Detect changes to LFS pointers for pruning and integrity check

Gitlab::Git::Blob.batch_lfs_metadata can be used to check for LFS pointers. It uses a lazy enumorator and filters by blob size

lib/gitlab/git/blob.rb

@@ -12,6 +12,12 @@ module Gitlab
       # blob data should use load_all_data!.
       MAX_DATA_DISPLAY_SIZE = 10.megabytes
 
+      # These limits are used as a heuristic to ignore files which can't be LFS
+      # pointers. The format of these is described in
+      # https://github.com/git-lfs/git-lfs/blob/master/docs/spec.md#the-pointer
+      LFS_POINTER_MIN_SIZE = 120.bytes
+      LFS_POINTER_MAX_SIZE = 200.bytes
+
       attr_accessor :name, :path, :size, :data, :mode, :id, :commit_id, :loaded_size, :binary
 
       class << self
@@ -30,16 +36,7 @@ module Gitlab
             if is_enabled
               Gitlab::GitalyClient::BlobService.new(repository).get_blob(oid: sha, limit: MAX_DATA_DISPLAY_SIZE)
             else
-              blob = repository.lookup(sha)
-
-              next unless blob.is_a?(Rugged::Blob)
-
-              new(
-                id: blob.oid,
-                size: blob.size,
-                data: blob.content(MAX_DATA_DISPLAY_SIZE),
-                binary: blob.binary?
-              )
+              rugged_raw(repository, sha, limit: MAX_DATA_DISPLAY_SIZE)
             end
           end
         end
@@ -59,10 +56,25 @@ module Gitlab
           end
         end
 
+        # Find LFS blobs given an array of sha ids
+        # Returns array of Gitlab::Git::Blob
+        # Does not guarantee blob data will be set
+        def batch_lfs_pointers(repository, blob_ids)
+          blob_ids.lazy
+                  .select { |sha| possible_lfs_blob?(repository, sha) }
+                  .map { |sha| rugged_raw(repository, sha, limit: LFS_POINTER_MAX_SIZE) }
+                  .select(&:lfs_pointer?)
+                  .force
+        end
+
         def binary?(data)
           EncodingHelper.detect_libgit2_binary?(data)
         end
 
+        def size_could_be_lfs?(size)
+          size.between?(LFS_POINTER_MIN_SIZE, LFS_POINTER_MAX_SIZE)
+        end
+
         private
 
         # Recursive search of blob id by path
@@ -167,6 +179,29 @@ module Gitlab
             end
           end
         end
+
+        def rugged_raw(repository, sha, limit:)
+          blob = repository.lookup(sha)
+
+          return unless blob.is_a?(Rugged::Blob)
+
+          new(
+            id: blob.oid,
+            size: blob.size,
+            data: blob.content(limit),
+            binary: blob.binary?
+          )
+        end
+
+        # Efficient lookup to determine if object size
+        # and type make it a possible LFS blob without loading
+        # blob content into memory with repository.lookup(sha)
+        def possible_lfs_blob?(repository, sha)
+          object_header = repository.rugged.read_header(sha)
+
+          object_header[:type] == :blob &&
+            size_could_be_lfs?(object_header[:len])
+        end
       end
 
       def initialize(options)
@@ -226,7 +261,7 @@ module Gitlab
       # size
       # see https://github.com/github/git-lfs/blob/v1.1.0/docs/spec.md#the-pointer
       def lfs_pointer?
-        has_lfs_version_key? && lfs_oid.present? && lfs_size.present?
+        self.class.size_could_be_lfs?(size) && has_lfs_version_key? && lfs_oid.present? && lfs_size.present?
       end
 
       def lfs_oid

lib/gitlab/git/lfs_changes.rb

+module Gitlab
+  module Git
+    class LfsChanges
+      def initialize(repository, newrev)
+        @repository = repository
+        @newrev = newrev
+      end
+
+      def new_pointers(object_limit: nil, not_in: nil)
+        @new_pointers ||= begin
+          object_ids = new_objects(not_in: not_in)
+          object_ids = object_ids.take(object_limit) if object_limit
+
+          Gitlab::Git::Blob.batch_lfs_pointers(@repository, object_ids)
+        end
+      end
+
+      def all_pointers
+        object_ids = rev_list.all_objects(require_path: true)
+
+        Gitlab::Git::Blob.batch_lfs_pointers(@repository, object_ids)
+      end
+
+      private
+
+      def new_objects(not_in:)
+        rev_list.new_objects(require_path: true, lazy: true, not_in: not_in)
+      end
+
+      def rev_list
+        ::Gitlab::Git::RevList.new(path_to_repo: @repository.path_to_repo,
+                                   newrev: @newrev)
+      end
+    end
+  end
+end

lib/gitlab/git/repository.rb

@@ -290,6 +290,14 @@ module Gitlab
         end
       end
 
+      def batch_existence(object_ids, existing: true)
+        filter_method = existing ? :select : :reject
+
+        object_ids.public_send(filter_method) do |oid| # rubocop:disable GitlabSecurity/PublicSend
+          rugged.exists?(oid)
+        end
+      end
+
       # Returns an Array of branch and tag names
       def ref_names
         branch_names + tag_names

lib/gitlab/git/rev_list.rb

@@ -13,11 +13,31 @@ module Gitlab
         @path_to_repo = path_to_repo
       end
 
-      # This method returns an array of new references
+      # This method returns an array of new commit references
       def new_refs
         execute([*base_args, newrev, '--not', '--all'])
       end
 
+      # Finds newly added objects
+      # Returns an array of shas
+      #
+      # Can skip objects which do not have a path using required_path: true
+      # This skips commit objects and root trees, which might not be needed when
+      # looking for blobs
+      #
+      # Can return a lazy enumerator to limit work done on megabytes of data
+      def new_objects(require_path: nil, lazy: false, not_in: nil)
+        object_output = execute([*base_args, newrev, *not_in_refs(not_in), '--objects'])
+
+        objects_from_output(object_output, require_path: require_path, lazy: lazy)
+      end
+
+      def all_objects(require_path: nil)
+        object_output = execute([*base_args, '--all', '--objects'])
+
+        objects_from_output(object_output, require_path: require_path, lazy: true)
+      end
+
       # This methods returns an array of missed references
       #
       # Should become obsolete after https://gitlab.com/gitlab-org/gitaly/issues/348.
@@ -27,6 +47,13 @@ module Gitlab
 
       private
 
+      def not_in_refs(references)
+        return ['--not', '--all'] unless references
+        return [] if references.empty?
+
+        references.prepend('--not')
+      end
+
       def execute(args)
         output, status = popen(args, nil, Gitlab::Git::Env.to_env_hash)
 
@@ -44,6 +71,22 @@ module Gitlab
           'rev-list'
         ]
       end
+
+      def objects_from_output(object_output, require_path: nil, lazy: nil)
+        objects = object_output.lazy.map do |output_line|
+          sha, path = output_line.split(' ', 2)
+
+          next if require_path && path.blank?
+
+          sha
+        end.reject(&:nil?)
+
+        if lazy
+          objects
+        else
+          objects.force
+        end
+      end
     end
   end
 end

spec/lib/gitlab/git/blob_spec.rb

@@ -143,6 +143,16 @@ describe Gitlab::Git::Blob, seed_helper: true do
         expect(blob.loaded_size).to eq(blob_size)
       end
     end
+
+    context 'when sha references a tree' do
+      it 'returns nil' do
+        tree = Gitlab::Git::Commit.find(repository, 'master').tree
+
+        blob = Gitlab::Git::Blob.raw(repository, tree.oid)
+
+        expect(blob).to be_nil
+      end
+    end
   end
 
   describe '.raw' do
@@ -226,6 +236,51 @@ describe Gitlab::Git::Blob, seed_helper: true do
     end
   end
 
+  describe '.batch_lfs_pointers' do
+    let(:tree_object) { Gitlab::Git::Commit.find(repository, 'master').tree }
+
+    let(:non_lfs_blob) do
+      Gitlab::Git::Blob.find(
+        repository,
+        'master',
+        'README.md'
+      )
+    end
+
+    let(:lfs_blob) do
+      Gitlab::Git::Blob.find(
+        repository,
+        '33bcff41c232a11727ac6d660bd4b0c2ba86d63d',
+        'files/lfs/image.jpg'
+      )
+    end
+
+    it 'returns a list of Gitlab::Git::Blob' do
+      blobs = described_class.batch_lfs_pointers(repository, [lfs_blob.id])
+
+      expect(blobs.count).to eq(1)
+      expect(blobs).to all( be_a(Gitlab::Git::Blob) )
+    end
+
+    it 'silently ignores tree objects' do
+      blobs = described_class.batch_lfs_pointers(repository, [tree_object.oid])
+
+      expect(blobs).to eq([])
+    end
+
+    it 'silently ignores non lfs objects' do
+      blobs = described_class.batch_lfs_pointers(repository, [non_lfs_blob.id])
+
+      expect(blobs).to eq([])
+    end
+
+    it 'avoids loading large blobs into memory' do
+      expect(repository).not_to receive(:lookup)
+
+      described_class.batch_lfs_pointers(repository, [non_lfs_blob.id])
+    end
+  end
+
   describe 'encoding' do
     context 'file with russian text' do
       let(:blob) { Gitlab::Git::Blob.find(repository, SeedRepo::Commit::ID, "encoding/russian.rb") }

spec/lib/gitlab/git/lfs_changes_spec.rb

+require 'spec_helper'
+
+describe Gitlab::Git::LfsChanges do
+  let(:project) { create(:project, :repository) }
+  let(:newrev) { '54fcc214b94e78d7a41a9a8fe6d87a5e59500e51' }
+  let(:blob_object_id) { '0c304a93cb8430108629bbbcaa27db3343299bc0' }
+
+  subject { described_class.new(project.repository, newrev) }
+
+  describe 'new_pointers' do
+    before do
+      allow_any_instance_of(Gitlab::Git::RevList).to receive(:new_objects).and_return([blob_object_id])
+    end
+
+    it 'uses rev-list to find new objects' do
+      rev_list = double
+      allow(Gitlab::Git::RevList).to receive(:new).and_return(rev_list)
+
+      expect(rev_list).to receive(:new_objects).and_return([])
+
+      subject.new_pointers
+    end
+
+    it 'filters new objects to find lfs pointers' do
+      expect(Gitlab::Git::Blob).to receive(:batch_lfs_pointers).with(project.repository, [blob_object_id])
+
+      subject.new_pointers(object_limit: 1)
+    end
+
+    it 'limits new_objects using object_limit' do
+      expect(Gitlab::Git::Blob).to receive(:batch_lfs_pointers).with(project.repository, [])
+
+      subject.new_pointers(object_limit: 0)
+    end
+  end
+
+  describe 'all_pointers' do
+    it 'uses rev-list to find all objects' do
+      rev_list = double
+      allow(Gitlab::Git::RevList).to receive(:new).and_return(rev_list)
+      allow(rev_list).to receive(:all_objects).and_return([blob_object_id])
+
+      expect(Gitlab::Git::Blob).to receive(:batch_lfs_pointers).with(project.repository, [blob_object_id])
+
+      subject.all_pointers
+    end
+  end
+end

spec/lib/gitlab/git/repository_spec.rb

@@ -1310,6 +1310,24 @@ describe Gitlab::Git::Repository, seed_helper: true do
     end
   end
 
+  describe '#batch_existence' do
+    let(:refs) { ['deadbeef', SeedRepo::RubyBlob::ID, '909e6157199'] }
+
+    it 'returns existing refs back' do
+      result = repository.batch_existence(refs)
+
+      expect(result).to eq([SeedRepo::RubyBlob::ID])
+    end
+
+    context 'existing: true' do
+      it 'inverts meaning and returns non-existing refs' do
+        result = repository.batch_existence(refs, existing: false)
+
+        expect(result).to eq(%w(deadbeef 909e6157199))
+      end
+    end
+  end
+
   describe '#local_branches' do
     before(:all) do
       @repo = Gitlab::Git::Repository.new('default', TEST_MUTABLE_REPO_PATH, '')

spec/lib/gitlab/git/rev_list_spec.rb

@@ -2,53 +2,82 @@ require 'spec_helper'
 
 describe Gitlab::Git::RevList do
   let(:project) { create(:project, :repository) }
+  let(:rev_list) { described_class.new(newrev: 'newrev', path_to_repo: project.repository.path_to_repo) }
 
   before do
-    expect(Gitlab::Git::Env).to receive(:all).and_return({
+    allow(Gitlab::Git::Env).to receive(:all).and_return({
       GIT_OBJECT_DIRECTORY: 'foo',
       GIT_ALTERNATE_OBJECT_DIRECTORIES: 'bar'
     })
   end
 
-  context "#new_refs" do
-    let(:rev_list) { described_class.new(newrev: 'newrev', path_to_repo: project.repository.path_to_repo) }
+  def stub_popen_rev_list(*additional_args, output:)
+    expect(rev_list).to receive(:popen).with([
+      Gitlab.config.git.bin_path,
+      "--git-dir=#{project.repository.path_to_repo}",
+      'rev-list',
+      *additional_args
+    ],
+    nil,
+    {
+      'GIT_OBJECT_DIRECTORY' => 'foo',
+      'GIT_ALTERNATE_OBJECT_DIRECTORIES' => 'bar'
+    }).and_return([output, 0])
+  end
 
+  context "#new_refs" do
     it 'calls out to `popen`' do
-      expect(rev_list).to receive(:popen).with([
-        Gitlab.config.git.bin_path,
-        "--git-dir=#{project.repository.path_to_repo}",
-        'rev-list',
-        'newrev',
-        '--not',
-        '--all'
-      ],
-      nil,
-      {
-        'GIT_OBJECT_DIRECTORY' => 'foo',
-        'GIT_ALTERNATE_OBJECT_DIRECTORIES' => 'bar'
-      }).and_return(["sha1\nsha2", 0])
+      stub_popen_rev_list('newrev', '--not', '--all', output: "sha1\nsha2")
 
       expect(rev_list.new_refs).to eq(%w[sha1 sha2])
     end
   end
 
+  context '#new_objects' do
+    it 'fetches list of newly pushed objects using rev-list' do
+      stub_popen_rev_list('newrev', '--not', '--all', '--objects', output: "sha1\nsha2")
+
+      expect(rev_list.new_objects).to eq(%w[sha1 sha2])
+    end
+
+    it 'can skip pathless objects' do
+      stub_popen_rev_list('newrev', '--not', '--all', '--objects', output: "sha1\nsha2 path/to/file")
+
+      expect(rev_list.new_objects(require_path: true)).to eq(%w[sha2])
+    end
+
+    it 'can return a lazy enumerator' do
+      stub_popen_rev_list('newrev', '--not', '--all', '--objects', output: "sha1\nsha2")
+
+      expect(rev_list.new_objects(lazy: true)).to be_a Enumerator::Lazy
+    end
+
+    it 'can accept list of references to exclude' do
+      stub_popen_rev_list('newrev', '--not', 'master', '--objects', output: "sha1\nsha2")
+
+      expect(rev_list.new_objects(not_in: ['master'])).to eq(%w[sha1 sha2])
+    end
+
+    it 'handles empty list of references to exclude as listing all known objects' do
+      stub_popen_rev_list('newrev', '--objects', output: "sha1\nsha2")
+
+      expect(rev_list.new_objects(not_in: [])).to eq(%w[sha1 sha2])
+    end
+  end
+
+  context '#all_objects' do
+    it 'fetches list of all pushed objects using rev-list' do
+      stub_popen_rev_list('--all', '--objects', output: "sha1\nsha2")
+
+      expect(rev_list.all_objects.force).to eq(%w[sha1 sha2])
+    end
+  end
+
   context "#missed_ref" do
     let(:rev_list) { described_class.new(oldrev: 'oldrev', newrev: 'newrev', path_to_repo: project.repository.path_to_repo) }
 
     it 'calls out to `popen`' do
-      expect(rev_list).to receive(:popen).with([
-        Gitlab.config.git.bin_path,
-        "--git-dir=#{project.repository.path_to_repo}",
-        'rev-list',
-        '--max-count=1',
-        'oldrev',
-        '^newrev'
-      ],
-      nil,
-      {
-        'GIT_OBJECT_DIRECTORY' => 'foo',
-        'GIT_ALTERNATE_OBJECT_DIRECTORIES' => 'bar'
-      }).and_return(["sha1\nsha2", 0])
+      stub_popen_rev_list('--max-count=1', 'oldrev', '^newrev', output: "sha1\nsha2")
 
       expect(rev_list.missed_ref).to eq(%w[sha1 sha2])
     end