In the previous article on EurekaClient automatic assembly and startup process analysis , we mentioned that when constructing DiscoveryClienta class, it will register itself to the server. This article will analyze this registration process.
Client initiates registration
boolean register() throws Throwable {
logger.info(PREFIX + "{}: registering service...", appPathIdentifier);
EurekaHttpResponse<Void> httpResponse;
try {
httpResponse = eurekaTransport.registrationClient.register(instanceInfo);
} catch (Exception e) {
logger.warn(PREFIX + "{} - registration failed {}", appPathIdentifier, e.getMessage(), e);
throw e;
}
if (logger.isInfoEnabled()) {
logger.info(PREFIX + "{} - registration status: {}", appPathIdentifier, httpResponse.getStatusCode());
}
return httpResponse.getStatusCode() == 204;
}
registrationClientThe two objects contained in this method instanceInfohave been taken out separately in the previous article: Important objects in Eureka
Server accepts registration
The server accepts the registered Controller in the ApplicationResourceclass. It should be noted here that the parameter of the normal client registration isReplicationis false. This parameter is the representation of controlling whether the cluster is synchronized or not.
@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);
// 一系列的参数校验
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();
}
// AWS的一些东西，不用细看
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());
}
}
}
//注册
registry.register(info, "true".equals(isReplication));
return Response.status(204).build(); // 204 to be backwards compatible
}
Then look down at the processing logic of registration
public void register(final InstanceInfo info, final boolean isReplication) {
// 租约过期时间
int leaseDuration = Lease.DEFAULT_DURATION_IN_SECS;
if (info.getLeaseInfo() != null && info.getLeaseInfo().getDurationInSecs() > 0) {
leaseDuration = info.getLeaseInfo().getDurationInSecs();
}
// 注册
super.register(info, leaseDuration, isReplication);
//集群复制
replicateToPeers(Action.Register, info.getAppName(), info.getId(), info, null, isReplication);
}
LeaseThe lease class has also been analyzed before, and will no longer be expanded.
The server saves the registration information
public void register(InstanceInfo registrant, int leaseDuration, boolean isReplication) {
try {
//获取锁
read.lock();
//获取该实例的注册信息
Map<String, Lease<InstanceInfo>> gMap = registry.get(registrant.getAppName());
REGISTER.increment(isReplication);
if (gMap == null) {
final ConcurrentHashMap<String, Lease<InstanceInfo>> gNewMap = new ConcurrentHashMap<String, Lease<InstanceInfo>>();
//如果不存在则添加
gMap = registry.putIfAbsent(registrant.getAppName(), gNewMap);
if (gMap == null) {
gMap = gNewMap;
}
}
Lease<InstanceInfo> existingLease = gMap.get(registrant.getId());
// 当存在这个应用的注册信息时
if (existingLease != null && (existingLease.getHolder() != null)) {
Long existingLastDirtyTimestamp = existingLease.getHolder().getLastDirtyTimestamp();
Long registrationLastDirtyTimestamp = registrant.getLastDirtyTimestamp();
logger.debug("Existing lease found (existing={}, provided={}", existingLastDirtyTimestamp, registrationLastDirtyTimestamp);
//使用注册时间长的一方的应用信息
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 {
synchronized (lock) {
if (this.expectedNumberOfRenewsPerMin > 0) {
this.expectedNumberOfRenewsPerMin = this.expectedNumberOfRenewsPerMin + 2;
this.numberOfRenewsPerMinThreshold =
(int) (this.expectedNumberOfRenewsPerMin * serverConfig.getRenewalPercentThreshold());
}
}
logger.debug("No previous lease information found; it is new registration");
}
//创建租约
Lease<InstanceInfo> lease = new Lease<InstanceInfo>(registrant, leaseDuration);
//如果存在租约则更新开始时间
if (existingLease != null) {
lease.setServiceUpTimestamp(existingLease.getServiceUpTimestamp());
}
gMap.put(registrant.getId(), lease);
synchronized (recentRegisteredQueue) {
//添加到最近注册队列
recentRegisteredQueue.add(new Pair<Long, String>(
System.currentTimeMillis(),
registrant.getAppName() + "(" + registrant.getId() + ")"));
}
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);
}
// 获得应用实例最终状态
InstanceStatus overriddenInstanceStatus = getOverriddenInstanceStatus(registrant, existingLease, isReplication);
registrant.setStatusWithoutDirty(overriddenInstanceStatus);
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();
}
}
- Instance information is saved by a map object. In this map, the key is the appName of the application, and the value is another map. In this map, the key is the id of the application, and the value is the lease information of the application. The map object is as follows:
private final ConcurrentHashMap<String, Map<String, Lease<InstanceInfo>>>
registry = new ConcurrentHashMap<String, Map<String, Lease<InstanceInfo>>>();
- The general process is to first check whether the registration information of the appName exists, and create it if it does not exist.
- Then check whether the registration information of the id exists, if there is the last modification time of the client, record the last modified instance, if not, set several parameters of the self-protection mode
- Create the corresponding lease information according to the instance, and then add it to the map object
- Add to recent registration queue
- Add to application instance override state map
- Set the final state of the application instance, add the latest lease change queue, set the cache, etc.
Cluster data synchronization
When the isReplicationattribute is true, it will involve the synchronization of cluster information
private void replicateToPeers(Action action, String appName, String id,
InstanceInfo info ,
InstanceStatus newStatus , boolean isReplication) {
Stopwatch tracer = action.getTimer().start();
try {
if (isReplication) {
numberOfReplicationsLastMin.increment();
}
if (peerEurekaNodes == Collections.EMPTY_LIST || isReplication) {
return;
}
for (final PeerEurekaNode node : peerEurekaNodes.getPeerEurekaNodes()) {
if (peerEurekaNodes.isThisMyUrl(node.getServiceUrl())) {
continue;
}
replicateInstanceActionsToPeers(action, appName, id, info, newStatus, node);
}
} finally {
tracer.stop();
}
}
As PeerEurekaNodementioned in the previous article, the cluster node information is saved. Here you can see that all cluster nodes are looped, and then the replicateInstanceActionsToPeersmethod is called after excluding its own information.
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);
}
}
Focus on the Register branch here
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<Void> execute() {
return replicationClient.register(info);
}
},
expiryTime
);
}
Under the premise of not caring about Eureka's own scheduling processing, the core code is replicationClient.register(info), that is to say, if the client is registered to specify that the cluster information needs to be synchronized, Eureka will re-register the client to other clusters in the cluster where it is located. on the node
The server initiates cluster data synchronization
In the previous article on EurekaServer automatic assembly and startup process analysis , we mentioned that data will be synchronized from the EurekaServer cluster when the server is initialized, which is the following code:
public class EurekaServerBootstrap {
protected void initEurekaServerContext() throws Exception {
//xxxx
EurekaServerContextHolder.initialize(this.serverContext);
log.info("Initialized server context");
// 从其他 Eureka-Server 拉取注册信息
int registryCount = this.registry.syncUp();
this.registry.openForTraffic(this.applicationInfoManager, registryCount);
// Register all monitoring statistics.
EurekaMonitors.registerAllStats();
}
The code for data synchronization is syncUpin
public int syncUp() {
int count = 0;
for (int i = 0; ((i < serverConfig.getRegistrySyncRetries()) && (count == 0)); i++) {
if (i > 0) {
//未读取到注册信息则开始等待
try {
Thread.sleep(serverConfig.getRegistrySyncRetryWaitMs());
} catch (InterruptedException e) {
logger.warn("Interrupted during registry transfer..");
break;
}
}
// 获取注册信息
Applications apps = eurekaClient.getApplications();
for (Application app : apps.getRegisteredApplications()) {
for (InstanceInfo instance : app.getInstances()) {
try {
//判断是否可以注册，这里基于AWS环境的判断，如果不是AWS环境直接返回true，故不需要关心这个问题
if (isRegisterable(instance)) {
//注册
register(instance, instance.getLeaseInfo().getDurationInSecs(), true);
count++;
}
} catch (Throwable t) {
logger.error("During DS init copy", t);
}
}
}
}
return count;
}
The processing flow here is that after the current EurekaServer obtains the registration information of the client, it will call the registermethod called by the server controller mentioned above again. Of course, the isReplicationparameter becomes true this time.
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