AWS Lambda check instances

check-instances.js

function findTag(tags, key) {
  for (var i = tags.length - 1; i >= 0; i--) {
    if (tags[i].Key === key) {
      return tags[i].Value;
    }
  }
}

exports.handler = (event, context, callback) => {
    var AWS = require('aws-sdk');
    var ec2 = new AWS.EC2();
    var params = {
      DryRun: false,
      Filters: [
        {
          Name: 'tag:managed_by',
          Values: [
              'ansible'
          ],
        },
        {
          Name: 'instance-state-code',
          Values: [
            '16',  
          ]
        }
      ]
    };
    
    ec2.describeInstances(params, function (err, data) {
      if (err) {
        context.fail(err);
      } else {
        var instancesToTerminate = [];
        var instancesToUpdate = [];
        var response = [];
        if (data.Reservations && data.Reservations.length > 0) {
          for (var i = data.Reservations.length - 1; i >= 0; i--) {
            var instances = data.Reservations[i].Instances;
            if (instances && instances.length > 0) {
              for (var j = instances.length - 1; j >= 0; j--) {
                var instance = instances[j];
                var ttl = parseInt(findTag(instance.Tags, 'ttl'), 10);
                if (ttl <= 0) {
                  instancesToTerminate.push(instance.InstanceId);
                } else {
                  instancesToUpdate.push({
                    id: instance.InstanceId,
                    ttl: ttl
                  });
                }
              } 
            }
          }
        }
        if (instancesToTerminate.length > 0) {
          var params = {
            InstanceIds: instancesToTerminate,
            DryRun: false,
          };
          ec2.terminateInstances(params, function(err, data) {
            if (err) {
              console.log(err, err.stack);
              context.fail(err);
            } else {
              context.succeed("Terminated instances: " + instancesToTerminate);
            }
          });
        }
        else {
          var tasksNum = instancesToUpdate.length;
          response.push('No instances to terminate');
          for (var i = instancesToUpdate.length - 1; i >= 0; i--) {
            var toUpdate = instancesToUpdate[i];
            function doUpdate(toUpdate) {
              ec2.createTags({
                Resources: [
                  toUpdate.id 
                ],
                Tags: [
                  {
                    Key: 'ttl',
                    Value: (toUpdate.ttl - 1) + ''
                  }  
                ]
              }, function(err, data) {
                tasksNum--;
                if (err) {
                  console.log(err, err.stack);
                  context.fail(err);
                } else {
                  response.push('Updated ttl of ' + toUpdate.id + ' to ' + (ttl - 5));
                }
                if (tasksNum <= 0) {
                  context.succeed(response.join(', '));
                }
              });
            }
            doUpdate(toUpdate);
          }
        }
      }
    });
};