Why Containerize?

Talk about the need for containerization and the tenets of micro-services architecture. Containerize an application consisting of three services and build/run it using docker-compose. Explain Dockerfile, docker-compose file and what happens behind the scenes in detail.

Transcript

1. WHY CONTAINERIZE?
   what & why of containerization of apps
   Rupak Ganguly April 18th, 2020
   

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2. AGENDA
   Micro-services
   Tenets of micro-services
   Store App Architecture
   Local app architecture
   Containerized app architecture (composing services)
   Containerization the Store App
   Building the App Docker Image (Dockerfile)
   Running the App in containers (compose file)
   Behind the scenes of a docker-compose
   Demo
   Commands
   

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3. MICRO-SERVICES
   breaking the monolith
   

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4. “
   Microservices architecture essentially follows the
   Unix philosophy of
   "Do one thing and do it well"
   

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5. MONOLITHIC TO MICRO-SERVICES
   https://martinfowler.com/articles/microservices.html
   

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6. THE SERVICE MINDSET
   ➤ Independent unit of functionality (separation of concerns)
   ➤ Organized around business capabilities
   ➤ One process and communicate with lightweight mechanisms
   ➤ Autonomously developed (has its own SDLC)
   ➤ Polyglot in nature (various programming languages)
   ➤ Different data storage technologies
   ➤ Independently versioned
   ➤ Independently deployable
   ➤ Built/Deployed via automated processes (CI/CD)
   ➤ Easily scaled up/down based on criteria
   

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7. STORE APP
   containerizing the store app
   

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8. THE LOCAL STORE APP
   Frontend Web (react app)
   Products API (nodejs app)
   Database (mongo db)
   Local Development Environment
   Frontend Web
   Products API
   Database
   Port: 27017
   Port: 5000
   Port: 3000
   Overlay Network
   

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9. COMPOSING SERVICES
   Frontend Web
   Products API
   Database
   27017
   8081:5000
   8080:3000
   Host Port:Container Port
   Overlay Network
   docker-compose up
   Note: The database port is NOT exposed to the host
   since the database is only required to be accessed by
   the Products API service. That makes the database
   access secured.
   services:
   web:
   build:
   context: ./basic-react-project
   ports:
   - 8080:3000
   depends_on:
   - mongo
   - api
   api:
   build:
   context: ./MyNodeJsProject
   ports:
   - 8081:5000
   depends_on:
   - mongo
   healthcheck:
   mongo:
   image: mongo:3.6.3
   ports:
   - "27017"
   volumes:
   - api-mongo-db:/data/db
   

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10. DOCKERFILE
    FROM node:12.16.1-alpine
    ARG BUILD_ENV=development
    ENV APP_SOURCE_DIR=/some/path
    RUN apk --no-cache add bash curl
    WORKDIR $APP_SOURCE_DIR
    COPY . $APP_SOURCE_DIR
    CMD ["npm", "start"]
    A Dockerfile is a declarative way to express how to build your service or app into a
    Docker image that can then be run as a container. A Docker image is immutable and
    can be tagged to represent a snapshot (like a version).
    
    FROM: specifies the base image for your application. In this case we are using
    the node:12.16.1 image that provides node.
    
    ARG: specifies the build arguments that can passed via a build command to
    customize the build. e.g. docker build -—build-args
    BUILD_ENV=production —t myimage:1.0 .
    
    ENV: specifies the runtime environment variable that can be passed to the docker
    run command. e.g. docker run -e APP_SOURCE_DIR=/another/path myapp
    
    RUN: specifies the commands that you need to execute to install the software
    that you want in your image
    
    WORKDIR: specifies the working directory and all commands thereafter will use
    that
    
    COPY: used to copy files from current folder to the container
    
    CMD: specifies the command that will be run when a container starts. See
    ENTRYPOINT as well.
    
    Building a Docker image:
    
    docker build -t myimage:1.0 .
    (the . at the end represents the path of the Dockerfile)
    

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11. DOCKER-COMPOSE.YML
    services:
    web:
    build:
    context: ./basic-react-project
    ports:
    - 8080:3000
    depends_on:
    - mongo
    - api
    api:
    build:
    context: ./MyNodeJsProject
    ports:
    - 8081:5000
    depends_on:
    - mongo
    healthcheck:
    mongo:
    image: mongo:3.6.3
    ports:
    - "27017"
    volumes:
    - api-mongo-db:/data/db
    A docker compose file is a declarative way to express services that make up
    an application. It is an YAML file and in plain text.
    
    services: list all services that make up the app
    
    web: represents the service ‘web’ and its corresponding configuration
    
    build: specifies how to build the service using a path to the code
    
    image: instead of building the service, use an already built image
    
    ports: represents the ports for the service ‘host port: container port’
    
    depends_on: represents the dependent services for the service
    
    healthcheck: configures a command used to validate that a service is
    ‘healthy’
    
    volumes: is used for a stateful service to persist data after a container
    exits. It creates a bridge between the host and the container. The bridge is
    two-way i.e. data written on the host is available on the container and vice-
    versa.
    

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12. BEHIND THE SCENES
    services:
    web:
    build:
    context: ./basic-react-project
    ports:
    - 8080:3000
    depends_on:
    - mongo
    - api
    api:
    build:
    context: ./MyNodeJsProject
    ports:
    - 8081:5000
    depends_on:
    - mongo
    healthcheck:
    mongo:
    image: mongo:3.6.3
    ports:
    - "27017"
    volumes:
    - api-mongo-db:/data/db
    When you run docker-compose up, the following happens:
    
    1.A network named storeapp_default is created by default
    
    2.A container named storeapp_web_1 is created
    
    3.A container named storeapp_api_1 is created
    
    4.A container named storeapp_mongo_1 is created
    5.All the services joins the network storeapp_default
    ➤App is named after the directory it lives in but can be overridden by the -p flag
    
    ➤The default network is named _default i.e.
    storeapp_default
    ➤Each container for a service joins the default network,
    
    ➤and is both reachable by other containers on that network,
    
    ➤and discoverable by them at a hostname identical to the container name.
    
    ➤Networked service-to-service communication use the CONTAINER_PORT.
    
    ➤When HOST_PORT is defined, the service is accessible outside the swarm as
    well.
    
    ➤Within the storeapp_web_1 container, your connection string to Mongo
    database would look like mongodb://mongo:27017/
    docker-compose -p storeapp up
    

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13. DEMO
    running the store app
    

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14. DOCKER COMPOSE COMMANDS
    Build images from Dockerfile and then run the app interactively:
    docker-compose up —build
    Run the app in background (daemon):
    docker-compose up -d
    List the containers:
    docker-compose ps
    Set number of containers for a service (scale up/down):
    docker-compose up --scale =
    Stop and remove containers, networks, images, and volumes:
    docker-compose down
    

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15. DEMO COMMANDS - UP WITH BUILD
    Build images from Dockerfile and then run the app interactively:
    docker-compose up —build
    Creating network "storeapp_default" with the default driver
    Building api
    Step 1/19 : FROM node:12.16.2-alpine
    Successfully tagged storeapp_api:latest
    Building web
    Step 1/19 : FROM node:12.16.2-alpine
    Successfully tagged storeapp_web:latest
    Creating storeapp_mongo_1 ... done
    Creating storeapp_api_1 ... done
    Creating storeapp_web_1 ... done
    Attaching to storeapp_mongo_1, storeapp_api_1, storeapp_web_1
    mongo_1 | 2020-04-17T08:21:49.284+0000 I CONTROL [initandlisten] MongoDB starting
    mongo_1 | 2020-04-17T08:21:49.285+0000 I CONTROL [initandlisten] db version v3.6.3
    api_1 | $ nodemon server.js
    api_1 | [nodemon] starting `node server.js`
    web_1 | $ react-scripts start
    api_1 | Server running on port 5000
    web_1 | Starting the development server...
    

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16. DEMO COMMANDS - UP
    Run the app in background (daemon):
    docker-compose up -d
    Starting storeapp_mongo_1 ... done
    Starting storeapp_api_1 ... done
    Starting storeapp_web_1 ... done
    List the containers:
    docker-compose ps
    CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
    c0f3471a3ae6 storeapp_web "docker-entrypoint.s " 6 seconds ago Up 3 seconds (health: starting) 0.0.0.0:8080->3000/tcp storeapp_web_1
    f8150d450359 storeapp_api "docker-entrypoint.s " 7 seconds ago Up 5 seconds (health: starting) 0.0.0.0:8081->5000/tcp storeapp_api_1
    309a9f2cd5f7 mongo:3.6.3 "docker-entrypoint.s " 8 seconds ago Up 6 seconds (health: starting) 0.0.0.0:27017->27017/tcp storeapp_mongo_1
    

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17. DEMO COMMANDS - SCALING (PORT CONFLICTS)
    Set number of containers for a service (scale up/down):
    docker-compose up --scale api=3
    WARNING: The "api" service specifies a port on the host.
    If multiple containers for this service are created on a single host, the port will clash.
    Starting storeapp_api_1 ... done
    Creating storeapp_api_2 ...
    Creating storeapp_api_3 ...
    Creating storeapp_api_2 ... error
    WARNING: Host is already in use by another container
    ERROR: for storeapp_api_3 Cannot start service api: driver failed programming external connectivity
    on endpoint storeapp_api_3 (664b85882427d28ed4a694d7b46042128c590328e3d2e9bc6057f281371c0428): Bind
    for 0.0.0.0:8081 failed: port is already allocated
    ERROR: for storeapp_api_2 Cannot start service api: driver failed programming external connectivity
    on endpoint storeapp_api_2 (70d6c8df937a93e476ef8adf001c1a3c42ee270648321182029811eaaceee72e): Bind
    for 0.0.0.0:8081 failed: port is already allocated
    ERROR: for api Cannot start service api: driver failed programming external connectivity on endpoint
    storeapp_api_3 (664b85882427d28ed4a694d7b46042128c590328e3d2e9bc6057f281371c0428): Bind for
    0.0.0.0:8081 failed: port is already allocated
    api:
    ports:
    - 8081:5000
    

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18. DEMO COMMANDS - SCALING (DYNAMIC PORTS)
    Set number of containers for a service (scale up/down):
    docker-compose up --scale api=3
    Creating network "storeapp_default" with the default driver
    Creating storeapp_mongo_1 ... done
    Creating storeapp_api_1 ... done
    Creating storeapp_api_2 ... done
    Creating storeapp_api_3 ... done
    Creating storeapp_web_1 ... done
    docker-compose ps
    CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
    ff68c5d9741d storeapp_web "docker-entrypoint.s " 7 seconds ago Up 5 seconds (health: starting) 0.0.0.0:8080->3000/tcp storeapp_web_1
    f6da8ba063b1 storeapp_api "docker-entrypoint.s " 10 seconds ago Up 6 seconds (health: starting) 0.0.0.0:32774->5000/tcp storeapp_api_1
    6f2d277985c9 storeapp_api "docker-entrypoint.s " 10 seconds ago Up 6 seconds (health: starting) 0.0.0.0:32773->5000/tcp storeapp_api_3
    e395e272d360 storeapp_api "docker-entrypoint.s " 10 seconds ago Up 7 seconds (health: starting) 0.0.0.0:32772->5000/tcp storeapp_api_2
    8a370985695a mongo:3.6.3 "docker-entrypoint.s " 11 seconds ago Up 9 seconds (health: starting) 0.0.0.0:27017->27017/tcp storeapp_mongo_1
    api:
    ports:
    - 5000
    

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19. DEMO COMMANDS - DOWN
    Stop and remove containers, networks, images, and volumes:
    docker-compose down
    Stopping storeapp_web_1 ... done
    Stopping storeapp_api_1 ... done
    Stopping storeapp_mongo_1 ... done
    Removing storeapp_web_1 ... done
    Removing storeapp_api_1 ... done
    Removing storeapp_mongo_1 ... done
    Removing network storeapp_default
    

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20. RESOURCES
    What is a container: https://www.docker.com/resources/what-container
    Getting started with Docker: https://docs.docker.com/get-started/overview/
    Install Docker: https://www.docker.com/products/docker-desktop
    Docker Developer Tools: https://www.docker.com/products/developer-tools
    Docker Engine: https://docs.docker.com/engine/
    Docker Compose: https://docs.docker.com/compose/
    Docker Hub: https://docs.docker.com/docker-hub/
    Docker Enterprise Platform: https://docs.docker.com/ee/
    Docker Kubernetes Service: https://docs.docker.com/ee/#docker-kubernetes-service
    

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21. QUESTIONS?
    @rupakg
    rupakganguly.com
    Slides: https://speakerdeck.com/rupakg/why-containerize
    

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