Eureka获取注册信息(服务列表)
- EurekaClient端从EurekaServer端获取注册信息列表并缓存到本地是Eureka所提供的核心功能之一,EurekaClient端启动时发起全量获取,启动后默认30秒发起一次差别获取(这个叫法有点别扭,主要因为EurekaServer端处理请求的方法叫getContainerDifferential)。本文基于https://github.com/Netflix/eureka上的master分支。最近在github上fork了一下eureka项目,更详细的注释可以去我的git上看:https://github.com/qiuyangli/eureka
EurekaClient发起全量获取请求+EurekaServer处理全量获取请求
- EurekaClient启动初始化时,会发起一次全量获取注册信息,代码如下:
// 拉取配置信息
if (clientConfig.shouldFetchRegistry() && !fetchRegistry(false)) {
fetchRegistryFromBackup();
}
- 调用到fetchRegistry(boolean forceFullRegistryFetch)方法:
// 拉取注册信息
private boolean fetchRegistry(boolean forceFullRegistryFetch) {
Stopwatch tracer = FETCH_REGISTRY_TIMER.start();
try {
// If the delta is disabled or if it is the first time, get all
// applications
// 获取本地缓存的注册信息
Applications applications = getApplications();
// 全量获取
if (clientConfig.shouldDisableDelta()// 默认为false
|| (!Strings.isNullOrEmpty(clientConfig.getRegistryRefreshSingleVipAddress()))
|| forceFullRegistryFetch
|| (applications == null)
|| (applications.getRegisteredApplications().size() == 0)
|| (applications.getVersion() == -1)) //Client application does not have latest library supporting delta
{
logger.info("Disable delta property : {}", clientConfig.shouldDisableDelta());
logger.info("Single vip registry refresh property : {}", clientConfig.getRegistryRefreshSingleVipAddress());
logger.info("Force full registry fetch : {}", forceFullRegistryFetch);
logger.info("Application is null : {}", (applications == null));
logger.info("Registered Applications size is zero : {}",
(applications.getRegisteredApplications().size() == 0));
logger.info("Application version is -1: {}", (applications.getVersion() == -1));
getAndStoreFullRegistry();// 全量获取注册信息并存到本地缓存
} else {
// 差别获取
getAndUpdateDelta(applications);
}
applications.setAppsHashCode(applications.getReconcileHashCode());
// 打印EurekaClient端保存的注册信息的数量
logTotalInstances();
} catch (Throwable e) {
logger.error(PREFIX + "{} - was unable to refresh its cache! status = {}", appPathIdentifier, e.getMessage(), e);
return false;
} finally {
if (tracer != null) {
tracer.stop();
}
}
// Notify about cache refresh before updating the instance remote status
onCacheRefreshed();
// Update remote status based on refreshed data held in the cache
updateInstanceRemoteStatus();
// registry was fetched successfully, so return true
return true;
}
- 其中通过getAndStoreFullRegistry()方法进行全量获取,代码如下:
// 全量获取注册信息并存到本地缓存
private void getAndStoreFullRegistry() throws Throwable {
long currentUpdateGeneration = fetchRegistryGeneration.get();
logger.info("Getting all instance registry info from the eureka server");
Applications apps = null;
// 调用到EurekaServer的ApplicationsResource-getContainers()方法全量获取注册信息
EurekaHttpResponse<Applications> httpResponse = clientConfig.getRegistryRefreshSingleVipAddress() == null
? eurekaTransport.queryClient.getApplications(remoteRegionsRef.get())
: eurekaTransport.queryClient.getVip(clientConfig.getRegistryRefreshSingleVipAddress(), remoteRegionsRef.get());
if (httpResponse.getStatusCode() == Status.OK.getStatusCode()) {
apps = httpResponse.getEntity();
}
logger.info("The response status is {}", httpResponse.getStatusCode());
// 设置缓存
if (apps == null) {
logger.error("The application is null for some reason. Not storing this information");
} else if (fetchRegistryGeneration.compareAndSet(currentUpdateGeneration, currentUpdateGeneration + 1)) {
// 对注册信息进行过滤,过滤后只缓存服务状态为UP的实例
// 本地缓存数据结构为AtomicReference<Applications>
localRegionApps.set(this.filterAndShuffle(apps));
// 打印过滤后实例的哈希值
logger.debug("Got full registry with apps hashcode {}", apps.getAppsHashCode());
} else {
logger.warn("Not updating applications as another thread is updating it already");
}
}
- EurekaServer端接收全量获取请求的代码在eureka-core包下的ApplicationsResource-getContainers()方法,具体代码如下:
// 接收EurekaClient端发送的获取全量注册信息请求
@GET
public Response getContainers(@PathParam("version") String version,
@HeaderParam(HEADER_ACCEPT) String acceptHeader,
@HeaderParam(HEADER_ACCEPT_ENCODING) String acceptEncoding,
@HeaderParam(EurekaAccept.HTTP_X_EUREKA_ACCEPT) String eurekaAccept,
@Context UriInfo uriInfo,
@Nullable @QueryParam("regions") String regionsStr) {
boolean isRemoteRegionRequested = null != regionsStr && !regionsStr.isEmpty();
String[] regions = null;
if (!isRemoteRegionRequested) {
EurekaMonitors.GET_ALL.increment();
} else {
regions = regionsStr.toLowerCase().split(",");
Arrays.sort(regions); // So we don't have different caches for same regions queried in different order.
EurekaMonitors.GET_ALL_WITH_REMOTE_REGIONS.increment();
}
// Check if the server allows the access to the registry. The server can
// restrict access if it is not
// ready to serve traffic depending on various reasons.
// EurekaServer无法提供服务,返回403
if (!registry.shouldAllowAccess(isRemoteRegionRequested)) {
return Response.status(Status.FORBIDDEN).build();
}
// 默认V2
CurrentRequestVersion.set(Version.toEnum(version));
// 设置返回数据格式,默认JSON
KeyType keyType = Key.KeyType.JSON;
String returnMediaType = MediaType.APPLICATION_JSON;
if (acceptHeader == null || !acceptHeader.contains(HEADER_JSON_VALUE)) {
// 如果接收到的请求头部没有具体格式信息,则返回格式为XML
keyType = Key.KeyType.XML;
returnMediaType = MediaType.APPLICATION_XML;
}
// 构建缓存键
Key cacheKey = new Key(Key.EntityType.Application,
ResponseCacheImpl.ALL_APPS,
keyType, CurrentRequestVersion.get(), EurekaAccept.fromString(eurekaAccept), regions
);
// 根据缓存键读取缓存
Response response;
// 返回不同的编码类型的数据,去缓存中取数据的方法基本一致
if (acceptEncoding != null && acceptEncoding.contains(HEADER_GZIP_VALUE)) {
response = Response.ok(responseCache.getGZIP(cacheKey))
.header(HEADER_CONTENT_ENCODING, HEADER_GZIP_VALUE)
.header(HEADER_CONTENT_TYPE, returnMediaType)
.build();
} else {
response = Response.ok(responseCache.get(cacheKey))
.build();
}
return response;
}
- 通过getGZIP(cacheKey)/get(cacheKey)方法,调用到getValue(key,useReadOnlyCache)方法读取到缓存里的实例注册信息返给EurekaClient端,代码如下:
@VisibleForTesting
Value getValue(final Key key, boolean useReadOnlyCache) {
Value payload = null;
try {
// 默认为true,允许使用只读缓存
if (useReadOnlyCache) {
// 先从readOnlyCacheMap读取
// 若读不到,则从readWriteCacheMap读取,并将结果存入readOnlyCacheMap
// 缓存设计成了两级,请求进来的时候先读readOnlyCacheMap,读不到再从readWriteCacheMap读取
// readWriteCacheMap里再读不到,则从registry里读
// readOnlyCacheMap是一个ConcurrentMap
// readWriteCacheMap是一个LoadingCache
// 不是很理解为什么要设置这两级缓存?
final Value currentPayload = readOnlyCacheMap.get(key);
if (currentPayload != null) {
payload = currentPayload;
} else {
payload = readWriteCacheMap.get(key);
readOnlyCacheMap.put(key, payload);
}
} else {
// 不允许使用只读缓存,读取readWriteCacheMap
payload = readWriteCacheMap.get(key);
}
} catch (Throwable t) {
logger.error("Cannot get value for key : {}", key, t);
}
return payload;
}
- 差别获取失败时也会发起全量获取,代码在下面会有介绍
EurekaClient发起差别获取请求+EurekaServer处理差别获取请求
- EurekaClient启动初始化的定时任务,默认30秒发起一次差别获取请求,初始化代码就不再贴出来了,前面文章有详细解析,初始化后真正发起差别获取请求的方法是getAndUpdateDelta(applications)代码如下:
// 差别获取后合并到本地缓存
private void getAndUpdateDelta(Applications applications) throws Throwable {
long currentUpdateGeneration = fetchRegistryGeneration.get();
Applications delta = null;
// 发送差别获取注册信息的请求
// 具体通过AbstractJerseyEurekaHttpClient-getApplicationsInternal(urlPath, regions)方法调用
// 最终调用到EurekaServer中ApplicationsResource-getContainerDifferential()方法,目测和获取全量注册信息差别不大
EurekaHttpResponse<Applications> httpResponse = eurekaTransport.queryClient.getDelta(remoteRegionsRef.get());
if (httpResponse.getStatusCode() == Status.OK.getStatusCode()) {
delta = httpResponse.getEntity();
}
// 差别获取注册信息未获取到,转为全量获取
if (delta == null) {
logger.warn("The server does not allow the delta revision to be applied because it is not safe. "
+ "Hence got the full registry.");
getAndStoreFullRegistry();
} else if (fetchRegistryGeneration.compareAndSet(currentUpdateGeneration, currentUpdateGeneration + 1)) {
logger.debug("Got delta update with apps hashcode {}", delta.getAppsHashCode());
String reconcileHashCode = "";
// 目测合并注册信息时要加锁
// 拉取注册信息是从每个EurekaClient发起的如果定时30秒获取一次的话应该没有并发?
if (fetchRegistryUpdateLock.tryLock()) {
try {
// 差别获取的注册信息与本地缓存的注册信息进行合并
updateDelta(delta);
// 本地注册信息一致哈希值
reconcileHashCode = getReconcileHashCode(applications);
} finally {
// 释放锁
fetchRegistryUpdateLock.unlock();
}
} else {
logger.warn("Cannot acquire update lock, aborting getAndUpdateDelta");
}
// There is a diff in number of instances for some reason
// 合并后本地注册信息和EurekaServer端的哈希值不一致
// 调用reconcileAndLogDifference方法,内部实现基本和全量获取一样,并设置到本地缓存
if (!reconcileHashCode.equals(delta.getAppsHashCode()) || clientConfig.shouldLogDeltaDiff()) {
reconcileAndLogDifference(delta, reconcileHashCode); // this makes a remoteCall
}
} else {
logger.warn("Not updating application delta as another thread is updating it already");
logger.debug("Ignoring delta update with apps hashcode {}, as another thread is updating it already", delta.getAppsHashCode());
}
}
- EurekaServer端接收差别获取请求的方法是eureka-core包里的ApplicationsResource-getContainerDifferential()方法,具体处理方法与全量获取差别不大,这里不再做详细解析
- EurekaClient端接收到EurekaServer端返回的实例注册信息后的操作比较关键,对注册信息在本地进行了合并,并进行哈希值比较,具体调用到了updateDelta(delta)方法,代码如下:
// 注册信息合并
private void updateDelta(Applications delta) {
int deltaCount = 0;
// 遍历从EurekaServer端拉取的实例信息集合
for (Application app : delta.getRegisteredApplications()) {
// 遍历出每个instance
for (InstanceInfo instance : app.getInstances()) {
Applications applications = getApplications();
String instanceRegion = instanceRegionChecker.getInstanceRegion(instance);
if (!instanceRegionChecker.isLocalRegion(instanceRegion)) {
Applications remoteApps = remoteRegionVsApps.get(instanceRegion);
if (null == remoteApps) {
remoteApps = new Applications();
remoteRegionVsApps.put(instanceRegion, remoteApps);
}
applications = remoteApps;
}
++deltaCount;
// 根据获取的delta数据的ActionType修改本地数据
if (ActionType.ADDED.equals(instance.getActionType())) {
Application existingApp = applications.getRegisteredApplications(instance.getAppName());
if (existingApp == null) {
applications.addApplication(app);
}
logger.debug("Added instance {} to the existing apps in region {}", instance.getId(), instanceRegion);
// 调用addInstance方法
applications.getRegisteredApplications(instance.getAppName()).addInstance(instance);
} else if (ActionType.MODIFIED.equals(instance.getActionType())) {
Application existingApp = applications.getRegisteredApplications(instance.getAppName());
if (existingApp == null) {
applications.addApplication(app);
}
logger.debug("Modified instance {} to the existing apps ", instance.getId());
// 调用addInstance方法
applications.getRegisteredApplications(instance.getAppName()).addInstance(instance);
} else if (ActionType.DELETED.equals(instance.getActionType())) {
Application existingApp = applications.getRegisteredApplications(instance.getAppName());
if (existingApp == null) {
applications.addApplication(app);
}
logger.debug("Deleted instance {} to the existing apps ", instance.getId());
// 调用removeInstance方法
applications.getRegisteredApplications(instance.getAppName()).removeInstance(instance);
}
}
}
logger.debug("The total number of instances fetched by the delta processor : {}", deltaCount);
getApplications().setVersion(delta.getVersion());
// 过滤后只保留实例状态为UP的实例信息
getApplications().shuffleInstances(clientConfig.shouldFilterOnlyUpInstances());
for (Applications applications : remoteRegionVsApps.values()) {
applications.setVersion(delta.getVersion());
applications.shuffleInstances(clientConfig.shouldFilterOnlyUpInstances());
}
}
- 其中用到了addInstance(instance)方法和removeInstance(instance)方法:
public void addInstance(InstanceInfo i) {
// 实例信息添加到instancesMap
instancesMap.put(i.getId(), i);
synchronized (instances) {
// 移除集合重原有的实例信息
instances.remove(i);
// 把实例信息重新添加到集合中
instances.add(i);
isDirty = true;
}
}
private void removeInstance(InstanceInfo i, boolean markAsDirty) {
// 在instancesMap移除实例信息
instancesMap.remove(i.getId());
synchronized (instances) {
// 在集合中移除实例信息
instances.remove(i);
if (markAsDirty) {
isDirty = true;
}
}
}
版权声明:「DDKK.COM 弟弟快看,程序员编程资料站」本站文章,版权归原作者所有