can`t link mongo docker container - mongodb

Question

I have an image (gepick:latest) with node app created from Dockerfile:
FROM centos:7
# Create app directory
WORKDIR /usr/src/app
RUN curl --silent --location https://rpm.nodesource.com/setup_8.x | bash -
RUN yum install -y nodejs
RUN curl --silent --location https://dl.yarnpkg.com/rpm/yarn.repo | tee /etc/yum.repos.d/yarn.repo
RUN rpm --import https://dl.yarnpkg.com/rpm/pubkey.gpg
RUN yum install -y yarn
RUN yarn
COPY . .
EXPOSE 8080
CMD [ "yarn", "test-matches-collecting-job"]
My goal is run tests in docker. But it requires mongodb
docker run gepick:latest :
...
Mongoose default connection error: MongoError: failed to connect to server [localhost:27017] on first connect [MongoError: connect ECONNREFUSED 127.0.0.1:27017]
...
I tried link mongo:4 images container docker run --link 0d24c3a35d5a gepick:latest but get same error.

Answer 1

When you launch your container using a docker-compose yaml file Docker bridges the containers together and allows you to have it launch the mongo container before other containers which rely on mongo to be active ... try something like this
cat my-docker-compose.yml
version: '3'
services:
my-gepick:
image: gepick:latest
container_name: blah_gepick
restart: always
depends_on:
- loudmongo
volumes:
- /cryptdata5/var/log/blobs:/blobs
- /webapp/enduser/bundle:/tmp
environment:
- MONGO_SERVICE_HOST=loudmongo
- MONGO_SERVICE_PORT=$GKE_MONGO_PORT
- MONGO_URL=mongodb://loudmongo:$GKE_MONGO_PORT/test
- METEOR_SETTINGS=${METEOR_SETTINGS}
- MAIL_URL=smtp://support#${GKE_DOMAIN_NAME}:blah#loudmail:587/
links:
- loudmongo
ports:
- 127.0.0.1:3000:3000
working_dir: /tmp
command: /usr/bin/supervisord -c /etc/supervisor/conf.d/supervisord.conf
loudmongo:
image: mongo
container_name: loud_mongo
restart: always
ports:
- 127.0.0.1:$GKE_MONGO_PORT:$GKE_MONGO_PORT
volumes:
- /cryptdata7/var/data/db:/data/db
so your launch sequence may look like
docker-compose -f /somedir/my-docker-compose.yml pull
docker-compose -f /somedir/my-docker-compose.yml up -d