Add feed variants with shuffle post-ranking (#6766) [deploy]

* Add feed variants with shuffle post-ranking

* Refactor tests and fix erroneous shuffle

app/controllers/stories/feeds_controller.rb

@@ -39,6 +39,12 @@ class Stories::FeedsController < ApplicationController
       feed.more_comments_experiment
     when "more_experience_level_weight_experiment"
       feed.more_experience_level_weight_experiment
+    when "more_tag_weight_randomized_at_end_experiment"
+      feed.more_tag_weight_randomized_at_end_experiment
+    when "more_experience_level_weight_randomized_at_end_experiment"
+      feed.more_experience_level_weight_randomized_at_end_experiment
+    when "more_comments_randomized_at_end_experiment"
+      feed.more_comments_randomized_at_end_experiment
     when "mix_of_everything_experiment" # mix of all experiments. New experiments also added. This is the "index fund" version.
       feed.mix_of_everything_experiment
     else

app/services/articles/feed.rb

@@ -1,6 +1,6 @@
 module Articles
   class Feed
-    RANDOM_OFFSET_VALUES = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 3, 3, 4, 5, 6, 7, 8, 9, 10, 11].freeze
+    RANDOM_OFFSET_VALUES = [0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 3, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13].freeze
 
     def initialize(user: nil, number_of_articles: 35, page: 1, tag: nil)
       @user = user
@@ -100,7 +100,7 @@ module Articles
     end
 
     def mix_of_everything_experiment
-      case rand(7)
+      case rand(10)
       when 0
         default_home_feed(user_signed_in: true)
       when 1
@@ -115,11 +115,40 @@ module Articles
         more_comments_experiment
       when 6
         more_experience_level_weight_experiment
+      when 7
+        more_tag_weight_randomized_at_end_experiment
+      when 8
+        more_experience_level_weight_randomized_at_end_experiment
+      when 9
+        more_comments_randomized_at_end_experiment
       else
         default_home_feed(user_signed_in: true)
       end
     end
 
+    # Randomized at end group for next three experiments
+    # Rather than randomizing *during* the ranking, rank solely by quality/match
+    # and randomize the top half of the ranked results.
+    # Resulting in more relevance and still more freshness.
+
+    def more_tag_weight_randomized_at_end_experiment
+      @randomness = 0
+      results = more_tag_weight_experiment
+      first_half(results).shuffle + last_half(results)
+    end
+
+    def more_experience_level_weight_randomized_at_end_experiment
+      @randomness = 0
+      results = more_experience_level_weight_experiment
+      first_half(results).shuffle + last_half(results)
+    end
+
+    def more_comments_randomized_at_end_experiment
+      @randomness = 0
+      results = more_comments_experiment
+      first_half(results).shuffle + last_half(results)
+    end
+
     def rank_and_sort_articles(articles)
       ranked_articles = articles.each_with_object({}) do |article, result|
         article_points = score_single_article(article)
@@ -176,7 +205,7 @@ module Articles
 
     def globally_hot_articles(user_signed_in)
       hot_stories = published_articles_by_tag.
-        where("score > ? OR featured = ?", 8, true).
+        where("score > ? OR featured = ?", 7, true).
         order("hotness_score DESC")
       featured_story = hot_stories.where.not(main_image: nil).first
       if user_signed_in
@@ -203,5 +232,13 @@ module Articles
     def user_following_users_ids
       @user_following_users_ids ||= (@user&.cached_following_users_ids || [])
     end
+
+    def first_half(array)
+      array[0...(array.length / 2)]
+    end
+
+    def last_half(array)
+      array[(array.length / 2)..array.length]
+    end
   end
 end

config/field_test.yml

@@ -9,15 +9,21 @@ experiments:
       - more_comments_experiment
       - more_experience_level_weight_experiment
       - mix_of_everything_experiment
+      - more_tag_weight_randomized_at_end_experiment
+      - more_experience_level_weight_randomized_at_end_experiment
+      - more_comments_randomized_at_end_experiment
     weights:
       - 25
+      - 5
       - 10
-      - 10
-      - 15
+      - 5
+      - 5
       - 10
       - 10
       - 10
+      - 5
       - 10
+      - 5
     goals:
       - user_creates_comment
       - user_creates_reaction

spec/services/articles/feed_spec.rb

@@ -1,5 +1,18 @@
 require "rails_helper"
 
+NON_DEFAULT_EXPERIMENTS = %i[
+  default_home_feed_with_more_randomness_experiment
+  mix_default_and_more_random_experiment
+  more_tag_weight_experiment
+  more_tag_weight_more_random_experiment
+  more_comments_experiment
+  more_experience_level_weight_experiment
+  more_tag_weight_randomized_at_end_experiment
+  more_experience_level_weight_randomized_at_end_experiment
+  more_comments_randomized_at_end_experiment
+  mix_of_everything_experiment
+].freeze
+
 RSpec.describe Articles::Feed, type: :service do
   let(:user) { create(:user) }
   let!(:feed) { described_class.new(user: user, number_of_articles: 100, page: 1) }
@@ -137,63 +150,14 @@ RSpec.describe Articles::Feed, type: :service do
     end
   end
 
-  describe "#default_home_feed_with_more_randomness_experiment" do
-    let!(:new_story) { create(:article, published_at: 10.minutes.ago, score: 10) }
-    let(:stories) { feed.default_home_feed_with_more_randomness_experiment }
-
-    it "includes stories" do
-      expect(stories).to include(old_story)
-      expect(stories).to include(new_story)
-    end
-  end
-
-  describe "#mix_default_and_more_random_experiment" do
-    let!(:new_story) { create(:article, published_at: 10.minutes.ago, score: 10) }
-    let(:stories) { feed.mix_default_and_more_random_experiment }
-
-    it "includes stories" do
-      expect(stories).to include(old_story)
-      expect(stories).to include(new_story)
-    end
-  end
-
-  describe "#more_tag_weight_experiment" do
-    let!(:new_story) { create(:article, published_at: 10.minutes.ago, score: 10) }
-    let(:stories) { feed.more_tag_weight_experiment }
-
-    it "includes stories" do
-      expect(stories).to include(old_story)
-      expect(stories).to include(new_story)
-    end
-  end
-
-  describe "#more_experience_level_weight_experiment" do
-    let!(:new_story) { create(:article, published_at: 10.minutes.ago, score: 10) }
-    let(:stories) { feed.more_experience_level_weight_experiment }
-
-    it "includes stories" do
-      expect(stories).to include(old_story)
-      expect(stories).to include(new_story)
-    end
-  end
-
-  describe "#more_tag_weight_more_random_experiment" do
-    let!(:new_story) { create(:article, published_at: 10.minutes.ago, score: 10) }
-    let(:stories) { feed.more_tag_weight_more_random_experiment }
-
-    it "includes stories" do
-      expect(stories).to include(old_story)
-      expect(stories).to include(new_story)
-    end
-  end
-
-  describe "#mix_of_everything_experiment" do
-    let!(:new_story) { create(:article, published_at: 10.minutes.ago, score: 10) }
-    let(:stories) { feed.mix_of_everything_experiment }
-
-    it "includes stories" do
-      expect(stories).to include(old_story)
-      expect(stories).to include(new_story)
+  describe "all non-default experiments" do
+    it "returns articles for all experiments" do
+      new_story = create(:article, published_at: 10.minutes.ago, score: 10)
+      NON_DEFAULT_EXPERIMENTS.each do |method|
+        stories = feed.default_home_feed_with_more_randomness_experiment
+        expect(stories).to include(old_story)
+        expect(stories).to include(new_story)
+      end
     end
   end