feat: Added support for custom lambda function (#172)

Author: sobi3ch

README.md

@@ -12,6 +12,7 @@ Doing serverless with Terraform? Check out [serverless.tf framework](https://ser
 - Create new SNS topic or use existing one
 - Support plaintext and encrypted version of Slack webhook URL
 - Most of Slack message options are customizable
+- Custom Lambda function
 - Various event types are supported, even generic messages:
   - AWS CloudWatch Alarms
   - AWS CloudWatch LogMetrics Alarms
@@ -114,6 +115,7 @@ See the [functions](https://github.com/terraform-aws-modules/terraform-aws-notif
 | <a name="input_lambda_function_vpc_security_group_ids"></a> [lambda\_function\_vpc\_security\_group\_ids](#input\_lambda\_function\_vpc\_security\_group\_ids) | List of security group ids when Lambda Function should run in the VPC. | `list(string)` | `null` | no |
 | <a name="input_lambda_function_vpc_subnet_ids"></a> [lambda\_function\_vpc\_subnet\_ids](#input\_lambda\_function\_vpc\_subnet\_ids) | List of subnet ids when Lambda Function should run in the VPC. Usually private or intra subnets. | `list(string)` | `null` | no |
 | <a name="input_lambda_role"></a> [lambda\_role](#input\_lambda\_role) | IAM role attached to the Lambda Function.  If this is set then a role will not be created for you. | `string` | `""` | no |
+| <a name="input_lambda_source_path"></a> [lambda\_source\_path](#input\_lambda\_source\_path) | The source path of the custom Lambda function | `string` | `null` | no |
 | <a name="input_log_events"></a> [log\_events](#input\_log\_events) | Boolean flag to enabled/disable logging of incoming events | `bool` | `false` | no |
 | <a name="input_recreate_missing_package"></a> [recreate\_missing\_package](#input\_recreate\_missing\_package) | Whether to recreate missing Lambda package if it is missing locally or not | `bool` | `true` | no |
 | <a name="input_reserved_concurrent_executions"></a> [reserved\_concurrent\_executions](#input\_reserved\_concurrent\_executions) | The amount of reserved concurrent executions for this lambda function. A value of 0 disables lambda from being triggered and -1 removes any concurrency limitations | `number` | `-1` | no |

examples/notify-slack-simple/README.md

@@ -38,12 +38,14 @@ Note that this example may create resources which can cost money (AWS Elastic IP
 
 | Name | Source | Version |
 |------|--------|---------|
+| <a name="module_custom_lambda"></a> [custom\_lambda](#module\_custom\_lambda) | ../../ | n/a |
 | <a name="module_notify_slack"></a> [notify\_slack](#module\_notify\_slack) | ../../ | n/a |
 
 ## Resources
 
 | Name | Type |
 |------|------|
+| [aws_sns_topic.custom_lambda](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/sns_topic) | resource |
 | [aws_sns_topic.example](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/sns_topic) | resource |
 | [local_file.integration_testing](https://registry.terraform.io/providers/hashicorp/local/latest/docs/resources/file) | resource |
 

examples/notify-slack-simple/custom-lambda.tf

@@ -0,0 +1,36 @@
+locals {
+  custom = {
+    name = "ex-${replace(basename(path.cwd), "_", "-")}-custom"
+    tags = merge({ "Type" = "custom" }, local.tags)
+  }
+}
+
+################################################################################
+# Supporting Resources
+################################################################################
+
+resource "aws_sns_topic" "custom_lambda" {
+  name = local.custom.name
+  tags = local.custom.tags
+}
+
+################################################################################
+# Slack Notify Module
+################################################################################
+
+module "custom_lambda" {
+  source = "../../"
+
+  lambda_function_name = "custom_lambda"
+  lambda_source_path   = "../../functions/mylambda.py"
+
+  iam_role_name_prefix = "custom"
+
+  sns_topic_name = aws_sns_topic.custom_lambda.name
+
+  slack_webhook_url = "https://hooks.slack.com/services/AAA/BBB/CCC"
+  slack_channel     = "aws-notification"
+  slack_username    = "reporter"
+
+  tags = local.custom.tags
+}

functions/mylambda.py

@@ -0,0 +1,25 @@
+#!/usr/bin/python3.6
+# CUSTOM LAMBDA FUNCTION
+
+import urllib3
+import json
+import os
+http = urllib3.PoolManager()
+
+
+def lambda_handler(event, context):
+    url = os.environ["SLACK_WEBHOOK_URL"]
+    msg = {
+        "channel": "#channel-name",
+        "username": "Prometheus",
+        "text": event['Records'][0]['Sns']['Message'],
+        "icon_emoji": ""
+    }
+
+    encoded_msg = json.dumps(msg).encode('utf-8')
+    resp = http.request('POST', url, body=encoded_msg)
+    print({
+        "message": event['Records'][0]['Sns']['Message'],
+        "status_code": resp.status,
+        "response": resp.data
+    })

main.tf

@@ -22,6 +22,8 @@ locals {
     actions   = ["kms:Decrypt"]
     resources = [var.kms_key_arn]
   }
+
+  lambda_handler = try(split(".", basename(var.lambda_source_path))[0], "notify_slack")
 }
 
 data "aws_iam_policy_document" "lambda" {
@@ -77,8 +79,8 @@ module "lambda" {
   function_name = var.lambda_function_name
   description   = var.lambda_description
 
-  handler                        = "notify_slack.lambda_handler"
-  source_path                    = "${path.module}/functions/notify_slack.py"
+  handler                        = "${local.lambda_handler}.lambda_handler"
+  source_path                    = var.lambda_source_path != null ? "${path.root}/${var.lambda_source_path}" : "${path.module}/functions/notify_slack.py"
   recreate_missing_package       = var.recreate_missing_package
   runtime                        = "python3.8"
   timeout                        = 30

variables.tf

@@ -28,6 +28,12 @@ variable "lambda_description" {
   default     = null
 }
 
+variable "lambda_source_path" {
+  description = "The source path of the custom Lambda function"
+  type        = string
+  default     = null
+}
+
 variable "sns_topic_name" {
   description = "The name of the SNS topic to create"
   type        = string