QCIF Code Challenge

Author: Joshua Bowden Date: 16/05/024

Original Code and Instructions from: https://earthly.dev/blog/mongodb-docker/

To run,

Get application code
Set up a MongoDB in a docker container
Run the Flask Python application

1/ Get the application code

git clone https://github.com/jcbowden/qcif_chat.git  
cd qcif_chat  
pip install -r requirements.txt

2/ Setup of MongoDB in Docker

# we use a volume, so data is persisted if container is stopped
sudo docker run -d \
    -p 27017:27017 \
    --name test-mongo \
    -v data-vol:/data/db \
    mongo:latest

# or, with security
docker run -d 
    -p 27017:27017 \
    --name secure-mongo \
    -v mongo-data:/data/db \
    -e MONGODB_INITDB_ROOT_USERNAME=db-user \
    -e MONGODB_INITDB_ROOT_PASSWORD_FILE=/run/secrets/mongo-root-pw \
    mongo:latest

3/ Run the application, exposing all the network interfaces

(change IP address first - currently using localhost in all html template files)

ip -4 address
(find the machines externally acessible address)
cd templates
sed -i -e 's/localhost/<YOUR_IP_ADDRESS>/g' *
cd ..

#  N.B. using --host=0.0.0.0  so we can access the webpages
#  from outside the machine in which it is running.
python -m flask --app app_session --debug run  --host=0.0.0.0

Architecture Description

The application creates a database table of usernames and a separate table of messages. The messages have a Sender (the current user) and a Receiver field, that correspond to a User in the usernames table. The Sender is a user that has his/her User username string added to the sessions['chatuser'] cookies. The Receiver is selected from a list of users that are presented in the chatwith.htmlpage table.
Once a Receiver is chosen by the Sender then the /chatwithme/<Receiver> page is presented. The page presents a text area , that allows a message to be written and then inserted into the database when the (form_a) Send Message button is pressed. A formatted version of the message is also added in a list to the /chatwithme/<Receiver> page. All previous messages between the Sender and the Receiver are presented, and sorted in chronological order using the message time stamp. A user (Sender) can check for messages from the Receiver by pressing the (form_b) Update Messages button, and can also opt to chat with someone else (form_c) Chat with another user button, which brings them back to the chatwith.htmlpage table.
A user can then logout as the current Sender, which removes the session['chatuser'] field from the session dictionary.

Advanced (and untested)

Automatic updates from DB changes

There is probably an easier Javascript polling option to do this, however, there is this option too.
To get changestream, we need MongoDB run as a replica set. Set up a Docker network and connect 3 images to it

docker network create mongoCluster
docker run -d --rm -p 27017:27017 --name mongo1 --network mongoCluster mongo:5 mongod --replSet myReplicaSet --bind_ip localhost,mongo1
docker run -d --rm -p 27018:27017 --name mongo2 --network mongoCluster mongo:5 mongod --replSet myReplicaSet --bind_ip localhost,mongo2
docker run -d --rm -p 27019:27017 --name mongo3 --network mongoCluster mongo:5 mongod --replSet myReplicaSet --bind_ip localhost,mongo3

# Access the MongoDB command line
docker exec -it mongo1 mongosh --eval "rs.initiate({
 _id: \"myReplicaSet\",
 members: [
   {_id: 0, host: \"mongo1\"},
   {_id: 1, host: \"mongo2\"},
   {_id: 2, host: \"mongo3\"}
 ]
})"


# Check that the replica set is running:
docker exec -it mongo2 mongosh --eval "rs.status()"