Being collecting blob size metrics

lib/gitlab/git/blob.rb

@@ -124,6 +124,8 @@ module Gitlab
           self.__send__("#{key}=", options[key.to_sym]) # rubocop:disable GitlabSecurity/PublicSend
         end
 
+        record_metric_blob_size
+
         # Retain the actual size before it is encoded
         @loaded_size = @data.bytesize if @data
         @loaded_all_data = @loaded_size == size
@@ -202,6 +204,12 @@ module Gitlab
 
       private
 
+      def record_metric_blob_size
+        return unless size
+
+        self.class.gitlab_blob_size.observe({}, size)
+      end
+
       def has_lfs_version_key?
         !empty? && text_in_repo? && data.start_with?("version https://git-lfs.github.com/spec")
       end

spec/lib/gitlab/git/blob_spec.rb

@@ -12,10 +12,18 @@ describe Gitlab::Git::Blob, :seed_helper do
     let(:blob) { Gitlab::Git::Blob.new(name: 'test') }
 
     it 'handles nil data' do
+      expect(described_class).not_to receive(:gitlab_blob_size)
+
       expect(blob.name).to eq('test')
       expect(blob.size).to eq(nil)
       expect(blob.loaded_size).to eq(nil)
     end
+
+    it 'records blob size' do
+      expect(described_class).to receive(:gitlab_blob_size).and_call_original
+
+      Gitlab::Git::Blob.new(name: 'test', size: 1234)
+    end
   end
 
   shared_examples '.find' do