docker-compose java application connection to mongodb

Question

2 Containers, one Java application and the second mongodb.

If I run my java app locally and mongodb in a container, it connects but if both run inside a container, java

Answer 1

You probably cant connect because you set the MONGO_HOST as localhost and mongo is a linked service.

In order to use linked services network, you must specify the MONGO_HOST as the name of the service - mongo, like that:

 MONGO_HOST=mongo

Answer 2

At 2019 July, official docker documentation :

Source: https://docs.docker.com/compose/compose-file/#links

Possible solution

Centralize all configurations in a file with environment variables and execute it before docker-compose up

The following approach helped me in this scenarios:

• If you need to run several docker-compose.yml files with dependencies between them
• Some of your services in your docker-compose needs to connect to another process in the same machine. This process could be a docker container or not.
• You need to share variables between several docker-compose files like host, passwords, etc

Steps

Create one file to centralize configurations

This file could be named: /env/company_environments with extension or not.

export MACHINE_HOST=$(hostname -I | awk '{print $1}')
export GLOBAL_LOG_PATH=/my/org/log
export MONGO_PASSWORD=mypass
export ANOTHER_GLOBAL_VARIABLE=123456

docker-compose A

app1:
  environment:
    - MONGO_HOST=$MACHINE_HOST
    - MY_TOKEN=$ANOTHER_GLOBAL_VARIABLE

docker-compose B

app2:
  environment:
    - LOG_PATH=$GLOBAL_LOG_PATH
    - MONGO_PASSWORD=$MONGO_PASSWORD
    - NOT_DOCKER_POSTGRESS_JDBC_URL_IN_SAME_MACHINE=jdbc:postgresql://$MACHINE_HOST/database

Startup your apps

Just add source before docker-compose commands:

source /env/company_environments
docker-compose up -d

If you have another docker-compose.yml file , you just need to execute the same commands in the folder of your another docker-compose.yml:

source /env/company_environments
docker-compose up -d