Rate limit requests to GOV.UK Notify

This limits the number of requests we send to GOV.UK Notify each minute
to ensure that we stay within their rate limits. If we were to breach
these limits, the jobs would keep retrying until they succeed.

Author: thomasleese

app/jobs/concerns/notify_throttling_concern.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+module NotifyThrottlingConcern
+  extend ActiveSupport::Concern
+
+  include Sidekiq::Job
+  include Sidekiq::Throttled::Job
+
+  included do
+    self.queue_adapter = :sidekiq unless Rails.env.test?
+
+    sidekiq_throttle_as :notify
+
+    queue_as :notifications
+  end
+end

app/jobs/email_delivery_job.rb

@@ -1,6 +1,8 @@
 # frozen_string_literal: true
 
 class EmailDeliveryJob < NotifyDeliveryJob
+  include NotifyThrottlingConcern
+
   def perform(
     template_name,
     consent: nil,

app/jobs/notify_delivery_job.rb

@@ -3,12 +3,6 @@
 require "notifications/client"
 
 class NotifyDeliveryJob < ApplicationJob
-  self.queue_adapter = :sidekiq unless Rails.env.test?
-
-  queue_as :notifications
-
-  retry_on Notifications::Client::ServerError, wait: :polynomially_longer
-
   def self.client
     @client ||=
       Notifications::Client.new(
@@ -20,13 +14,9 @@ def self.deliveries
     @deliveries ||= []
   end
 
-  def self.send_via_notify?
-    Settings.govuk_notify&.enabled
-  end
+  def self.send_via_notify? = Settings.govuk_notify&.enabled
 
-  def self.send_via_test?
-    Rails.env.test?
-  end
+  def self.send_via_test? = Rails.env.test?
 
   class UnknownTemplate < StandardError
   end

app/jobs/sms_delivery_job.rb

@@ -1,6 +1,8 @@
 # frozen_string_literal: true
 
 class SMSDeliveryJob < NotifyDeliveryJob
+  include NotifyThrottlingConcern
+
   def perform(
     template_name,
     consent: nil,

app/jobs/status_updater_job.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-class StatusUpdaterJob < NotifyDeliveryJob
+class StatusUpdaterJob < ApplicationJob
   include GoodJob::ActiveJobExtensions::Concurrency
 
   queue_as :statuses

config/initializers/sidekiq.rb

@@ -18,6 +18,15 @@
   config.cooldown_threshold = 1000
 end
 
+# https://docs.notifications.service.gov.uk/rest-api.html#rate-limits
+Sidekiq::Throttled::Registry.add(
+  :notify,
+  threshold: {
+    limit: Settings.govuk_notify.rate_limit_per_minute.to_i,
+    period: 1.minute
+  }
+)
+
 Sidekiq::Throttled::Registry.add(
   :pds,
   threshold: {

config/settings.yml

@@ -28,6 +28,7 @@ govuk_notify:
   team_key: <%= Rails.application.credentials.govuk_notify&.team_key %>
   live_key: <%= Rails.application.credentials.govuk_notify&.live_key %>
   callback_bearer_token: <%= Rails.application.credentials.govuk_notify&.callback_bearer_token %>
+  rate_limit_per_minute: 3000
 
 nhs_api:
   api_key: <%= Rails.application.credentials.nhs_api&.api_key %>