Lambda function to tidy up stale Packer instances

assume-role.json

+{
+  "Version": "2012-10-17",
+  "Statement": [
+    {
+      "Action": "sts:AssumeRole",
+      "Principal": {
+        "Service": "lambda.amazonaws.com"
+      },
+      "Effect": "Allow",
+      "Sid": ""
+    }
+  ]
+}
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iam-policy.json

+{
+"Version": "2012-10-17",
+"Statement": [
+    {
+        "Effect": "Allow",
+        "Action": "ec2:Describe*",
+        "Resource": "*"
+    },
+    {
+        "Effect": "Allow",
+        "Action": "ec2:TerminateInstances",
+        "Resource": "*"
+    }
+]
+}
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main.tf

+resource "aws_iam_role" "packer_janitor" {
+    name = "iam_packer_janitor"
+    assume_role_policy = "${file("${path.module}/assume-role.json")}"
+}
+
+resource "aws_iam_policy" "packer_janitor" {
+    name = "packer_janitor"
+    policy = "${file("${path.module}/iam-policy.json")}"
+}
+
+resource "aws_iam_role_policy_attachment" "packer_janitor" {
+    role = "${aws_iam_role.packer_janitor.name}"
+    policy_arn = "${aws_iam_policy.packer_janitor.arn}"
+}
+
+resource "aws_lambda_function" "packer_janitor" {
+    filename = "${path.module}/packer_janitor.zip"
+    function_name = "packer_janitor"
+    role = "${aws_iam_role.packer_janitor.arn}"
+    handler = "packer_janitor.lambda_handler"
+    timeout = "300"
+    runtime = "python2.7"
+    source_code_hash = "${base64sha256(file("${path.module}/packer_janitor.zip"))}"
+}
+
+variable "cloudwatch_schedule" {
+  description = "Schedule for cloudwatch event to invoke Lambda function"
+  default = "cron(*/2 * ? * * *)"
+}
+
+resource "aws_cloudwatch_event_rule" "packer_janitor" {
+  name = "packer_janitor"
+  description = "Run packer janitor to tidy up stale packer instances."
+  schedule_expression = "${var.cloudwatch_schedule}"
+}
+
+resource "aws_cloudwatch_event_target" "packer_janitor" {
+    rule = "${aws_cloudwatch_event_rule.packer_janitor.name}"
+    arn = "${aws_lambda_function.packer_janitor.arn}"
+}
+
+resource "aws_lambda_permission" "allow_cloudwatch" {
+    statement_id = "AllowExecutionFromCloudWatch"
+    action = "lambda:InvokeFunction"
+    function_name = "${aws_lambda_function.packer_janitor.arn}"
+    principal = "events.amazonaws.com"
+}
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packer_janitor.py

+import boto3
+import datetime
+import logging
+import sys
+from dateutil.parser import *
+from datetime import timedelta
+
+"""
+This function lists all stale packer instances and terminates them. 
+"""
+
+# Define the Tag of the packer instances
+PACKER_TAG = 'Packer Builder'
+REGION = 'eu-west-1'
+DRYRUN = False
+# Define the Connection
+ec2 = boto3.resource('ec2', region_name=REGION)
+
+date = datetime.datetime.now()
+
+logger = logging.getLogger()
+logger.setLevel(logging.INFO)
+
+ch = logging.StreamHandler(sys.stdout)
+ch.setLevel(logging.INFO)
+formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
+ch.setFormatter(formatter)
+logger.addHandler(ch)
+
+logger.info('Packer Tag: %s', PACKER_TAG)
+
+def lambda_handler (event, context):
+  logger.info('Starting scan for instances')
+
+  instances = ec2.instances.filter(Filters=[
+      {'Name': 'tag:Name', 'Values': [PACKER_TAG]},
+      {'Name': 'instance-state-name', 'Values': ['running']},
+  ])
+
+  for instance in instances:
+    instance_tags = tags_dict(instance.tags)
+    instance_launch_time = instance.launch_time
+    logger.info('Found New Instance, ID: [%s]', instance.id)
+    logger.info('[%s]: Tags: %s', instance.id, instance_tags)
+    logger.info('[%s]: Launch Time: %s', instance.id, instance_launch_time)
+
+    current_time = datetime.datetime.now(instance_launch_time.tzinfo)
+    logger.debug('Current Time: %s', current_time)
+
+    runtime = time_diff(instance_launch_time, current_time)
+    runtime_days = runtime.days
+    runtime_minutes = runtime.seconds/60
+    logger.info('[%s]: Runtime: %s days', instance.id, runtime_days)
+    logger.info('[%s]: Runtime: %s mins', instance.id, runtime_minutes)
+
+    if (runtime_days >= 1) or (runtime_minutes >= 120):
+
+      logger.info('[%s]: Instance has been running for %s days and %s mins. Marking for termination', instance.id, runtime.days, runtime_minutes)
+      instance.terminate(DryRun=DRYRUN)
+      logger.info('[%s]: Stopped Instance', instance.id)
+  return True
+
+def time_diff(launch_time, current_time):
+  running_time = current_time - launch_time
+  return running_time
+
+def tags_dict(tags):
+  '''Flatten a list of tags dicts into a single dict'''
+  return {t['Key']: t['Value'] for t in tags} if tags else {}
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