From 5bd042e7d67143f09b4908fc449dd06b33086cde Mon Sep 17 00:00:00 2001
From: Ben Halpern <bendhalpern@gmail.com>
Date: Mon, 9 Mar 2020 16:22:42 -0400
Subject: [PATCH] Prune old field tests for ongoing tests (#6540) [deploy]

---
 .../prune_old_experiments_worker.rb           | 13 +++++++++++
 lib/tasks/fetch.rake                          |  7 ++++++
 spec/factories/field_test_memberships.rb      |  8 +++++++
 .../prune_old_experiments_worker_spec.rb      | 22 +++++++++++++++++++
 4 files changed, 50 insertions(+)
 create mode 100644 app/workers/field_tests/prune_old_experiments_worker.rb
 create mode 100644 spec/factories/field_test_memberships.rb
 create mode 100644 spec/workers/field_tests/prune_old_experiments_worker_spec.rb

diff --git a/app/workers/field_tests/prune_old_experiments_worker.rb b/app/workers/field_tests/prune_old_experiments_worker.rb
new file mode 100644
index 000000000..952be381b
--- /dev/null
+++ b/app/workers/field_tests/prune_old_experiments_worker.rb
@@ -0,0 +1,13 @@
+module FieldTests
+  class PruneOldExperimentsWorker
+    include Sidekiq::Worker
+    sidekiq_options queue: :low_priority, retry: 10
+
+    def perform
+      five_precent_membership_count = FieldTest::Membership.count / 20
+      memberships = FieldTest::Membership.first(five_precent_membership_count)
+      FieldTest::Event.where(field_test_membership_id: memberships.pluck(:id)).delete_all
+      memberships.map(&:delete)
+    end
+  end
+end
diff --git a/lib/tasks/fetch.rake b/lib/tasks/fetch.rake
index 75ed7dbba..4422f11fa 100644
--- a/lib/tasks/fetch.rake
+++ b/lib/tasks/fetch.rake
@@ -98,6 +98,13 @@ task award_contributor_badges_from_github: :environment do
   BadgeRewarder.award_contributor_badges_from_github
 end
 
+# This task is meant to be scheduled daily
+task prune_old_field_tests: :environment do
+  # For rolling ongoing experiemnts, we remove old experiment memberships
+  # So that they can be re-tested.
+  FieldTests::PruneOldExperimentsWorker.perform_async
+end
+
 task remove_old_html_variant_data: :environment do
   HtmlVariantTrial.where("created_at < ?", 2.weeks.ago).destroy_all
   HtmlVariantSuccess.where("created_at < ?", 2.weeks.ago).destroy_all
diff --git a/spec/factories/field_test_memberships.rb b/spec/factories/field_test_memberships.rb
new file mode 100644
index 000000000..13129e48e
--- /dev/null
+++ b/spec/factories/field_test_memberships.rb
@@ -0,0 +1,8 @@
+FactoryBot.define do
+  factory :field_test_memberships, class: "FieldTest::Membership" do
+    converted         { false }
+    experiment        { :user_home_feed }
+    participant_type  { "User" }
+    variant           { "base" }
+  end
+end
diff --git a/spec/workers/field_tests/prune_old_experiments_worker_spec.rb b/spec/workers/field_tests/prune_old_experiments_worker_spec.rb
new file mode 100644
index 000000000..1255f06ff
--- /dev/null
+++ b/spec/workers/field_tests/prune_old_experiments_worker_spec.rb
@@ -0,0 +1,22 @@
+require "rails_helper"
+
+RSpec.describe FieldTests::PruneOldExperimentsWorker, type: :worker do
+  include_examples "#enqueues_on_correct_queue", "low_priority", 1
+  include FieldTest::Helpers
+
+  describe "#perform" do
+    let(:worker) { subject }
+
+    it "prunes first 5% of memberships and events" do
+      create_list(:user, 40)
+      User.all.each do |user|
+        create(:field_test_memberships, participant_id: user.id.to_s)
+        field_test_converted(:user_home_feed, participant: user, goal: "user_creates_comment")
+      end
+      worker.perform
+      expect(FieldTest::Membership.count).to be(38)
+      expect(FieldTest::Event.count).to be(38)
+      expect(FieldTest::Event.pluck(:field_test_membership_id).sort).to eq(FieldTest::Membership.pluck(:id).sort)
+    end
+  end
+end