Retarget hard links pointing to deleted files by emitting the deleted file contents under the first hard link instance. This fixes a breakage in the squashed TAR where we were pointing hard links to missing data.
Fixes https://jira.coreos.com/browse/QUAY-885
This commit is contained in:
Joseph Schorr
parent
041a7fcd36
commit
110366f656
8 changed files with 337 additions and 252 deletions
|
|
@ -2,93 +2,169 @@ import os
|
|||
import tarfile
|
||||
import copy
|
||||
|
||||
from abc import ABCMeta, abstractmethod
|
||||
from collections import defaultdict
|
||||
from six import add_metaclass
|
||||
|
||||
|
||||
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 TarLayerFormat(object):
|
||||
""" Class which creates a generator of the combined TAR data. """
|
||||
def __init__(self, tar_iterator, path_prefix=None):
|
||||
self.tar_iterator = tar_iterator
|
||||
self.path_prefix = path_prefix
|
||||
def __init__(self, tar_stream_getter_iterator, path_prefix=None):
|
||||
self.tar_stream_getter_iterator = tar_stream_getter_iterator
|
||||
self.path_prefix = path_prefix or ''
|
||||
|
||||
def get_generator(self):
|
||||
for current_tar in self.tar_iterator():
|
||||
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 = None
|
||||
try:
|
||||
tar_file = tarfile.open(mode='r|*', fileobj=current_tar)
|
||||
except tarfile.ReadError as re:
|
||||
if re.message != 'empty file':
|
||||
raise TarLayerReadException('Could not read layer')
|
||||
|
||||
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.
|
||||
|
||||
# 9MB (+ padding below) so that it matches the 10MB expected by Gzip.
|
||||
chunk_size = 1024 * 1024 * 9
|
||||
|
||||
dangling_hard_links = defaultdict(list)
|
||||
for tar_info in tar_file:
|
||||
if not self.check_tar_info(tar_info):
|
||||
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.
|
||||
if self.path_prefix:
|
||||
# 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:
|
||||
clone.linkname = os.path.join(self.path_prefix, clone.linkname)
|
||||
|
||||
yield clone.tobuf()
|
||||
else:
|
||||
yield tar_info.tobuf()
|
||||
yield clone.tobuf()
|
||||
|
||||
# Try to extract any file contents for the tar. If found, we yield them as well.
|
||||
if tar_info.isreg():
|
||||
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))
|
||||
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(current_tar)
|
||||
self.after_tar_layer()
|
||||
|
||||
# Last two records are empty in TAR spec.
|
||||
yield '\0' * 512
|
||||
yield '\0' * 512
|
||||
|
||||
|
||||
def check_tar_info(self, tar_info):
|
||||
""" Returns true if the current tar_info should be added to the combined tar. False
|
||||
otherwise.
|
||||
@abstractmethod
|
||||
def is_skipped_file(self, filename):
|
||||
""" Returns true if the file with the given name will be skipped during append.
|
||||
"""
|
||||
raise NotImplementedError()
|
||||
pass
|
||||
|
||||
def after_tar_layer(self, current_tar):
|
||||
@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. """
|
||||
raise NotImplementedError()
|
||||
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))
|
||||
|
||||
Reference in a new issue