Spring Microservices Cannot Connect Via Eureka When Inside Docker Container

So I have been trying to fix this problem, and 4 days later I still haven’t been able to find a solution. I have built an API Gateway using Spring Boot which acts as a Eureka Server via Zuul, and I have a microservice which acts as a Eureka Client. When I run it locally within Intellij, everything works perfect and they discover and connect to eachother. When they are in a container however, I get the following exception:

2022-05-16 12:42:49.087 WARN 1 — [nfoReplicator-0] c.n.d.s.t.d.RetryableEurekaHttpClient : Request execution failed
with m essage: java.net.UnknownHostException: http 2022-05-16
12:42:49.088 WARN 1 — [nfoReplicator-0] com.netflix.discovery.DiscoveryClient :
DiscoveryClient_USER/8322e6fdb2 35:user:8082 – registration failed
Cannot execute request on any known server

com.netflix.discovery.shared.transport.TransportException: Cannot
execute request on any known server
at com.netflix.discovery.shared.transport.decorator.RetryableEurekaHttpClient.execute(RetryableEurekaHttpClient.java:112
) ~[eureka-client-1.9.17.jar!/:1.9.17] at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56
) ~[eureka-client-1.9.17.jar!/:1.9.17] at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$1.execute(EurekaHttpClientDecorator.java:5
9) ~[eureka-client-1.9.17.jar!/:1.9.17] at com.netflix.discovery.shared.transport.decorator.SessionedEurekaHttpClient.execute(SessionedEurekaHttpClient.java:77)
~[eureka-client-1.9.17.jar!/:1.9.17] at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56
) ~[eureka-client-1.9.17.jar!/:1.9.17] at com.netflix.discovery.DiscoveryClient.register(DiscoveryClient.java:850)
~[eureka-client-1.9.17.jar!/:1.9.17] at com.netflix.discovery.InstanceInfoReplicator.run(InstanceInfoReplicator.java:121)
[eureka-client-1.9.17.jar!/:1.9.17] at com.netflix.discovery.InstanceInfoReplicator$1.run(InstanceInfoReplicator.java:101)
[eureka-client-1.9.17.jar!/:1.9.1 7] at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
[na:1.8.0_332] at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_332] at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180)
[na:1.8.0_332] at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
[na:1.
8.0_332] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
[na:1.8.0_332] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
[na:1.8.0_332] at java.lang.Thread.run(Thread.java:750) [na:1.8.0_332]

My Eureka Server looks like this:

Docker-compose.yaml

version: '3.8'
services:

  kwettergateway-docker:
    image: user/kwettergateway
    ports:
      - "8761:8761"
  userservice-docker:
    image: user/userservice
    ports:
      - "8082:8082"
    links:
      - kwettergateway-docker

Application.properties:

server.port=8761

#Gateway properties
spring.application.name=gateway
eureka.instance.prefer-ip-address=true
eureka.client.register-with-eureka=false
eureka.client.fetch-registry=false
eureka.server.wait-time-in-ms-when-sync-empty=0
zuul.prefix=/api
zuul.routes.user.path=/user/**
zuul.routes.user.url=http://localhost:8082/

Dockerfile:

FROM openjdk:8
EXPOSE 8080
ADD target/kwettergateway-docker.jar kwettergateway-docker.jar
ENTRYPOINT ["java", "-jar", "/kwettergateway-docker.jar"]

My Eureka Client looks like this:

Application.properties:

server.port=8082

#Gateway properties
spring.application.name=user
eureka.instance.prefer-ip-address=true
eureka.client.register-with-eureka=true
eureka.client.fetch-registry=true
eureka.client.serviceUrl.defaultZone=http://localhost:8761/eureka/