Add support for layers

Author: raymondbutcher

README.md

@@ -80,6 +80,7 @@ function name unique per region, for example by setting
 | function\_name | A unique name for your Lambda function (and related IAM resources) | string | n/a | yes |
 | handler | The function entrypoint in your code | string | n/a | yes |
 | lambda\_at\_edge | Set this to true if using Lambda@Edge, to enable publishing, limit the timeout, and allow edgelambda.amazonaws.com to invoke the function | string | `"false"` | no |
+| layers | List of Lambda Layer Version ARNs to attach to your Lambda Function. | list | `<list>` | no |
 | memory\_size | Amount of memory in MB your Lambda function can use at runtime | string | `"128"` | no |
 | policy | An addional policy to attach to the Lambda function | string | `""` | no |
 | publish | Whether to publish creation/change as new Lambda Function Version | string | `"false"` | no |

lambda.tf

@@ -13,6 +13,7 @@ resource "aws_lambda_function" "lambda" {
   memory_size                    = "${var.memory_size}"
   reserved_concurrent_executions = "${var.reserved_concurrent_executions}"
   runtime                        = "${var.runtime}"
+  layers                         = "${var.layers}"
   timeout                        = "${local.timeout}"
   publish                        = "${local.publish}"
   tags                           = "${var.tags}"
@@ -57,6 +58,7 @@ resource "aws_lambda_function" "lambda_with_dl" {
   memory_size                    = "${var.memory_size}"
   reserved_concurrent_executions = "${var.reserved_concurrent_executions}"
   runtime                        = "${var.runtime}"
+  layers                         = "${var.layers}"
   timeout                        = "${local.timeout}"
   publish                        = "${local.publish}"
   tags                           = "${var.tags}"
@@ -85,6 +87,7 @@ resource "aws_lambda_function" "lambda_with_vpc" {
   memory_size                    = "${var.memory_size}"
   reserved_concurrent_executions = "${var.reserved_concurrent_executions}"
   runtime                        = "${var.runtime}"
+  layers                         = "${var.layers}"
   timeout                        = "${local.timeout}"
   publish                        = "${local.publish}"
   tags                           = "${var.tags}"
@@ -117,6 +120,7 @@ resource "aws_lambda_function" "lambda_with_dl_and_vpc" {
   memory_size                    = "${var.memory_size}"
   reserved_concurrent_executions = "${var.reserved_concurrent_executions}"
   runtime                        = "${var.runtime}"
+  layers                         = "${var.layers}"
   timeout                        = "${local.timeout}"
   publish                        = "${local.publish}"
   tags                           = "${var.tags}"

tests/layers/lambda.py

@@ -0,0 +1,8 @@
+import subprocess
+
+
+def lambda_handler(event, context):
+
+    subprocess.run(['git'])
+
+    return 'test passed'

tests/layers/main.tf

@@ -0,0 +1,25 @@
+terraform {
+  backend "local" {
+    path = "terraform.tfstate"
+  }
+}
+
+provider "aws" {
+  region = "eu-west-1"
+}
+
+module "lambda" {
+  source = "../../"
+
+  function_name = "terraform-aws-lambda-test-layers"
+  description   = "Test layers in terraform-aws-lambda"
+  handler       = "lambda.lambda_handler"
+  runtime       = "python3.7"
+
+  layers = [
+    "arn:aws:lambda:::awslayer:AmazonLinux1803",         # https://aws.amazon.com/blogs/compute/upcoming-updates-to-the-aws-lambda-execution-environment/
+    "arn:aws:lambda:eu-west-1:553035198032:layer:git:5", # https://github.com/lambci/git-lambda-layer
+  ]
+
+  source_path = "${path.module}/lambda.py"
+}

variables.tf

@@ -25,6 +25,12 @@ variable "runtime" {
   type        = "string"
 }
 
+variable "layers" {
+  description = "List of Lambda Layer Version ARNs to attach to your Lambda Function."
+  type        = "list"
+  default     = []
+}
+
 variable "timeout" {
   description = "The amount of time your Lambda function had to run in seconds"
   type        = "string"