Docker from Node

Wouldn’t it be awesome if you could use the power of Docker and docker containers together with the flexibility of NodeJs? Well it turns out you can and it’s not very difficult.

Node has a module called spawn with which you can spawn any process you want, which includes Docker (as long as it is installed on your system).

Code of the Day

const {spawn} = require('child_process');
const readline = require('readline');

async function buildDocker() {
  await runCommand('docker build -t exector-test:test .');
}

async function runDocker() {
  await runCommand('docker run exector-test:test');
}

function runCommand(fullCommand) {
    return new Promise((resolve, reject) => {
      const commandParts = fullCommand.split(' ');
        const command = commandParts[0]
        const compileProcess = spawn(
            command,
            commandParts.slice(1),
            {
                shell: true
            });
        compileProcess.on('close', (code) => {
            if(code === 0) {
                resolve();
            } else {
                reject(`Process finished with exit code ${code}`)
            }
        });
        connectOutputs(compileProcess, console.log, console.error);


  })
}

function connectOutputs(childProcess, stdout, stderr) {
   childProcess.stdout && createInterface(childProcess.stdout, stdout);
   childProcess.stderr && createInterface(childProcess.stderr, stderr);
}

function createInterface(input, output) {
    const rlInterface = readline.createInterface ( {
        input: input
    });
    rlInterface.on ( 'line', output);
}

The whole connectOutputs story is to connect the output from the spawned process into the terminal output.