Adding VariantQuery reseed randomization option (#17942)

Prior to this change, we setup our feed variant query to have a cached
randomization seed.  For a given user this seed is cached for 15
minutes.  The goal of this is to provide mostly consistent sort orders
on the feed articles during that 15 minute window.

With this change, we allow for a feed variant to say ignore the cached
seed and generate a new one for this call.

I have also added explicit settings to each of the feed variants to
reflect our desired intentions for those features.

Relates to

- forem/forem#17833
- forem/forem#17826

Closes forem/forem#17940

app/models/articles/feeds/variant_assembler.rb

@@ -85,6 +85,7 @@ module Articles
           description: config.fetch("description", ""),
           order_by: catalog.fetch_order_by(config.fetch("order_by")),
           max_days_since_published: config.fetch("max_days_since_published"),
+          reseed_randomizer_on_each_request: config.fetch("reseed_randomizer_on_each_request"),
         )
       end
       private_class_method :build_with

app/services/articles/feeds/variant_query.rb

@@ -34,15 +34,23 @@ module Articles
         :levers, # Array <Articles::Feeds::RelevancyLever::Configured>
         :order_by, # Articles::Feeds::OrderByLever
         :max_days_since_published,
+        # when true, each time you call the query you will get different randomized numbers; when
+        # false, the resulting randomized numbers will be the same within a window of time.
+        :reseed_randomizer_on_each_request,
         keyword_init: true,
-      )
+      ) do
+        alias_method :reseed_randomizer_on_each_request?, :reseed_randomizer_on_each_request
+      end
 
       # @param config [Articles::Feeds::VariantQuery::Config]
       # @param user [User,NilClass]
       # @param number_of_articles [Integer, #to_i]
       # @param page [Integer, #to_i]
       # @param tag [NilClass] not used
-      # @param seed [Number] used in the `setseed` Postgresql function to set the randomization seed.
+      #
+      # @param seed [Number] used in the `setseed` Postgresql function to set the randomization
+      #        seed.  This parameter allows the caller (and debugger) to use the same randomization
+      #        order in the queries; the hope being that this might help in any debugging.
       def initialize(config:, user: nil, number_of_articles: 50, page: 1, tag: nil, seed: nil)
         @user = user
         @number_of_articles = number_of_articles
@@ -297,6 +305,8 @@ module Articles
       def randomizer_seed_for(seed:, user:)
         return Float(seed) if seed
 
+        return rand if config.reseed_randomizer_on_each_request?
+
         # This is added as a short-circuit in-case the caching proves to be non-performant.  Once
         # this has been merged, given that it's part of the main loop, we can remove the FeatureFlag
         # a week or so after we merge.

config/feed-variants/20220415-incumbent.json

@@ -1,5 +1,6 @@
 {
   "max_days_since_published": 15,
+  "reseed_randomizer_on_each_request": false,
   "order_by": "relevancy_score_and_publication_date",
   "levers": {
     "daily_decay": {

config/feed-variants/20220422-variant.json

@@ -1,5 +1,6 @@
 {
   "max_days_since_published": 15,
+  "reseed_randomizer_on_each_request": false,
   "order_by": "relevancy_score_and_publication_date",
   "levers": {
     "daily_decay": {

config/feed-variants/20220509-variant.json

@@ -1,5 +1,6 @@
 {
   "max_days_since_published": 15,
+  "reseed_randomizer_on_each_request": false,
   "order_by": "relevancy_score_and_publication_date",
   "levers": {
     "daily_decay": {

config/feed-variants/20220518-variant.json

@@ -1,5 +1,6 @@
 {
   "max_days_since_published": 15,
+  "reseed_randomizer_on_each_request": false,
   "order_by": "relevancy_score_and_publication_date",
   "levers": {
     "daily_decay": {

config/feed-variants/20220525-variant.json

@@ -1,5 +1,6 @@
 {
   "max_days_since_published": 15,
+  "reseed_randomizer_on_each_request": false,
   "order_by": "relevancy_score_and_publication_date",
   "levers": {
     "featured_article": { "cases": [[1, 1]], "fallback": 0.85 },

config/feed-variants/20220603-variant-a.json

@@ -1,5 +1,6 @@
 {
   "max_days_since_published": 15,
+  "reseed_randomizer_on_each_request": false,
   "description": "As 202205518-variant but with modificiation to `matching_positive_tags_intersection_count`.",
   "order_by": "relevancy_score_and_publication_date",
   "levers": {

config/feed-variants/20220603-variant-b.json

@@ -1,5 +1,6 @@
 {
   "max_days_since_published": 15,
+  "reseed_randomizer_on_each_request": false,
   "description": "As 202205518-variant but with modificiation to `order_by` lever.",
   "order_by": "final_order_by_random_weighted_to_score",
   "levers": {

config/feed-variants/README.md

@@ -40,3 +40,7 @@ and as of <2022-05-06 Fri> are:
 
 - **_max_days_since_published_:** only consider articles that were published no
   more than the _max_days_since_published_.
+
+- **_reseed_randomizer_on_each_request_:** when true, each time you call the
+  query you will get different randomized numbers; when false, the resulting
+  randomized numbers will be the same within a window of time.

config/feed-variants/original.json

@@ -1,5 +1,6 @@
 {
   "max_days_since_published": 15,
+  "reseed_randomizer_on_each_request": false,
   "order_by": "relevancy_score_and_publication_date",
   "levers": {
     "daily_decay": {