Spring Cloud Eureka Server self preservation and renew threshold - spring

Question

(It is basically two Eureka server and three Eureka client microservices)
I want to remove the following message:
EMERGENCY! EUREKA MAY BE INCORRECTLY CLAIMING INSTANCES ARE UP WHEN THEY'RE NOT. RENEWALS ARE LESSER THAN THRESHOLD AND HENCE THE INSTANCES ARE NOT BEING EXPIRED JUST TO BE SAFE.
error image
Eureka Server1:
spring.application.name=ms-service-discovery-1
server.port=8761
eureka.client.register-with-eureka=false
eureka.client.fetch-registry=false
eureka.server.enableSelfPreservation= true
eureka.instance.leaseRenewalIntervalInSeconds=1
eviction-interval-timer-in-ms: 1000
eureka.server.wait-time-in-ms-when-sync-empty: 1000
eureka.server.responseCacheUpdateIntervalMs: 1000
Eureka Server2:
spring.application.name=ms-service-discovery-2
server.port=8761
eureka.client.register-with-eureka=false
eureka.client.fetch-registry=false
eureka.server.enableSelfPreservation= true
eureka.instance.leaseRenewalIntervalInSeconds=1
eviction-interval-timer-in-ms: 1000
eureka.server.wait-time-in-ms-when-sync-empty: 1000

Answer 1

It's due to Eureka's self-preservation mode. Eureka servers will stop the eviction of all instances if the number of heartbeats renewals is below the expected threshold. The warning in your Eureka servers shows this situation happened.
Please try to adjust the below property. 85% is the default value. First, just try to lower the below property like 0.50
eureka.renewalPercentThreshold=0.85
Alternatively, you can disable self-preservation mode with the below property.
eureka.enableSelfPreservation=false
Note
Basically, all Eureka client unregister itself when it shuts down. If it unregisters itself successfully, the above problem will not happen.
Unfortunately, sometimes the Spring Cloud based Eureka client doesn't unregister itself when it shuts down and the symptom is different based on the Spring Cloud version. Dalston and Edgware release unregister itself well in most cases. But Finchley releases seem not to unregister itself now.
Also, you start to run MANY instances in your Eureka environment, the above message will disappear because just one or two instances shutdown will not reach the threshold.
You can find more information about self-preservation mode here