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Intro to DevOps - Week 2 Project Starter Code

Goal

Containerize two Flask web services and use Docker Compose to orchestrate them

For our week 2 project, we will be containerizing two Flask apps, one generates a Random Quote, and the other service consumes this and displays it on a neat front end.

Then we shall be using Docker Swarm to orchestrate the services to achieve our end goal. This exercise will help us understand a real-world use case of Docker and Docker Swarm better.

Prerequisites


Basic knowledge of programming and APIs is needed.

The tutorial on how to start a Docker Container is here - https://docs.docker.com/language/python/build-images/

Environment Setup - Things needed to run Project 2

Install Docker Desktop from here - https://docs.docker.com/desktop/. Choose the distribution of your choice but we will be using Windows. Docker compose, the CLI tools come along with Docker Desktop.

Download the starter file from here - (https://github.com/sb2nov/corise-zignite-devops-cc)

Test if Docker is installed by running the following command in the terminal

docker run hello-world

If everything is installed right you get a response 'Hello from Docker! We are all good to go, let's start off our Week 2 project then!

Steps

Download or Clone the repo https://github.com/sb2nov/corise-zignite-devops-cc/tree/starter_code

Create a Docker File within the cloned Repository

vim Dockerfile

The Python application directory structure should now look like the following:

quote_gen
|____ static
|____ templates
|____ app.py
|____ requirements.txt
|____ Dockerfile
quote_disp
|____ static
|____ templates
|____ app.py
|____ requirements.txt
|____ Dockerfile

Let's create a basic container in each of the directories

FROM python:3.8-slim-buster
COPY . /app
WORKDIR /app
RUN pip install -r requirements.txt
ENTRYPOINT [ "python" ]
CMD [ "app.py" ]

Let's see what each of these commands means -


FROM python - gets a Python distribution from Docker Images

WORKDIR Changes the working directory

COPY Copies the content of Workdir into a new directory

Build the Docker Images -

cd quote_gen
docker build --tag quote-gen-service .
cd quote_disp
docker build --tag quote-disp-service .

Run Docker Container

With the Docker images created, let’s get the containers up and running

cd quote_gen
docker run --name quote-gen-container -p 84:84 quote-gen-service
cd quote_disp
docker run --name quote-disp-container -p 85:85 quote-disp-service

Let’s run docker container ls to get a list of containers created

Create Docker Network

docker network create quote-network

and running the followng command

docker network inspect quote-network

Let's add our containers to the quote-network

docker network connect quote-network quote-gen-container
docker network connect quote-network quote-disp-container
docker network inspect quote-network

You see the following output -

[
    {
        "Name": "quote-network",
        "Id": "999c81eb87c4b687921ea474abd1e59875447a96d2477ae190dcccc40f882d8a",
        "Created": "2023-04-24T04:45:15.9081804Z",
        "Scope": "local",
        "Driver": "bridge",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": {},
            "Config": [
                {
                    "Subnet": "172.19.0.0/16",
                    "Gateway": "172.19.0.1"
                }
            ]
        },
        "Internal": false,
        "Attachable": false,
        "Ingress": false,
        "ConfigFrom": {
            "Network": ""
        },
        "ConfigOnly": false,
        "Containers": {
            "2636f9d91e5468029981d499fc7e0b46a204d8fc3b16e5e7e6e912651ce8dd4a": {
                "Name": "quote-disp-container",
                "EndpointID": "a4eb7320b1585b43a10499a73059e8f50fb8d5e33f9aee433b1b7e5e0b1dee85",
                "MacAddress": "02:42:ac:13:00:03",
                "IPv4Address": "172.19.0.3/16",
                "IPv6Address": ""
            },
            "557e1ff9f220704ad9f76d94ebe5d3c433dc20ed44798831af6f2bfe68176583": {
                "Name": "quote-gen-container",
                "EndpointID": "191f2b22ec8a92256d47b152a06eeaeead9f05a13799f48d43d9c5410daceebb",
                "MacAddress": "02:42:ac:13:00:02",
                "IPv4Address": "172.19.0.2/16",
                "IPv6Address": ""
            }
        },
        "Options": {},
        "Labels": {}
    }
]

Let's see if the dockers are communicating

StatusCode        : 200
StatusDescription : OK
Content           : <link rel="stylesheet" href="/static/css/style.css">
                    <title>Docker App Quote </title>
                    <div class="screen">
                      <div class="screen-image"></div>
                      <div class="screen-overlay"></div>
                      <div class="screen-...
RawContent        : HTTP/1.1 200 OK
                    Connection: close
                    Content-Length: 503
                    Content-Type: text/html; charset=utf-8
                    Date: Mon, 24 Apr 2023 04:51:36 GMT
                    Server: Werkzeug/2.2.3 Python/3.8.16

                    <link rel="stylesheet" hre...
Forms             : {}
Headers           : {[Connection, close], [Content-Length, 503], [Content-Type, text/html; charset=utf-8], [Date, Mon, 24 Apr  
                    2023 04:51:36 GMT]...}
Images            : {}
InputFields       : {}
Links             : {@{innerHTML=; innerText=; outerHTML=<A class=link href="https://youtube.com/@Hyperplexed"
                    target=_blank></A>; outerText=; tagName=A; class=link; href=https://youtube.com/@Hyperplexed;
                    target=_blank}}
ParsedHtml        : mshtml.HTMLDocumentClass
RawContentLength  : 503

They seem to be working!

Let's create a Docker Compose Manifest to orchestrate our services

version: "3.7"
services:
  web1:
    build: ./quote_gen
    container_name: gen
    ports:
      - "5000:5000"
  web2:
    build: ./quote_disp
    container_name: disp
    expose:
      - "5000"
    ports:
      - "5001:5000"
    depends_on:
      - web1

Let's understand the commands in our Compose YAML file -

version: - Compose file versions that run our Docker Compose

services: the components or services that run within the docker-compose manifest

Eg - Our website is a service, we can have a database service or a unit testing service, an application server, etc

Under service, we have our website - service name, build - looks for a docker image, context - specifies where to look

ports: -80:80

Run Docker Compose

docker-compose up
[+] Running 3/3
 - Network corise-zignite-devops-cc_default  Created                                                                      0.8s 
 - Container gen                             Created                                                                      0.6s
 - Container disp                            Created                                                                      0.1s
Attaching to disp, gen
gen   |  * Serving Flask app 'app'
gen   |  * Debug mode: on
gen   | WARNING: This is a development server. Do not use it in a production deployment. Use a production WSGI server instead. 
gen   |  * Running on all addresses (0.0.0.0)
gen   |  * Running on http://127.0.0.1:5000
gen   |  * Running on http://172.26.0.2:5000
gen   | Press CTRL+C to quit
gen   |  * Restarting with stat
gen   |  * Debugger is active!
gen   |  * Debugger PIN: 930-011-562
disp  |  * Serving Flask app 'app'
disp  |  * Debug mode: on
disp  | WARNING: This is a development server. Do not use it in a production deployment. Use a production WSGI server instead.
disp  |  * Running on all addresses (0.0.0.0)
disp  |  * Running on http://127.0.0.1:5000
disp  |  * Running on http://172.26.0.3:5000
disp  | Press CTRL+C to quit
disp  |  * Restarting with stat
disp  |  * Debugger is active!
disp  |  * Debugger PIN: 112-266-209

You can find a link to the Docker Compose tutorial https://docs.docker.com/compose/gettingstarted/

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