DeleteOldSnapshots.js

/*
    // Copyright 2017 Amazon.com, Inc. or its affiliates. All Rights Reserved.
    // SPDX-License-Identifier: MIT-0
*/
var AWS = require('aws-sdk');
var ec2 = new AWS.EC2();

exports.handler = (event, context, callback) => {

    //Pull the list of Snapshots from the event
    var snapshots = event.snapshotList.Snapshots;

    /*
    Need to ensure the list of snapshots are sorted by date in descending order

    return positive number is a is older than b
    return negative if a is more recent than b
    return 0 if equivalent
    */
    snapshots.sort(function(a, b) {
      var dateA = new Date(a.StartTime); //convert to date
      var dateB = new Date(b.StartTime); // convert to date
      if (dateA < dateB) {
        return 1;
      }
      if (dateA > dateB) {
        return -1;
      }

      // dates must be equal
      console.log("[WARN] - Snapshot dates are equal - may be issue with snapshot creation");
      return 0;
    });

    var numSnapshotsDeleted = 0;
    var retention = parseInt(process.env.retentionPeriod);
    var deletedSnapshots = [];

    if((retention - event.snapshotList.numSnapshots) < 0)
    {
        //Snapshots are sorted in descending order
        var snapshotsToDelete = snapshots.slice(retention - event.snapshotList.numSnapshots);
        console.log("Snapshots to Delete: " + JSON.stringify(snapshotsToDelete));

        //delete the snapshots
        snapshotsToDelete.forEach(function(snapshot) {
            var params = {
                SnapshotId: snapshot.SnapshotId
            };
            console.log("deleting snapshot:" + snapshot.SnapshotId);
            deletedSnapshots.push(ec2.deleteSnapshot(params).promise());
        });

        Promise.all(deletedSnapshots).then(values => {
          console.log("Number of deleted snapshots: " + values.length);
          callback(null, values.length);
        }, reason => {
          console.log("[ERROR] - Error Deleting snapshot");
          callback("[ERROR]-Error Deleting snapshot");
        });
    }
    else
    {
        //you shouldn't be here!
        var msg = "[ERROR] - You shouldn't be here, check that your retention " +
         "period defined in the environment variable matches the value for the retention defined in your state machine.";
        console.log(msg);
        callback(msg);
    }
};