Merge branch '11-7-rugged-stable-backport' into '11-7-stable'

[11.7] Backport Rugged implementations for Git access

See merge request gitlab-org/gitlab-ce!27537

30 files changed, 775 insertions, 25 deletions

diff --git a/app/helpers/tree_helper.rb b/app/helpers/tree_helper.rb
index e2879bfdcf1..c5bab877c00 100644
--- a/app/helpers/tree_helper.rb
+++ b/app/helpers/tree_helper.rb
@@ -136,18 +136,9 @@ module TreeHelper
   end
 
   # returns the relative path of the first subdir that doesn't have only one directory descendant
-  # rubocop: disable CodeReuse/ActiveRecord
   def flatten_tree(root_path, tree)
-    return tree.flat_path.sub(%r{\A#{Regexp.escape(root_path)}/}, '') if tree.flat_path.present?
-
-    subtree = Gitlab::Git::Tree.where(@repository, @commit.id, tree.path)
-    if subtree.count == 1 && subtree.first.dir?
-      return tree_join(tree.name, flatten_tree(root_path, subtree.first))
-    else
-      return tree.name
-    end
+    tree.flat_path.sub(%r{\A#{Regexp.escape(root_path)}/}, '')
   end
-  # rubocop: enable CodeReuse/ActiveRecord
 
   def selected_branch
     @branch_name || tree_edit_branch
diff --git a/changelogs/unreleased/sh-backport-list-commits-by-oid-rugged.yml b/changelogs/unreleased/sh-backport-list-commits-by-oid-rugged.yml
new file mode 100644
index 00000000000..eb8774d652f
--- /dev/null
+++ b/changelogs/unreleased/sh-backport-list-commits-by-oid-rugged.yml
@@ -0,0 +1,5 @@
+---
+title: Bring back Rugged implementation of ListCommitsByOid
+merge_request: 27441
+author:
+type: performance
diff --git a/changelogs/unreleased/sh-fix-rugged-tree-entries.yml b/changelogs/unreleased/sh-fix-rugged-tree-entries.yml
new file mode 100644
index 00000000000..97b27678905
--- /dev/null
+++ b/changelogs/unreleased/sh-fix-rugged-tree-entries.yml
@@ -0,0 +1,5 @@
+---
+title: Avoid excessive recursive calls with Rugged TreeEntries
+merge_request: 26813
+author:
+type: fixed
diff --git a/changelogs/unreleased/sh-rugged-commit-is-ancestor.yml b/changelogs/unreleased/sh-rugged-commit-is-ancestor.yml
new file mode 100644
index 00000000000..0f62176b4a5
--- /dev/null
+++ b/changelogs/unreleased/sh-rugged-commit-is-ancestor.yml
@@ -0,0 +1,5 @@
+---
+title: Bring back Rugged implementation of CommitIsAncestor
+merge_request: 25702
+author:
+type: other
diff --git a/changelogs/unreleased/sh-rugged-commit-tree-entry.yml b/changelogs/unreleased/sh-rugged-commit-tree-entry.yml
new file mode 100644
index 00000000000..bcefa2c7112
--- /dev/null
+++ b/changelogs/unreleased/sh-rugged-commit-tree-entry.yml
@@ -0,0 +1,5 @@
+---
+title: Bring back Rugged implementation of commit_tree_entry
+merge_request: 25896
+author:
+type: other
diff --git a/changelogs/unreleased/sh-rugged-find-commit.yml b/changelogs/unreleased/sh-rugged-find-commit.yml
new file mode 100644
index 00000000000..85b5936c9ba
--- /dev/null
+++ b/changelogs/unreleased/sh-rugged-find-commit.yml
@@ -0,0 +1,5 @@
+---
+title: Bring back Rugged implementation of find_commit
+merge_request: 25477
+author:
+type: fixed
diff --git a/changelogs/unreleased/sh-rugged-get-tree-entry.yml b/changelogs/unreleased/sh-rugged-get-tree-entry.yml
new file mode 100644
index 00000000000..4d46b764022
--- /dev/null
+++ b/changelogs/unreleased/sh-rugged-get-tree-entry.yml
@@ -0,0 +1,5 @@
+---
+title: Bring back Rugged implementation of TreeEntry
+merge_request: 25706
+author:
+type: other
diff --git a/changelogs/unreleased/sh-rugged-tree-entries.yml b/changelogs/unreleased/sh-rugged-tree-entries.yml
new file mode 100644
index 00000000000..fca1f204b9b
--- /dev/null
+++ b/changelogs/unreleased/sh-rugged-tree-entries.yml
@@ -0,0 +1,5 @@
+---
+title: Bring back Rugged implementation of GetTreeEntries
+merge_request: 25674
+author:
+type: other
diff --git a/doc/administration/high_availability/nfs.md b/doc/administration/high_availability/nfs.md
index 74b0e2c8184..78ebf8a083b 100644
--- a/doc/administration/high_availability/nfs.md
+++ b/doc/administration/high_availability/nfs.md
@@ -37,6 +37,28 @@ options:
   circumstances it could lead to data loss if a failure occurs before data has
   synced.
 
+### Improving NFS performance with GitLab
+
+If you are using NFS to share Git data, we recommend that you enable a
+number of feature flags that will allow GitLab application processes to
+access Git data directly instead of going through the [Gitaly
+service](../gitaly/index.md). Depending on your workload and disk
+performance, these flags may help improve performance. See [the
+issue](https://gitlab.com/gitlab-org/gitlab-ce/issues/57317) for more
+details.
+
+To do this, run the Rake task:
+
+```sh
+gitlab-rake gitlab:features:enable_rugged
+```
+
+If you need to undo this setting for some reason, run:
+
+```sh
+gitlab-rake gitlab:features:disable_rugged
+```
+
 ### Known issues
 
 On some customer systems, we have seen NFS clients slow precipitously due to
diff --git a/doc/development/gitaly.md b/doc/development/gitaly.md
index fdae69bddd7..906585f6f21 100644
--- a/doc/development/gitaly.md
+++ b/doc/development/gitaly.md
@@ -56,6 +56,46 @@ If your test-suite is failing with Gitaly issues, as a first step, try running:
 rm -rf tmp/tests/gitaly
 ```
 
+## Legacy Rugged code
+
+While Gitaly can handle all Git access, many of GitLab customers still
+run Gitaly atop NFS. The legacy Rugged implementation for Git calls may
+be faster than the Gitaly RPC due to N+1 Gitaly calls and other
+reasons. See [the
+issue](https://gitlab.com/gitlab-org/gitlab-ce/issues/57317) for more
+details.
+
+Until GitLab has eliminated most of these inefficiencies or the use of
+NFS is discontinued for Git data, Rugged implementations of some of the
+most commonly-used RPCs can be enabled via feature flags:
+
+* `rugged_find_commit`
+* `rugged_get_tree_entries`
+* `rugged_tree_entry`
+* `rugged_commit_is_ancestor`
+* `rugged_commit_tree_entry`
+* `rugged_list_commits_by_oid`
+
+A convenience Rake task can be used to enable or disable these flags
+all together. To enable:
+
+```sh
+bundle exec rake gitlab:features:enable_rugged
+```
+
+To disable:
+
+```sh
+bundle exec rake gitlab:features:disable_rugged
+```
+
+Most of this code exists in the `lib/gitlab/git/rugged_impl` directory.
+
+NOTE: **Note:** You should NOT need to add or modify code related to
+Rugged unless explicitly discussed with the [Gitaly
+Team](https://gitlab.com/groups/gl-gitaly/group_members). This code will
+NOT work on GitLab.com or other GitLab instances that do not use NFS.
+
 ## `TooManyInvocationsError` errors
 
 During development and testing, you may experience `Gitlab::GitalyClient::TooManyInvocationsError` failures.
diff --git a/lib/gitlab/git/blob.rb b/lib/gitlab/git/blob.rb
index 259a2b7911a..10df4ed72d9 100644
--- a/lib/gitlab/git/blob.rb
+++ b/lib/gitlab/git/blob.rb
@@ -23,6 +23,10 @@ module Gitlab
 
       class << self
         def find(repository, sha, path, limit: MAX_DATA_DISPLAY_SIZE)
+          tree_entry(repository, sha, path, limit)
+        end
+
+        def tree_entry(repository, sha, path, limit)
           return unless path
 
           path = path.sub(%r{\A/*}, '')
@@ -179,3 +183,5 @@ module Gitlab
     end
   end
 end
+
+Gitlab::Git::Blob.singleton_class.prepend Gitlab::Git::RuggedImpl::Blob::ClassMethods
diff --git a/lib/gitlab/git/commit.rb b/lib/gitlab/git/commit.rb
index 5863815ca85..7be8539f380 100644
--- a/lib/gitlab/git/commit.rb
+++ b/lib/gitlab/git/commit.rb
@@ -5,6 +5,7 @@ module Gitlab
   module Git
     class Commit
       include Gitlab::EncodingHelper
+      prepend Gitlab::Git::RuggedImpl::Commit
       extend Gitlab::Git::WrapsGitalyErrors
 
       attr_accessor :raw_commit, :head
@@ -62,15 +63,19 @@ module Gitlab
           # This saves us an RPC round trip.
           return nil if commit_id.include?(':')
 
-          commit = wrapped_gitaly_errors do
-            repo.gitaly_commit_client.find_commit(commit_id)
-          end
+          commit = find_commit(repo, commit_id)
 
           decorate(repo, commit) if commit
         rescue Gitlab::Git::CommandError, Gitlab::Git::Repository::NoRepository, ArgumentError
           nil
         end
 
+        def find_commit(repo, commit_id)
+          wrapped_gitaly_errors do
+            repo.gitaly_commit_client.find_commit(commit_id)
+          end
+        end
+
         # Get last commit for HEAD
         #
         # Ex.
@@ -185,6 +190,10 @@ module Gitlab
         @repository = repository
         @head = head
 
+        init_commit(raw_commit)
+      end
+
+      def init_commit(raw_commit)
         case raw_commit
         when Hash
           init_from_hash(raw_commit)
@@ -305,11 +314,16 @@ module Gitlab
       def tree_entry(path)
         return unless path.present?
 
+        commit_tree_entry(path)
+      end
+
+      def commit_tree_entry(path)
         # We're only interested in metadata, so limit actual data to 1 byte
         # since Gitaly doesn't support "send no data" option.
         entry = @repository.gitaly_commit_client.tree_entry(id, path, 1)
         return unless entry
 
+        # To be compatible with the rugged format
         entry = entry.to_h
         entry.delete(:data)
         entry[:name] = File.basename(path)
@@ -400,3 +414,5 @@ module Gitlab
     end
   end
 end
+
+Gitlab::Git::Commit.singleton_class.prepend Gitlab::Git::RuggedImpl::Commit::ClassMethods
diff --git a/lib/gitlab/git/ref.rb b/lib/gitlab/git/ref.rb
index eec91194949..47cfb483509 100644
--- a/lib/gitlab/git/ref.rb
+++ b/lib/gitlab/git/ref.rb
@@ -4,6 +4,7 @@ module Gitlab
   module Git
     class Ref
       include Gitlab::EncodingHelper
+      include Gitlab::Git::RuggedImpl::Ref
 
       # Branch or tag name
       # without "refs/tags|heads" prefix
diff --git a/lib/gitlab/git/repository.rb b/lib/gitlab/git/repository.rb
index 786c90f9272..72ab0ee6f0e 100644
--- a/lib/gitlab/git/repository.rb
+++ b/lib/gitlab/git/repository.rb
@@ -11,6 +11,7 @@ module Gitlab
       include Gitlab::Git::WrapsGitalyErrors
       include Gitlab::EncodingHelper
       include Gitlab::Utils::StrongMemoize
+      prepend Gitlab::Git::RuggedImpl::Repository
 
       SEARCH_CONTEXT_LINES = 3
       REV_LIST_COMMIT_LIMIT = 2_000
diff --git a/lib/gitlab/git/rugged_impl/blob.rb b/lib/gitlab/git/rugged_impl/blob.rb
new file mode 100644
index 00000000000..11ee4ebda4b
--- /dev/null
+++ b/lib/gitlab/git/rugged_impl/blob.rb
@@ -0,0 +1,106 @@
+# frozen_string_literal: true
+
+# NOTE: This code is legacy. Do not add/modify code here unless you have
+# discussed with the Gitaly team.  See
+# https://docs.gitlab.com/ee/development/gitaly.html#legacy-rugged-code
+# for more details.
+
+module Gitlab
+  module Git
+    module RuggedImpl
+      module Blob
+        module ClassMethods
+          extend ::Gitlab::Utils::Override
+
+          override :tree_entry
+          def tree_entry(repository, sha, path, limit)
+            if Feature.enabled?(:rugged_tree_entry)
+              rugged_tree_entry(repository, sha, path, limit)
+            else
+              super
+            end
+          end
+
+          private
+
+          def rugged_tree_entry(repository, sha, path, limit)
+            return unless path
+
+            # Strip any leading / characters from the path
+            path = path.sub(%r{\A/*}, '')
+
+            rugged_commit = repository.lookup(sha)
+            root_tree = rugged_commit.tree
+
+            blob_entry = find_entry_by_path(repository, root_tree.oid, *path.split('/'))
+
+            return unless blob_entry
+
+            if blob_entry[:type] == :commit
+              submodule_blob(blob_entry, path, sha)
+            else
+              blob = repository.lookup(blob_entry[:oid])
+
+              if blob
+                new(
+                  id: blob.oid,
+                  name: blob_entry[:name],
+                  size: blob.size,
+                  # Rugged::Blob#content is expensive; don't call it if we don't have to.
+                  data: limit.zero? ? '' : blob.content(limit),
+                  mode: blob_entry[:filemode].to_s(8),
+                  path: path,
+                  commit_id: sha,
+                  binary: blob.binary?
+                )
+              end
+            end
+          rescue Rugged::ReferenceError
+            nil
+          end
+
+          # Recursive search of blob id by path
+          #
+          # Ex.
+          #   blog/            # oid: 1a
+          #     app/           # oid: 2a
+          #       models/      # oid: 3a
+          #       file.rb      # oid: 4a
+          #
+          #
+          # Blob.find_entry_by_path(repo, '1a', 'blog', 'app', 'file.rb') # => '4a'
+          #
+          def find_entry_by_path(repository, root_id, *path_parts)
+            root_tree = repository.lookup(root_id)
+
+            entry = root_tree.find do |entry|
+              entry[:name] == path_parts[0]
+            end
+
+            return unless entry
+
+            if path_parts.size > 1
+              return unless entry[:type] == :tree
+
+              path_parts.shift
+              find_entry_by_path(repository, entry[:oid], *path_parts)
+            else
+              [:blob, :commit].include?(entry[:type]) ? entry : nil
+            end
+          end
+
+          def submodule_blob(blob_entry, path, sha)
+            new(
+              id: blob_entry[:oid],
+              name: blob_entry[:name],
+              size: 0,
+              data: '',
+              path: path,
+              commit_id: sha
+            )
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/git/rugged_impl/commit.rb b/lib/gitlab/git/rugged_impl/commit.rb
new file mode 100644
index 00000000000..bce4fa14fb4
--- /dev/null
+++ b/lib/gitlab/git/rugged_impl/commit.rb
@@ -0,0 +1,109 @@
+# frozen_string_literal: true
+
+# NOTE: This code is legacy. Do not add/modify code here unless you have
+# discussed with the Gitaly team.  See
+# https://docs.gitlab.com/ee/development/gitaly.html#legacy-rugged-code
+# for more details.
+
+# rubocop:disable Gitlab/ModuleWithInstanceVariables
+module Gitlab
+  module Git
+    module RuggedImpl
+      module Commit
+        module ClassMethods
+          extend ::Gitlab::Utils::Override
+
+          def rugged_find(repo, commit_id)
+            obj = repo.rev_parse_target(commit_id)
+
+            obj.is_a?(::Rugged::Commit) ? obj : nil
+          rescue ::Rugged::Error
+            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)
+              rugged_find(repo, commit_id)
+            else
+              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
+
+        override :init_commit
+        def init_commit(raw_commit)
+          case raw_commit
+          when ::Rugged::Commit
+            init_from_rugged(raw_commit)
+          else
+            super
+          end
+        end
+
+        override :commit_tree_entry
+        def commit_tree_entry(path)
+          if Feature.enabled?(:rugged_commit_tree_entry)
+            rugged_tree_entry(path)
+          else
+            super
+          end
+        end
+
+        # Is this the same as Blob.find_entry_by_path ?
+        def rugged_tree_entry(path)
+          rugged_commit.tree.path(path)
+        rescue Rugged::TreeError
+          nil
+        end
+
+        def rugged_commit
+          @rugged_commit ||= if raw_commit.is_a?(Rugged::Commit)
+                               raw_commit
+                             else
+                               @repository.rev_parse_target(id)
+                             end
+        end
+
+        def init_from_rugged(commit)
+          author = commit.author
+          committer = commit.committer
+
+          @raw_commit = commit
+          @id = commit.oid
+          @message = commit.message
+          @authored_date = author[:time]
+          @committed_date = committer[:time]
+          @author_name = author[:name]
+          @author_email = author[:email]
+          @committer_name = committer[:name]
+          @committer_email = committer[:email]
+          @parent_ids = commit.parents.map(&:oid)
+        end
+      end
+    end
+  end
+end
+# rubocop:enable Gitlab/ModuleWithInstanceVariables
diff --git a/lib/gitlab/git/rugged_impl/ref.rb b/lib/gitlab/git/rugged_impl/ref.rb
new file mode 100644
index 00000000000..b553e82dc47
--- /dev/null
+++ b/lib/gitlab/git/rugged_impl/ref.rb
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+# NOTE: This code is legacy. Do not add/modify code here unless you have
+# discussed with the Gitaly team.  See
+# https://docs.gitlab.com/ee/development/gitaly.html#legacy-rugged-code
+# for more details.
+
+module Gitlab
+  module Git
+    module RuggedImpl
+      module Ref
+        def self.dereference_object(object)
+          object = object.target while object.is_a?(::Rugged::Tag::Annotation)
+
+          object
+        end
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/git/rugged_impl/repository.rb b/lib/gitlab/git/rugged_impl/repository.rb
new file mode 100644
index 00000000000..e91b0ddcd31
--- /dev/null
+++ b/lib/gitlab/git/rugged_impl/repository.rb
@@ -0,0 +1,78 @@
+# frozen_string_literal: true
+
+# NOTE: This code is legacy. Do not add/modify code here unless you have
+# discussed with the Gitaly team.  See
+# https://docs.gitlab.com/ee/development/gitaly.html#legacy-rugged-code
+# for more details.
+
+# rubocop:disable Gitlab/ModuleWithInstanceVariables
+module Gitlab
+  module Git
+    module RuggedImpl
+      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 rugged_list_commits_by_oid).freeze
+
+        def alternate_object_directories
+          relative_object_directories.map { |d| File.join(path, d) }
+        end
+
+        ALLOWED_OBJECT_RELATIVE_DIRECTORIES_VARIABLES = %w[
+          GIT_OBJECT_DIRECTORY_RELATIVE
+          GIT_ALTERNATE_OBJECT_DIRECTORIES_RELATIVE
+        ].freeze
+
+        def relative_object_directories
+          Gitlab::Git::HookEnv.all(gl_repository).values_at(*ALLOWED_OBJECT_RELATIVE_DIRECTORIES_VARIABLES).flatten.compact
+        end
+
+        def rugged
+          @rugged ||= ::Rugged::Repository.new(path, alternates: alternate_object_directories)
+        rescue ::Rugged::RepositoryError, ::Rugged::OSError
+          raise ::Gitlab::Git::Repository::NoRepository.new('no repository for such path')
+        end
+
+        def cleanup
+          @rugged&.close
+        end
+
+        # Return the object that +revspec+ points to.  If +revspec+ is an
+        # annotated tag, then return the tag's target instead.
+        def rev_parse_target(revspec)
+          obj = rugged.rev_parse(revspec)
+          Ref.dereference_object(obj)
+        end
+
+        override :ancestor?
+        def ancestor?(from, to)
+          if Feature.enabled?(:rugged_commit_is_ancestor)
+            rugged_is_ancestor?(from, to)
+          else
+            super
+          end
+        end
+
+        def rugged_is_ancestor?(ancestor_id, descendant_id)
+          return false if ancestor_id.nil? || descendant_id.nil?
+
+          rugged_merge_base(ancestor_id, descendant_id) == ancestor_id
+        rescue Rugged::OdbError
+          false
+        end
+
+        def rugged_merge_base(from, to)
+          rugged.merge_base(from, to)
+        rescue Rugged::ReferenceError
+          nil
+        end
+
+        # Lookup for rugged object by oid or ref name
+        def lookup(oid_or_ref_name)
+          rugged.rev_parse(oid_or_ref_name)
+        end
+      end
+    end
+  end
+end
+# rubocop:enable Gitlab/ModuleWithInstanceVariables
diff --git a/lib/gitlab/git/rugged_impl/tree.rb b/lib/gitlab/git/rugged_impl/tree.rb
new file mode 100644
index 00000000000..bb13d114d46
--- /dev/null
+++ b/lib/gitlab/git/rugged_impl/tree.rb
@@ -0,0 +1,109 @@
+# frozen_string_literal: true
+
+# NOTE: This code is legacy. Do not add/modify code here unless you have
+# discussed with the Gitaly team.  See
+# https://docs.gitlab.com/ee/development/gitaly.html#legacy-rugged-code
+# for more details.
+
+module Gitlab
+  module Git
+    module RuggedImpl
+      module Tree
+        module ClassMethods
+          extend ::Gitlab::Utils::Override
+
+          override :tree_entries
+          def tree_entries(repository, sha, path, recursive)
+            if Feature.enabled?(:rugged_tree_entries)
+              tree_entries_with_flat_path_from_rugged(repository, sha, path, recursive)
+            else
+              super
+            end
+          end
+
+          def tree_entries_with_flat_path_from_rugged(repository, sha, path, recursive)
+            tree_entries_from_rugged(repository, sha, path, recursive).tap do |entries|
+              # This was an optimization to reduce N+1 queries for Gitaly
+              # (https://gitlab.com/gitlab-org/gitaly/issues/530).  It
+              # used to be done lazily in the view via
+              # TreeHelper#flatten_tree, so it's possible there's a
+              # performance impact by loading this eagerly.
+              rugged_populate_flat_path(repository, sha, path, entries)
+            end
+          end
+
+          def tree_entries_from_rugged(repository, sha, path, recursive)
+            current_path_entries = get_tree_entries_from_rugged(repository, sha, path)
+            ordered_entries = []
+
+            current_path_entries.each do |entry|
+              ordered_entries << entry
+
+              if recursive && entry.dir?
+                ordered_entries.concat(tree_entries_from_rugged(repository, sha, entry.path, true))
+              end
+            end
+          end
+
+          def rugged_populate_flat_path(repository, sha, path, entries)
+            entries.each do |entry|
+              entry.flat_path = entry.path
+
+              next unless entry.dir?
+
+              entry.flat_path =
+                if path
+                  File.join(path, rugged_flatten_tree(repository, sha, entry, path))
+                else
+                  rugged_flatten_tree(repository, sha, entry, path)
+                end
+            end
+          end
+
+          # Returns the relative path of the first subdir that doesn't have only one directory descendant
+          def rugged_flatten_tree(repository, sha, tree, root_path)
+            subtree = tree_entries_from_rugged(repository, sha, tree.path, false)
+
+            if subtree.count == 1 && subtree.first.dir?
+              File.join(tree.name, rugged_flatten_tree(repository, sha, subtree.first, root_path))
+            else
+              tree.name
+            end
+          end
+
+          def get_tree_entries_from_rugged(repository, sha, path)
+            commit = repository.lookup(sha)
+            root_tree = commit.tree
+
+            tree = if path
+                     id = find_id_by_path(repository, root_tree.oid, path)
+                     if id
+                       repository.lookup(id)
+                     else
+                       []
+                     end
+                   else
+                     root_tree
+                   end
+
+            tree.map do |entry|
+              current_path = path ? File.join(path, entry[:name]) : entry[:name]
+
+              new(
+                id: entry[:oid],
+                root_id: root_tree.oid,
+                name: entry[:name],
+                type: entry[:type],
+                mode: entry[:filemode].to_s(8),
+                path: current_path,
+                commit_id: sha
+              )
+            end
+          rescue Rugged::ReferenceError
+            []
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/git/tree.rb b/lib/gitlab/git/tree.rb
index 51542bcaaa2..33505372eaf 100644
--- a/lib/gitlab/git/tree.rb
+++ b/lib/gitlab/git/tree.rb
@@ -18,6 +18,10 @@ module Gitlab
         def where(repository, sha, path = nil, recursive = false)
           path = nil if path == '' || path == '/'
 
+          tree_entries(repository, sha, path, recursive)
+        end
+
+        def tree_entries(repository, sha, path, recursive)
           wrapped_gitaly_errors do
             repository.gitaly_commit_client.tree_entries(repository, sha, path, recursive)
           end
@@ -95,3 +99,5 @@ module Gitlab
     end
   end
 end
+
+Gitlab::Git::Tree.singleton_class.prepend Gitlab::Git::RuggedImpl::Tree::ClassMethods
diff --git a/lib/gitlab/gitaly_client/storage_settings.rb b/lib/gitlab/gitaly_client/storage_settings.rb
index 754cccb6b3f..78ef6bfc0ec 100644
--- a/lib/gitlab/gitaly_client/storage_settings.rb
+++ b/lib/gitlab/gitaly_client/storage_settings.rb
@@ -32,11 +32,19 @@ module Gitlab
       end
 
       def self.disk_access_denied?
+        return false if rugged_enabled?
+
         !temporarily_allowed?(ALLOW_KEY) && GitalyClient.feature_enabled?(DISK_ACCESS_DENIED_FLAG)
       rescue
         false # Err on the side of caution, don't break gitlab for people
       end
 
+      def self.rugged_enabled?
+        Gitlab::Git::RuggedImpl::Repository::FEATURE_FLAGS.any? do |flag|
+          Feature.enabled?(flag)
+        end
+      end
+
       def initialize(storage)
         raise InvalidConfigurationError, "expected a Hash, got a #{storage.class.name}" unless storage.is_a?(Hash)
         raise InvalidConfigurationError, INVALID_STORAGE_MESSAGE unless storage.has_key?('path')
diff --git a/lib/tasks/gitlab/features.rake b/lib/tasks/gitlab/features.rake
new file mode 100644
index 00000000000..d115961108e
--- /dev/null
+++ b/lib/tasks/gitlab/features.rake
@@ -0,0 +1,24 @@
+namespace :gitlab do
+  namespace :features do
+    desc 'GitLab | Features | Enable direct Git access via Rugged for NFS'
+    task enable_rugged: :environment do
+      set_rugged_feature_flags(true)
+      puts 'All Rugged feature flags were enabled.'
+    end
+
+    task disable_rugged: :environment do
+      set_rugged_feature_flags(false)
+      puts 'All Rugged feature flags were disabled.'
+    end
+  end
+
+  def set_rugged_feature_flags(status)
+    Gitlab::Git::RuggedImpl::Repository::FEATURE_FLAGS.each do |flag|
+      if status
+        Feature.enable(flag)
+      else
+        Feature.disable(flag)
+      end
+    end
+  end
+end
diff --git a/scripts/lint-rugged b/scripts/lint-rugged
index 22e3e1f1505..9466c62a415 100755
--- a/scripts/lint-rugged
+++ b/scripts/lint-rugged
@@ -5,12 +5,18 @@ ALLOWED = [
   'lib/gitlab/bare_repository_import/repository.rb',
 
   # Needed to avoid using the git binary to validate a branch name
-  'lib/gitlab/git_ref_validator.rb'
+  'lib/gitlab/git_ref_validator.rb',
+
+  # Reverted Rugged calls due to Gitaly atop NFS performance
+  # See https://docs.gitlab.com/ee/development/gitaly.html#legacy-rugged-code.
+  'lib/gitlab/git/rugged_impl/',
+  'lib/gitlab/gitaly_client/storage_settings.rb'
 ].freeze
 
 rugged_lines = IO.popen(%w[git grep -i -n rugged -- app config lib], &:read).lines
 rugged_lines = rugged_lines.select { |l| /^[^:]*\.rb:/ =~ l }
 rugged_lines = rugged_lines.reject { |l| l.start_with?(*ALLOWED) }
+rugged_lines = rugged_lines.reject { |l| /(include|prepend) Gitlab::Git::RuggedImpl/ =~ l}
 rugged_lines = rugged_lines.reject do |line|
   code, _comment = line.split('# ', 2)
   code !~ /rugged/i
diff --git a/spec/lib/gitlab/git/blob_spec.rb b/spec/lib/gitlab/git/blob_spec.rb
index 1bcec04d28f..9c46df02062 100644
--- a/spec/lib/gitlab/git/blob_spec.rb
+++ b/spec/lib/gitlab/git/blob_spec.rb
@@ -18,7 +18,7 @@ describe Gitlab::Git::Blob, :seed_helper do
     end
   end
 
-  describe '.find' do
+  shared_examples '.find' do
     context 'nil path' do
       let(:blob) { Gitlab::Git::Blob.find(repository, SeedRepo::Commit::ID, nil) }
 
@@ -128,6 +128,20 @@ describe Gitlab::Git::Blob, :seed_helper do
     end
   end
 
+  describe '.find with Gitaly enabled' do
+    it_behaves_like '.find'
+  end
+
+  describe '.find with Rugged enabled', :enable_rugged do
+    it 'calls out to the Rugged implementation' do
+      allow_any_instance_of(Rugged).to receive(:rev_parse).with(SeedRepo::Commit::ID).and_call_original
+
+      described_class.find(repository, SeedRepo::Commit::ID, 'files/images/6049019_460s.jpg')
+    end
+
+    it_behaves_like '.find'
+  end
+
   describe '.raw' do
     let(:raw_blob) { Gitlab::Git::Blob.raw(repository, SeedRepo::RubyBlob::ID) }
     let(:bad_blob) { Gitlab::Git::Blob.raw(repository, SeedRepo::BigCommit::ID) }
diff --git a/spec/lib/gitlab/git/commit_spec.rb b/spec/lib/gitlab/git/commit_spec.rb
index db68062e433..e06131d3039 100644
--- a/spec/lib/gitlab/git/commit_spec.rb
+++ b/spec/lib/gitlab/git/commit_spec.rb
@@ -112,7 +112,7 @@ describe Gitlab::Git::Commit, :seed_helper do
   end
 
   context 'Class methods' do
-    describe '.find' do
+    shared_examples '.find' do
       it "should return first head commit if without params" do
         expect(described_class.last(repository).id).to eq(
           rugged_repo.head.target.oid
@@ -154,6 +154,20 @@ describe Gitlab::Git::Commit, :seed_helper do
       end
     end
 
+    describe '.find with Gitaly enabled' do
+      it_should_behave_like '.find'
+    end
+
+    describe '.find with Rugged enabled', :enable_rugged do
+      it 'calls out to the Rugged implementation' do
+        allow_any_instance_of(Rugged).to receive(:rev_parse).with(SeedRepo::Commit::ID).and_call_original
+
+        described_class.find(repository, SeedRepo::Commit::ID)
+      end
+
+      it_should_behave_like '.find'
+    end
+
     describe '.last_for_path' do
       context 'no path' do
         subject { described_class.last_for_path(repository, 'master') }
@@ -366,7 +380,32 @@ describe Gitlab::Git::Commit, :seed_helper do
       end
     end
 
-    describe '#batch_by_oid' do
+    shared_examples '.batch_by_oid' do
+      context 'with multiple OIDs' do
+        let(:oids) { [SeedRepo::Commit::ID, SeedRepo::FirstCommit::ID] }
+
+        it 'returns multiple commits' do
+          commits = described_class.batch_by_oid(repository, oids)
+
+          expect(commits.count).to eq(2)
+          expect(commits).to all( be_a(Gitlab::Git::Commit) )
+          expect(commits.first.sha).to eq(SeedRepo::Commit::ID)
+          expect(commits.second.sha).to eq(SeedRepo::FirstCommit::ID)
+        end
+      end
+
+      context 'when oids is empty' do
+        it 'returns empty commits' do
+          commits = described_class.batch_by_oid(repository, [])
+
+          expect(commits.count).to eq(0)
+        end
+      end
+    end
+
+    describe '.batch_by_oid with Gitaly enabled' do
+      it_should_behave_like '.batch_by_oid'
+
       context 'when oids is empty' do
         it 'makes no Gitaly request' do
           expect(Gitlab::GitalyClient).not_to receive(:call)
@@ -376,6 +415,16 @@ describe Gitlab::Git::Commit, :seed_helper do
       end
     end
 
+    describe '.batch_by_oid with Rugged enabled', :enable_rugged do
+      it_should_behave_like '.batch_by_oid'
+
+      it 'calls out to the Rugged implementation' do
+        allow_any_instance_of(Rugged).to receive(:rev_parse).with(SeedRepo::Commit::ID).and_call_original
+
+        described_class.batch_by_oid(repository, [SeedRepo::Commit::ID])
+      end
+    end
+
     shared_examples 'extracting commit signature' do
       context 'when the commit is signed' do
         let(:commit_id) { '0b4bc9a49b562e85de7cc9e834518ea6828729b9' }
diff --git a/spec/lib/gitlab/git/tree_spec.rb b/spec/lib/gitlab/git/tree_spec.rb
index bec875fb03d..c27c415c5ab 100644
--- a/spec/lib/gitlab/git/tree_spec.rb
+++ b/spec/lib/gitlab/git/tree_spec.rb
@@ -3,7 +3,7 @@ require "spec_helper"
 describe Gitlab::Git::Tree, :seed_helper do
   let(:repository) { Gitlab::Git::Repository.new('default', TEST_REPO_PATH, '') }
 
-  context :repo do
+  shared_examples :repo do
     let(:tree) { Gitlab::Git::Tree.where(repository, SeedRepo::Commit::ID) }
 
     it { expect(tree).to be_kind_of Array }
@@ -12,6 +12,17 @@ describe Gitlab::Git::Tree, :seed_helper do
     it { expect(tree.select(&:file?).size).to eq(10) }
     it { expect(tree.select(&:submodule?).size).to eq(2) }
 
+    it 'returns an empty array when called with an invalid ref' do
+      expect(described_class.where(repository, 'foobar-does-not-exist')).to eq([])
+    end
+
+    it 'returns a list of tree objects' do
+      entries = described_class.where(repository, SeedRepo::Commit::ID, 'files', true)
+
+      expect(entries.count).to be >= 5
+      expect(entries).to all(be_a(Gitlab::Git::Tree))
+    end
+
     describe '#dir?' do
       let(:dir) { tree.select(&:dir?).first }
 
@@ -20,8 +31,8 @@ describe Gitlab::Git::Tree, :seed_helper do
       it { expect(dir.commit_id).to eq(SeedRepo::Commit::ID) }
       it { expect(dir.name).to eq('encoding') }
       it { expect(dir.path).to eq('encoding') }
-      it { expect(dir.flat_path).to eq('encoding') }
       it { expect(dir.mode).to eq('40000') }
+      it { expect(dir.flat_path).to eq('encoding') }
 
       context :subdir do
         let(:subdir) { Gitlab::Git::Tree.where(repository, SeedRepo::Commit::ID, 'files').first }
@@ -44,6 +55,51 @@ describe Gitlab::Git::Tree, :seed_helper do
         it { expect(subdir_file.path).to eq('files/ruby/popen.rb') }
         it { expect(subdir_file.flat_path).to eq('files/ruby/popen.rb') }
       end
+
+      context :flat_path do
+        let(:filename) { 'files/flat/path/correct/content.txt' }
+        let(:oid) { create_file(filename) }
+        let(:subdir_file) { Gitlab::Git::Tree.where(repository, oid, 'files/flat').first }
+        let(:repository_rugged) { Rugged::Repository.new(File.join(SEED_STORAGE_PATH, TEST_REPO_PATH)) }
+
+        it { expect(subdir_file.flat_path).to eq('files/flat/path/correct') }
+      end
+
+      def create_file(path)
+        oid = repository_rugged.write('test', :blob)
+        index = repository_rugged.index
+        index.add(path: filename, oid: oid, mode: 0100644)
+
+        options = commit_options(
+          repository_rugged,
+          index,
+          repository_rugged.head.target,
+          'HEAD',
+          'Add new file')
+
+        Rugged::Commit.create(repository_rugged, options)
+      end
+
+      # Build the options hash that's passed to Rugged::Commit#create
+      def commit_options(repo, index, target, ref, message)
+        options = {}
+        options[:tree] = index.write_tree(repo)
+        options[:author] = {
+          email: "test@example.com",
+          name: "Test Author",
+          time: Time.gm(2014, "mar", 3, 20, 15, 1)
+        }
+        options[:committer] = {
+          email: "test@example.com",
+          name: "Test Author",
+          time: Time.gm(2014, "mar", 3, 20, 15, 1)
+        }
+        options[:message] ||= message
+        options[:parents] = repo.empty? ? [] : [target].compact
+        options[:update_ref] = ref
+
+        options
+      end
     end
 
     describe '#file?' do
@@ -79,9 +135,17 @@ describe Gitlab::Git::Tree, :seed_helper do
     end
   end
 
-  describe '#where' do
-    it 'returns an empty array when called with an invalid ref' do
-      expect(described_class.where(repository, 'foobar-does-not-exist')).to eq([])
+  describe '.where with Gitaly enabled' do
+    it_behaves_like :repo
+  end
+
+  describe '.where with Rugged enabled', :enable_rugged do
+    it 'calls out to the Rugged implementation' do
+      allow_any_instance_of(Rugged).to receive(:lookup).with(SeedRepo::Commit::ID)
+
+      described_class.where(repository, SeedRepo::Commit::ID, 'files', false)
     end
+
+    it_behaves_like :repo
   end
 end
diff --git a/spec/lib/gitlab/gitaly_client/storage_settings_spec.rb b/spec/lib/gitlab/gitaly_client/storage_settings_spec.rb
index c89913ec8e9..bb10be2a4dc 100644
--- a/spec/lib/gitlab/gitaly_client/storage_settings_spec.rb
+++ b/spec/lib/gitlab/gitaly_client/storage_settings_spec.rb
@@ -26,4 +26,14 @@ describe Gitlab::GitalyClient::StorageSettings do
       end
     end
   end
+
+  describe '.disk_access_denied?' do
+    it 'return false when Rugged is enabled', :enable_rugged do
+      expect(described_class.disk_access_denied?).to be_falsey
+    end
+
+    it 'returns true' do
+      expect(described_class.disk_access_denied?).to be_truthy
+    end
+  end
 end
diff --git a/spec/models/commit_spec.rb b/spec/models/commit_spec.rb
index baad8352185..9d4e18534ae 100644
--- a/spec/models/commit_spec.rb
+++ b/spec/models/commit_spec.rb
@@ -542,7 +542,7 @@ eos
     end
   end
 
-  describe '#uri_type' do
+  shared_examples '#uri_type' do
     it 'returns the URI type at the given path' do
       expect(commit.uri_type('files/html')).to be(:tree)
       expect(commit.uri_type('files/images/logo-black.png')).to be(:raw)
@@ -561,6 +561,20 @@ eos
     end
   end
 
+  describe '#uri_type with Gitaly enabled' do
+    it_behaves_like "#uri_type"
+  end
+
+  describe '#uri_type with Rugged enabled', :enable_rugged do
+    it 'calls out to the Rugged implementation' do
+      allow_any_instance_of(Rugged::Tree).to receive(:path).with('files/html').and_call_original
+
+      commit.uri_type('files/html')
+    end
+
+    it_behaves_like '#uri_type'
+  end
+
   describe '.from_hash' do
     let(:new_commit) { described_class.from_hash(commit.to_hash, project) }
 
diff --git a/spec/models/repository_spec.rb b/spec/models/repository_spec.rb
index 4978c43c9b5..c66cc99b113 100644
--- a/spec/models/repository_spec.rb
+++ b/spec/models/repository_spec.rb
@@ -2214,7 +2214,7 @@ describe Repository do
     rugged.references.create("refs/remotes/#{remote_name}/#{branch_name}", target.id)
   end
 
-  describe '#ancestor?' do
+  shared_examples '#ancestor?' do
     let(:commit) { repository.commit }
     let(:ancestor) { commit.parents.first }
 
@@ -2238,6 +2238,20 @@ describe Repository do
     end
   end
 
+  describe '#ancestor? with Gitaly enabled' do
+    it_behaves_like "#ancestor?"
+  end
+
+  describe '#ancestor? with Rugged enabled', :enable_rugged do
+    it 'calls out to the Rugged implementation' do
+      allow_any_instance_of(Rugged).to receive(:merge_base).with(repository.commit.id, Gitlab::Git::BLANK_SHA).and_call_original
+
+      repository.ancestor?(repository.commit.id, Gitlab::Git::BLANK_SHA)
+    end
+
+    it_behaves_like '#ancestor?'
+  end
+
   describe '#archive_metadata' do
     let(:ref) { 'master' }
     let(:storage_path) { '/tmp' }
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 89357056c93..efd88f4605d 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -115,10 +115,17 @@ RSpec.configure do |config|
     TestEnv.clean_test_path
   end
 
-  config.before do
+  config.before do |example|
     # Enable all features by default for testing
     allow(Feature).to receive(:enabled?) { true }
 
+    enabled = example.metadata[:enable_rugged].present?
+
+    # Disable Rugged features by default
+    Gitlab::Git::RuggedImpl::Repository::FEATURE_FLAGS.each do |flag|
+      allow(Feature).to receive(:enabled?).with(flag).and_return(enabled)
+    end
+
     # The following can be removed when we remove the staged rollout strategy
     # and we can just enable it using instance wide settings
     # (ie. ApplicationSetting#auto_devops_enabled)