feat: add cron schedule trigger option

CHANGELOG.md

 # Change Log
 
+## [0.3.0]
+
+### Added
+
+- Crontab style schedule option added to terraform module
+
 ## [0.2.0]
 
 ### Added

pyproject.toml

 [tool.poetry]
 name = "ucam-faas"
-version = "0.2.0"
+version = "0.3.0"
 description = "Opinionated FaaS support framework extending Google's functions-framework"
 authors = ["University of Cambridge Information Services <devops-wilson@uis.cam.ac.uk>"]
 readme = "README.md"
@@ -70,6 +70,10 @@ cwd = "terraform"
 cmd = "logan --workspace=development terraform apply"
 cwd = "terraform"
 
+[tool.poe.tasks."terraform:dev"]
+cmd = "logan --workspace=development terraform"
+cwd = "terraform"
+
 [tool.poetry.dependencies]
 python = "^3.9.1"
 requests = "^2.31.0"

terraform/faas.tf

@@ -58,3 +58,32 @@ module "faas_service_set_retry" {
   }
 
 }
+
+module "faas_service_cron" {
+
+  source                   = "./modules/faas"
+  name                     = "faas-test-cron"
+  project                  = local.project
+  function_container_image = "${local.container_images.function_base}:${local.container_images.function_tag}"
+  function                 = "example_cloud_event"
+
+  timeout_seconds = 20
+
+  triggers = {
+    cron_schedules = ["00 0 */7 * *", "0 12 */7 * *", ]
+  }
+
+  retry_count = 4
+
+  function_env = [
+    {
+      name  = "TEST_VAR"
+      value = "WORKING"
+    }
+  ]
+
+  concurrency = {
+    max_concurrent_functions = 1
+  }
+
+}

terraform/modules/faas/main.tf

@@ -99,13 +99,19 @@ resource "google_cloud_run_v2_service" "faas" {
   }
 }
 
-resource "google_pubsub_subscription" "provided_topic" {
+locals {
 
-  for_each = { for i, v in [var.triggers.pubsub_topic_id] : i => v }
+  cron_schedules_supplied = length(var.triggers.cron_schedules) > 0
 
-  name  = var.name
-  topic = var.triggers.pubsub_topic_id
+}
+
+resource "google_pubsub_subscription" "main" {
 
+  # Set count to aid adding non-pubsub based trigger if needed in the future
+  count = 1
+
+  name  = var.name
+  topic = local.cron_schedules_supplied ? google_pubsub_topic.scheduler_pubsub[0].id : var.triggers.pubsub_topic_id
 
   push_config {
     push_endpoint = google_cloud_run_v2_service.faas.uri
@@ -136,6 +142,32 @@ resource "google_pubsub_subscription" "provided_topic" {
 
 }
 
+resource "google_pubsub_topic" "scheduler_pubsub" {
+
+  count = local.cron_schedules_supplied ? 1 : 0
+
+  name    = "${var.name}-cron"
+  project = var.project
+
+}
+
+resource "google_cloud_scheduler_job" "cron" {
+
+  for_each = { for index, cron in var.triggers.cron_schedules : index => cron }
+
+  name    = "${var.name}-${each.key}"
+  project = var.project
+
+  schedule  = each.value
+  time_zone = "Europe/London"
+
+  pubsub_target {
+    topic_name = google_pubsub_topic.scheduler_pubsub[0].id
+    data       = base64encode(jsonencode({ "cron_schedule" : each.value }))
+  }
+
+}
+
 # FIXME when deadletter functionality added, ensure subscription exists
 # Currently just used to provider retry count control
 resource "google_pubsub_topic" "dead_letter" {

terraform/modules/faas/variables.tf

@@ -114,15 +114,23 @@ variable "triggers" {
   type = object({
 
     pubsub_topic_id = optional(string, null)
+    cron_schedules  = optional(list(string), [])
 
   })
 
   description = <<EOI
   pubsub_topic_id - PUB/SUB topic ID to subscribe to and trigger function from.
+  cron_schedules - list of crontab style scheduler strings, e.g. ["30 16 * * 7"]
+  See http://man7.org/linux/man-pages/man5/crontab.5.html
   EOI
 
   validation {
-    condition     = var.triggers.pubsub_topic_id != null
-    error_message = "pubsub_topic_id must be set"
+    condition     = var.triggers.pubsub_topic_id != null || length(var.triggers.cron_schedules) > 0
+    error_message = "either pubsub_topic_id must be set or cron_schedules must be of length > 0"
+  }
+
+  validation {
+    condition     = var.triggers.pubsub_topic_id == null || length(var.triggers.cron_schedules) < 1
+    error_message = "only one of pubsub_topic_id or cron_schedules must be set"
   }
 }