Add a reporter for verbs to track number of storage streams are needed

util/registry/tarlayerformat.py

@@ -6,6 +6,7 @@ from abc import ABCMeta, abstractmethod
 from collections import defaultdict
 from six import add_metaclass
 
+from util.abchelpers import nooper
 
 class TarLayerReadException(Exception):
   """ Exception raised when reading a layer has failed. """
@@ -15,13 +16,26 @@ class TarLayerReadException(Exception):
 # 9MB (+ padding below) so that it matches the 10MB expected by Gzip.
 CHUNK_SIZE = 1024 * 1024 * 9
 
+@add_metaclass(ABCMeta)
+class TarLayerFormatterReporter(object):
+  @abstractmethod
+  def report_pass(self, stream_count):
+    """ Reports a formatting pass. """
+    pass
+
+
+@nooper
+class NoopReporter(TarLayerFormatterReporter):
+  pass
+
 
 @add_metaclass(ABCMeta)
 class TarLayerFormat(object):
   """ Class which creates a generator of the combined TAR data. """
-  def __init__(self, tar_stream_getter_iterator, path_prefix=None):
+  def __init__(self, tar_stream_getter_iterator, path_prefix=None, reporter=None):
     self.tar_stream_getter_iterator = tar_stream_getter_iterator
     self.path_prefix = path_prefix or ''
+    self.reporter = reporter or NoopReporter()
 
   def get_generator(self):
     for stream_getter in self.tar_stream_getter_iterator():
@@ -115,6 +129,7 @@ class TarLayerFormat(object):
 
       # Conduct any post-tar work.
       self.after_tar_layer()
+      self.reporter.report_pass(2 if len(dangling_hard_links) > 0 else 1)
 
     # Last two records are empty in TAR spec.
     yield '\0' * 512