Spring Cloud - Eureka Zone Awareness

Eureka also supports the concept of zone awareness. Zone awareness as a concept is very useful when we have a cluster across different geographies. Say, we get an incoming request for a service and we need to choose the server which should service the request. Instead of sending and processing that request on a server which is located far, it is more fruitful to choose a server which is in the same zone. This is because, network bottleneck is very common in a distributed application and thus we should avoid it.

Let us now try to setup Eureka clients and make them Zone aware. For doing that, let us add application-za.yml

spring:
   application:
      name: customer-service
server:
   port: ${app_port}
eureka:
   instance:
      metadataMap:
         zone: ${zoneName}
   client:
      serviceURL:
         defaultZone: http://localhost:8900/eureka

Let us now recompile our Eureka client project.

[INFO] Scanning for projects...
[INFO] 
[INFO] [1m------------------< [0;36mcom.tutorialspoint:eurekaclient[0;1m >-------------------[m
[INFO] [1mBuilding eurekaclient 0.0.1-SNAPSHOT[m
[INFO]   from pom.xml
[INFO] [1m--------------------------------[ jar ]---------------------------------[m
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[INFO] [1m--- [0;32mresources:3.3.1:resources[m [1m(default-resources)[m @ [36meurekaclient[0;1m ---[m
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[INFO] Copying 0 resource from src\main\resources to target\classes
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[INFO] [1m--- [0;32mcompiler:3.14.0:compile[m [1m(default-compile)[m @ [36meurekaclient[0;1m ---[m
[INFO] Recompiling the module because of [1madded or removed source files[m.
[INFO] Compiling 2 source files with javac [debug parameters release 21] to target\classes
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[INFO] skip non existing resourceDirectory D:\Projects\eurekaclient\src\test\resources
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[INFO] [1m--- [0;32mcompiler:3.14.0:testCompile[m [1m(default-testCompile)[m @ [36meurekaclient[0;1m ---[m
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[INFO] Compiling 1 source file with javac [debug parameters release 21] to target\test-classes
[INFO] 
[INFO] [1m--- [0;32msurefire:3.5.4:test[m [1m(default-test)[m @ [36meurekaclient[0;1m ---[m
[INFO] Using auto detected provider org.apache.maven.surefire.junitplatform.JUnitPlatformProvider
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[INFO] -------------------------------------------------------
[INFO]  T E S T S
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[INFO] Running com.tutorialspoint.eurekaclient.[1mEurekaclientApplicationTests[m
17:45:05.033 [main] INFO org.springframework.test.context.support.AnnotationConfigContextLoaderUtils -- Could not detect default configuration classes for test class [com.tutorialspoint.eurekaclient.EurekaclientApplicationTests]: EurekaclientApplicationTests does not declare any static, non-private, non-final, nested classes annotated with @Configuration.
17:45:05.150 [main] INFO org.springframework.boot.test.context.SpringBootTestContextBootstrapper -- Found @SpringBootConfiguration com.tutorialspoint.eurekaclient.EurekaclientApplication for test class com.tutorialspoint.eurekaclient.EurekaclientApplicationTests

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/

 :: Spring Boot ::                (v3.5.6)

2025-10-07T17:45:05.775+05:30  INFO 32456 --- [eurekaclient] [           main] c.t.e.EurekaclientApplicationTests       : Starting EurekaclientApplicationTests using Java 21.0.6 with PID 32456 (started by mahes in D:\Projects\eurekaclient)
2025-10-07T17:45:05.776+05:30  INFO 32456 --- [eurekaclient] [           main] c.t.e.EurekaclientApplicationTests       : No active profile set, falling back to 1 default profile: "default"
2025-10-07T17:45:06.558+05:30  INFO 32456 --- [eurekaclient] [           main] o.s.cloud.context.scope.GenericScope     : BeanFactory id=61598357-3a65-347a-b2c3-05819b0e284d
2025-10-07T17:45:07.313+05:30  INFO 32456 --- [eurekaclient] [           main] DiscoveryClientOptionalArgsConfiguration : Eureka HTTP Client uses RestTemplate.
2025-10-07T17:45:07.348+05:30  WARN 32456 --- [eurekaclient] [           main] iguration$LoadBalancerCaffeineWarnLogger : Spring Cloud LoadBalancer is currently working with the default cache. While this cache implementation is useful for development and tests, it's recommended to use Caffeine cache in production.You can switch to using Caffeine cache, by adding it and org.springframework.cache.caffeine.CaffeineCacheManager to the classpath.
2025-10-07T17:45:07.377+05:30  INFO 32456 --- [eurekaclient] [           main] o.s.c.n.eureka.InstanceInfoFactory       : Setting initial instance status as: STARTING
2025-10-07T17:45:07.425+05:30  INFO 32456 --- [eurekaclient] [           main] com.netflix.discovery.DiscoveryClient    : Initializing Eureka in region us-east-1
2025-10-07T17:45:07.425+05:30  INFO 32456 --- [eurekaclient] [           main] c.n.d.s.r.aws.ConfigClusterResolver      : Resolving eureka endpoints via configuration
2025-10-07T17:45:07.440+05:30  INFO 32456 --- [eurekaclient] [           main] com.netflix.discovery.DiscoveryClient    : Disable delta property : false
2025-10-07T17:45:07.452+05:30  INFO 32456 --- [eurekaclient] [           main] com.netflix.discovery.DiscoveryClient    : Single vip registry refresh property : null
2025-10-07T17:45:07.452+05:30  INFO 32456 --- [eurekaclient] [           main] com.netflix.discovery.DiscoveryClient    : Force full registry fetch : false
2025-10-07T17:45:07.452+05:30  INFO 32456 --- [eurekaclient] [           main] com.netflix.discovery.DiscoveryClient    : Application is null : false
2025-10-07T17:45:07.452+05:30  INFO 32456 --- [eurekaclient] [           main] com.netflix.discovery.DiscoveryClient    : Registered Applications size is zero : true
2025-10-07T17:45:07.452+05:30  INFO 32456 --- [eurekaclient] [           main] com.netflix.discovery.DiscoveryClient    : Application version is -1: true
2025-10-07T17:45:07.452+05:30  INFO 32456 --- [eurekaclient] [           main] com.netflix.discovery.DiscoveryClient    : Getting all instance registry info from the eureka server
2025-10-07T17:45:08.103+05:30  INFO 32456 --- [eurekaclient] [           main] com.netflix.discovery.DiscoveryClient    : The response status is 200
2025-10-07T17:45:08.106+05:30  INFO 32456 --- [eurekaclient] [           main] com.netflix.discovery.DiscoveryClient    : Starting heartbeat executor: renew interval is: 30
2025-10-07T17:45:08.108+05:30  INFO 32456 --- [eurekaclient] [           main] c.n.discovery.InstanceInfoReplicator     : InstanceInfoReplicator onDemand update allowed rate per min is 4
2025-10-07T17:45:08.108+05:30  INFO 32456 --- [eurekaclient] [           main] com.netflix.discovery.DiscoveryClient    : Discovery Client initialized at timestamp 1759839308108 with initial instances count: 0
2025-10-07T17:45:08.108+05:30  INFO 32456 --- [eurekaclient] [           main] o.s.c.n.e.s.EurekaServiceRegistry        : Registering application EUREKACLIENT with eureka with status UP
2025-10-07T17:45:08.108+05:30  INFO 32456 --- [eurekaclient] [           main] com.netflix.discovery.DiscoveryClient    : Saw local status change event StatusChangeEvent [timestamp=1759839308108, current=UP, previous=STARTING]
2025-10-07T17:45:08.108+05:30  INFO 32456 --- [eurekaclient] [foReplicator-%d] com.netflix.discovery.DiscoveryClient    : DiscoveryClient_EUREKACLIENT/Home:eurekaclient: registering service...
2025-10-07T17:45:08.122+05:30  INFO 32456 --- [eurekaclient] [           main] c.t.e.EurekaclientApplicationTests       : Started EurekaclientApplicationTests in 2.678 seconds (process running for 3.698)
Mockito is currently self-attaching to enable the inline-mock-maker. This will no longer work in future releases of the JDK. Please add Mockito as an agent to your build as described in Mockito's documentation: https://javadoc.io/doc/org.mockito/mockito-core/latest/org.mockito/org/mockito/Mockito.html#0.3
2025-10-07T17:45:08.272+05:30  INFO 32456 --- [eurekaclient] [foReplicator-%d] com.netflix.discovery.DiscoveryClient    : DiscoveryClient_EUREKACLIENT/Home:eurekaclient - registration status: 204
OpenJDK 64-Bit Server VM warning: Sharing is only supported for boot loader classes because bootstrap classpath has been appended
WARNING: A Java agent has been loaded dynamically (C:\Users\mahes\.m2\repository\net\bytebuddy\byte-buddy-agent\1.17.7\byte-buddy-agent-1.17.7.jar)
WARNING: If a serviceability tool is in use, please run with -XX:+EnableDynamicAgentLoading to hide this warning
WARNING: If a serviceability tool is not in use, please run with -Djdk.instrument.traceUsage for more information
WARNING: Dynamic loading of agents will be disallowed by default in a future release
[INFO] [1;32mTests run: [0;1;32m1[m, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 3.790 s -- in com.tutorialspoint.eurekaclient.[1mEurekaclientApplicationTests[m
[INFO] 
[INFO] Results:
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[INFO] [1;32mTests run: 1, Failures: 0, Errors: 0, Skipped: 0[m
[INFO] 
[INFO] 
[INFO] [1m--- [0;32mjar:3.4.2:jar[m [1m(default-jar)[m @ [36meurekaclient[0;1m ---[m
[INFO] Building jar: D:\Projects\eurekaclient\target\eurekaclient-0.0.1-SNAPSHOT.jar
[INFO] 
[INFO] [1m--- [0;32mspring-boot:3.5.6:repackage[m [1m(repackage)[m @ [36meurekaclient[0;1m ---[m
[INFO] Replacing main artifact D:\Projects\eurekaclient\target\eurekaclient-0.0.1-SNAPSHOT.jar with repackaged archive, adding nested dependencies in BOOT-INF/.
[INFO] The original artifact has been renamed to D:\Projects\eurekaclient\target\eurekaclient-0.0.1-SNAPSHOT.jar.original
[INFO] 
[INFO] [1m--- [0;32minstall:3.1.4:install[m [1m(default-install)[m @ [36meurekaclient[0;1m ---[m
[INFO] Installing D:\Projects\eurekaclient\pom.xml to C:\Users\mahes\.m2\repository\com\tutorialspoint\eurekaclient\0.0.1-SNAPSHOT\eurekaclient-0.0.1-SNAPSHOT.pom
[INFO] Installing D:\Projects\eurekaclient\target\eurekaclient-0.0.1-SNAPSHOT.jar to C:\Users\mahes\.m2\repository\com\tutorialspoint\eurekaclient\0.0.1-SNAPSHOT\eurekaclient-0.0.1-SNAPSHOT.jar
[INFO] [1m------------------------------------------------------------------------[m
[INFO] [1;32mBUILD SUCCESS[m
[INFO] [1m------------------------------------------------------------------------[m
[INFO] Total time:  9.863 s
[INFO] Finished at: 2025-10-07T17:45:11+05:30
[INFO] [1m------------------------------------------------------------------------[m

For execution, we will have two service instances running. To do that, let's open two shells and then execute the following command on one shell −

java -jar .\target\eurekaclient-0.0.1-SNAPSHOT.jar --app_port=8080 --zone_name=USA --spring.config.location=classpath:application-za.yml

And execute the following on the other shell −

java -jar .\target\eurekaclient-0.0.1-SNAPSHOT.jar --app_port=8081 --zone_name=EU --spring.config.location=classpath:application-za.yml

We can go back to the dashboard to verify that the Eureka Server registers the zone of the services. As seen in the following image, we have two availability zones instead of 1, which we have been seeing till now.

Now, any client can look at the zone it is present in. Say the client is located in USA, it would prefer the service instance of USA. And it can get the zone information from the Eureka Server.