Flask server in Docker container

[pgraverdy]

In the document, it is stated that all components should be dockerized.

• [x] create a Dockerfile to build the Docker Image containing the Flask server
• [x] add the component in the docker-compose file
• [x] discuss two different solutions for connecting the flask container and the rabbitmq container (i.e., hostname/IP address to use)
• [x] test that the deployment works properly (automatically builds the image if not available)

[azlaanmsamad]

@pgraverdy

• I have added another branch named flask_in_docker where I have dockerised the flask app. I have added the instructions to run it in the readme. It automatically builds image and runs the app.
• Regarding the discussion on two solutions to connect different containers I am adding it in the readme file of this very branch.

Let me know if I should create a PR for this issue.

[azlaanmsamad]

@pgraverdy

Ways to connect containers:

1. Communicating through networking: Using network provided by the docker to connect between two containers. This network can be user modified.
2. By Using Volumes: by writing their files into volumes which can be shared between two containers.

[pgraverdy]

@azlaanmsamad

Regarding the apps in the two containers (flask and rabbitmq) the communication protocol between them is AMQP, so its a networking protocol. There is no shared data/state between them. Hence the two solutions are

• using a dedicated network. between the containers (easy to specify with docker compose) and use the container name defined in the docker compose to communicate (e.g., connect to the rabbitmq server). In this setup, the "IP Address" can be replaced by the container name : if a URL is required for some operation, it would be http://container_name:port/ (e.g., http://rabbitmq_container:15672/ for the dashboard).Docker takes care of the name to IP resolution.
• consider that the ports of the application are mapped to ports on the host. Then entering the IP address of the host with the mapped port will connect to the proper service/application (for HTTP protocol, you can also have a proxy server, on the host or as a container in the docker compose, that redirects based on URL paths.

As a side note, sharing volumes between containers (when relevant) has to be carefully done, You just can't access the files containing the data from a DB from another container (it will definitively create inconsistencies in the database). Sharing a volume for read access is fine, not for write access.

[azlaanmsamad]

@pgraverdy

Okay thank you for the explanation. In case two app containers are using the same database to write files, how do we avoid inconsistency?

[azlaanmsamad]

@pgraverdy

Should I create a PR for this?