Route53 updater in conjunction with ECS

demoroute53.js

let AWS = require('aws-sdk');
let ec2 = new AWS.EC2();
let ecs = new AWS.ECS();
let route53 = new AWS.Route53();

/**
 * expects an environment variable with name "entryparam" and the following value / structure:
 * [{
 *      "cluster": "mycluster1",
 *      "domain": "demo.mydomain.com",
 *      "zoneid": "Z1Q3ZVS8H41111"
 *  },
 *  {
 *      "cluster": "mycluster2",
 *      "domain": "demo.mydomain2.de",
 *      "zoneid": "Z1Q3Z44444EG25"
 *  }]
 *
 * The cluster is the ecs cluster name to look into. The domain indicates the records to create
 * for the zone with the zoneid in Route53.
 *
 * @param event Lambda event object
 * @param context Lambda context object
 */

exports.handler = function (event, context) {
    console.log("********************************************");
    console.log(context.functionName);
    console.log("event: ", JSON.stringify(event));
    console.log("entryparam:", process.env.entryparam);
    console.log("********************************************");


    const result = async () => {

        let configArray = JSON.parse(process.env.entryparam);
        for (let i = 0; i < configArray.length; i++) {
            console.log("--- Processing Cluster: " + configArray[i].cluster + " ---");
            let publicIp = await getPublicIpForCluster(configArray[i].cluster);
            console.log("Updating record '" + configArray[i].domain
                + "' (" + configArray[i].zoneid + ") with Public IP: " + publicIp);
            modifyDnsRecord(configArray[i].cluster, configArray[i].domain, publicIp, configArray[i].zoneid);
            console.log("--- End of Processing Cluster ---");
        }
    };

    result().then(() => {
        context.done(null, event);
    }).catch(reason => {
        let error = new Error('failed!');
        context.done(error, event);
    });

};

function modifyDnsRecord(clusterName, domain, publicIp, hostedZoneId) {
    let param = {
        ChangeBatch: {
            "Comment": "Auto generated Record for ECS Fargate Instance " + clusterName,
            "Changes": [
                {
                    "Action": "UPSERT",
                    "ResourceRecordSet": {
                        "Name": domain,
                        "Type": "A",
                        "TTL": 300,
                        "ResourceRecords": [
                            {
                                "Value": publicIp
                            }
                        ]
                    }
                }
            ]
        },
        HostedZoneId: hostedZoneId
    };

    route53.changeResourceRecordSets(param, function (err, data) {
        if (err) {
            console.log(err, err.stack);
        }
    });
}


async function getPublicIpForCluster(clusterName) {
    // lists tasks of cluster
    let data = await ecs.listTasks({
        cluster: clusterName
    }).promise();
    let taskId = data.taskArns[0].split("/")[1];

    // get Task data
    data = await ecs.describeTasks({
        cluster: clusterName,
        tasks: [
            taskId
        ]
    }).promise();
    let eniId = "";

    // extract "Elastic Network Interface" ENI Id
    let detailsArray = data.tasks[0].attachments[0].details;
    for (let i = 0; i < detailsArray.length; i++) {
        if (detailsArray[i].name === "networkInterfaceId") {
            eniId = detailsArray[i].value;
            break;
        }
    }

    // get Public IP of the extracted ENI
    data = await ec2.describeNetworkInterfaces({
        NetworkInterfaceIds: [
            eniId
        ]
    }).promise();

    return data.NetworkInterfaces[0].PrivateIpAddresses[0].Association.PublicIp;
}