initial commit

README.md

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+# service_shuffler
+
+A Terraform module that shuffles AWS ECS services using lambda during autoscaling events. 
+It will spin up a lambda and all underlying resources so that when an autoscaling group scales up or down your defined service will automatically adjust to the required number - keeping a predetermained number of tasks running on each host. Useful for tasks like fluentd where you need to have it running on the host before launching other tasks that will require it! 
+Shuffle your AWS ECS Services on scale up and down!
+
+## Usage
+
+```hcl
+module "container_service_cluster" {
+  source = "https://github.com/kgirthofer/service_shuffler?ref=0.1.0"
+
+  cluster_name            = "test-cluster"
+  autoscaling_group_name  = "testClusterASG"
+  lambda_name             = "test-shuffler"
+  region                  = "us-east-1"
+}
+```
+
+## Variables
+
+- `cluster_name`  - ECS Cluster name
+- `autoscaling_group_name`  - Name of the ASG you want to monitor for scale events
+- `lambda_name`  - What you want your lambda function to be 
+- `region`  - region for everything 

cloudwatch_event.tf

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+# Scale Up
+
+resource "aws_cloudwatch_event_rule" "scale_up" {
+  name        = "${var.cluster_name}-asg-scale-up"
+  description = "Capture each scale up"
+
+  event_pattern = <<PATTERN
+{
+  "source": [
+    "aws.autoscaling"
+  ],
+  "detail-type": [
+    "EC2 Instance Launch Successful"
+  ],
+  "detail": {
+    "AutoScalingGroupName": [
+      "${var.auto_scaling_group_name}"
+    ]
+  }
+}
+PATTERN
+}
+
+resource "aws_cloudwatch_event_target" "lambdaTriggerUp" {
+  rule      = "${aws_cloudwatch_event_rule.scale_up.name}"
+  target_id = "lamdaFunction"
+  arn       = "${aws_lambda_function.lambda_shuffler.arn}"
+}
+
+# Scale Down
+
+resource "aws_cloudwatch_event_rule" "scale_down" {
+  name        = "${var.cluster_name}-asg-scale-down"
+  description = "Capture each scale down"
+
+  event_pattern = <<PATTERN
+{
+  "source": [
+    "aws.autoscaling"
+  ],
+  "detail-type": [
+    "EC2 Instance Terminate Successful"
+  ],
+  "detail": {
+    "AutoScalingGroupName": [
+      "${var.auto_scaling_group_name}"
+    ]
+  }
+}
+PATTERN
+}
+
+resource "aws_cloudwatch_event_target" "lambdaTriggerDown" {
+  rule      = "${aws_cloudwatch_event_rule.scale_down.name}"
+  target_id = "lamdaFunction"
+  arn       = "${aws_lambda_function.lambda_shuffler.arn}"
+}
+

iam.tf

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+data "aws_iam_policy_document" "cloudwatchAccess" {
+  statement {
+    sid = "1"
+
+    actions = [
+      "logs:CreateLogGroup",
+      "logs:CreateLogStream",
+      "logs:PutLogEvents"
+    ]
+    resources = ["arn:aws:logs:*:*:*"]
+  }
+  statement {
+    sid = "2"
+
+    actions = [
+      "ecs:DescribeServices",
+      "ecs:UpdateService",
+      "autoscaling:DescribeAutoScalingGroups"
+    ]
+    resources = ["*"]
+  }
+}
+
+resource "aws_iam_policy" "cloudwatchAccess" {
+  name   = "${var.lambda_name}-policy"
+  path   = "/"
+  policy = "${data.aws_iam_policy_document.cloudwatchAccess.json}"
+}
+
+resource "aws_iam_policy_attachment" "attachment" {
+  name       = "ecs-attachment"
+  roles      = ["${aws_iam_role.lambda_shuffler_role.name}"]
+  policy_arn = "${aws_iam_policy.cloudwatchAccess.arn}"
+}

lambda.tf

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+resource "aws_iam_role" "lambda_shuffler_role" {
+  name = "${var.lambda_name}_role"
+  assume_role_policy = <<EOF
+{
+  "Version": "2012-10-17",
+  "Statement": [
+    {
+      "Action": "sts:AssumeRole",
+      "Principal": {
+        "Service": "lambda.amazonaws.com"
+      },
+      "Effect": "Allow",
+      "Sid": ""
+    }
+  ]
+}
+EOF
+}
+
+resource "aws_lambda_function" "lambda_shuffler" {
+    function_name = "${var.lambda_name}"
+    handler = "shuffler.lambda_handler"
+    runtime = "python2.7"
+    filename = "shuffler.zip"
+    role = "${aws_iam_role.lambda_shuffler_role.arn}"
+    source_code_hash = "${base64sha256(file("shuffler.zip"))}"
+    environment {
+      variables = {
+        REGION       = "${var.region}"
+        ASG_NAME     = "${var.auto_scaling_group_name}"
+        CLUSTER_NAME = "${var.cluster_name}"
+        SERVICE_NAME = "${var.service_name}"
+      }
+    }
+}
+
+# Scale Up Trigger
+resource "aws_lambda_permission" "allow_cloudwatch_up" {
+  statement_id   = "AllowExecutionFromCloudWatchUp"
+  action         = "lambda:InvokeFunction"
+  function_name  = "${aws_lambda_function.lambda_shuffler.function_name}"
+  principal      = "events.amazonaws.com"
+  source_arn     = "${aws_cloudwatch_event_rule.scale_up.arn}"
+}
+
+# Scale Down Trigger
+resource "aws_lambda_permission" "allow_cloudwatch_down" {
+  statement_id   = "AllowExecutionFromCloudWatchDown"
+  action         = "lambda:InvokeFunction"
+  function_name  = "${aws_lambda_function.lambda_shuffler.function_name}"
+  principal      = "events.amazonaws.com"
+  source_arn     = "${aws_cloudwatch_event_rule.scale_down.arn}"
+}
+

main.tf

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+provider "aws" {
+    region = "${var.region}"
+}

shuffler.py

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+from __future__ import print_function
+import boto3
+import os
+
+region = os.environ['REGION']
+asg_name = os.environ['ASG_NAME']
+service_name = os.environ['SERVICE_NAME']
+cluster_name = os.environ['CLUSTER_NAME']
+
+ecs = boto3.client('ecs', region)
+asg = boto3.client('autoscaling')
+
+def lambda_handler(event, context):
+    print('Getting the current ASG Desired Capacity')
+    total = asg.describe_auto_scaling_groups(
+        AutoScalingGroupNames=[
+            asg_name
+        ]
+    )['AutoScalingGroups'][0]['DesiredCapacity']
+    print('Desired Capacity: {}'.format(total))
+    print('Adjsitng Service to Desired Capacity')
+    response = ecs.update_service(
+        cluster=cluster_name,
+        service=service_name,
+        desiredCount=total
+    )
+    return total