Merge branch 'fix/get-cached-rendered-html-using-single-redis-request' into 'master'

Retrieve rendered HTML from cache in one request

## What does this MR do?
It consolidates requests made to cache store to check for cached HTML of multiple Markdown texts (for reference extracting purposes) into one request.

## Are there points in the code the reviewer needs to double check?
N/A

## Why was this MR needed?
To improve the performance of `Participable#raw_participants`

## What are the relevant issue numbers?
#19985 

## Screenshots (if relevant)
N/A

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- ~~[ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)~~
- ~~[ ] API support added~~
- ~~Tests~~
  - ~~[ ] Added for this feature/bug~~
  - ~~[ ] All builds are passing~~
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5406

3 files changed, 30 insertions, 20 deletions

diff --git a/CHANGELOG b/CHANGELOG
index 017cf92160f..8fe2caac7bd 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -3,6 +3,7 @@ Please view this file on the master branch, on stable branches it's out of date.
 v 8.11.0 (unreleased)
   - Fix of 'Commits being passed to custom hooks are already reachable when using the UI'
   - Limit git rev-list output count to one in forced push check
+  - Retrieve rendered HTML from cache in one request
 
 v 8.10.0 (unreleased)
   - Fix profile activity heatmap to show correct day name (eanplatter)
diff --git a/lib/banzai/reference_extractor.rb b/lib/banzai/reference_extractor.rb
index bf366962aef..b26a41a1f3b 100644
--- a/lib/banzai/reference_extractor.rb
+++ b/lib/banzai/reference_extractor.rb
@@ -2,11 +2,11 @@ module Banzai
   # Extract possible GFM references from an arbitrary String for further processing.
   class ReferenceExtractor
     def initialize
-      @texts = []
+      @texts_and_contexts = []
     end
 
     def analyze(text, context = {})
-      @texts << Renderer.render(text, context)
+      @texts_and_contexts << { text: text, context: context }
     end
 
     def references(type, project, current_user = nil)
@@ -21,9 +21,10 @@ module Banzai
     def html_documents
       # This ensures that we don't memoize anything until we have a number of
       # text blobs to parse.
-      return [] if @texts.empty?
+      return [] if @texts_and_contexts.empty?
 
-      @html_documents ||= @texts.map { |html| Nokogiri::HTML.fragment(html) }
+      @html_documents ||= Renderer.cache_collection_render(@texts_and_contexts)
+        .map { |html| Nokogiri::HTML.fragment(html) }
     end
   end
 end
diff --git a/spec/models/note_spec.rb b/spec/models/note_spec.rb
index 7d0697dab42..1243f5420a7 100644
--- a/spec/models/note_spec.rb
+++ b/spec/models/note_spec.rb
@@ -135,22 +135,30 @@ describe Note, models: true do
     let!(:note2) { create(:note_on_issue) }
 
     it "reads the rendered note body from the cache" do
-      expect(Banzai::Renderer).to receive(:render).
-        with(note1.note,
-             pipeline: :note,
-             cache_key: [note1, "note"],
-             project: note1.project,
-             author: note1.author)
-
-      expect(Banzai::Renderer).to receive(:render).
-        with(note2.note,
-             pipeline: :note,
-             cache_key: [note2, "note"],
-             project: note2.project,
-             author: note2.author)
-
-      note1.all_references
-      note2.all_references
+      expect(Banzai::Renderer).to receive(:cache_collection_render).
+        with([{
+          text: note1.note,
+          context: {
+            pipeline: :note,
+            cache_key: [note1, "note"],
+            project: note1.project,
+            author: note1.author
+          }
+        }]).and_call_original
+
+      expect(Banzai::Renderer).to receive(:cache_collection_render).
+        with([{
+          text: note2.note,
+          context: {
+            pipeline: :note,
+            cache_key: [note2, "note"],
+            project: note2.project,
+            author: note2.author
+          }
+        }]).and_call_original
+
+      note1.all_references.users
+      note2.all_references.users
     end
   end