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

Answer 1

Try not defining the ports of Mongo.

version: '3'

services:

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

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

Answer 2

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 3

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