import os import tarfile import copy 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. """ pass # 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, 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(): current_tar_stream = stream_getter() # Read the current TAR. If it is empty, we just continue # to the next one. tar_file = TarLayerFormat._tar_file_from_stream(current_tar_stream) if not tar_file: continue # For each of the tar entries, yield them IF and ONLY IF we have not # encountered the path before. dangling_hard_links = defaultdict(list) for tar_info in tar_file: if not self.should_append_file(tar_info.name): continue # Note: We use a copy here because we need to make sure we copy over all the internal # data of the tar header. We cannot use frombuf(tobuf()), however, because it doesn't # properly handle large filenames. clone = copy.deepcopy(tar_info) clone.name = os.path.join(self.path_prefix, clone.name) # If the entry is a *hard* link, then prefix it as well. Soft links are relative. if clone.linkname and clone.type == tarfile.LNKTYPE: # If the entry is a dangling hard link, we skip here. Dangling hard links will be handled # in a second pass. if self.is_skipped_file(tar_info.linkname): dangling_hard_links[tar_info.linkname].append(tar_info) continue clone.linkname = os.path.join(self.path_prefix, clone.linkname) # Yield the tar header. yield clone.tobuf() # Try to extract any file contents for the tar. If found, we yield them as well. if tar_info.isreg(): for block in TarLayerFormat._emit_file(tar_file, tar_info): yield block # Close the layer stream now that we're done with it. tar_file.close() # If there are any dangling hard links, open a new stream and retarget the dangling hard # links to a new copy of the contents, which will be placed under the *first* dangling hard # link's name. if len(dangling_hard_links) > 0: tar_file = TarLayerFormat._tar_file_from_stream(stream_getter()) if not tar_file: raise TarLayerReadException('Could not re-read tar layer') for tar_info in tar_file: # If we encounter a file that holds the data for a dangling link, # emit it under the name of the first dangling hard link. All other # dangling hard links will be retargeted to this first name. if tar_info.name in dangling_hard_links: first_dangling = dangling_hard_links[tar_info.name][0] # Copy the first dangling hard link, change it to a normal file, # and emit the deleted file's contents for it. clone = copy.deepcopy(first_dangling) clone.name = os.path.join(self.path_prefix, first_dangling.name) clone.type = tar_info.type clone.size = tar_info.size clone.pax_headers = tar_info.pax_headers yield clone.tobuf() for block in TarLayerFormat._emit_file(tar_file, tar_info): yield block elif (tar_info.type == tarfile.LNKTYPE and tar_info.linkname in dangling_hard_links and not self.is_skipped_file(tar_info.name)): # Retarget if necessary. All dangling hard links (but the first) will # need to be retargeted. first_dangling = dangling_hard_links[tar_info.linkname][0] if tar_info.name == first_dangling.name: # Skip; the first dangling is handled above. continue # Retarget the hard link to the first dangling hard link. clone = copy.deepcopy(tar_info) clone.name = os.path.join(self.path_prefix, clone.name) clone.linkname = os.path.join(self.path_prefix, first_dangling.name) yield clone.tobuf() # Close the layer stream now that we're done with it. tar_file.close() # 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 yield '\0' * 512 @abstractmethod def is_skipped_file(self, filename): """ Returns true if the file with the given name will be skipped during append. """ pass @abstractmethod def should_append_file(self, filename): """ Returns true if the file with the given name should be appended when producing the new TAR. """ pass @abstractmethod def after_tar_layer(self): """ Invoked after a TAR layer is added, to do any post-add work. """ pass @staticmethod def _tar_file_from_stream(stream): tar_file = None try: tar_file = tarfile.open(mode='r|*', fileobj=stream) except tarfile.ReadError as re: if re.message != 'empty file': raise TarLayerReadException('Could not read layer') return tar_file @staticmethod def _emit_file(tar_file, tar_info): file_stream = tar_file.extractfile(tar_info) if file_stream is not None: length = 0 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))