相关参数
eureka.instance.leaseRenewalIntervalInSeconds = 30 # hearbeat interval
eureka.server.renewalPercentThreshold = 0.85
eureka.server.renewalThresholdUpdateIntervalMs = 15 * 60 * 1000 # 15mins
leaseRenewalIntervalInSeconds
client发送心跳的频率
renewalPercentThreshold
触发自我保护的心跳数比例阈值
renewalThresholdUpdateIntervalMs
多久重置一下心跳阈值
计算公式
Number of heartbeats expected from one client instance / min
factor = 60/leaseRenewalIntervalInSeconds
Number of heartbeats expected from N instances / min
factor * N
Minimum expected heartbeat threshold / min
factor * N * renewalPercentThreshold
源代码
this.expectedNumberOfRenewsPerMin = N * 2;
this.numberOfRenewsPerMinThreshold = (int) (this.expectedNumberOfRenewsPerMin * serverConfig.getRenewalPercentThreshold());
eureka启动时
eureka-core-1.4.12-sources.jar!/com/netflix/eureka/registry/PeerAwareInstanceRegistryImpl.java
@Override
public void openForTraffic(ApplicationInfoManager applicationInfoManager, int count) {
// Renewals happen every 30 seconds and for a minute it should be a factor of 2.
this.expectedNumberOfRenewsPerMin = count * 2;
this.numberOfRenewsPerMinThreshold =
(int) (this.expectedNumberOfRenewsPerMin * serverConfig.getRenewalPercentThreshold());
logger.info("Got " + count + " instances from neighboring DS node");
logger.info("Renew threshold is: " + numberOfRenewsPerMinThreshold);
this.startupTime = System.currentTimeMillis();
if (count > 0) {
this.peerInstancesTransferEmptyOnStartup = false;
}
DataCenterInfo.Name selfName = applicationInfoManager.getInfo().getDataCenterInfo().getName();
boolean isAws = Name.Amazon == selfName;
if (isAws && serverConfig.shouldPrimeAwsReplicaConnections()) {
logger.info("Priming AWS connections for all replicas..");
primeAwsReplicas(applicationInfoManager);
}
logger.info("Changing status to UP");
applicationInfoManager.setInstanceStatus(InstanceStatus.UP);
super.postInit();
}
count为eureka个数，此时expectedNumberOfRenewsPerMin为2(1个注册中心，每30秒发送一次心跳，则每分钟对于每个client，应该发送2次心跳)，numberOfRenewsPerMinThreshold=（int）2*0.85 =1
client注册时
eureka-core-1.4.12-sources.jar!/com/netflix/eureka/registry/AbstractInstanceRegistry.java
public void register(InstanceInfo registrant, int leaseDuration, boolean isReplication) {
try {
read.lock();
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>>();
gMap = registry.putIfAbsent(registrant.getAppName(), gNewMap);
if (gMap == null) {
gMap = gNewMap;
}
}
Lease<InstanceInfo> 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);
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.expectedNumberOfRenewsPerMin > 0) {
// Since the client wants to cancel it, reduce the threshold
// (1
// for 30 seconds, 2 for a minute)
this.expectedNumberOfRenewsPerMin = this.expectedNumberOfRenewsPerMin + 2;
this.numberOfRenewsPerMinThreshold =
(int) (this.expectedNumberOfRenewsPerMin * serverConfig.getRenewalPercentThreshold());
}
}
logger.debug("No previous lease information found; it is new registration");
}
Lease<InstanceInfo> lease = new Lease<InstanceInfo>(registrant, leaseDuration);
if (existingLease != null) {
lease.setServiceUpTimestamp(existingLease.getServiceUpTimestamp());
}
gMap.put(registrant.getId(), lease);
synchronized (recentRegisteredQueue) {
recentRegisteredQueue.add(new Pair<Long, String>(
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();
}
}
其中，重点看这段
synchronized (lock) {
if (this.expectedNumberOfRenewsPerMin > 0) {
// Since the client wants to cancel it, reduce the threshold
// (1
// for 30 seconds, 2 for a minute)
this.expectedNumberOfRenewsPerMin = this.expectedNumberOfRenewsPerMin + 2;
this.numberOfRenewsPerMinThreshold =
(int) (this.expectedNumberOfRenewsPerMin * serverConfig.getRenewalPercentThreshold());
}
}
每注册上一个实例，重新算一下，即
this.expectedNumberOfRenewsPerMin = this.expectedNumberOfRenewsPerMin + 2;
this.numberOfRenewsPerMinThreshold = (int) (this.expectedNumberOfRenewsPerMin * serverConfig.getRenewalPercentThreshold());
总的来说，所有实例都注册上了，就是
this.expectedNumberOfRenewsPerMin = N * 2;
this.numberOfRenewsPerMinThreshold = (int) (this.expectedNumberOfRenewsPerMin * serverConfig.getRenewalPercentThreshold());
计算例子
2个eureka,算在内,factor=6,N:16
leaseRenewalIntervalInSeconds: 10 --> 每分钟6次
this.expectedNumberOfRenewsPerMin = N * 2 = 32 ;
this.numberOfRenewsPerMinThreshold = (int) (32 * 0.85) = (int)27.2 = 27;
2个eureka,算在内,factor=2,N=3
leaseRenewalIntervalInSeconds: 30 --> 每分钟2次
this.expectedNumberOfRenewsPerMin = N * 2 = 6 ;
this.numberOfRenewsPerMinThreshold = (int) (6* 0.85) = (int)5.1 = 5;
对于单机版eureka的，比较特殊，由于openForTraffic这个方法里头
this.expectedNumberOfRenewsPerMin = count * 2;
这里count=1多算了一个实例的心跳次数，所以如下：
1个eureka,不注册,factor=2,N=1
leaseRenewalIntervalInSeconds: 30 --> 每分钟2次
this.expectedNumberOfRenewsPerMin = N * 2 = 2 ;
this.numberOfRenewsPerMinThreshold = (int) (2 * 0.85) = (int)1.7 = 1;
实际显示是3，应该是按N=2算
this.expectedNumberOfRenewsPerMin = N * 2 = 4 ;
this.numberOfRenewsPerMinThreshold = (int) (4 * 0.85) = (int)3.4 = 3;
1个eureka,不注册,factor=2,N=2
leaseRenewalIntervalInSeconds: 30 --> 每分钟2次
this.expectedNumberOfRenewsPerMin = N * 2 = 4 ;
this.numberOfRenewsPerMinThreshold = (int) (4 * 0.85) = (int)3.4 = 3;
实际显示是5，应该是按N=3算
this.expectedNumberOfRenewsPerMin = N * 2 = 6 ;
this.numberOfRenewsPerMinThreshold = (int) (6 * 0.85) = (int)5.1 = 5;
反思源码
由于eureka-core-1.4.12版本里头，你去调整eureka.instance.leaseRenewalIntervalInSeconds的话，代码里头没有相应调整factor，也就是代码还是60/30=2，所以会破坏eureka内置的设计思路。不过对于小型项目来说，没有跨机房，网络没有那么恶劣的话，想避免自我保护导致的服务注册列表不能修改的问题，可以选择以下任一方式尝试下：
- 关闭自我保护eureka.server.enableSelfPreservation=false
- 调小eureka.instance.leaseRenewalIntervalInSeconds，比如设置为10秒
- 调小renewalPercentThreshold，比如改为0.49
另外，还有一个参数可以调整，就是心跳阈值重新计算的周期：
eureka.server.renewalThresholdUpdateIntervalMs = 15 * 60 * 1000 # 15mins
默认是15分钟可以改小一点，比如5分钟=5601000
doc
- 了解Spring Cloud Eureka Server自我保护和更新阈值
- the-mystery-of-eurekas-self-preservation
- spring cloud eureka
- Understanding Spring Cloud Eureka Server self preservation and renew threshold
- Eureka's self-preservation mode never recovers
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