"""
from __future__ import division
+import os, re, sha, tarfile, tempfile, thread
from pysqlite2 import dbapi2 as sqlite3
+# Maximum number of nested indirect references allowed in a snapshot.
+MAX_RECURSION_DEPTH = 3
+
class Struct:
"""A class which merely acts as a data container.
def __repr__(self):
return "<%s %s>" % (self.__class__, self.__dict__)
+CHECKSUM_ALGORITHMS = {
+ 'sha1': sha.new
+}
+
+class ChecksumCreator:
+ """Compute an LBS checksum for provided data.
+
+ The algorithm used is selectable, but currently defaults to sha1.
+ """
+
+ def __init__(self, algorithm='sha1'):
+ self.algorithm = algorithm
+ self.hash = CHECKSUM_ALGORITHMS[algorithm]()
+
+ def update(self, data):
+ self.hash.update(data)
+ return self
+
+ def compute(self):
+ return "%s=%s" % (self.algorithm, self.hash.hexdigest())
+
+class ChecksumVerifier:
+ """Verify whether a checksum from a snapshot matches the supplied data."""
+
+ def __init__(self, checksumstr):
+ """Create an object to check the supplied checksum."""
+
+ (algo, checksum) = checksumstr.split("=", 1)
+ self.checksum = checksum
+ self.hash = CHECKSUM_ALGORITHMS[algo]()
+
+ def update(self, data):
+ self.hash.update(data)
+
+ def valid(self):
+ """Return a boolean indicating whether the checksum matches."""
+
+ result = self.hash.hexdigest()
+ return result == self.checksum
+
+class LowlevelDataStore:
+ """Access to the backup store containing segments and snapshot descriptors.
+
+ Instances of this class are used to get direct filesystem-level access to
+ the backup data. To read a backup, a caller will ordinarily not care about
+ direct access to backup segments, but will instead merely need to access
+ objects from those segments. The ObjectStore class provides a suitable
+ wrapper around a DataStore to give this high-level access.
+ """
+
+ def __init__(self, path):
+ self.path = path
+
+ # Low-level filesystem access. These methods could be overwritten to
+ # provide access to remote data stores.
+ def lowlevel_list(self):
+ """Get a listing of files stored."""
+
+ return os.listdir(self.path)
+
+ def lowlevel_open(self, filename):
+ """Return a file-like object for reading data from the given file."""
+
+ return open(os.path.join(self.path, filename), 'rb')
+
+ def lowlevel_stat(self, filename):
+ """Return a dictionary of information about the given file.
+
+ Currently, the only defined field is 'size', giving the size of the
+ file in bytes.
+ """
+
+ stat = os.stat(os.path.join(self.path, filename))
+ return {'size': stat.st_size}
+
+ # Slightly higher-level list methods.
+ def list_snapshots(self):
+ for f in self.lowlevel_list():
+ m = re.match(r"^snapshot-(.*)\.lbs$", f)
+ if m:
+ yield m.group(1)
+
+ def list_segments(self):
+ for f in self.lowlevel_list():
+ m = re.match(r"^([0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12})(\.\S+)?$", f)
+ if m:
+ yield m.group(1)
+
+class ObjectStore:
+ def __init__(self, data_store):
+ self.store = data_store
+ self.cachedir = None
+ self.CACHE_SIZE = 16
+ self.lru_list = []
+
+ def get_cachedir(self):
+ if self.cachedir is None:
+ self.cachedir = tempfile.mkdtemp(".lbs")
+ return self.cachedir
+
+ def cleanup(self):
+ if self.cachedir is not None:
+ # TODO: Avoid use of system, make this safer
+ os.system("rm -rv " + self.cachedir)
+ self.cachedir = None
+
+ @staticmethod
+ def parse_ref(refstr):
+ m = re.match(r"^([-0-9a-f]+)\/([0-9a-f]+)(\(\S+\))?(\[(\d+)\+(\d+)\])?$", refstr)
+ if not m: return
+
+ segment = m.group(1)
+ object = m.group(2)
+ checksum = m.group(3)
+ slice = m.group(4)
+
+ if checksum is not None:
+ checksum = checksum.lstrip("(").rstrip(")")
+
+ if slice is not None:
+ slice = (int(m.group(5)), int(m.group(6)))
+
+ return (segment, object, checksum, slice)
+
+ def get_segment(self, segment):
+ raw = self.store.lowlevel_open(segment + ".tar.gpg")
+
+ (input, output) = os.popen2("lbs-filter-gpg --decrypt")
+ def copy_thread(src, dst):
+ BLOCK_SIZE = 4096
+ while True:
+ block = src.read(BLOCK_SIZE)
+ if len(block) == 0: break
+ dst.write(block)
+ dst.close()
+
+ thread.start_new_thread(copy_thread, (raw, input))
+ return output
+
+ def load_segment(self, segment):
+ seg = tarfile.open(segment, 'r|', self.get_segment(segment))
+ for item in seg:
+ data_obj = seg.extractfile(item)
+ path = item.name.split('/')
+ if len(path) == 2 and path[0] == segment:
+ yield (path[1], data_obj.read())
+
+ def load_snapshot(self, snapshot):
+ file = self.store.lowlevel_open("snapshot-" + snapshot + ".lbs")
+ return file.read().splitlines(True)
+
+ def extract_segment(self, segment):
+ segdir = os.path.join(self.get_cachedir(), segment)
+ os.mkdir(segdir)
+ for (object, data) in self.load_segment(segment):
+ f = open(os.path.join(segdir, object), 'wb')
+ f.write(data)
+ f.close()
+
+ def load_object(self, segment, object):
+ path = os.path.join(self.get_cachedir(), segment, object)
+ if not os.access(path, os.R_OK):
+ print "Extracting", segment
+ self.extract_segment(segment)
+ if segment in self.lru_list: self.lru_list.remove(segment)
+ self.lru_list.append(segment)
+ while len(self.lru_list) > self.CACHE_SIZE:
+ os.system("rm -rv " + os.path.join(self.cachedir, self.lru_list[0]))
+ self.lru_list = self.lru_list[1:]
+ return open(path, 'rb').read()
+
+ def get(self, refstr):
+ """Fetch the given object and return it.
+
+ The input should be an object reference, in string form.
+ """
+
+ (segment, object, checksum, slice) = self.parse_ref(refstr)
+
+ data = self.load_object(segment, object)
+
+ if checksum is not None:
+ verifier = ChecksumVerifier(checksum)
+ verifier.update(data)
+ if not verifier.valid():
+ raise ValueError
+
+ if slice is not None:
+ (start, length) = slice
+ data = data[start:start+length]
+ if len(data) != length: raise IndexError
+
+ return data
+
+def parse(lines, terminate=None):
+ """Generic parser for RFC822-style "Key: Value" data streams.
+
+ This parser can be used to read metadata logs and snapshot root descriptor
+ files.
+
+ lines must be an iterable object which yields a sequence of lines of input.
+
+ If terminate is specified, it is used as a predicate to determine when to
+ stop reading input lines.
+ """
+
+ dict = {}
+ last_key = None
+
+ for l in lines:
+ # Strip off a trailing newline, if present
+ if len(l) > 0 and l[-1] == "\n":
+ l = l[:-1]
+
+ if terminate is not None and terminate(l):
+ if len(dict) > 0: yield dict
+ dict = {}
+ last_key = None
+ continue
+
+ m = re.match(r"^(\w+):\s*(.*)$", l)
+ if m:
+ dict[m.group(1)] = m.group(2)
+ last_key = m.group(1)
+ elif len(l) > 0 and l[0].isspace() and last_key is not None:
+ dict[last_key] += l
+ else:
+ last_key = None
+
+ if len(dict) > 0: yield dict
+
+def parse_full(lines):
+ try:
+ return parse(lines).next()
+ except StopIteration:
+ return {}
+
+def read_metadata(object_store, root):
+ """Iterate through all lines in the metadata log, following references."""
+
+ # Stack for keeping track of recursion when following references to
+ # portions of the log. The last entry in the stack corresponds to the
+ # object currently being parsed. Each entry is a list of lines which have
+ # been reversed, so that popping successive lines from the end of each list
+ # will return lines of the metadata log in order.
+ stack = []
+
+ def follow_ref(refstr):
+ if len(stack) >= MAX_RECURSION_DEPTH: raise OverflowError
+ lines = object_store.get(refstr).splitlines(True)
+ lines.reverse()
+ stack.append(lines)
+
+ follow_ref(root)
+
+ while len(stack) > 0:
+ top = stack[-1]
+ if len(top) == 0:
+ stack.pop()
+ continue
+ line = top.pop()
+
+ # An indirect reference which we must follow?
+ if len(line) > 0 and line[0] == '@':
+ ref = line[1:]
+ ref.strip()
+ follow_ref(ref)
+ else:
+ yield line
+
+class MetadataItem:
+ """Metadata for a single file (or directory or...) from a snapshot."""
+
+ def __init__(self, fields, object_store):
+ """Initialize from a dictionary of key/value pairs from metadata log."""
+
+ self.fields = fields
+ self.object_store = object_store
+
+ def data(self):
+ """Return an iterator for the data blocks that make up a file."""
+
+ # This traverses the list of blocks that make up a file, following
+ # indirect references. It is implemented in much the same way as
+ # read_metadata, so see that function for details of the technique.
+
+ objects = self.fields['data'].split()
+ objects.reverse()
+ stack = [objects]
+
+ def follow_ref(refstr):
+ if len(stack) >= MAX_RECURSION_DEPTH: raise OverflowError
+ objects = self.object_store.get(refstr).split()
+ objects.reverse()
+ stack.append(objects)
+
+ while len(stack) > 0:
+ top = stack[-1]
+ if len(top) == 0:
+ stack.pop()
+ continue
+ ref = top.pop()
+
+ # An indirect reference which we must follow?
+ if len(ref) > 0 and ref[0] == '@':
+ follow_ref(ref[1:])
+ else:
+ yield ref
+
+def iterate_metadata(object_store, root):
+ for d in parse(read_metadata(object_store, root), lambda l: len(l) == 0):
+ yield MetadataItem(d, object_store)
+
class LocalDatabase:
"""Access to the local database of snapshot contents and object checksums.
projects / cumulus.git / blobdiff