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 app can't connect to mongodb.

docker-compose file is as follows, am I missing something

version: "3"

services:

  user:
    image: jboss/wildfly
    container_name: "user"
    restart: always
    ports:
      - 8081:8080
      - 65194:65193
    volumes:
      - ./User/target/User.war:/opt/jboss/wildfly/standalone/deployments/User.war
    environment:
      - JAVA_OPTS=-agentlib:jdwp=transport=dt_socket,address=0.0.0.0:65193,suspend=n,server=y -Djava.net.preferIPv4Stack=true
      - MONGO_HOST=localhost
      - MONGO_PORT=27017
      - MONGO_USERNAME=myuser
      - MONGO_PASSWORD=mypass
      - MONGO_DATABASE=mydb
      - MONGO_AUTHDB=admin
    command: >
      bash -c "/opt/jboss/wildfly/bin/add-user.sh admin Admin#007 --silent && /opt/jboss/wildfly/bin/standalone.sh -b 0.0.0.0 -bmanagement 0.0.0.0"
    links:
      - mongo

  mongo:
    image: mongo:4.0.10
    container_name: mongo
    restart: always
    volumes:
       - ./assets:/docker-entrypoint-initdb.d/
    environment:
      - MONGO_INITDB_ROOT_USERNAME=myuser
      - MONGO_INITDB_ROOT_PASSWORD=mypass
    ports:
      - 27017:27017
      - 27018:27018
      - 27019:27019

Edit

I'm also confused about the following.

links:
  - mongo

depends_on:
  - mongo

thanks, I'm also confused about links and depends_on, mind explaining me a bit, thanks — AppDeveloper
– AppDeveloper, Commented Jul 28, 2019 at 13:18

JRichardsz · Accepted Answer · 2022-01-03 01:51:44Z

2

At 2019 July, official docker documentation :

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

Solution #1 : environment file before start

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

The following approach helped me in these scenarios:

Your docker-compose.yml has several containers with complex 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

1.- 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 MY_TOKEN=123456

2.- Use the env variables in your docker-compose.yml

container A

app_who_needs_mongo:
  environment:
    - MONGO_HOST=$MACHINE_HOST
    - MONGO_PASSWORD=$MONGO_PASSWORD
    - TOKEN=$MY_TOKEN
    - LOG_PATH=$GLOBAL_LOG_PATH/app1

container B

app_who_needs_another_db_in_same_host:
  environment:
    - POSTGRESS_HOST=$MACHINE_HOST
    - LOG_PATH=$GLOBAL_LOG_PATH/app1

3.- Startup your containers

Just add source before docker-compose commands:

source /env/company_environments
docker-compose up -d

Solution #2 : host.docker.internal

https://stackoverflow.com/a/63207679/3957754

Basically use a feature of docker in which host.docker.internal could be used as the ip of the server in which your docker-compose has started several containers

edited Jan 3, 2022 at 1:51

answered Jul 28, 2019 at 13:53

JRichardsz

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4 Comments

AppDeveloper Over a year ago

thanks, can you please also explain depends_on and link property?

JRichardsz Over a year ago

depends_on is like your <dependency> in java maven. app A with depends_on app B, does not start if app B is wrong or at first attempt, docker-compose start app B before app A. links is a way to reach a hostname if value is identical to the alias, or the service name. Links is deprecated!!

AppDeveloper Over a year ago

so I should use depends_on: -mongo and delete links, hopefully it wont break? I've env variables set for mongo connection.

JRichardsz Over a year ago

I edited my answer, please check it. Also, links are deprecated!. depends_on: mongo just starts the mongo process before your java process, but does not configure the hostname of mongo in your java app.

ykit9 · Accepted Answer · 2019-07-28 13:09:21Z

0

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

answered Jul 28, 2019 at 13:09

ykit9

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2 Comments

AppDeveloper Over a year ago

thanks, yes it worked. I'm also confused about links: - mongo and depends_on: - mongo, see my edit please

JRichardsz Over a year ago

links is deprecated docs.docker.com/compose/compose-file/#links

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docker-compose java application connection to mongodb

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Solution #1 : environment file before start

Solution #2 : host.docker.internal

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