Bring back Rugged implementation of ListCommitsByOid

This brings back changes in
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/20432.

For users using Gitaly on top of NFS, accessing the Git data directly
via Rugged may be faster than going through than Gitaly. This merge
request introduces the feature flag `rugged_list_commits_by_oid` to
activate the Rugged method.

For one customer, we saw that ListCommitsByOid was the second highest
used endpoint that may be causing increased load.

2 files changed, 21 insertions, 1 deletions

diff --git a/lib/gitlab/git/rugged_impl/commit.rb b/lib/gitlab/git/rugged_impl/commit.rb
index f6777dfa0c3..bce4fa14fb4 100644
--- a/lib/gitlab/git/rugged_impl/commit.rb
+++ b/lib/gitlab/git/rugged_impl/commit.rb
@@ -21,6 +21,17 @@ module Gitlab
             nil
           end
 
+          # This needs to return an array of Gitlab::Git:Commit objects
+          # instead of Rugged::Commit objects to ensure upstream models
+          # operate on a consistent interface. Unlike
+          # Gitlab::Git::Commit.find, Gitlab::Git::Commit.batch_by_oid
+          # doesn't attempt to decorate the result.
+          def rugged_batch_by_oid(repo, oids)
+            oids.map { |oid| rugged_find(repo, oid) }
+              .compact
+              .map { |commit| decorate(repo, commit) }
+          end
+
           override :find_commit
           def find_commit(repo, commit_id)
             if Feature.enabled?(:rugged_find_commit)
@@ -29,6 +40,15 @@ module Gitlab
               super
             end
           end
+
+          override :batch_by_oid
+          def batch_by_oid(repo, oids)
+            if Feature.enabled?(:rugged_list_commits_by_oid)
+              rugged_batch_by_oid(repo, oids)
+            else
+              super
+            end
+          end
         end
 
         extend ::Gitlab::Utils::Override
diff --git a/lib/gitlab/git/rugged_impl/repository.rb b/lib/gitlab/git/rugged_impl/repository.rb
index c0a91f59ab9..e91b0ddcd31 100644
--- a/lib/gitlab/git/rugged_impl/repository.rb
+++ b/lib/gitlab/git/rugged_impl/repository.rb
@@ -12,7 +12,7 @@ module Gitlab
       module Repository
         extend ::Gitlab::Utils::Override
 
-        FEATURE_FLAGS = %i(rugged_find_commit rugged_tree_entries rugged_tree_entry rugged_commit_is_ancestor rugged_commit_tree_entry).freeze
+        FEATURE_FLAGS = %i(rugged_find_commit rugged_tree_entries rugged_tree_entry rugged_commit_is_ancestor rugged_commit_tree_entry rugged_list_commits_by_oid).freeze
 
         def alternate_object_directories
           relative_object_directories.map { |d| File.join(path, d) }