Fix: Timeout creating and viewing merge request for binary file

changelogs/unreleased/timeout-merge-request-for-binary-file.yml

+---
+title: Timeout creating and viewing merge request for binary file
+merge_request: 
+author: 

lib/gitlab/diff/file_collection/merge_request_diff.rb

@@ -20,7 +20,7 @@ module Gitlab
         # Extracted method to highlight in the same iteration to the diff_collection.
         def decorate_diff!(diff)
           diff_file = super
-          cache_highlight!(diff_file) if cacheable?
+          cache_highlight!(diff_file) if cacheable?(diff_file)
           diff_file
         end
 
@@ -60,8 +60,8 @@ module Gitlab
           Rails.cache.write(cache_key, highlight_cache) if @highlight_cache_was_empty
         end
 
-        def cacheable?
-          @merge_request_diff.present?
+        def cacheable?(diff_file)
+          @merge_request_diff.present? && diff_file.blob.text?
         end
 
         def cache_key

spec/lib/gitlab/diff/file_collection/merge_request_diff_spec.rb

+require 'spec_helper'
+
+describe Gitlab::Diff::FileCollection::MergeRequestDiff do
+  let(:merge_request) { create :merge_request }
+
+  it 'does not hightlight binary files' do
+    allow_any_instance_of(Gitlab::Diff::File).to receive(:blob).and_return(double("text?" => false))
+
+    expect_any_instance_of(Gitlab::Diff::File).not_to receive(:highlighted_diff_lines)
+
+    described_class.new(merge_request.merge_request_diff, diff_options: nil).diff_files
+  end
+end

spec/services/merge_requests/merge_request_diff_cache_service_spec.rb

@@ -10,6 +10,7 @@ describe MergeRequests::MergeRequestDiffCacheService do
 
       expect(Rails.cache).to receive(:read).with(cache_key).and_return({})
       expect(Rails.cache).to receive(:write).with(cache_key, anything)
+      allow_any_instance_of(Gitlab::Diff::File).to receive(:blob).and_return(double("text?" => true))
 
       subject.execute(merge_request)
     end