Understanding Docker Volumes in-depth with real-time scenarios. Where the MongoDB is the backend tier Database and frontend web application using - Mongo-Express container.
Use Case 1: MongoDB container without volume observe what happens to the data.
Use Case 2: After attaching volume = persistence - confirm re-create containers data persist
Use Case 3: Database containerversion changes does not impacts the Data persisted
Let's start the experiment on data persistance.
 |
| Docker Volume deep dive - MongoDB persistant |
To share the sensitive data we use network isolation, which is already discussed in Docker Networks post.
# Create Network docker network create mynetNow let's use this mynet throughout all our use-case examples. MongoDB Connect to Mongo-express which is a member in the same network so that it can access the database
Use Case 1: MongoDB Without any volume - Non Persistence
MongoDB Container without any persistance storage :
docker run -d --name mongodb01 --network mynet \
-e MONGO_INITDB_ROOT_USERNAME=admin \
-e MONGO_INITDB_ROOT_PASSWORD="vybhavatechnologies" mongo
Aa we have not mentioned any tag after mongo so it will pull the latest mongo image from the docker hub. Validate mongodb container
docker ps -a
If you don't see running docker container for mongodb check the logs using
docker logs mangodb -fhere -f is optional to see the floating log content. If all good, we can run the next container Mongo-express
# Web client - based on nodejs express fraework package
docker run -it --rm \
--network mynet \
--name mongo-express \
-p 8081:8081 \
-e ME_CONFIG_OPTIONS_EDITORTHEME="ambiance" \
-e ME_CONFIG_MONGODB_SERVER="mongodb01" \
-e ME_CONFIG_BASICAUTH_USERNAME="admin" \
-e ME_CONFIG_BASICAUTH_PASSWORD="vybhavatechnologies" \
mongo-express
This container is for the use-and-throw container so used --rm in the above command.
On the browser open the mongoexpress web application for example as : http://192.168.33.250:8081/ Enter the user: admin and password as vybhavatechnologies
 |
| Build Stateful application with MongoDB container |
after login to the mongo-express webpage and perform above steps looks as
 |
| Collection adding document on mongo-express |
Use Case 2: Docker Volume attached to mongo container
In Use Case 2 let's create the volume and use it while creating the mongo database container:
docker volume create myvol docker volume lsNow let's use the volume which is created as named volume on the Docker host machine. Attach it to the MongoDB container.
docker run -d --name mongodb02 --network mynet \
-v myvol:/data/db \
-e MONGO_INITDB_ROOT_USERNAME=admin \
-e MANGO_INITDB_ROOT_PASSWORD="vybhavatechnologies" mongo:4.4.5-bionic
This time image tag I'm using mongo:4.4.5-bionic, I've tried windows server but it didn't work!
# Check the contianer up
docker ps
# Web client - nodejs express
docker run -it --rm \
--network mynet \
--name mongo-express \
-p 8081:8081 \
-e ME_CONFIG_OPTIONS_EDITORTHEME="ambiance" \
-e ME_CONFIG_MONGODB_SERVER="mongodb02" \
-e ME_CONFIG_BASICAUTH_USERNAME="admin" \
-e ME_CONFIG_BASICAUTH_PASSWORD="vybhavatechnologies" \
mongo-express
Now let's add documents for each student data[
{ "name": "Vignesh", "Course": "Automations"},
{ "name": "Srinivas", "Course": "AWS Solutions"},
{ "name": "Abhijoy", "Course": "WebLogic"},
{ "name": "Shammi", "Course": "Continerized Solutions"},
{ "name": "Rajsekhar", "Course": "Microsoft Azure DevOps"},
{ "name": "Srikant", "Course": "DB Solutions"},
{ "name": "Viswasri", "Course": "AWS DevOps Solutions"},
{ "name": "Melvin", "Course": "DevOps Solutions"}
]
Now run the removal of containers, add the following alias to .bashrc your docker host machine.
alias dc='docker rm -v -f $(docker ps -aq)' dc docker ps -a # confirm all containers removedNow run the same steps to create the mongodb02 and mongoexpress containers check the data exists and now try to add new document:
{
_id: ObjectId(),
"name": 'Pranavsai',
"Course": 'Analytics'
}
 |
| Document collection added to MongoDB |
 |
| MongoDB with Volume |
The data volume attached so we can re-start the container any time number of times !!!
Use Case 3: Database container version changes do not impact Data persistence
In this Use Case 3 experiment, I thought of taking MongoDB 3 and MongoDB 4 version images. But unfortunately, it didn't work for me the issue was with the version 3 image. So this experiment we can do with the same major version 4 and it's sub-versions then it is compatible to test this use-case.
docker run -d --name mongodb03 --network mynet \
-v myvol:/data/db \
-e MONGO_INITDB_ROOT_USERNAME=admin \
-e MONGO_INITDB_ROOT_PASSWORD="vybhavatechnologies" mongo:4
The rest of the steps are the same as the above use case 2
We can pick the latest version (say n) then before version (n-1 if exists) but here is the current (year 2021) mongo version tags are here:
 |
| Docker Hub mongo DB image tags |
