Node script to print out all running docker containers by IP

get-docker-ips.js

#!/usr/bin/env node

const child_process = require( 'child_process' );

/**
 * Execute a command as a spawned process.
 *
 * @param {String}   command A bash command string, excluding arguments.
 * @param {String[]} args    An array of argument strings for the provided command.
 */
const spawn = ( command, args ) => {
    const output = [];
	return new Promise( ( resolve, reject ) => {
        const spawnedProcess = child_process.spawn( command, args );
        
        spawnedProcess.stdout.on( 'data', ( message ) => {
            output.push( message.toString() );
        } );

		spawnedProcess.on( 'error', err => reject( err ) );

		spawnedProcess.on( 'close', ( code, signal ) => {
			if ( code ) {
				reject();
				return;
            }
			resolve( output.join( '\n' ) );
		} );
	} );
};

/**
 * Use child_process to run `docker ps` and `docker inspect` commands to return
 * a JSON object with the ID, name, and IPs of all running containers.
 *
 * @async
 * @returns {Object[]} Array of { name, id, ips } container objects.
 */
const getContainers = async () => {
    try {
        const psOutput = await spawn( 'docker', [
            'ps',
            '--format',
            '{{.ID}},{{.Names}}',
        ] );
        const containers = psOutput.trim().split( '\n' )
            .map( ( line ) => {
                const [ id, name ] = line.split( ',' );
                return { id, name };
            } );

        for ( let container of containers ) {
            // Hat-tip https://www.freecodecamp.org/news/how-to-get-a-docker-container-ip-address-explained-with-examples/
            const ips = await spawn( 'docker', [
                'inspect',
                '--format',
                '{{.NetworkSettings.IPAddress}},{{range .NetworkSettings.Networks}}{{.IPAddress}},{{end}}',
                container.id,
            ] );

            container.ips = ips.split( ',' )
                .map( ( str ) => str.trim().replace( '<no value>', 'No IP' ) )
                .filter( Boolean )
                .sort();
        }
        return containers;
    } catch ( e ) {
        throw e;
    }
};

const containersPromise = getContainers();

/**
 * Given a URL, return the object defining the associated container.
 *
 * If no container is using an IP which appears in the URL, return null.
 *
 * @async
 * @param {String} url A url e.g. http://172.18.0.8:8080
 * @returns {Object|null} Container object { id, name, ips }, or else null.
 */
const getContainerByURL = async ( url ) => {
    const containers = await containersPromise;
    for ( let container of containers ) {
        for ( let ip of container.ips ) {
            if ( url.indexOf( ip ) > -1 ) {
                return container;
            }
        }
    }
    return null;
}

/**
 * Pretty-print the container namess by IP address.
 *
 * @async
 * @returns {String} Nicely formatted table of containers by IP.
 */
const describeContainers = async () => {
    const containers = await containersPromise;
    const longestIPLength = containers.reduce( ( max, container ) => Math.max( max, container.ips.join( ', ' ).length ), 0 );
    const longestNameLength = containers.reduce( ( max, container ) => Math.max( max, container.name.length ), 0 );
    const pad = ( str, length ) => {
        while ( str.length < length ) {
            str = `${ str } `;
        }
        return str;
    }
    const sortedContainers = containers
        .map( ( { ips, id, name } ) => `${
            pad( `${ ips.join( ', ' ) }`, longestIPLength )
        } ${
            pad( name, longestNameLength )
        } ${ id }` )
        .sort();
    return `\nDocker Containers by IP:\n\n${
        `${ pad( 'IPs', longestIPLength ) } ${ pad( 'Name', longestNameLength ) } ID`
    }\n${ sortedContainers.join( '\n' ) }`;
};

if ( require.main === module ) {
    ( async () => {
        console.log( await describeContainers() );
    } )();
}

module.exports = {
    getContainers,
    getContainerByURL,
};