Lambda-Assign-EIP-Lifecyclehook

assignEIP.js

/*Problem: Integration into 3rd party API requires IP whitelisting. Servers are dynamically started and stopped.

Solution: assign predefined EIPs to EC2 instances as the Auto Scaling group size increases
Limitations: Need to predefine and preallocate all IP addresses
Other possible solutions:
  1) Proxy all requests through single NAT instance
    i. limitation: single point of failure
    ii. need similar solution to make sure NAT is highly available
  2) Remove whitelisting requirement
    i. no...just no ... not gonna happen
  3) Possibly integrate with 3rd party to dynamically whitelist new IP addresses
    i. Not all APIs have that ability
*/



//Steps:
// 1: Create Auto Scale Group
// 2: Create Role for Lambda
// 3: Create Lambda Function
// 4: Attach 

aws autoscaling put-lifecycle-hook \
  --lifecycle-hook-name 'Name'  \
  --auto-scaling-group-name 'ASG Name' \
  --lifecycle-transition autoscaling:EC2_INSTANCE_LAUNCHING \ 
  --notification-target-arn 'SNS Topic'  \
  --role-arn 'Role'

//TODO: send email when running "low" on Elastic IPs

var AWS = require('aws-sdk');
exports.handler = (event, context, callback) => {
    var Lifecycleparams = {
        AutoScalingGroupName: event.detail.AutoScalingGroupName,
        LifecycleActionResult: 'CONTINUE',
        LifecycleHookName: event.detail.LifecycleHookName,
        LifecycleActionToken: event.detail.LifecycleActionToken
    };
    var autoscaling = new AWS.AutoScaling();
    var ec2 = new AWS.EC2();
    //EIPs that are whitelisted on 3rd party service
    var descr_EIP_params = {
        //Replace with own EIPs that you have already created  
        PublicIps: ['192.168.1.2', '192.168.1.3', '192.168.1.4'],
        Filters: [{
            Name: "domain",
            Values: [
                "vpc"
            ]
        }]
    };
    //Get EIP AssociationId and AllocationId
    ec2.describeAddresses(descr_EIP_params, function(err, data) {
        if (err) {
            console.log(err, err.stack);
            callback(err);
        } // an error occurred
        else {
            //Iterate through EIPs that are whitelisted to find an open one
            for (var i = 0; i < data.Addresses.length; i++) {
                if (data.Addresses[i].AssociationId == undefined) {
                    var assoc_EIP_params = {
                        AllowReassociation: true,
                        DryRun: false,
                        InstanceId: event.detail.EC2InstanceId
                    };
                    assoc_EIP_params.AllocationId = data.Addresses[i].AllocationId;
                    //Associate unattached EIP with new instance
                    ec2.associateAddress(assoc_EIP_params, function(err, data) {
                        if (err) {
                            console.log(err, err.stack);
                            callback(err);
                        } // an error occurred
                        else {
                            //Complete autoscaling Lifecycle action
                            autoscaling.completeLifecycleAction(Lifecycleparams, function(err, data) {
                                if (err) {
                                    console.log(err, err.stack);
                                    callback(err);
                                } // an error occurred
                                else {
                                    //End lambda
                                    callback(null,'Success');
                                }
                            });
                        }
                    });
                break;
                }
            }
        }
    });
};