Why Mongo With Docker
"Decoupled" From The Host
The mongo instance, itself, is not explicitly on a host. For a group of software engineers building content, this can be important when people may end up with different versions of the db, different versions of the cli, different data, different auth setup, etc.
DB Setup Explicitly Defined in Code
Does the DB instance require authentication? See the code.
Is there 'seed' type data that we can assume we need for our setup? See the code.
What Version of of mongod are we using? See the code.
What version of the cli tool are we using? See the code.
Freedom to decide on Statefulness
Does one person on the team want to retain some data & another person on the team want a "fresh" instance of data? Putting Mongo up in a container allows for some quick-win flexibility between a "stateless" instance and an instance which uses data that is mounted from "outside" the container, making a "stateful" instance more available.
Running Mongo In Docker
First, download docker. Docker unlocks the "magic" for making the development environment similar across hosts.
Pulling and Starting a Mongo Instance
- Pull An Image: an officially supported image will get pulled as an image onto the host by using the docker cli. Enter this into the terminal
- Run The Image as a Container: with an image stored on your machine, docker can use the image and run it as an ephemeral container
- Use the Mongo CLI: run a few commands to interact with the db
Pull An Image
This will "pull" the docker image onto your host machine, assumedly a laptop or desktop. Run this in a command line terminal:
docker pull mongo:4dockeris the cli toolpullis the command we are running withdocker(see the docs for more on that)mongo:4is the tagged image that we are pulling: here, we are pulling the highest "major"4.*.*version of mongo, which at the time of writing looks like it is using4.4.10
To inspect that this image is, indeed, downloaded to your machine, run docker image ls -a in the terminal and you should see something like:
REPOSITORY TAG IMAGE ID CREATED SIZE
mongo 4 29915542a1ef 4 weeks ago 413MBRun the Image as a Container
This will start a mongo instance from the docker image mongo:4. Run this in a terminal:
docker run --rm --name mongobox mongo:4docker, again, is the cli toolrunis the command we are running withdocker--rmwill automatically remove the container when it exits, a "cleanup" command--name mongoboxgives the container a "friendly" name: docker automatically could generate a random friendly name without this command. This is a chosen namemongoboxmongo:4tells docker to use that image+tag combo to use as the "base" for the container
Running that will start a docker container that runs a mongo instance on startup. the Terminal should return a bunch of logs about the mongo instance running. This mongo instance is tightly coupled to the current terminal window.
NOTE: Another flag is often used to run the mongo instance "in the background" so that the terminal window that ran the above docker run command can be used for other terminal commands. the flag here is -d, which runs the container in "detached" mode && could be integrated into the run command like docker run --rm -d --name mongobox mongo:4. Running the container this way will not output the mongo logs, only the container ID.
To inspect that this container is running (without the -d flag), the terminal should output the mongo instance logs. This shows the successful startup of the container. Another way to inspect running containers in docker is to use a new terminal window and type docker container ls -a. The output should look something like:
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
a474b4331069 mongo:4 "docker-entrypoint.s…" About a minute ago Up About a minute 27017/tcp mongoboxthis shows the container ID, the image used to run the container, and some more details about the container.
Access the DB through the Mongo CLI
Start a shell in the running mongo container
Start a terminal instance inside the mongo container. In a new terminal, run
docker exec -it mongobox bashdockeris the cli tool being usedexecwill run a command in a container-itis a cmbo of the-iand-tflags, where-ilets us as devs interact with the container through the stdin, or command-line input, and the-tlets us as devs see a terminal shell of the container in our terminalmongoboxis the friendly name of the container we are using to run this command onbashis the command that will be run in the container
Use the Mongo CLI to interact with mongo
After that command, the terminal will be a 'virtual' terminal inside the running mongo container. With this 'virtual' terminal instance running, run
mongo
This will start the mongo cli. A handful of lines should print to the terminal, showing that the mongo cli has started, starting with something like
MongoDB shell version v4.4.10
connecting to: mongodb://127.0.0.1:27017/?compressors=disabled&gssapiServiceName=mongodb
Implicit session: session { "id" : UUID("5ee2c722-2500-4d69-bbd3-17b36ff1347a") }
MongoDB server version: 4.4.10Now, mongo commands will interact with mongo db. Try things like
show dbs
# should print 3 dbs that come with a default instance of mongo
use water
# will tell mongo to "use" a new db called "water"
db
# will print `db`, showing that commands run against the `db` will run against the `water` db
db.melon.insertOne({juice:'box'})
# will insert a single document into a "melon" collection in the "water" database
db.melon.find()
# should return something like
{ "_id" : ObjectId("61c269050bc2632999960793"), "juice" : "box" }
To exit the mongo cli, press Ctrl + C.
To exit the shell into the docker container, type exit and press enter/return.
To stop the running container, navigate to the terminal that is running the container & type Ctrl + C. A handful of logs will print to the terminal. The last line should read something like
{"t":{"$date":"2021-01-01T23:56:53.988+00:00"},"s":"I", "c":"CONTROL", "id":23138, "ctx":"SignalHandler","msg":"Shutting down","attr":{"exitCode":0}}