Add heartbeat monitor for statuscake

app/jobs/heartbeat_job.rb

@@ -1,12 +1,15 @@
-# Writes "Heartbeat job performed" to the logs every minute. This message is
-# evidence that the worker is working properly. We can use a log alerting tool
-# to alert us if too much time passes without seeing one of these messages.
+require "net/http"
+
 class HeartbeatJob < CronJob
   self.cron_expression = "* * * * *"
 
   queue_as :heartbeat
 
   def perform
-    logger.info "Heartbeat job performed"
+    if ENV.key?("HEARTBEAT_CHECK_URL") # Not available in dev and review environments
+      url = URI.parse(ENV["HEARTBEAT_CHECK_URL"])
+      req = Net::HTTP::Get.new(url.to_s)
+      Net::HTTP.start(url.host, url.port) { |http| http.request(req) }
+    end
   end
 end

terraform/application/application.tf

@@ -17,9 +17,14 @@ module "application_configuration" {
       PGSSLMODE          = local.postgres_ssl_mode
       CANONICAL_HOSTNAME = local.canonical_hostname
   })
-  secret_variables = {
-    DATABASE_URL = module.postgres.url
-  }
+  secret_variables = merge(
+    {
+      DATABASE_URL        = module.postgres.url
+    },
+    var.enable_monitoring ? {
+      HEARTBEAT_CHECK_URL = module.statuscake[0].heartbeat_check_urls[local.heartbeat_check_name]
+    } : {}
+  )
 }
 
 module "web_application" {

terraform/application/statuscake.tf

@@ -7,4 +7,6 @@ module "statuscake" {
   ssl_urls    = compact([var.external_url])
 
   contact_groups = var.statuscake_contact_groups
+
+  heartbeat_names  = [local.heartbeat_check_name]
 }

terraform/application/variables.tf

@@ -89,4 +89,5 @@ locals {
   canonical_hostname      = var.canonical_hostname != null ? var.canonical_hostname : "${var.service_name}-${var.environment}-web.test.teacherservices.cloud"
   app_env_values_from_yml = yamldecode(file("${path.module}/config/${var.config}_app_env.yml"))
   app_env_values          = merge(local.app_env_values_from_yml)
+  heartbeat_check_name    = "heartbeat-check"
 }