5/28 TIL: Docker Compose, Volumes, cURL

Docker-compose

version: '3'
  services:
    server:
      build: .
      volumes:
        - .:/app
      ports:
        - 9090:9090
      command: ['wait-for-it.sh', 'db:3306', '--', 'air']
      depends_on:
        - db
    db:
      image: mysql
      restart: always
      environment:
        MYSQL_USER: admin
        MYSQL_PASSWORD: password
        MYSQL_ROOT_PASSWORD: password
        MYSQL_DATABASE: sampleDb
      ports:
        - '3306:3306'
      volumes:
        - mysql_db:/var/lib/mysql
      command:
        [
          'mysqld',
          '--character-set-server=utf8mb4',
          '--collation-server=utf8mb4_unicode_ci',
        ]
  volumes:
    mysql_db:

• Two containers: server & db
• server
  • builds the Dockerfile in the current path
  • runs on port 9090 on both the host and within the container
  • executes 'wait-for-it.sh' to wait on the availability of port 3306 before running 'air'--using wait-for-it.sh is just an example and this shell script has to be installed as part of the Dockerfilehttps://github.com/vishnubob/wait-for-it
  • depends on db container
• db
  • runs on mysql image
  • we have a 'named volume' called mysql_db at the last line of this docker-compose.yml file and we have that mounted to 'var/lib/mysql' directory in the db container's virtual file systems (watch 3:40 here for details https://www.youtube.com/watch?v=p2PH_YPCsis&ab_channel=TechWorldwithNanaTechWorldwithNana)

cURL & its flags

• curl is a tool to transfer data from or to a server, using one of the supported protocols (FTP, HTTP, SFTP, and many more)
• Example:

RUN curl -fLo [install.sh](http://install.sh/) [https://raw.githubusercontent.com/cosmtrek/air/master/install.sh](https://raw.githubusercontent.com/cosmtrek/air/master/install.sh)

• -f allows the HTTP to fail silently on server errors
• -L will make curl redo the request on the new place if the server reports that the requested page has moved to a different location
• -o writes the output to the specified file
• -s is silent mode
• -S is used with -s and it makes curl show an error message if it fails. ex) -sSfL