Work in progress. This is currently broken!

util/dockerimportformat.py

@@ -0,0 +1,123 @@
+from util.gzipwrap import GzipWrap
+from util.streamlayerformat import StreamLayerMerger
+
+import copy
+import json
+import tarfile
+
+from itertools import chain, islice
+class some_magic_adaptor(object):
+    def __init__(self, src):
+        self.src = chain.from_iterable(src)
+    def read(self, n):
+        return "".join(islice(self.src, None, n))
+
+def build_docker_import_stream(namespace, repository, tag, synthetic_image_id,
+                               layer_json, get_image_iterator, get_layer_iterator):
+  """ Builds and streams a synthetic .tar.gz that represents a squashed version
+      of the given layers, in `docker import` V1 format.
+  """
+  return some_magic_adaptor(_import_format_generator(namespace, repository, tag,
+                                                     synthetic_image_id, layer_json,
+                                                     get_image_iterator, get_layer_iterator))
+
+
+def _import_format_generator(namespace, repository, tag, synthetic_image_id,
+                             layer_json, get_image_iterator, get_layer_iterator):
+
+  # Docker import V1 Format (.tar):
+  #  repositories - JSON file containing a repo -> tag -> image map
+  #  {image ID folder}:
+  #     json - The layer JSON
+  #     layer.tar - The TARed contents of the layer
+  #     VERSION - The docker import version: '1.0'
+  layer_merger = StreamLayerMerger(get_layer_iterator)
+  
+  # Yield the repositories file:
+  synthetic_layer_info = {}
+  synthetic_layer_info[tag + '.squash'] = synthetic_image_id
+
+  repositories = {}
+  repositories[namespace + '/' + repository] = synthetic_layer_info
+
+  yield _tar_file('repositories', json.dumps(repositories))
+
+  # Yield the image ID folder.
+  yield _tar_folder(synthetic_image_id)
+
+  # Yield the JSON layer data.
+  layer_json = _build_layer_json(layer_json, synthetic_image_id)
+  yield _tar_file(synthetic_image_id + '/json', json.dumps(layer_json))
+
+  # Yield the VERSION file.
+  yield _tar_file(synthetic_image_id + '/VERSION', '1.0')
+
+  # Yield the merged layer data's header.
+  estimated_file_size = 0
+  for image in get_image_iterator():
+    estimated_file_size += image.storage.uncompressed_size or 0
+
+  yield _tar_file_header(synthetic_image_id + '/layer.tar', estimated_file_size)
+
+  # Yield the contents of the merged layer.
+  yielded_size = 0
+  for entry in layer_merger.get_generator():
+    yield entry
+    yielded_size += len(entry)
+
+  # If the yielded size is less than the estimated size (which is likely), fill the rest with
+  # zeros.
+  if yielded_size < estimated_file_size:
+    yield '\0' * (estimated_file_size - yielded_size)
+
+  print estimated_file_size
+  print yielded_size
+
+  # Yield any file padding to 512 bytes that is necessary.
+  yield _tar_file_padding(estimated_file_size)
+
+  # Last two records are empty in TAR spec.
+  yield '\0' * 512
+  yield '\0' * 512
+
+
+def _build_layer_json(layer_json, synthetic_image_id):
+  updated_json = copy.deepcopy(layer_json)
+  updated_json['id'] = synthetic_image_id
+
+  if 'parent' in updated_json:
+    del updated_json['parent']
+      
+  if 'config' in updated_json and 'Image' in updated_json['config']:
+    updated_json['config']['Image'] = synthetic_image_id
+
+  if 'container_config' in updated_json and 'Image' in updated_json['container_config']:
+    updated_json['container_config']['Image'] = synthetic_image_id
+
+  return updated_json
+
+
+def _tar_file(name, contents):
+  length = len(contents)
+  tar_data = _tar_file_header(name, length)
+  tar_data += contents
+  tar_data += _tar_file_padding(length)
+  return tar_data
+
+
+def _tar_file_padding(length):
+  if length % 512 != 0:
+    return '\0' * (512 - (length % 512))
+
+
+def _tar_file_header(name, file_size):
+  info = tarfile.TarInfo(name=name)
+  info.type = tarfile.REGTYPE
+  info.size = file_size
+  return info.tobuf()
+
+
+def _tar_folder(name):
+  info = tarfile.TarInfo(name=name)
+  info.type = tarfile.DIRTYPE
+  return info.tobuf()

util/gzipwrap.py

@@ -0,0 +1,42 @@
+from gzip import GzipFile
+
+class GzipWrap(object):
+  def __init__(self, input, filename=None, compresslevel=1):
+    self.input = iter(input)
+    self.buffer = ''
+    self.zipper = GzipFile(filename, mode='wb', fileobj=self, compresslevel=compresslevel)
+    
+  def read(self, size=-1):
+    # If the buffer already has enough bytes, then simply pop them off of
+    # the beginning and return them.
+    if len(self.buffer) >= size:
+      ret = self.buffer[0:size]
+      self.buffer = self.buffer[size:]
+      return ret
+
+    # Otherwise, zip the input until we have enough bytes.
+    while True:
+      # Attempt to retrieve the next bytes to write.
+      is_done = False
+      try:
+        s = self.input.next()
+        self.zipper.write(s)
+      except StopIteration:
+        is_done = True
+
+      if len(self.buffer) < size or is_done:
+        self.zipper.flush()
+
+      if len(self.buffer) >= size or is_done:
+        ret = self.buffer[0:size]
+        self.buffer = self.buffer[size:]
+        return ret
+
+  def flush(self):
+    pass
+  
+  def write(self, data):
+    self.buffer += data
+
+  def close(self):
+    self.input.close()

util/streamlayerformat.py

@@ -0,0 +1,99 @@
+import marisa_trie
+import os
+import tarfile
+import StringIO
+import traceback
+
+AUFS_METADATA = u'.wh..wh.'
+
+AUFS_WHITEOUT = u'.wh.'
+AUFS_WHITEOUT_PREFIX_LENGTH = len(AUFS_WHITEOUT)
+
+class StreamLayerMerger(object):
+  """ Class which creates a generator of the combined TAR data for a set of Docker layers. """
+  def __init__(self, layer_iterator):
+    self.trie = marisa_trie.Trie()
+    self.layer_iterator = layer_iterator
+    self.encountered = []
+
+  def get_generator(self):
+    for current_layer in self.layer_iterator():
+      # Read the current layer as TAR. If it is empty, we just continue
+      # to the next layer.
+      try:
+        tar_file = tarfile.open(mode='r|*', fileobj=current_layer)
+      except tarfile.ReadError as re:
+        continue
+
+      # For each of the tar entries, yield them IF and ONLY IF we have not
+      # encountered the path before.
+
+      # 9MB (+ padding below) so that it matches the 10MB expected by Gzip.
+      chunk_size = 1024 * 1024 * 9
+
+      for tar_info in tar_file:
+        result = self.process_tar_info(tar_info)
+        if not result:
+          continue
+
+        (tarinfo, filebuf) = result
+
+        yield tarinfo.tobuf()
+
+        if filebuf:
+          length = 0
+          file_stream = tar_file.extractfile(tarinfo)
+          while True:
+            current_block = file_stream.read(chunk_size)
+            if not len(current_block):
+              break
+
+            yield current_block
+            length += len(current_block)
+
+          file_stream.close()
+
+          # Files must be padding to 512 byte multiples.
+          if length % 512 != 0:
+            yield '\0' * (512 - (length % 512))
+
+      # Close the layer stream now that we're done with it.
+      tar_file.close()
+
+      # Update the trie with the new encountered entries.
+      self.trie = marisa_trie.Trie(self.encountered)
+      
+    # Last two records are empty in TAR spec.
+    yield '\0' * 512
+    yield '\0' * 512
+
+
+  def process_tar_info(self, tar_info):
+    absolute = os.path.relpath(tar_info.name.decode('utf-8'), './')
+    dirname = os.path.dirname(absolute)
+    filename = os.path.basename(absolute)
+
+    # Skip directories and metadata
+    if (filename.startswith(AUFS_METADATA) or
+        absolute.startswith(AUFS_METADATA)):
+      # Skip
+      return None
+
+    elif filename.startswith(AUFS_WHITEOUT):
+      removed_filename = filename[AUFS_WHITEOUT_PREFIX_LENGTH:]
+      removed_prefix = os.path.join('/', dirname, removed_filename)
+      self.encountered.append(removed_prefix)
+      return None
+
+    # Check if this file has already been encountered somewhere. If so,
+    # skip it.
+    if unicode(absolute) in self.trie:
+      return None
+
+    self.encountered.append(absolute)
+
+    if tar_info.isdir() or tar_info.issym() or tar_info.islnk():
+      return (tar_info, False)
+      
+    elif tar_info.isfile():
+      return (tar_info, True)