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Append-only mode for repositories

New repository config item, repository.append_only, causes Borg to never
delete or append to existing data files. Hints and indices are handled
as before, old ones are deleted, because they can get quite large, but
are automatically reconstructed: no need to keep them.

When append_only is activated a file /path/to/repo/transactions/<NUMBER>
will be created for every commit.
Deleting all segments <NUMBER+1> and higher will rollback to that commit.

Note that this only influences Borg behaviour. Since repository config
can't be altered remotely (except for repository.key) this can't be
disabled when accessed remotely over SSH with "borg serve" as the
forced command.

This is only a feature to support the use case, and does not replace
appropriate file system permissions or monitoring.

Resolves #809
This commit is contained in:
Marian Beermann 2016-03-31 16:24:10 +02:00
parent bf208479d7
commit ffc8cf6c97
2 changed files with 39 additions and 1 deletions

View file

@ -84,6 +84,7 @@ def create(self, path):
config.set('repository', 'version', '1')
config.set('repository', 'segments_per_dir', str(self.DEFAULT_SEGMENTS_PER_DIR))
config.set('repository', 'max_segment_size', str(self.DEFAULT_MAX_SEGMENT_SIZE))
config.set('repository', 'append_only', '0')
config.set('repository', 'id', hexlify(os.urandom(32)).decode('ascii'))
self.save_config(path, config)
@ -105,6 +106,8 @@ def load_key(self):
def destroy(self):
"""Destroy the repository at `self.path`
"""
if self.append_only:
raise ValueError(self.path + " is in append-only mode")
self.close()
os.remove(os.path.join(self.path, 'config')) # kill config first
shutil.rmtree(self.path)
@ -148,6 +151,7 @@ def open(self, path, exclusive, lock_wait=None, lock=True):
raise self.InvalidRepository(path)
self.max_segment_size = self.config.getint('repository', 'max_segment_size')
self.segments_per_dir = self.config.getint('repository', 'segments_per_dir')
self.append_only = self.config.getboolean('repository', 'append_only', fallback=False)
self.id = unhexlify(self.config.get('repository', 'id').strip())
self.io = LoggedIO(self.path, self.max_segment_size, self.segments_per_dir)
@ -163,7 +167,8 @@ def commit(self, save_space=False):
"""Commit transaction
"""
self.io.write_commit()
self.compact_segments(save_space=save_space)
if not self.append_only:
self.compact_segments(save_space=save_space)
self.write_index()
self.rollback()
@ -211,6 +216,11 @@ def write_index(self):
self.index.write(os.path.join(self.path, 'index.tmp'))
os.rename(os.path.join(self.path, 'index.tmp'),
os.path.join(self.path, 'index.%d' % transaction_id))
if self.append_only:
transaction_log = os.path.join(self.path, 'transactions')
if not os.path.exists(transaction_log):
os.mkdir(transaction_log)
open(os.path.join(transaction_log, str(transaction_id)), 'w').close()
# Remove old indices
current = '.%d' % transaction_id
for name in os.listdir(self.path):

View file

@ -187,6 +187,34 @@ def test_crash_before_deleting_compacted_segments(self):
self.assert_equal(len(self.repository), 3)
class RepositoryAppendOnlyTestCase(RepositoryTestCaseBase):
def test_destroy_append_only(self):
# Can't destroy append only repo (via the API)
self.repository.append_only = True
with self.assert_raises(ValueError):
self.repository.destroy()
def test_append_only(self):
def segments_in_repository():
return len(list(self.repository.io.segment_iterator()))
self.repository.put(b'00000000000000000000000000000000', b'foo')
self.repository.commit()
self.repository.append_only = False
assert segments_in_repository() == 1
self.repository.put(b'00000000000000000000000000000000', b'foo')
self.repository.commit()
# normal: compact squashes the data together, only one segment
assert segments_in_repository() == 1
self.repository.append_only = True
assert segments_in_repository() == 1
self.repository.put(b'00000000000000000000000000000000', b'foo')
self.repository.commit()
# append only: does not compact, only new segments written
assert segments_in_repository() == 2
class RepositoryCheckTestCase(RepositoryTestCaseBase):
def list_indices(self):