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repository: Fix potential race condition 

If we crash between compact_segments() and write_index() and the
transaction deletes objects that are newer than the current index
might become undeleted.
This commit is contained in:
Jonas Borgström 2014-02-21 20:20:17 +01:00
parent bd22bc8cb2
commit 6425d16aa8
2 changed files with 53 additions and 63 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

93
attic/repository.py
View File

@ -6,7 +6,6 @@ import os
import shutil
import struct
import sys
import time
from zlib import crc32
from .hashindex import NSIndex
@ -87,15 +86,17 @@ class Repository(object):
def get_transaction_id(self):
index_transaction_id = self.get_index_transaction_id()
segments_transaction_id = self.io.get_segments_transaction_id()
if index_transaction_id is not None and segments_transaction_id is None:
raise self.CheckNeeded(self.path)
# Attempt to automatically rebuild index if we crashed between commit
# tag write and index save
if (index_transaction_id if index_transaction_id is not None else -1) < (segments_transaction_id if segments_transaction_id is not None else -1):
self.replay_segments(index_transaction_id, segments_transaction_id)
index_transaction_id = self.get_index_transaction_id()
if index_transaction_id != segments_transaction_id:
raise self.CheckNeeded(self.path)
return index_transaction_id
if index_transaction_id is not None and index_transaction_id > segments_transaction_id:
replay_from = None
else:
replay_from = index_transaction_id
self.replay_segments(replay_from, segments_transaction_id)
return self.get_index_transaction_id()
def open(self, path):
self.path = path
@ -175,21 +176,24 @@ class Repository(object):
"""
if not self.compact:
return
def lookup(tag, key):
return tag == TAG_PUT and self.index.get(key, (-1, -1))[0] == segment
index_transaction_id = self.get_index_transaction_id()
segments = self.segments
for segment in sorted(self.compact):
if segments[segment] > 0:
for tag, key, data in self.io.iter_objects(segment, lookup, include_data=True):
new_segment, offset = self.io.write_put(key, data)
self.index[key] = new_segment, offset
segments.setdefault(new_segment, 0)
segments[new_segment] += 1
segments[segment] -= 1
if self.io.segment_exists(segment):
for tag, key, data in self.io.iter_objects(segment, include_data=True):
if tag == TAG_PUT and self.index.get(key, (-1, -1))[0] == segment:
new_segment, offset = self.io.write_put(key, data)
self.index[key] = new_segment, offset
segments.setdefault(new_segment, 0)
segments[new_segment] += 1
segments[segment] -= 1
elif tag == TAG_DELETE:
if index_transaction_id is None or segment > index_transaction_id:
self.io.write_delete(key)
assert segments[segment] == 0
self.io.write_commit()
for segment in self.compact:
for segment in sorted(self.compact):
assert self.segments.pop(segment) == 0
self.io.delete_segment(segment)
self.compact = set()
@ -215,10 +219,10 @@ class Repository(object):
elif tag == TAG_DELETE:
try:
s, _ = self.index.pop(key)
self.segments[s] -= 1
self.compact.add(s)
except KeyError:
raise self.CheckNeeded(self.path)
self.segments[s] -= 1
self.compact.add(s)
pass
self.compact.add(segment)
elif tag == TAG_COMMIT:
continue
@ -246,21 +250,16 @@ class Repository(object):
assert not self._active_txn
report_progress('Starting repository check...')
index_transaction_id = self.get_index_transaction_id()
segments_transaction_id = self.io.get_segments_transaction_id()
if index_transaction_id is None and segments_transaction_id is None:
return True
if segments_transaction_id is not None:
transaction_id = segments_transaction_id
else:
transaction_id = index_transaction_id
self.get_index(None)
if index_transaction_id == segments_transaction_id:
try:
transaction_id = self.get_transaction_id()
current_index = self.get_read_only_index(transaction_id)
else:
except Exception:
transaction_id = self.io.get_segments_transaction_id()
current_index = None
report_progress('No suitable index found', error=True)
if transaction_id is None:
transaction_id = self.get_index_transaction_id()
segments_transaction_id = self.io.get_segments_transaction_id()
self.get_index(None)
for segment, filename in self.io.segment_iterator():
if segment > transaction_id:
continue
@ -302,7 +301,7 @@ class Repository(object):
self.io.write_commit()
self.io.close_segment()
if current_index and not repair:
if len(current_index) != len(self.index) and False:
if len(current_index) != len(self.index):
report_progress('Index object count mismatch. {} != {}'.format(len(current_index), len(self.index)), error=True)
elif current_index:
for key, value in self.index.iteritems():
@ -369,13 +368,13 @@ class Repository(object):
self.get_index(self.get_transaction_id())
try:
segment, offset = self.index.pop(id)
self.segments[segment] -= 1
self.compact.add(segment)
segment = self.io.write_delete(id)
self.compact.add(segment)
self.segments.setdefault(segment, 0)
except KeyError:
raise self.DoesNotExist(self.path)
self.segments[segment] -= 1
self.compact.add(segment)
segment = self.io.write_delete(id)
self.compact.add(segment)
self.segments.setdefault(segment, 0)
def preload(self, ids):
"""Preload objects (only applies to remote repositories
@ -479,7 +478,10 @@ class LoggedIO(object):
except OSError:
pass
def iter_objects(self, segment, lookup=None, include_data=False):
def segment_exists(self, segment):
return os.path.exists(self.segment_filename(segment))
def iter_objects(self, segment, include_data=False):
fd = self.get_fd(segment)
fd.seek(0)
if fd.read(8) != MAGIC:
@ -498,11 +500,10 @@ class LoggedIO(object):
key = None
if tag in (TAG_PUT, TAG_DELETE):
key = rest[:32]
if not lookup or lookup(tag, key):
if include_data:
yield tag, key, rest[32:]
else:
yield tag, key, offset
if include_data:
yield tag, key, rest[32:]
else:
yield tag, key, offset
offset += size
header = fd.read(self.header_fmt.size)

23
attic/testsuite/repository.py
View File

@ -115,9 +115,11 @@ class RepositoryCommitTestCase(RepositoryTestCaseBase):
def add_keys(self):
self.repository.put(b'00000000000000000000000000000000', b'foo')
self.repository.put(b'00000000000000000000000000000001', b'bar')
self.repository.put(b'00000000000000000000000000000003', b'bar')
self.repository.commit()
self.repository.put(b'00000000000000000000000000000001', b'bar2')
self.repository.put(b'00000000000000000000000000000002', b'boo')
self.repository.delete(b'00000000000000000000000000000003')
def test_replay_of_missing_index(self):
self.add_keys()
@ -125,7 +127,7 @@ class RepositoryCommitTestCase(RepositoryTestCaseBase):
if name.startswith('index.'):
os.unlink(os.path.join(self.repository.path, name))
self.reopen()
self.assert_equal(len(self.repository), 2)
self.assert_equal(len(self.repository), 3)
self.assert_equal(self.repository.check(), True)
def test_crash_before_compact_segments(self):
@ -174,7 +176,6 @@ class RepositoryCommitTestCase(RepositoryTestCaseBase):
self.assert_equal(len(self.repository), 3)
class RepositoryCheckTestCase(RepositoryTestCaseBase):
def list_indices(self):
@ -249,10 +250,6 @@ class RepositoryCheckTestCase(RepositoryTestCaseBase):
def test_repair_missing_commit_segment(self):
self.add_objects([[1, 2, 3], [4, 5, 6]])
self.delete_segment(1)
self.assert_raises(Repository.CheckNeeded, lambda: self.get_objects(4))
self.check(status=False)
self.assert_raises(Repository.CheckNeeded, lambda: self.get_objects(4))
self.check(repair=True, status=True)
self.assert_raises(Repository.DoesNotExist, lambda: self.get_objects(4))
self.assert_equal(set([1, 2, 3]), self.list_objects())
@ -261,11 +258,9 @@ class RepositoryCheckTestCase(RepositoryTestCaseBase):
with open(os.path.join(self.tmppath, 'repository', 'data', '0', '1'), 'r+b') as fd:
fd.seek(-1, os.SEEK_END)
fd.write(b'X')
self.assert_raises(Repository.CheckNeeded, lambda: self.get_objects(4))
self.check(status=False)
self.check(repair=True, status=True)
self.get_objects(3)
self.assert_raises(Repository.DoesNotExist, lambda: self.get_objects(4))
self.check(status=True)
self.get_objects(3)
self.assert_equal(set([1, 2, 3]), self.list_objects())
def test_repair_no_commits(self):
@ -286,8 +281,6 @@ class RepositoryCheckTestCase(RepositoryTestCaseBase):
def test_repair_missing_index(self):
self.add_objects([[1, 2, 3], [4, 5, 6]])
self.delete_index()
self.check(status=False)
self.check(repair=True, status=True)
self.check(status=True)
self.get_objects(4)
self.assert_equal(set([1, 2, 3, 4, 5, 6]), self.list_objects())
@ -296,12 +289,8 @@ class RepositoryCheckTestCase(RepositoryTestCaseBase):
self.add_objects([[1, 2, 3], [4, 5, 6]])
self.assert_equal(self.list_indices(), ['index.1'])
self.rename_index('index.100')
self.assert_equal(self.list_indices(), ['index.100'])
self.assert_raises(Repository.CheckNeeded, lambda: self.get_objects(4))
self.check(status=False)
self.check(repair=True, status=True)
self.assert_equal(self.list_indices(), ['index.1'])
self.check(status=True)
self.assert_equal(self.list_indices(), ['index.1'])
self.get_objects(4)
self.assert_equal(set([1, 2, 3, 4, 5, 6]), self.list_objects())