Eureka架构图
Eureka Client会通过jerseyClient发送REST请求的方式向Eureka Server注册自己的服务，提供自身的元数据，比如ip地址、端 口、运行状况指标的url、主页地址等信息。Eureka Server接收到注册请求后，就会把这些元数据信息存储在一个双层的Map中。
从客户端源码分析中可知道客户端发起服务注册入口如下：
@Singleton
public class DiscoveryClient implements EurekaClient {
/**
* Register with the eureka service by making the appropriate REST call.
*/
boolean register() throws Throwable {
// ...
// 这里的registrationClient是EurekaHttpClientDecorator
httpResponse = eurekaTransport.registrationClient.register(instanceInfo);
// ...
}
}
}public abstract class EurekaHttpClientDecorator implements EurekaHttpClient {
@Override
public EurekaHttpResponse register(final InstanceInfo info) {
return execute(new RequestExecutor() {
@Override
public EurekaHttpResponse execute(EurekaHttpClient delegate) {
// 这里会代理到AbstractJerseyEurekaHttpClient中register方法
return delegate.register(info);
}
@Override
public RequestType getRequestType() {
return RequestType.Register;
}
});
} public abstract class AbstractJerseyEurekaHttpClient implements EurekaHttpClient {
@Override
public EurekaHttpResponse register(InstanceInfo info) {
String urlPath = "apps/" + info.getAppName();
ClientResponse response = null;
try {
// 发起REST调用
Builder resourceBuilder = jerseyClient.resource(serviceUrl).path(urlPath).getRequestBuilder();
addExtraHeaders(resourceBuilder);
response = resourceBuilder
.header("Accept-Encoding", "gzip")
.type(MediaType.APPLICATION_JSON_TYPE)
.accept(MediaType.APPLICATION_JSON)
.post(ClientResponse.class, info);
return anEurekaHttpResponse(response.getStatus()).headers(headersOf(response)).build();
} finally {
if (logger.isDebugEnabled()) {
logger.debug("Jersey HTTP POST {}/{} with instance {}; statusCode={}", serviceUrl, urlPath, info.getId(),
response == null ? "N/A" : response.getStatus());
}
if (response != null) {
response.close();
}
}
}
} 服务端接收注册的入口
@Produces({"application/xml", "application/json"})
public class ApplicationResource {
@POST
@Consumes({"application/json", "application/xml"})
public Response addInstance(InstanceInfo info,
@HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication) {
// 客户端服务注册时， isReplication为null
// 而Eureka集群同步时， isReplication为true
registry.register(info, "true".equals(isReplication));
}
}@Singleton
public class PeerAwareInstanceRegistryImpl extends AbstractInstanceRegistry implements PeerAwareInstanceRegistry {
// 注册实例信息，并将该实例信息复制到其它节点
@Override
public void register(final InstanceInfo info, final boolean isReplication) {
int leaseDuration = Lease.DEFAULT_DURATION_IN_SECS;
if (info.getLeaseInfo() != null && info.getLeaseInfo().getDurationInSecs() > 0) {
leaseDuration = info.getLeaseInfo().getDurationInSecs();
}
// 注册实例信息
super.register(info, leaseDuration, isReplication);
// 将该实例信息复制到其它节点
replicateToPeers(Action.Register, info.getAppName(), info.getId(), info, null, isReplication);
}
}// 处理来自eureka客户端的所有注册请求。
// 主要的操作包括注册、续订、取消、过期和状态更改。注册表还只存储增量操作
public abstract class AbstractInstanceRegistry implements InstanceRegistry {
// 注册实例
// isReplication：当服务端启动时发起节点信息同步时，这个值为true
public void register(InstanceInfo registrant, int leaseDuration, boolean isReplication) {
try {
read.lock();
// 根据应用名（可以通过spring.application.name配置）查询注册表
Map> gMap = registry.get(registrant.getAppName());
REGISTER.increment(isReplication);
if (gMap == null) {
final ConcurrentHashMap> gNewMap = new ConcurrentHashMap>();
gMap = registry.putIfAbsent(registrant.getAppName(), gNewMap);
if (gMap == null) {
gMap = gNewMap;
}
}
// 根据实例id（可通过eureka.instance.instance-id配置，默认是ip:应用名:端口）查询
Lease existingLease = gMap.get(registrant.getId());
// Retain the last dirty timestamp without overwriting it, if there is already a lease
if (existingLease != null && (existingLease.getHolder() != null)) {
Long existingLastDirtyTimestamp = existingLease.getHolder().getLastDirtyTimestamp();
Long registrationLastDirtyTimestamp = registrant.getLastDirtyTimestamp();
logger.debug("Existing lease found (existing={}, provided={}", existingLastDirtyTimestamp, registrationLastDirtyTimestamp);
// this is a > instead of a >= because if the timestamps are equal, we still take the remote transmitted
// InstanceInfo instead of the server local copy.
if (existingLastDirtyTimestamp > registrationLastDirtyTimestamp) {
logger.warn("There is an existing lease and the existing lease's dirty timestamp {} is greater" +
" than the one that is being registered {}", existingLastDirtyTimestamp, registrationLastDirtyTimestamp);
logger.warn("Using the existing instanceInfo instead of the new instanceInfo as the registrant");
registrant = existingLease.getHolder();
}
} else {
// The lease does not exist and hence it is a new registration
synchronized (lock) {
if (this.expectedNumberOfClientsSendingRenews > 0) {
// Since the client wants to register it, increase the number of clients sending renews
// 更新客户端数量
this.expectedNumberOfClientsSendingRenews = this.expectedNumberOfClientsSendingRenews + 1;
// 更新触发自我保护的最小阈值，默认是85%的实例续约
updateRenewsPerMinThreshold();
}
}
logger.debug("No previous lease information found; it is new registration");
}
Lease lease = new Lease(registrant, leaseDuration);
if (existingLease != null) {
// 如果注册的实例已存在，则使用存在的服务启动时间
lease.setServiceUpTimestamp(existingLease.getServiceUpTimestamp());
}
// 重新写入map
gMap.put(registrant.getId(), lease);
recentRegisteredQueue.add(new Pair(
System.currentTimeMillis(),
registrant.getAppName() + "(" + registrant.getId() + ")"));
// This is where the initial state transfer of overridden status happens
if (!InstanceStatus.UNKNOWN.equals(registrant.getOverriddenStatus())) {
logger.debug("Found overridden status {} for instance {}. Checking to see if needs to be add to the "
+ "overrides", registrant.getOverriddenStatus(), registrant.getId());
if (!overriddenInstanceStatusMap.containsKey(registrant.getId())) {
logger.info("Not found overridden id {} and hence adding it", registrant.getId());
overriddenInstanceStatusMap.put(registrant.getId(), registrant.getOverriddenStatus());
}
}
// 缓存实例的状态，过期时间为1小时
// Cache.asMap().get(Object) and Cache.asMap().put(K, V)会重置过期时间
// containsKey(Object)则不会
InstanceStatus overriddenStatusFromMap = overriddenInstanceStatusMap.get(registrant.getId());
if (overriddenStatusFromMap != null) {
logger.info("Storing overridden status {} from map", overriddenStatusFromMap);
registrant.setOverriddenStatus(overriddenStatusFromMap);
}
// Set the status based on the overridden status rules
InstanceStatus overriddenInstanceStatus = getOverriddenInstanceStatus(registrant, existingLease, isReplication);
registrant.setStatusWithoutDirty(overriddenInstanceStatus);
// If the lease is registered with UP status, set lease service up timestamp
if (InstanceStatus.UP.equals(registrant.getStatus())) {
// 设置服务启动时间为当前时间
lease.serviceUp();
}
// 设置注册类型
registrant.setActionType(ActionType.ADDED);
// 放入队列，recentRegisteredQueue和recentlyChangedQueue当前仅用于调试和统计
recentlyChangedQueue.add(new RecentlyChangedItem(lease));
// 设置最后一次更新时间
registrant.setLastUpdatedTimestamp();
// 清除当前appName的缓存，这是google的private final LoadingCache readWriteCacheMap;
invalidateCache(registrant.getAppName(), registrant.getVIPAddress(), registrant.getSecureVipAddress());
logger.info("Registered instance {}/{} with status {} (replication={})",
registrant.getAppName(), registrant.getId(), registrant.getStatus(), isReplication);
} finally {
read.unlock();
}
}
}
服务消费者（Eureka Client）在启动的时候，会发送一个REST请求给Eureka Server，获取上面注册的服务清 单，并且缓存在Eureka Client本地，默认缓存30秒(eureka.client.registryFetchIntervalSeconds)。同时，为了性能考虑，Eureka Server也会维护一份只读的服务清单缓存，该缓存每隔30秒更新一次。
从客户端源码分析中可知道客户端发起获取服务的入口如下：
@Path("/{version}/apps")
@Produces({"application/xml", "application/json"})
public class ApplicationsResource {
@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) {
Response response;
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 {
// 从只读缓存中读取
response = Response.ok(responseCache.get(cacheKey))
.build();
}
CurrentRequestVersion.remove();
return response;
}
}public class ResponseCacheImpl implements ResponseCache {
// 通过配置eureka.server.useReadOnlyResponseCache可以配置是否启用只读缓存
@VisibleForTesting
Value getValue(final Key key, boolean useReadOnlyCache) {
Value payload = null;
try {
if (useReadOnlyCache) {
// 从只读缓存中读取，是一个ConcurrentMap readOnlyCacheMap
final Value currentPayload = readOnlyCacheMap.get(key);
if (currentPayload != null) {
payload = currentPayload;
} else {
// 只读缓存不存在时，从读写缓存中获取，并写入只读缓存
payload = readWriteCacheMap.get(key);
readOnlyCacheMap.put(key, payload);
}
} else {
payload = readWriteCacheMap.get(key);
}
} catch (Throwable t) {
logger.error("Cannot get value for key : {}", key, t);
}
return payload;
}
} 若读写缓存还没有，它不就为空了？猜测是从最原始的注册表中读取进行初始化的。初始化过程是怎样的呢？
ResponseCacheImpl(EurekaServerConfig serverConfig, ServerCodecs serverCodecs, AbstractInstanceRegistry registry) {
this.serverConfig = serverConfig;
this.serverCodecs = serverCodecs;
this.shouldUseReadOnlyResponseCache = serverConfig.shouldUseReadOnlyResponseCache();
this.registry = registry;
long responseCacheUpdateIntervalMs = serverConfig.getResponseCacheUpdateIntervalMs();
this.readWriteCacheMap =
CacheBuilder.newBuilder().initialCapacity(serverConfig.getInitialCapacityOfResponseCache())
// 读写缓存过期时间，eureka.server.responseCacheAutoExpirationInSeconds，默认为180s
.expireAfterWrite(serverConfig.getResponseCacheAutoExpirationInSeconds(), TimeUnit.SECONDS)
.removalListener(new RemovalListener() {
@Override
public void onRemoval(RemovalNotification notification) {
Key removedKey = notification.getKey();
if (removedKey.hasRegions()) {
Key cloneWithNoRegions = removedKey.cloneWithoutRegions();
regionSpecificKeys.remove(cloneWithNoRegions, removedKey);
}
}
})
.build(new CacheLoader() {
@Override
public Value load(Key key) throws Exception {
if (key.hasRegions()) {
Key cloneWithNoRegions = key.cloneWithoutRegions();
regionSpecificKeys.put(cloneWithNoRegions, key);
}
Value value = generatePayload(key);
return value;
}
});
if (shouldUseReadOnlyResponseCache) {
// 每30s定时任务更新只读缓存（通过eureka.server.responseCacheUpdateIntervalMs配置，默认为30s）
timer.schedule(getCacheUpdateTask(),
new Date(((System.currentTimeMillis() / responseCacheUpdateIntervalMs) * responseCacheUpdateIntervalMs)
+ responseCacheUpdateIntervalMs),
responseCacheUpdateIntervalMs);
}
try {
Monitors.registerObject(this);
} catch (Throwable e) {
logger.warn("Cannot register the JMX monitor for the InstanceRegistry", e);
}
}
private TimerTask getCacheUpdateTask() {
return new TimerTask() {
@Override
public void run() {
logger.debug("Updating the client cache from response cache");
for (Key key : readOnlyCacheMap.keySet()) {
if (logger.isDebugEnabled()) {
logger.debug("Updating the client cache from response cache for key : {} {} {} {}",
key.getEntityType(), key.getName(), key.getVersion(), key.getType());
}
try {
CurrentRequestVersion.set(key.getVersion());
Value cacheValue = readWriteCacheMap.get(key);
Value currentCacheValue = readOnlyCacheMap.get(key);
if (cacheValue != currentCacheValue) {
readOnlyCacheMap.put(key, cacheValue);
}
} catch (Throwable th) {
logger.error("Error while updating the client cache from response cache for key {}", key.toStringCompact(), th);
} finally {
CurrentRequestVersion.remove();
}
}
}
};
} /*
* Generate pay load for the given key.
*/
// 从注册表中的双层map取数据初始化缓存
private Value generatePayload(Key key) {
Stopwatch tracer = null;
try {
String payload;
switch (key.getEntityType()) {
case Application:
boolean isRemoteRegionRequested = key.hasRegions();
if (ALL_APPS.equals(key.getName())) {
if (isRemoteRegionRequested) {
tracer = serializeAllAppsWithRemoteRegionTimer.start();
payload = getPayLoad(key, registry.getApplicationsFromMultipleRegions(key.getRegions()));
} else {
tracer = serializeAllAppsTimer.start();
// 全量获取
payload = getPayLoad(key, registry.getApplications());
}
} else if (ALL_APPS_DELTA.equals(key.getName())) {
if (isRemoteRegionRequested) {
tracer = serializeDeltaAppsWithRemoteRegionTimer.start();
versionDeltaWithRegions.incrementAndGet();
versionDeltaWithRegionsLegacy.incrementAndGet();
// 增量获取
payload = getPayLoad(key,
registry.getApplicationDeltasFromMultipleRegions(key.getRegions()));
} else {
tracer = serializeDeltaAppsTimer.start();
versionDelta.incrementAndGet();
versionDeltaLegacy.incrementAndGet();
payload = getPayLoad(key, registry.getApplicationDeltas());
}
} else {
tracer = serializeOneApptimer.start();
payload = getPayLoad(key, registry.getApplication(key.getName()));
}
break;
case VIP:
case SVIP:
tracer = serializeViptimer.start();
payload = getPayLoad(key, getApplicationsForVip(key, registry));
break;
default:
logger.error("Unidentified entity type: {} found in the cache key.", key.getEntityType());
payload = "";
break;
}
return new Value(payload);
} finally {
if (tracer != null) {
tracer.stop();
}
}
}public abstract class AbstractInstanceRegistry implements InstanceRegistry {
// 全量拉取
public Applications getApplicationsFromMultipleRegions(String[] remoteRegions) {
boolean includeRemoteRegion = null != remoteRegions && remoteRegions.length != 0;
logger.debug("Fetching applications registry with remote regions: {}, Regions argument {}",
includeRemoteRegion, remoteRegions);
if (includeRemoteRegion) {
GET_ALL_WITH_REMOTE_REGIONS_CACHE_MISS.increment();
} else {
GET_ALL_CACHE_MISS.increment();
}
Applications apps = new Applications();
apps.setVersion(1L);
for (Entry>> entry : registry.entrySet()) {
Application app = null;
if (entry.getValue() != null) {
// 遍历注册表
for (Entry> stringLeaseEntry : entry.getValue().entrySet()) {
Lease lease = stringLeaseEntry.getValue();
if (app == null) {
app = new Application(lease.getHolder().getAppName());
}
app.addInstance(decorateInstanceInfo(lease));
}
}
if (app != null) {
apps.addApplication(app);
}
}
if (includeRemoteRegion) {
for (String remoteRegion : remoteRegions) {
RemoteRegionRegistry remoteRegistry = regionNameVSRemoteRegistry.get(remoteRegion);
if (null != remoteRegistry) {
Applications remoteApps = remoteRegistry.getApplications();
for (Application application : remoteApps.getRegisteredApplications()) {
if (shouldFetchFromRemoteRegistry(application.getName(), remoteRegion)) {
logger.info("Application {} fetched from the remote region {}",
application.getName(), remoteRegion);
Application appInstanceTillNow = apps.getRegisteredApplications(application.getName());
if (appInstanceTillNow == null) {
appInstanceTillNow = new Application(application.getName());
apps.addApplication(appInstanceTillNow);
}
for (InstanceInfo instanceInfo : application.getInstances()) {
appInstanceTillNow.addInstance(instanceInfo);
}
} else {
logger.debug("Application {} not fetched from the remote region {} as there exists a "
+ "whitelist and this app is not in the whitelist.",
application.getName(), remoteRegion);
}
}
} else {
logger.warn("No remote registry available for the remote region {}", remoteRegion);
}
}
}
apps.setAppsHashCode(apps.getReconcileHashCode());
return apps;
}
// 增量拉取
public Applications getApplicationDeltasFromMultipleRegions(String[] remoteRegions) {
if (null == remoteRegions) {
remoteRegions = allKnownRemoteRegions; // null means all remote regions.
}
boolean includeRemoteRegion = remoteRegions.length != 0;
if (includeRemoteRegion) {
GET_ALL_WITH_REMOTE_REGIONS_CACHE_MISS_DELTA.increment();
} else {
GET_ALL_CACHE_MISS_DELTA.increment();
}
Applications apps = new Applications();
apps.setVersion(responseCache.getVersionDeltaWithRegions().get());
Map applicationInstancesMap = new HashMap();
try {
write.lock();
// recentlyChangedQueue是一个ConcurrentLinkedQueue();服务注册是设值
Iterator iter = this.recentlyChangedQueue.iterator();
logger.debug("The number of elements in the delta queue is :{}", this.recentlyChangedQueue.size());
while (iter.hasNext()) {
Lease lease = iter.next().getLeaseInfo();
InstanceInfo instanceInfo = lease.getHolder();
logger.debug("The instance id {} is found with status {} and actiontype {}",
instanceInfo.getId(), instanceInfo.getStatus().name(), instanceInfo.getActionType().name());
Application app = applicationInstancesMap.get(instanceInfo.getAppName());
if (app == null) {
app = new Application(instanceInfo.getAppName());
applicationInstancesMap.put(instanceInfo.getAppName(), app);
apps.addApplication(app);
}
app.addInstance(new InstanceInfo(decorateInstanceInfo(lease)));
}
if (includeRemoteRegion) {
for (String remoteRegion : remoteRegions) {
RemoteRegionRegistry remoteRegistry = regionNameVSRemoteRegistry.get(remoteRegion);
if (null != remoteRegistry) {
Applications remoteAppsDelta = remoteRegistry.getApplicationDeltas();
if (null != remoteAppsDelta) {
for (Application application : remoteAppsDelta.getRegisteredApplications()) {
if (shouldFetchFromRemoteRegistry(application.getName(), remoteRegion)) {
Application appInstanceTillNow =
apps.getRegisteredApplications(application.getName());
if (appInstanceTillNow == null) {
appInstanceTillNow = new Application(application.getName());
apps.addApplication(appInstanceTillNow);
}
for (InstanceInfo instanceInfo : application.getInstances()) {
appInstanceTillNow.addInstance(new InstanceInfo(instanceInfo));
}
}
}
}
}
}
}
Applications allApps = getApplicationsFromMultipleRegions(remoteRegions);
apps.setAppsHashCode(allApps.getReconcileHashCode());
return apps;
} finally {
write.unlock();
}
}
} 在服务注册后，Eureka Client会维护一个心跳来持续通知Eureka Server，说明服务一直处于可用状态，防止被剔 除。Eureka Client在默认的情况下会每隔30秒(eureka.instance.leaseRenewalIntervalInSeconds)发送一次心跳来进行服务续约。
@Produces({"application/xml", "application/json"})
public class InstanceResource {
@PUT
public Response renewLease(
@HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication,
@QueryParam("overriddenstatus") String overriddenStatus,
@QueryParam("status") String status,
@QueryParam("lastDirtyTimestamp") String lastDirtyTimestamp) {
boolean isFromReplicaNode = "true".equals(isReplication);
boolean isSuccess = registry.renew(app.getName(), id, isFromReplicaNode);
// Not found in the registry, immediately ask for a register
if (!isSuccess) {
logger.warn("Not Found (Renew): {} - {}", app.getName(), id);
return Response.status(Status.NOT_FOUND).build();
}
// Check if we need to sync based on dirty time stamp, the client
// instance might have changed some value
Response response;
if (lastDirtyTimestamp != null && serverConfig.shouldSyncWhenTimestampDiffers()) {
response = this.validateDirtyTimestamp(Long.valueOf(lastDirtyTimestamp), isFromReplicaNode);
// Store the overridden status since the validation found out the node that replicates wins
if (response.getStatus() == Response.Status.NOT_FOUND.getStatusCode()
&& (overriddenStatus != null)
&& !(InstanceStatus.UNKNOWN.name().equals(overriddenStatus))
&& isFromReplicaNode) {
registry.storeOverriddenStatusIfRequired(app.getAppName(), id, InstanceStatus.valueOf(overriddenStatus));
}
} else {
response = Response.ok().build();
}
logger.debug("Found (Renew): {} - {}; reply status={}", app.getName(), id, response.getStatus());
return response;
}
}public abstract class AbstractInstanceRegistry implements InstanceRegistry {
public boolean renew(String appName, String id, boolean isReplication) {
RENEW.increment(isReplication);
// 根据应用名获取实例
Map> gMap = registry.get(appName);
Lease leaseToRenew = null;
if (gMap != null) {
// 根据实例id获取实例
leaseToRenew = gMap.get(id);
}
if (leaseToRenew == null) {
RENEW_NOT_FOUND.increment(isReplication);
logger.warn("DS: Registry: lease doesn't exist, registering resource: {} - {}", appName, id);
return false;
} else {
InstanceInfo instanceInfo = leaseToRenew.getHolder();
if (instanceInfo != null) {
// touchASGCache(instanceInfo.getASGName());
InstanceStatus overriddenInstanceStatus = this.getOverriddenInstanceStatus(
instanceInfo, leaseToRenew, isReplication);
if (overriddenInstanceStatus == InstanceStatus.UNKNOWN) {
logger.info("Instance status UNKNOWN possibly due to deleted override for instance {}"
+ "; re-register required", instanceInfo.getId());
RENEW_NOT_FOUND.increment(isReplication);
return false;
}
if (!instanceInfo.getStatus().equals(overriddenInstanceStatus)) {
logger.info(
"The instance status {} is different from overridden instance status {} for instance {}. "
+ "Hence setting the status to overridden status", instanceInfo.getStatus().name(),
instanceInfo.getOverriddenStatus().name(),
instanceInfo.getId());
instanceInfo.setStatusWithoutDirty(overriddenInstanceStatus);
}
}
renewsLastMin.increment();
leaseToRenew.renew();
return true;
}
}
} public class Lease {
/**
* Renew the lease, use renewal duration if it was specified by the
* associated {@link T} during registration, otherwise default duration is
* {@link #DEFAULT_DURATION_IN_SECS}.
*/
public void renew() {
// 修改上次更新时间，+duration是Eureka的bug，导致服务剔除实际是在上次续约的180后没有再续约的情况下
lastUpdateTimestamp = System.currentTimeMillis() + duration;
}
} 有时候，服务实例可能会因为网络故障等原因导致不能提供服务，而此时该实例也没有发送请求给Eureka Server来进 行服务下线，所以，还需要有服务剔除的机制。Eureka Server在启动的时候会创建一个定时任务，每隔一段时间（默认60秒），从当前服务清单中把超时没有续约（默认90秒，eureka.instance.leaseExpirationDurationInSeconds）的服务剔除。180s被剔除。
服务剔除定时任务其实在Eureka Server端源码分析讲过流程了，不在赘述，只讲一下核心代码逻辑。
class EvictionTask extends TimerTask {
private final AtomicLong lastExecutionNanosRef = new AtomicLong(0l);
@Override
public void run() {
try {
long compensationTimeMs = getCompensationTimeMs();
logger.info("Running the evict task with compensationTime {}ms", compensationTimeMs);
evict(compensationTimeMs);
} catch (Throwable e) {
logger.error("Could not run the evict task", e);
}
}
/**
* compute a compensation time defined as the actual time this task was executed since the prev iteration,
* vs the configured amount of time for execution. This is useful for cases where changes in time (due to
* clock skew or gc for example) causes the actual eviction task to execute later than the desired time
* according to the configured cycle.
*/
long getCompensationTimeMs() {
long currNanos = getCurrentTimeNano();
long lastNanos = lastExecutionNanosRef.getAndSet(currNanos);
if (lastNanos == 0l) {
return 0l;
}
long elapsedMs = TimeUnit.NANOSECONDS.toMillis(currNanos - lastNanos);
long compensationTime = elapsedMs - serverConfig.getEvictionIntervalTimerInMs();
return compensationTime <= 0l ? 0l : compensationTime;
}
long getCurrentTimeNano() { // for testing
return System.nanoTime();
}
public abstract class AbstractInstanceRegistry implements InstanceRegistry {
public void evict(long additionalLeaseMs) {
logger.debug("Running the evict task");
// 判断是否开启并触发自我保护，
if (!isLeaseExpirationEnabled()) {
logger.debug("DS: lease expiration is currently disabled.");
return;
}
// We collect first all expired items, to evict them in random order. For large eviction sets,
// if we do not that, we might wipe out whole apps before self preservation kicks in. By randomizing it,
// the impact should be evenly distributed across all applications.
List> expiredLeases = new ArrayList<>();
for (Entry>> groupEntry : registry.entrySet()) {
Map> leaseMap = groupEntry.getValue();
if (leaseMap != null) {
for (Entry> leaseEntry : leaseMap.entrySet()) {
Lease lease = leaseEntry.getValue();
// 判断租约是否过期
if (lease.isExpired(additionalLeaseMs) && lease.getHolder() != null) {
expiredLeases.add(lease);
}
}
}
}
// To compensate for GC pauses or drifting local time, we need to use current registry size as a base for
// triggering self-preservation. Without that we would wipe out full registry.
//为了补偿GC暂停或本地时间漂移，我们需要使用当前注册表大小作为基础
// 触发自我保护。如果没有它，我们就会把整个注册表抹去。
int registrySize = (int) getLocalRegistrySize();
int registrySizeThreshold = (int) (registrySize * serverConfig.getRenewalPercentThreshold());
int evictionLimit = registrySize - registrySizeThreshold;
int toEvict = Math.min(expiredLeases.size(), evictionLimit);
if (toEvict > 0) {
logger.info("Evicting {} items (expired={}, evictionLimit={})", toEvict, expiredLeases.size(), evictionLimit);
Random random = new Random(System.currentTimeMillis());
for (int i = 0; i < toEvict; i++) {
// Pick a random item (Knuth shuffle algorithm)
// 随机剔除
int next = i + random.nextInt(expiredLeases.size() - i);
Collections.swap(expiredLeases, i, next);
Lease lease = expiredLeases.get(i);
String appName = lease.getHolder().getAppName();
String id = lease.getHolder().getId();
EXPIRED.increment();
logger.warn("DS: Registry: expired lease for {}/{}", appName, id);
// 移除注册表中的，移除读写缓存中的，继续看下面的源码
internalCancel(appName, id, false);
}
}
}
} @Override
public boolean isLeaseExpirationEnabled() {
// 关闭了自我保护机制时，允许实例过期
if (!isSelfPreservationModeEnabled()) {
// The self preservation mode is disabled, hence allowing the instances to expire.
return true;
}
// 续约数量大于触发自我保护机制的阈值
return numberOfRenewsPerMinThreshold > 0 && getNumOfRenewsInLastMin() > numberOfRenewsPerMinThreshold;
} public class Lease {
public boolean isExpired(long additionalLeaseMs) {
// 当前时间 > 上次续约时间 + 90s，因为上面续约lastUpdateTimestamp+90s，所以实际的服务剔除是180s
return (evictionTimestamp > 0 || System.currentTimeMillis() > (lastUpdateTimestamp + duration + additionalLeaseMs));
}
} protected boolean internalCancel(String appName, String id, boolean isReplication) {
try {
read.lock();
CANCEL.increment(isReplication);
// 根据应用名读取注册表中应用实例租约信息
Map> gMap = registry.get(appName);
Lease leaseToCancel = null;
if (gMap != null) {
// 从注册表中移除
leaseToCancel = gMap.remove(id);
}
recentCanceledQueue.add(new Pair(System.currentTimeMillis(), appName + "(" + id + ")"));
InstanceStatus instanceStatus = overriddenInstanceStatusMap.remove(id);
if (instanceStatus != null) {
logger.debug("Removed instance id {} from the overridden map which has value {}", id, instanceStatus.name());
}
if (leaseToCancel == null) {
CANCEL_NOT_FOUND.increment(isReplication);
logger.warn("DS: Registry: cancel failed because Lease is not registered for: {}/{}", appName, id);
return false;
} else {
// 设置剔除时间为当前时间
leaseToCancel.cancel();
InstanceInfo instanceInfo = leaseToCancel.getHolder();
String vip = null;
String svip = null;
if (instanceInfo != null) {
instanceInfo.setActionType(ActionType.DELETED);
recentlyChangedQueue.add(new RecentlyChangedItem(leaseToCancel));
instanceInfo.setLastUpdatedTimestamp();
vip = instanceInfo.getVIPAddress();
svip = instanceInfo.getSecureVipAddress();
}
// 失效readWriteCacheMap缓存的
invalidateCache(appName, vip, svip);
logger.info("Cancelled instance {}/{} (replication={})", appName, id, isReplication);
}
} finally {
read.unlock();
}
synchronized (lock) {
if (this.expectedNumberOfClientsSendingRenews > 0) {
// Since the client wants to cancel it, reduce the number of clients to send renews.
this.expectedNumberOfClientsSendingRenews = this.expectedNumberOfClientsSendingRenews - 1;
// 更新触发自我保护的预置
updateRenewsPerMinThreshold();
}
}
return true;
} 客户端在拉取注册表时
先从readOnlyCacheMap读取
若没有，从readWriteCacheMap读取
若没有，从最原始的双层Map注册表读取
多级缓存机制，只写最原始的双层Map，这样可以避免读写冲突，提高并发能力。
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