicationId, appNamespace.getAppId())) {
 continue;
 }
 String publicConfigAppId = appNamespace.getAppId();
 // 组装指定 Namespace 的 Watch Key 数组
 watchedKeysMap.putAll(appNamespace.getName(), assembleWatchKeys(publicConfigAppId, clusterName, appNamespace.getName(), dataCenter));
 }
 return watchedKeysMap;
}

private static final Joiner STRING_JOINER = Joiner.on(ConfigConsts.CLUSTER_NAMESPACE_SEPARATOR);

/**
 * 拼接 Watch Key
 *
 * @param appId App 编号
 * @param cluster Cluster 名
 * @param namespace Namespace 名
 * @return Watch Key
 */
private String assembleKey(String appId, String cluster, String namespace) {
 return STRING_JOINER.join(appId, cluster, namespace);
}

@Component
public class EntityManagerUtil extends EntityManagerFactoryAccessor {

 private static final Logger logger = LoggerFactory.getLogger(EntityManagerUtil.class);

 /**
 * close the entity manager.
 * Use it with caution! This is only intended for use with async request, which Spring won't
 * close the entity manager until the async request is finished.
 */
 public void closeEntityManager() {
 // 获得 EntityManagerHolder 对象
 EntityManagerHolder emHolder = (EntityManagerHolder) TransactionSynchronizationManager.getResource(getEntityManagerFactory());
 if (emHolder == null) {
 return;
 }
 logger.debug("Closing JPA EntityManager in EntityManagerUtil");
 // 关闭 EntityManager
 EntityManagerFactoryUtils.closeEntityManager(emHolder.getEntityManager());
 }

}