Adding PraefectInfoService as a gitaly service client

PraefectInfoService is a gRPC service in praefect that provides
information like the checksum of a repository and all of its replicas

lib/gitlab/git/repository.rb

@@ -944,6 +944,10 @@ module Gitlab
         Gitlab::GitalyClient::ConflictsService.new(self, our_commit_oid, their_commit_oid)
       end
 
+      def praefect_info_client
+        @praefect_info_client ||= Gitlab::GitalyClient::PraefectInfoService.new(self)
+      end
+
       def clean_stale_repository_files
         wrapped_gitaly_errors do
           gitaly_repository_client.cleanup if exists?
@@ -1019,6 +1023,12 @@ module Gitlab
         raise NoRepository # Guard against data races.
       end
 
+      def replicas
+        wrapped_gitaly_errors do
+          praefect_info_client.replicas
+        end
+      end
+
       private
 
       def empty_diff_stats

lib/gitlab/gitaly_client/praefect_info_service.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module GitalyClient
+    class PraefectInfoService
+      def initialize(repository)
+        @repository = repository
+        @gitaly_repo = repository.gitaly_repository
+        @storage = repository.storage
+      end
+
+      def replicas
+        request = Gitaly::RepositoryReplicasRequest.new(repository: @gitaly_repo)
+
+        GitalyClient.call(@storage, :praefect_info_service, :repository_replicas, request, timeout: GitalyClient.fast_timeout)
+      end
+    end
+  end
+end

spec/lib/gitlab/git/repository_spec.rb

@@ -1919,6 +1919,15 @@ describe Gitlab::Git::Repository, :seed_helper do
     end
   end
 
+  describe '#replicas', :praefect do
+    it 'gets the replica checksum through praefect' do
+      resp = repository.replicas
+
+      expect(resp.replicas).to be_empty
+      expect(resp.primary.checksum).to eq(repository.checksum)
+    end
+  end
+
   describe '#clean_stale_repository_files' do
     let(:worktree_id) { 'rebase-1' }
     let(:gitlab_worktree_path) { File.join(repository_path, 'gitlab-worktree', worktree_id) }

spec/lib/gitlab/gitaly_client/praefect_info_service_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Gitlab::GitalyClient::PraefectInfoService do
+  let(:project) { create(:project, :repository) }
+  let(:repository) { project.repository }
+  let(:gitaly_repository) { repository.gitaly_repository }
+  let(:client) { described_class.new(repository) }
+
+  describe '#repository_replicas', :praefect do
+    it 'sends an RPC request' do
+      request = Gitaly::RepositoryReplicasRequest.new(repository: gitaly_repository)
+
+      expect_any_instance_of(Gitaly::PraefectInfoService::Stub).to receive(:repository_replicas).with(request, kind_of(Hash))
+
+      client.replicas
+    end
+  end
+end