06、源码解析 EurekaClient 心跳、续约源码解析
EurekaClient心跳、续约源码解析
1、整体流程图
2、客户端心跳入口
// new DiscoveryClient 的时候初始化心跳定时任务周期性的调度
// Heartbeat timer
scheduler.schedule(
new TimedSupervisorTask(
"heartbeat",
scheduler,
heartbeatExecutor,
// 续约周期是 30s.也就是每 30s 执行一次
renewalIntervalInSecs,
TimeUnit.SECONDS,
expBackOffBound,
new HeartbeatThread()
),
renewalIntervalInSecs, TimeUnit.SECONDS);
private class HeartbeatThread implements Runnable {
public void run() {
if (renew()) {
lastSuccessfulHeartbeatTimestamp = System.currentTimeMillis();
}
}
}
2.1 renew() 续约的方法
boolean renew() {
EurekaHttpResponse<InstanceInfo> httpResponse;
try {
// 1、通过jerseyclient 去发送心中请求
httpResponse = eurekaTransport.registrationClient.sendHeartBeat(instanceInfo.getAppName(), instanceInfo.getId(), instanceInfo, null);
logger.debug("{} - Heartbeat status: {}", PREFIX + appPathIdentifier, httpResponse.getStatusCode());
// 2、如果 404 的话去发起 register 请求
if (httpResponse.getStatusCode() == 404) {
REREGISTER_COUNTER.increment();// 这里是一个计数器，如果失败 + 1
logger.info("{} - Re-registering apps/{}", PREFIX + appPathIdentifier, instanceInfo.getAppName());
long timestamp = instanceInfo.setIsDirtyWithTime();
boolean success = register();
if (success) {
instanceInfo.unsetIsDirty(timestamp);
}
return success;
}
// 3、成功返回 200,续约成功
return httpResponse.getStatusCode() == 200;
} catch (Throwable e) {
logger.error("{} - was unable to send heartbeat!", PREFIX + appPathIdentifier, e);
return false;
}
}
3、服务端流程
可以通过断点调试知道，最终服务端调用的是 InstanceResource 的 renewLease 方法
3.1 renewLease(InstanceResource.renewLease())
@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);
// 如果注册表中没发现直接返回 404,那 client 发现 404 后就会执行 registry 逻辑去 addInstance(新增实例) 添加到 registry(注册表) 中去
// 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 = null;
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;
}
3.2 com.netflix.eureka.registry.PeerAwareInstanceRegistryImpl#renew
// super.renew() 主要是调用 AbstractInstanceRegistry 的 renew 方法
public boolean renew(final String appName, final String id, final boolean isReplication) {
if (super.renew(appName, id, isReplication)) {
//这个就是复制到其他 eureka 服务节点
replicateToPeers(Action.Heartbeat, appName, id, null, null, isReplication);
return true;
}
return false;
}
3.2.1 com.netflix.eureka.registry.AbstractInstanceRegistry#renew(renew 方法是抽象类来实现的)
public boolean renew(String appName, String id, boolean isReplication) {
// 1、统计信息新增 1
RENEW.increment(isReplication);
// 2、从 registry(注册表)中获取信息 appName 为 key 的 Map 信息
Map<String, Lease<InstanceInfo>> gMap = registry.get(appName);
Lease<InstanceInfo> leaseToRenew = null;
// 3、苑 Lease 信息
if (gMap != null) {
leaseToRenew = gMap.get(id);
}
// 4、如果为空则直接返回 404,客户端会发起 registry 请求(前面的文章看到过这样的逻辑处理)
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) {
// 4.1、InstanceStatus 判断，如果为 UNKNOWN，可能被删除覆盖了，所以可能客户端需要重新注册
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;
}
// 4.2、如果两者不一样，则更新 status
if (!instanceInfo.getStatus().equals(overriddenInstanceStatus)) {
Object[] args = {
instanceInfo.getStatus().name(),
instanceInfo.getOverriddenStatus().name(),
instanceInfo.getId()
};
logger.info(
"The instance status {} is different from overridden instance status {} for instance {}. "
+ "Hence setting the status to overridden status", args);
instanceInfo.setStatusWithoutDirty(overriddenInstanceStatus);
}
}
// 5、统计信息新增(上一分钟的续约次数)
renewsLastMin.increment();
// 6、更新 lastUpdateTimestamp
leaseToRenew.renew();
return true;
}
}
3.2.2 replicateToPeers(复制到其他 Eureka 服务节点 )
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:
// 这里我们可以知道会调用到这里来
// 从 overriddenInstanceStatusMap 中获取 InstanceStatus，默认是 1 个小时后过期。
InstanceStatus overriddenStatus = overriddenInstanceStatusMap.get(id);
// 这个方法说一下
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);
}
}
@Override
public InstanceInfo getInstanceByAppAndId(String appName, String id, boolean includeRemoteRegions) {
// 1、从注册表中获取 appName 为 key 的 Map
Map<String, Lease<InstanceInfo>> leaseMap = registry.get(appName);
Lease<InstanceInfo> lease = null;
if (leaseMap != null) {
lease = leaseMap.get(id);
}
// 2、判断 Lease 如果不为空，且(Lease 开启没有开启或者 lease 没有过期)则返回装饰的 InstanceInfo
if (lease != null
&& (!isLeaseExpirationEnabled() || !lease.isExpired())) {
return decorateInstanceInfo(lease);
} else if (includeRemoteRegions) {
for (RemoteRegionRegistry remoteRegistry : this.regionNameVSRemoteRegistry.values()) {
Application application = remoteRegistry.getApplication(appName);
if (application != null) {
return application.getByInstanceId(id);
}
}
}
return null;
}
@Override
public boolean isLeaseExpirationEnabled() {
// 1、这个是判断自我保护模式是否开启(这个模式是默认开启的，后面EurekaServer 自我保护源码解析的时候会分析一下，怎么来判断等等)
if (!isSelfPreservationModeEnabled()) {
// The self preservation mode is disabled, hence allowing the instances to expire.
//如果自我保护没有开启，说明此时是可以过期的，所以返回 true。
// 因为如果自我保护开启，就不会进来，说明此时要判断一下心跳来判断是否 lease过期开启
return true;
}
//2、阈值 > 0,且上一分钟的心跳数 > 阈值才说明 lease 过期开启否则返回 false
return numberOfRenewsPerMinThreshold > 0 && getNumOfRenewsInLastMin() > numberOfRenewsPerMinThreshold;
}
3.2.2.1 heartbeat
public void heartbeat(final String appName, final String id,
final InstanceInfo info, final InstanceStatus overriddenStatus,
boolean primeConnection) throws Throwable {
// 1、传递的是 false 不会进来
if (primeConnection) {
// We do not care about the result for priming request.
replicationClient.sendHeartBeat(appName, id, info, overriddenStatus);
return;
}
// 2、构造一个 ReplicationTask
ReplicationTask replicationTask = new InstanceReplicationTask(targetHost, Action.Heartbeat, info, overriddenStatus, false) {
@Override
public EurekaHttpResponse<InstanceInfo> execute() throws Throwable {
return replicationClient.sendHeartBeat(appName, id, info, overriddenStatus);
}
@Override
public void handleFailure(int statusCode, Object responseEntity) throws Throwable {
super.handleFailure(statusCode, responseEntity);
if (statusCode == 404) {
logger.warn("{}: missing entry.", getTaskName());
if (info != null) {
logger.warn("{}: cannot find instance id {} and hence replicating the instance with status {}",
getTaskName(), info.getId(), info.getStatus());
register(info);
}
} else if (config.shouldSyncWhenTimestampDiffers()) {
InstanceInfo peerInstanceInfo = (InstanceInfo) responseEntity;
if (peerInstanceInfo != null) {
syncInstancesIfTimestampDiffers(appName, id, info, peerInstanceInfo);
}
}
}
};
// 3、获取 expiryTime
long expiryTime = System.currentTimeMillis() + getLeaseRenewalOf(info);
// 4、分发到 batchingDispatcher
batchingDispatcher.process(taskId("heartbeat", info), replicationTask, expiryTime);
}
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