Add article cachebust backoff update script (#11472)

* Add article cachebust backoff update script

* ?i=i variant

* Change values

* Add select for optimization

lib/data_update_scripts/20201118141822_gradual_article_cache_bust.rb

@@ -0,0 +1,24 @@
+module DataUpdateScripts
+  class GradualArticleCacheBust
+    def run
+      # This script is designed to bust the cache on article pages sufficient such that significant changes to
+      # CSS will not create meaningful visual regressions for most users.
+      # All articles have their caches naturally recycle once per day to finalize the transition.
+
+      # This uses exponential backoff in order to bust the caches of more recent articles first, but not
+      # bust everything in too short a period, so that the edge cache can gradually re-heat without everything
+      # going cold at once. Articles with high "hotness score" (e.g. more recent) are the ones most in need of busting.
+
+      # It only busts the "?i=i" variant of the path which is the "internal nav" version, aka the page when swapped
+      # with internal navigation, not the one landed on directly (which wouldn't have cache mismatches)
+      Article.published.order("hotness_score DESC").limit(1500).select(:path).each_with_index do |article, index|
+        n = index + 300 # + 300 gives the server time to boot up
+        BustCachePathWorker.set(queue: :high_priority).perform_in(n.seconds, "#{article.path}?i=i")
+      end
+      Article.published.order("hotness_score DESC").offset(1500).limit(3000).select(:path).each_with_index do |article, index|
+        n = (index * 3) + 450
+        BustCachePathWorker.set(queue: :medium_priority).perform_in(n.seconds, "#{article.path}?i=i")
+      end
+    end
+  end
+end