SpringBoot in Docker not connecting to Mongo in Docker

Question

I have a Spring Boot Application and developed it with a mongo db which was running in brew services.

To get a connection to the db I just had to put the following into application.properties in Spring Boot

spring.data.mongodb.uri=mongodb://localhost:27017/db

changing the application properties to

spring.data.mongodb.uri=mongodb://mongo:27017/db

didtn't change anything, same Error as before.

Now I'm trying to put the SpringBoot Application and the MongoDB into Docker-Containers, but cant get any connection working.

So this is my Dockerfile in the SpringBoot Application:

FROM openjdk:8-jdk-alpine
VOLUME /tmp
EXPOSE 8080
ADD /build/libs/dg-0.0.1-SNAPSHOT.jar dg-0.0.1-SNAPSHOT.jar
ENTRYPOINT ["java","-Djava.security.egd=file:/dev/./urandom","-jar","/dg-0.0.1-SNAPSHOT.jar"]

This is my Docker-Compose.yml file:

version: '3'

services:

mongo:
 container_name: docker-mongo
 image: mongo:latest
 ports:
   - "27017:27017"
 volumes:
  - ./data/db:/data/db

spring:
 depends_on:
   - mongo
 image:
   docker-spring-http-alpine
 ports:
   - "8080:8080"
 links:
   - mongo

After executing Docker-Compose with

docker-compose up

I get the following error: (this is the actual error message )

2019-07-08 23:10:19.990  INFO 1 --- [localhost:27017] org.mongodb.driver.cluster: Exception in monitor thread while connecting to server localhost:27017


    com.mongodb.MongoSocketOpenException: Exception opening socket
at com.mongodb.internal.connection.SocketStream.open(SocketStream.java:67) ~[mongodb-driver-core-3.8.2.jar!/:na]
at com.mongodb.internal.connection.InternalStreamConnection.open(InternalStreamConnection.java:126) ~[mongodb-driver-core-3.8.2.jar!/:na]
at com.mongodb.internal.connection.DefaultServerMonitor$ServerMonitorRunnable.run(DefaultServerMonitor.java:117) ~[mongodb-driver-core-3.8.2.jar!/:na]
at java.lang.Thread.run(Thread.java:748) [na:1.8.0_212]
Caused by: java.net.ConnectException: Connection refused (Connection refused)
at java.net.PlainSocketImpl.socketConnect(Native Method) ~[na:1.8.0_212]
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350) ~[na:1.8.0_212]
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) ~[na:1.8.0_212]
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) ~[na:1.8.0_212]
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[na:1.8.0_212]
at java.net.Socket.connect(Socket.java:589) ~[na:1.8.0_212]
at com.mongodb.internal.connection.SocketStreamHelper.initialize(SocketStreamHelper.java:64) ~[mongodb-driver-core-3.8.2.jar!/:na]
at com.mongodb.internal.connection.SocketStream.open(SocketStream.java:62) ~[mongodb-driver-core-3.8.2.jar!/:na]
... 3 common frames omitted

Does someone know whats the problem here? In development environment it works like a charm.

Thanks in advance

Adding the following line to the Dockerfile

"-Dspring.data.mongodb.uri=mongodb://mongo:27017/dg"

into Entrypoint like this solved the connection issue

ENTRYPOINT ["java", "-Dspring.data.mongodb.uri=mongodb://mongo:27017/dg","-Djava.security.egd=file:/dev/./urandom","-jar","/dg-0.0.1-SNAPSHOT.jar"]

I was able to get connection to the db without the mentioned line above in the Entrypoint in the Dockerfile. I guess this is if you like to connect your db over "links"

But now I was able to connect over Network, this is my code:

version: '3.6'

services:

 mongo:
 container_name: docker_mongo
 networks:
   - gateway
 ports:
   - "27017:27017"
 hostname: mongo
 image: mongo:latest
 volumes:
   - ./data/db:/data/db

 spring:
 container_name: docker-spring
 networks:
   - gateway
 ports:
   - "8080:8080"
 hostname: spring
 depends_on:
   - mongo
 image: dg-docker-spring-http-alpine-j
 networks:
gateway:
driver: "bridge"

and the following in application properties

spring.data.mongodb.host=docker_mongo
spring.data.mongodb.port=27017
spring.data.mongodb.database=db

So it looks like the connection is working over Network now. The same code did not work with Version 3.0

To prevent SpringBoot to connect automatically to mongo over localhost it's also necessary to exclude MongoAutoConfiguration!

@SpringBootApplication(exclude={MongoAutoConfiguration.class})

Thank you all for your help

Answer 1

EDIT:

I've never done spring-boot development, but the error you are saying is being displayed may very well be unrelated to the mongo issue. However, here is an explanation as to why your mongo-connection is failing:

---

docker-compose creates a virtual network if one hasn't been specified in the file (like in your case).

All your applications run inside of this network, completely isolated from each other. As such, localhost in your spring-boot container actually refers to itself. Meaning your spring-boot application is expecting the mongo instance to be running inside of its container (which its not, it's in a different container).

This would have been fine when both the database and application was running on your laptop's network. But as mentioned, they are now running in the docker-compose network, in complete isolation.

However, docker-compose is really clever! It creates a DNS for each of your containers which uses the service-name (in your case mongo and spring) specified in your docker-compose file to allow for easy access to the containers inside of the network.

So, you should be able to change spring.data.mongodb.uri=mongodb://localhost:27017/dbto spring.data.mongodb.uri=mongodb://mongo:27017/db and that should allow it to connect.

Answer 2

Try the following docker-compose.yml. hostname should fix your problem

version: '3'
services:
  mongo:
    container_name: docker-mongo
    image: mongo:latest
    ports:
     - "27017:27017"
    volumes:
     - ./data/db:/data/db
    hostname: mongo

 spring:
   depends_on:
    - mongo
   image:docker-spring-http-alpine
   ports:
    - "8080:8080"
   hostname: spring
   links:
    - mongo