How do I seed a mongo database using docker-compose?

Question

I am trying to distribute a set of connected applications running in several linked containers that includes a mongo database that is required to:

• be distributed containing some seed data;
• allow users to add additional data.

Ideally the data will also be persisted in a linked data volume container.

I can get the data into the mongo container using a mongo base instance that doesn't mount any volumes (dockerhub image: psychemedia/mongo_nomount - this is essentially the base mongo Dockerfile without the VOLUME /data/db statement) and a Dockerfile config along the lines of:

ADD . /files
WORKDIR /files
RUN mkdir -p /data/db && mongod --fork --logpath=/tmp/mongodb.log && sleep 20 && \
mongoimport  --db testdb --collection testcoll  --type csv --headerline --file ./testdata.csv  #&& mongod --shutdown

where ./testdata.csv is in the same directory (./mongo-with-data) as the Dockerfile.

My docker-compose config file includes the following:

mongo:
  #image: mongo
  build: ./mongo-with-data
  ports:
    - "27017:27017"
  #Ideally we should be able to mount this against a host directory
  #volumes:
  #  - ./db/mongo/:/data/db
  #volumes_from:
  #  - devmongodata

#devmongodata:
#    command: echo created
#    image: busybox
#    volumes: 
#       - /data/db

Whenever I try to mount a VOLUME it seems as if the original seeded data - which is stored in /data/db - is deleted. I guess that when a volume is mounted to /data/db it replaces whatever is there currently.

That said, the docker userguide suggests that: Volumes are initialized when a container is created. If the container’s base image contains data at the specified mount point, that existing data is copied into the new volume upon volume initialization? So I expected the data to persist if I placed the VOLUME command after the seeding RUN command?

So what am I doing wrong?

The long view is that I want to automate the build of several linked containers, and then distribute a Vagrantfile/docker-compose YAML file that will fire up a set of linked apps, that includes a pre-seeded mongo database with a (partially pre-populated) persistent data container.

Answer 1

I do this using another docker container whose only purpose is to seed mongo, then exit. I suspect this is the same idea as ebaxt's, but when I was looking for an answer to this, I just wanted to see a quick-and-dirty, yet straightforward, example. So here is mine:

docker-compose.yml

mongodb:
  image: mongo
  ports:
    - "27017:27017"

mongo-seed:
  build: ./mongo-seed
  links:
    - mongodb

# my webserver which uses mongo (not shown in example)
webserver:
  build: ./webserver
  ports:
    - "80:80"
  links:
    - mongodb

mongo-seed/Dockerfile

FROM mongo

COPY init.json /init.json
CMD mongoimport --host mongodb --db reach-engine --collection MyDummyCollection --type json --file /init.json --jsonArray

mongo-seed/init.json

[
  {
    "name": "Joe Smith",
    "email": "[email protected]",
    "age": 40,
    "admin": false
  },
  {
    "name": "Jen Ford",
    "email": "[email protected]",
    "age": 45,
    "admin": true
  }
]