enable scheduling from cloudwatch

README.md

@@ -13,6 +13,7 @@ The purpose of this repo is to deploy AWS Lambda function that scrapes rising an
 
     ```sh
     terraform init
-    terraform apply
+    terraform plan -var-file="dev.tfvars"
+    terraform apply -var-file="dev.tfvars"
     ```
-    If you don't want to apply the changes to your aws account you can instead run `terraform plan`.
+    If you don't want to apply the changes to your aws account then just run the `terraform plan` command to see what changes would be applied.

main.tf

@@ -228,3 +228,25 @@ resource "aws_lambda_function" "lambda_function" {
     Project     = "viral-reddit-posts"
   }
 }
+
+# Attach event trigger to Lambda Function, see https://stackoverflow.com/questions/35895315/use-terraform-to-set-up-a-lambda-function-triggered-by-a-scheduled-event-source
+resource "aws_cloudwatch_event_rule" "every_one_minute" {
+    name = "every-one-minute"
+    description = "Fires every one minute"
+    schedule_expression = "rate(1 minute)"
+    is_enabled = var.enable_schedule
+}
+
+resource "aws_cloudwatch_event_target" "scrape_reddit_every_minute" {
+    rule = aws_cloudwatch_event_rule.every_one_minute.name
+    target_id = "scrape_reddit"
+    arn = aws_lambda_function.lambda_function.arn
+}
+
+resource "aws_lambda_permission" "allow_cloudwatch_to_call_lambda_function" {
+    statement_id = "AllowExecutionFromCloudWatch"
+    action = "lambda:InvokeFunction"
+    function_name = aws_lambda_function.lambda_function.function_name
+    principal = "events.amazonaws.com"
+    source_arn = aws_cloudwatch_event_rule.every_one_minute.arn
+}

variable.tf

@@ -0,0 +1,5 @@
+variable "enable_schedule" {
+  type = bool
+  default = false
+  description = "whether or not the lambda function schedule is enabled or not"
+}