eureka-server是通过提供rest接口来跟eureka-client交互，我们重点关注跟eureka-client相关的几个接口。
全量获取服务列表
注册的uri是GET /apps。入口在ApplicationResource。
@Path("/{version}/apps")
@Produces({"application/xml", "application/json"})
public class ApplicationsResource {
private final ResponseCache responseCache;
@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.
if (!registry.shouldAllowAccess(isRemoteRegionRequested)) {
return Response.status(Status.FORBIDDEN).build();
}
CurrentRequestVersion.set(Version.toEnum(version));
KeyType keyType = Key.KeyType.JSON;
String returnMediaType = MediaType.APPLICATION_JSON;
if (acceptHeader == null || !acceptHeader.contains(HEADER_JSON_VALUE)) {
keyType = Key.KeyType.XML;
returnMediaType = MediaType.APPLICATION_XML;
}
Key cacheKey = new Key(Key.EntityType.Application,
ResponseCacheImpl.ALL_APPS,
keyType, CurrentRequestVersion.get(), EurekaAccept.fromString(eurekaAccept), regions
);
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 {
response = Response.ok(responseCache.get(cacheKey))
.build();
}
return response;
}
} -
version为eureka版本号，最新API默认为V2，Spring Cloud Netfix Eureka 跟 Spring Boot 适配之后，提供的 REST API 与原始的 REST API 有一点点不同，其路径中的version值固定为eureka。 - 数据是从
responseCache里获取，从key的创建参数上可以看到，缓存里根据key分成了很多个类别。
public class ResponseCacheImpl implements ResponseCache {
private final ConcurrentMap readOnlyCacheMap = new ConcurrentHashMap();
private final LoadingCache readWriteCacheMap;
private final AbstractInstanceRegistry registry;
public String get(final Key key) {
return get(key, shouldUseReadOnlyResponseCache);
}
@VisibleForTesting
String get(final Key key, boolean useReadOnlyCache) {
Value payload = getValue(key, useReadOnlyCache);
if (payload == null || payload.getPayload().equals(EMPTY_PAYLOAD)) {
return null;
} else {
return payload.getPayload();
}
}
@VisibleForTesting
Value getValue(final Key key, boolean useReadOnlyCache) {
Value payload = null;
try {
if (useReadOnlyCache) {
final Value currentPayload = readOnlyCacheMap.get(key);
if (currentPayload != null) {
payload = currentPayload;
} else {
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;
}
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();
payload = getPayLoad(key, registry.getApplications());
}
} else if (ALL_APPS_DELTA.equals(key.getName())) {
if (isRemoteRegionRequested) {
tracer = serializeDeltaAppsWithRemoteRegionTimer.start();
versionDeltaWithRegions.incrementAndGet();
versionDeltaWithRegionsLegacy.incrementAndGet();
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();
}
}
}
} eureka为了保证性能，引入了三级缓存机制：
- 一级只读缓存
readOnlyCacheMap，是ConcurrentHashMap，springcloud项目可以通过配置eureka.server.use-read-only-response-cache来指定是否开启，默认为true。 - 二级缓存
readWriteCacheMap，是guava cache。 - 三级存储
register存储在线服务信息，ConcurrentHashMap类型，存储格式为ConcurrentHashMap<服务名,ConcurrentHashMap<机器ID(默认为“IP:服务名:配置的端口”), 服务信息(Lease)>>，例如
整体流程：
- 如果开启了
useReadOnlyCache，则从readOnlyCacheMap获取数据。 - 如果没有开启
useReadOnlyCache，或者readOnlyCacheMap获取不到数据，则从readWriteCacheMap获取；获取到数据后，如果开启了useReadOnlyCache，则将结果设置到readOnlyCacheMap中。 - 如果
readWriteCacheMap获取不到数据，则从register中获取数据，获取到数据后，将结果设置到readWriteCacheMap中。
public class ResponseCacheImpl implements ResponseCache {
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())
.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) {
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);
}
}
}
};
}
} - 一级只读缓存
readOnlyCacheMap，是通过定时任务，定时从readWriteCacheMap读取数据刷新值，定时任务默认30秒间隔。 - 二级缓存
readWriteCacheMap，通过guava cache自身的机制来实现过期并刷新，默认是从写入时间起算，30秒之后过期。
增量获取服务列表
注册的uri是GET /apps/delta。入口在ApplicationResource。
@Path("/{version}/apps")
@Produces({"application/xml", "application/json"})
public class ApplicationsResource {
@Path("delta")
@GET
public Response getContainerDifferential(
@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();
// If the delta flag is disabled in discovery or if the lease expiration
// has been disabled, redirect clients to get all instances
if ((serverConfig.shouldDisableDelta()) || (!registry.shouldAllowAccess(isRemoteRegionRequested))) {
return Response.status(Status.FORBIDDEN).build();
}
String[] regions = null;
if (!isRemoteRegionRequested) {
EurekaMonitors.GET_ALL_DELTA.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_DELTA_WITH_REMOTE_REGIONS.increment();
}
CurrentRequestVersion.set(Version.toEnum(version));
KeyType keyType = Key.KeyType.JSON;
String returnMediaType = MediaType.APPLICATION_JSON;
if (acceptHeader == null || !acceptHeader.contains(HEADER_JSON_VALUE)) {
keyType = Key.KeyType.XML;
returnMediaType = MediaType.APPLICATION_XML;
}
Key cacheKey = new Key(Key.EntityType.Application,
ResponseCacheImpl.ALL_APPS_DELTA,
keyType, CurrentRequestVersion.get(), EurekaAccept.fromString(eurekaAccept), regions
);
if (acceptEncoding != null
&& acceptEncoding.contains(HEADER_GZIP_VALUE)) {
return Response.ok(responseCache.getGZIP(cacheKey))
.header(HEADER_CONTENT_ENCODING, HEADER_GZIP_VALUE)
.header(HEADER_CONTENT_TYPE, returnMediaType)
.build();
} else {
return Response.ok(responseCache.get(cacheKey))
.build();
}
}
}增量的逻辑基本上跟全量一样，差别在于cacheKey的KeyType为ResponseCacheImpl.ALL_APPS_DELTA。ResponseCache里，全量获取是通过registry.getApplications()遍历registry的Map获取所有的服务；而增量的registry.getApplicationDeltas()方法，则是有专门的queue存储最近变化的信息。
public abstract class AbstractInstanceRegistry implements InstanceRegistry {
public Applications getApplicationDeltas() {
GET_ALL_CACHE_MISS_DELTA.increment();
Applications apps = new Applications();
apps.setVersion(responseCache.getVersionDelta().get());
Map applicationInstancesMap = new HashMap();
try {
write.lock();
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)));
}
boolean disableTransparentFallback = serverConfig.disableTransparentFallbackToOtherRegion();
if (!disableTransparentFallback) {
Applications allAppsInLocalRegion = getApplications(false);
for (RemoteRegionRegistry remoteRegistry : this.regionNameVSRemoteRegistry.values()) {
Applications applications = remoteRegistry.getApplicationDeltas();
for (Application application : applications.getRegisteredApplications()) {
Application appInLocalRegistry =
allAppsInLocalRegion.getRegisteredApplications(application.getName());
if (appInLocalRegistry == null) {
apps.addApplication(application);
}
}
}
}
Applications allApps = getApplications(!disableTransparentFallback);
apps.setAppsHashCode(allApps.getReconcileHashCode());
return apps;
} finally {
write.unlock();
}
}
} recentlyChangedQueue由定时任务定时清理过期数据，定时任务30秒执行一次，清理180秒之前的数据。
public abstract class AbstractInstanceRegistry implements InstanceRegistry {
protected AbstractInstanceRegistry(EurekaServerConfig serverConfig, EurekaClientConfig clientConfig, ServerCodecs serverCodecs) {
this.serverConfig = serverConfig;
this.clientConfig = clientConfig;
this.serverCodecs = serverCodecs;
this.recentCanceledQueue = new CircularQueue>(1000);
this.recentRegisteredQueue = new CircularQueue>(1000);
this.renewsLastMin = new MeasuredRate(1000 * 60 * 1);
this.deltaRetentionTimer.schedule(getDeltaRetentionTask(),
serverConfig.getDeltaRetentionTimerIntervalInMs(),
serverConfig.getDeltaRetentionTimerIntervalInMs());
}
private TimerTask getDeltaRetentionTask() {
return new TimerTask() {
@Override
public void run() {
Iterator it = recentlyChangedQueue.iterator();
while (it.hasNext()) {
if (it.next().getLastUpdateTime() <
System.currentTimeMillis() - serverConfig.getRetentionTimeInMSInDeltaQueue()) {
it.remove();
} else {
break;
}
}
}
};
}
} 获取服务整体流程如下：
注册
注册的uri是POST /apps/{serviceId}。入口在ApplicationResource。
@Produces({"application/xml", "application/json"})
public class ApplicationResource {
private static final Logger logger = LoggerFactory.getLogger(ApplicationResource.class);
private final PeerAwareInstanceRegistry registry;
/**
* Registers information about a particular instance for an
* {@link com.netflix.discovery.shared.Application}.
*
* @param info
* {@link InstanceInfo} information of the instance.
* @param isReplication
* a header parameter containing information whether this is
* replicated from other nodes.
*/
@POST
@Consumes({"application/json", "application/xml"})
public Response addInstance(InstanceInfo info,
@HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication) {
logger.debug("Registering instance {} (replication={})", info.getId(), isReplication);
// validate that the instanceinfo contains all the necessary required fields
if (isBlank(info.getId())) {
return Response.status(400).entity("Missing instanceId").build();
} else if (isBlank(info.getHostName())) {
return Response.status(400).entity("Missing hostname").build();
} else if (isBlank(info.getIPAddr())) {
return Response.status(400).entity("Missing ip address").build();
} else if (isBlank(info.getAppName())) {
return Response.status(400).entity("Missing appName").build();
} else if (!appName.equals(info.getAppName())) {
return Response.status(400).entity("Mismatched appName, expecting " + appName + " but was " + info.getAppName()).build();
} else if (info.getDataCenterInfo() == null) {
return Response.status(400).entity("Missing dataCenterInfo").build();
} else if (info.getDataCenterInfo().getName() == null) {
return Response.status(400).entity("Missing dataCenterInfo Name").build();
}
// handle cases where clients may be registering with bad DataCenterInfo with missing data
DataCenterInfo dataCenterInfo = info.getDataCenterInfo();
if (dataCenterInfo instanceof UniqueIdentifier) {
String dataCenterInfoId = ((UniqueIdentifier) dataCenterInfo).getId();
if (isBlank(dataCenterInfoId)) {
boolean experimental = "true".equalsIgnoreCase(serverConfig.getExperimental("registration.validation.dataCenterInfoId"));
if (experimental) {
String entity = "DataCenterInfo of type " + dataCenterInfo.getClass() + " must contain a valid id";
return Response.status(400).entity(entity).build();
} else if (dataCenterInfo instanceof AmazonInfo) {
AmazonInfo amazonInfo = (AmazonInfo) dataCenterInfo;
String effectiveId = amazonInfo.get(AmazonInfo.MetaDataKey.instanceId);
if (effectiveId == null) {
amazonInfo.getMetadata().put(AmazonInfo.MetaDataKey.instanceId.getName(), info.getId());
}
} else {
logger.warn("Registering DataCenterInfo of type {} without an appropriate id", dataCenterInfo.getClass());
}
}
}
registry.register(info, "true".equals(isReplication));
return Response.status(204).build(); // 204 to be backwards compatible
}
}InstanceInfo info是服务节点信息，String isReplication用来标识是否集群内其他eureka-server节点发送过来的复制信息。接口主要代码在PeerAwareInstanceRegistry.register。
@Singleton
public class PeerAwareInstanceRegistryImpl extends AbstractInstanceRegistry implements PeerAwareInstanceRegistry {
@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();
}
super.register(info, leaseDuration, isReplication);
replicateToPeers(Action.Register, info.getAppName(), info.getId(), info, null, isReplication);
}
}PeerAwareInstanceRegistry.register主要两件事，一是调用父类的register，再就是向集群内其他节点传播注册信息。先看下父类的注册方法。
public abstract class AbstractInstanceRegistry implements InstanceRegistry {
private final ConcurrentHashMap>> registry
= new ConcurrentHashMap>>();
protected volatile ResponseCache responseCache;
public void register(InstanceInfo registrant, int leaseDuration, boolean isReplication) {
try {
read.lock();
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;
}
}
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
this.expectedNumberOfClientsSendingRenews = this.expectedNumberOfClientsSendingRenews + 1;
updateRenewsPerMinThreshold();
}
}
logger.debug("No previous lease information found; it is new registration");
}
Lease lease = new Lease(registrant, leaseDuration);
if (existingLease != null) {
lease.setServiceUpTimestamp(existingLease.getServiceUpTimestamp());
}
gMap.put(registrant.getId(), lease);
synchronized (recentRegisteredQueue) {
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());
}
}
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())) {
lease.serviceUp();
}
registrant.setActionType(ActionType.ADDED);
recentlyChangedQueue.add(new RecentlyChangedItem(lease));
registrant.setLastUpdatedTimestamp();
invalidateCache(registrant.getAppName(), registrant.getVIPAddress(), registrant.getSecureVipAddress());
logger.info("Registered instance {}/{} with status {} (replication={})",
registrant.getAppName(), registrant.getId(), registrant.getStatus(), isReplication);
} finally {
read.unlock();
}
}
} 方法用lock保证线程安全，大概流程如下：
- 将注册信息放入
register，register存储在线服务信息，ConcurrentHashMap类型，存储格式为ConcurrentHashMap<服务名,ConcurrentHashMap<机器ID(默认为“IP:服务名:配置的端口”), 服务信息(Lease)>>，例如 - 将注册信息添加到
最近注册队列-recentRegisteredQueue中。 - 将注册信息添加到
最近变更队列-recentlyChangedQueue中。 - 清理缓存，
eureka为了保证性能，引入了三级缓存机制（后续会讲到）。
进入清理缓存看下：
protected volatile ResponseCache responseCache;
private void invalidateCache(String appName, @Nullable String vipAddress, @Nullable String secureVipAddress) {
// invalidate cache
responseCache.invalidate(appName, vipAddress, secureVipAddress);
}实际清理代码在ResponseCache内。
public class ResponseCacheImpl implements ResponseCache {
private final LoadingCache readWriteCacheMap;
@Override
public void invalidate(String appName, @Nullable String vipAddress, @Nullable String secureVipAddress) {
for (Key.KeyType type : Key.KeyType.values()) {
for (Version v : Version.values()) {
invalidate(
new Key(Key.EntityType.Application, appName, type, v, EurekaAccept.full),
new Key(Key.EntityType.Application, appName, type, v, EurekaAccept.compact),
new Key(Key.EntityType.Application, ALL_APPS, type, v, EurekaAccept.full),
new Key(Key.EntityType.Application, ALL_APPS, type, v, EurekaAccept.compact),
new Key(Key.EntityType.Application, ALL_APPS_DELTA, type, v, EurekaAccept.full),
new Key(Key.EntityType.Application, ALL_APPS_DELTA, type, v, EurekaAccept.compact)
);
if (null != vipAddress) {
invalidate(new Key(Key.EntityType.VIP, vipAddress, type, v, EurekaAccept.full));
}
if (null != secureVipAddress) {
invalidate(new Key(Key.EntityType.SVIP, secureVipAddress, type, v, EurekaAccept.full));
}
}
}
}
public void invalidate(Key... keys) {
for (Key key : keys) {
logger.debug("Invalidating the response cache key : {} {} {} {}, {}",
key.getEntityType(), key.getName(), key.getVersion(), key.getType(), key.getEurekaAccept());
readWriteCacheMap.invalidate(key);
Collection keysWithRegions = regionSpecificKeys.get(key);
if (null != keysWithRegions && !keysWithRegions.isEmpty()) {
for (Key keysWithRegion : keysWithRegions) {
logger.debug("Invalidating the response cache key : {} {} {} {} {}",
key.getEntityType(), key.getName(), key.getVersion(), key.getType(), key.getEurekaAccept());
readWriteCacheMap.invalidate(keysWithRegion);
}
}
}
}
,} 再回到PeerAwareInstanceRegistry.replicateToPeers看怎么传播信息到集群其他节点。
private void replicateToPeers(Action action, String appName, String id,
InstanceInfo info /* optional */,
InstanceStatus newStatus /* optional */, boolean isReplication) {
Stopwatch tracer = action.getTimer().start();
try {
if (isReplication) {
numberOfReplicationsLastMin.increment();
}
// If it is a replication already, do not replicate again as this will create a poison replication
if (peerEurekaNodes == Collections.EMPTY_LIST || isReplication) {
return;
}
for (final PeerEurekaNode node : peerEurekaNodes.getPeerEurekaNodes()) {
// If the url represents this host, do not replicate to yourself.
if (peerEurekaNodes.isThisMyUrl(node.getServiceUrl())) {
continue;
}
replicateInstanceActionsToPeers(action, appName, id, info, newStatus, node);
}
} finally {
tracer.stop();
}
}
private void replicateInstanceActionsToPeers(Action action, String appName,
String id, InstanceInfo info, InstanceStatus newStatus,
PeerEurekaNode node) {
try {
InstanceInfo infoFromRegistry = null;
CurrentRequestVersion.set(Version.V2);
switch (action) {
case Cancel:
node.cancel(appName, id);
break;
case Heartbeat:
InstanceStatus overriddenStatus = overriddenInstanceStatusMap.get(id);
infoFromRegistry = getInstanceByAppAndId(appName, id, false);
node.heartbeat(appName, id, infoFromRegistry, overriddenStatus, false);
break;
case Register:
node.register(info);
break;
case StatusUpdate:
infoFromRegistry = getInstanceByAppAndId(appName, id, false);
node.statusUpdate(appName, id, newStatus, infoFromRegistry);
break;
case DeleteStatusOverride:
infoFromRegistry = getInstanceByAppAndId(appName, id, false);
node.deleteStatusOverride(appName, id, infoFromRegistry);
break;
}
} catch (Throwable t) {
logger.error("Cannot replicate information to {} for action {}", node.getServiceUrl(), action.name(), t);
}
} Action为Register，进入到PeerEurekaNode.register方法
public class PeerEurekaNode {
public void register(final InstanceInfo info) throws Exception {
long expiryTime = System.currentTimeMillis() + getLeaseRenewalOf(info);
batchingDispatcher.process(
taskId("register", info),
new InstanceReplicationTask(targetHost, Action.Register, info, null, true) {
public EurekaHttpResponse execute() {
return replicationClient.register(info);
}
},
expiryTime
);
}
} 传播节点是通过TaskExecutors异步执行(也就是即使当eureka-client成功调用注册接口，也并不代表所有的eureka-server都已经有这个client的信息)，最终执行方法是HttpReplicationClient.register，HttpReplicationClient默认是JerseyReplicationClient。
public class JerseyReplicationClient extends AbstractJerseyEurekaHttpClient implements HttpReplicationClient {
@Override
protected void addExtraHeaders(Builder webResource) {
webResource.header(PeerEurekaNode.HEADER_REPLICATION, "true");
}
}JerseyReplicationClient是AbstractJerseyEurekaHttpClient，所以传播实际上也是调用其他节点的注册接口，只是额外在头部添加了x-netflix-discovery-replication为true，而通过前面的代码@HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication，我们知道如果isReplication为true时，表示这是一个集群其他节点的复制信息，就不会再做传播这一步。
由于传播是异步进行的，异步有失败的风险，这个在续约(renew)时会做补充。
续约
注册的uri是PUT apps/{serviceId}/{instanceId}。入口在InstanceResource。
public class InstanceResource {
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;
}
}renewLease方法主要做两件事：
- 调用
registry.renew执行续约。 - 检查
lastDirtyTimestamp。 - 如果失败，则返回
404。
public class PeerAwareInstanceRegistryImpl extends AbstractInstanceRegistry implements PeerAwareInstanceRegistry {
public boolean renew(final String appName, final String id, final boolean isReplication) {
if (super.renew(appName, id, isReplication)) {
replicateToPeers(Action.Heartbeat, appName, id, null, null, isReplication);
return true;
}
return false;
}
}跟注册一样，续约也是调用父类的方法，然后传播到集群其他节点。
public abstract class AbstractInstanceRegistry implements InstanceRegistry {
public boolean renew(String appName, String id, boolean isReplication) {
RENEW.increment(isReplication);
Map> gMap = registry.get(appName);
Lease leaseToRenew = null;
if (gMap != null) {
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 {
private volatile long lastUpdateTimestamp;
public void renew() {
lastUpdateTimestamp = System.currentTimeMillis() + duration;
}
} - 获取租期
Lease，如果没有，就返回失败。 - 如果应用的当前状态和
最终状态不一致，则用最终状态覆盖调当前状态。 - 更新租期时间。
传播续租给集群其他节点，跟注册也一样：异步调用其他节点的续租接口，@HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication参数为true。
下线
注册的uri是DELETE apps/{serviceId}/{instanceId}。入口在InstanceResource。
public class InstanceResource {
@DELETE
public Response cancelLease(
@HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication) {
try {
boolean isSuccess = registry.cancel(app.getName(), id,
"true".equals(isReplication));
if (isSuccess) {
logger.debug("Found (Cancel): {} - {}", app.getName(), id);
return Response.ok().build();
} else {
logger.info("Not Found (Cancel): {} - {}", app.getName(), id);
return Response.status(Status.NOT_FOUND).build();
}
} catch (Throwable e) {
logger.error("Error (cancel): {} - {}", app.getName(), id, e);
return Response.serverError().build();
}
}
}同样的，registry是PeerAwareInstanceRegistryImpl。
public class PeerAwareInstanceRegistryImpl extends AbstractInstanceRegistry implements PeerAwareInstanceRegistry {
@Override
public boolean cancel(final String appName, final String id,
final boolean isReplication) {
if (super.cancel(appName, id, isReplication)) {
replicateToPeers(Action.Cancel, appName, id, null, null, isReplication);
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;
updateRenewsPerMinThreshold();
}
}
return true;
}
return false;
}
protected void updateRenewsPerMinThreshold() {
this.numberOfRenewsPerMinThreshold = (int) (this.expectedNumberOfClientsSendingRenews
* (60.0 / serverConfig.getExpectedClientRenewalIntervalSeconds())
* serverConfig.getRenewalPercentThreshold());
}
}PeerAwareInstanceRegistryImpl除了调用父类的cancel、传播信息给集群其他节点之外，还会重新计算numberOfRenewsPerMinThreshold，numberOfRenewsPerMinThreshold在自我保护机子里会用到。
public abstract class AbstractInstanceRegistry implements InstanceRegistry {
@Override
public boolean cancel(String appName, String id, boolean isReplication) {
return internalCancel(appName, id, isReplication);
}
protected boolean internalCancel(String appName, String id, boolean isReplication) {
try {
read.lock();
CANCEL.increment(isReplication);
Map> gMap = registry.get(appName);
Lease leaseToCancel = null;
if (gMap != null) {
leaseToCancel = gMap.remove(id);
}
synchronized (recentCanceledQueue) {
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 {
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();
}
invalidateCache(appName, vip, svip);
logger.info("Cancelled instance {}/{} (replication={})", appName, id, isReplication);
return true;
}
} finally {
read.unlock();
}
}
} super.cancel主要做：清理数据（registry）、添加事件、清理缓存（清理readWriteCacheMap，但不清理readOnlyCacheMap，readOnlyCacheMap只通过定时任务来刷新）。
再回到PeerAwareInstanceRegistryImpl.replicateToPeers方法，跟注册/续租一样，是异步调其他eureka-server节点的接口，@HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication参数为true。
过期检查
正常情况下，应用实例下线时候会主动向eureka-Server发起下线请求。但实际情况下，应用实例可能异常崩溃，又或者是网络异常等原因，导致下线请求无法被成功提交。
public abstract class AbstractInstanceRegistry implements InstanceRegistry {
protected void postInit() {
renewsLastMin.start();
if (evictionTaskRef.get() != null) {
evictionTaskRef.get().cancel();
}
evictionTaskRef.set(new EvictionTask());
evictionTimer.schedule(evictionTaskRef.get(),
serverConfig.getEvictionIntervalTimerInMs(),
serverConfig.getEvictionIntervalTimerInMs());
}
}AbstractInstanceRegistry里会启动定时任务EvictionTask，定期下线/清理失效的服务信息，默认是60秒指定一次清理任务，清理超过90秒未续约服务，但实际上计算时，还会算上补偿时间（补偿时间 = 当前时间 - 最后任务执行时间 - 任务执行频率），至于为什么要算上补偿事件，可以看Lease.isExpired(long additionalLeaseMs)方法的注释。
public abstract class AbstractInstanceRegistry implements InstanceRegistry {
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);
}
}
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 void evict(long additionalLeaseMs) {
logger.debug("Running the evict task");
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();
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.
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)
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);
internalCancel(appName, id, false);
}
}
}
}
public class Lease {
/**
* Checks if the lease of a given {@link com.netflix.appinfo.InstanceInfo} has expired or not.
* 关于补偿时间的说明：
* Note that due to renew() doing the 'wrong" thing and setting lastUpdateTimestamp to +duration more than
* what it should be, the expiry will actually be 2 * duration. This is a minor bug and should only affect
* instances that ungracefully shutdown. Due to possible wide ranging impact to existing usage, this will
* not be fixed.
*
* @param additionalLeaseMs any additional lease time to add to the lease evaluation in ms.
*/
public boolean isExpired(long additionalLeaseMs) {
return (evictionTimestamp > 0 || System.currentTimeMillis() > (lastUpdateTimestamp + duration + additionalLeaseMs));
}
} isLeaseExpirationEnabled是判断是否开启了自我保护机制，当时是否符合自我保护机制条件。
清理的时候：
- 分批清理：限制单次清理的最大服务数量（默认保留当前服务数量的85%，即单次最多清理掉25%）。
- 随机清理：尽量避免单个应用被全部过期。
分批清理例子：
// 假设 20 个租约，其中有 10 个租约过期。
// 第一轮执行开始
int registrySize = 20;
int registrySizeThreshold = (int) (20 * 0.85) = 17;
int evictionLimit = 20 - 17 = 3;
int toEvict = Math.min(10, 3) = 3;
// 第一轮执行结束，剩余 17 个租约，其中有 7 个租约过期。
// 第二轮执行开始
int registrySize = 17;
int registrySizeThreshold = (int) (17 * 0.85) = 14;
int evictionLimit = 17 - 14 = 3;
int toEvict = Math.min(7, 3) = 3;
// 第二轮执行结束，剩余 14 个租约，其中有 4 个租约过期。
// 第三轮执行开始
int registrySize = 14;
int registrySizeThreshold = (int) (14 * 0.85) = 11;
int evictionLimit = 14 - 11 = 3;
int toEvict = Math.min(4, 3) = 3;
// 第三轮执行结束，剩余 11 个租约，其中有 1 个租约过期。
// 第四轮执行开始
int registrySize = 11;
int registrySizeThreshold = (int) (11 * 0.85) = 9;
int evictionLimit = 11 - 9 = 2;
int toEvict = Math.min(1, 2) = 1;
// 第四轮执行结束，剩余 10 个租约，其中有 0 个租约过期。结束。下线的代码internalCancel跟前面的下线是同一个方法。
参考：
《 Eureka 源码解析 —— 应用实例注册发现（五）之过期》