Data isn't persisted in the database when using MongoDB with Docker volumes? - windows

Question

There is a service that uses mongodb. But when I restart computer or docker machine, no data is stored in the database.
docker-compose.yml:
version: "3"
Services:
...
mongodb:
restart: always
image: mongo:latest
environment:
- MONGO_DATA_DIR=/dockerdata/db
volumes:
- ./dockerdata/db:/data/db
ports:
- 27017:27017
command: mongod
I tried to do database storage on the host, but it didn't help either:
docker-compose.yml:
version: "3"
Services:
...
mongodb:
restart: always
image: mongo:latest
environment:
- MONGO_DATA_DIR=/c/users/frol/mongodata/db
volumes:
- /c/users/frol/mongodata/db:/data/db
ports:
- 27017:27017
command: mongod
If you make a named volume, docker writes an error:
ERROR: for test_mongodb_1 Cannot create container for service mongodb: fa
To mount local volume: mount /c/users/frol/mongodata/db:/mnt/sda1/var/lib/d
ocker/volumes/test_mongodata/_data, flags: 0x1000: no such file or directory
docker-compose.yml:
version: "3"
services:
...
mongodb:
restart: always
image: mongo:latest
environment:
- MONGO_DATA_DIR=/c/users/frol/mongodata/db
volumes:
- mongodata:/data/db
ports:
- 27017:27017
command: mongod
volumes:
mongodata:
driver: local
driver_opts:
type: none
device: /c/users/frol/mongodata/db
o: bind
Host - win 8.1, docker toolbox 19.03.1 installed.
Help me, please, I'm a novice. How do I make sure that the database data isn't lost?

Answer 1

You first attempt would work if you just fix a simple typo in your compose file:
version: "3"
services:
...
mongodb:
restart: always
image: mongo:latest
environment:
- MONGO_DATA_DIR=/data/db # changed
volumes:
- ./dockerdata/db:/data/db
ports:
- 27017:27017
command: mongod
But, since /data/db is the default value of MONGO_DATA_DIR, setting it is pretty redundant.
But I'd prefer to use a named volume, that way the data persists but I don't have to see the "ugly" database storage folder:
version: "3"
services:
...
mongodb:
restart: always
image: mongo:latest
volumes:
- mongodata:/data/db
ports:
- 27017:27017
command: mongod
volumes:
mongodata:

Answer 2

Don't set $MONGO_DATA_DIR; leave it at its default of /data/db.
services:
mongodb:
restart: always
image: mongo:latest
# No need to specifically set $MONGO_DATA_DIR
volumes:
- ./dockerdata/db:/data/db
ports:
- 27017:27017
# No need to override command:
Docker containers have a separate filesystem space from the host filesystem. A typical setup for most databases is to have the database storage in a fixed location inside the container; for MongoDB that's the /data/db directory. You can mount a named volume or filesystem path there, but the code inside the container doesn't know the difference.
If you do set environment variables like $MONGO_DATA_DIR, they need to reflect paths inside the container; they can't directly specify host-system paths. (#ruohola's answer works because it changes the container-filesystem path of the bind mount to match the container-filesystem path in the environment variable; the host ./dockerdata and container /dockerdata paths are totally unrelated.)

Answer 3

As you are defining the data dir explicitly, you need to map the same directory in the volume to persist the data
version: "3"
services:
...
mongodb:
restart: always
image: mongo:latest
environment:
- MONGO_DATA_DIR=/data/db #data directory
volumes:
- ./dockerdata/db:/data/db #same data directory which you defined above
ports:
- 27017:27017
command: mongod