Swap RepositoryHashCache to UNLINK

Improves the delete performance for RepositoryHashCache by
sending a single UNLINK call for multiple keys, rather than
multiple DEL calls for each key. This is the same implementation
as used in Gitlab::SetCache.

changelogs/unreleased/hash-cache-unlink.yml

+---
+title: Swap RepositoryHashCache to UNLINK
+merge_request: 39105
+author:
+type: performance

lib/gitlab/repository_cache_adapter.rb

@@ -241,7 +241,7 @@ module Gitlab
     end
 
     def expire_redis_hash_method_caches(methods)
-      methods.each { |name| redis_hash_cache.delete(name) }
+      redis_hash_cache.delete(*methods)
     end
 
     # All cached repository methods depend on the existence of a Git repository,

lib/gitlab/repository_hash_cache.rb

@@ -31,10 +31,18 @@ module Gitlab
       "#{type}:#{namespace}:hash"
     end
 
-    # @param key [String]
-    # @return [Integer] 0 or 1 depending on success
-    def delete(key)
-      with { |redis| redis.del(cache_key(key)) }
+    # @param keys [String] one or multiple keys to delete
+    # @return [Integer] the number of keys successfully deleted
+    def delete(*keys)
+      return 0 if keys.empty?
+
+      with do |redis|
+        keys = keys.map { |key| cache_key(key) }
+
+        Gitlab::Instrumentation::RedisClusterValidator.allow_cross_slot_commands do
+          redis.unlink(*keys)
+        end
+      end
     end
 
     # Check if the provided hash key exists in the hash.

spec/lib/gitlab/repository_cache_adapter_spec.rb

@@ -212,8 +212,7 @@ RSpec.describe Gitlab::RepositoryCacheAdapter do
       expect(cache).to receive(:expire).with(:rendered_readme)
       expect(cache).to receive(:expire).with(:branch_names)
       expect(redis_set_cache).to receive(:expire).with(:rendered_readme, :branch_names)
-      expect(redis_hash_cache).to receive(:delete).with(:rendered_readme)
-      expect(redis_hash_cache).to receive(:delete).with(:branch_names)
+      expect(redis_hash_cache).to receive(:delete).with(:rendered_readme, :branch_names)
 
       repository.expire_method_caches(%i(rendered_readme branch_names))
     end

spec/lib/gitlab/repository_hash_cache_spec.rb

@@ -48,6 +48,24 @@ RSpec.describe Gitlab::RepositoryHashCache, :clean_gitlab_redis_cache do
     context "key doesn't exist" do
       it { is_expected.to eq(0) }
     end
+
+    context "multiple keys" do
+      before do
+        cache.write(:test1, test_hash)
+        cache.write(:test2, test_hash)
+      end
+
+      it "deletes multiple keys" do
+        cache.delete(:test1, :test2)
+
+        expect(cache.read_members(:test1, ["test"])).to eq("test" => nil)
+        expect(cache.read_members(:test2, ["test"])).to eq("test" => nil)
+      end
+
+      it "returns deleted key count" do
+        expect(cache.delete(:test1, :test2)).to eq(2)
+      end
+    end
   end
 
   describe "#key?" do

spec/models/repository_spec.rb

@@ -587,15 +587,19 @@ RSpec.describe Repository do
       end
 
       it "is expired when the branches caches are expired" do
-        expect(cache).to receive(:delete).with(:merged_branch_names).at_least(:once)
+        expect(cache).to receive(:delete) do |*args|
+          expect(args).to include(:merged_branch_names)
+        end
 
-        repository.send(:expire_branches_cache)
+        repository.expire_branches_cache
       end
 
       it "is expired when the repository caches are expired" do
-        expect(cache).to receive(:delete).with(:merged_branch_names).at_least(:once)
+        expect(cache).to receive(:delete) do |*args|
+          expect(args).to include(:merged_branch_names)
+        end
 
-        repository.send(:expire_all_method_caches)
+        repository.expire_all_method_caches
       end
     end