mirror of https://github.com/borgbackup/borg.git
448 lines
16 KiB
Python
448 lines
16 KiB
Python
from __future__ import with_statement
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from ConfigParser import RawConfigParser
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import fcntl
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import os
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import re
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import shutil
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import struct
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import tempfile
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import unittest
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from zlib import crc32
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from .hashindex import NSIndex
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from .helpers import IntegrityError, deferrable, read_msgpack, write_msgpack
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from .lrucache import LRUCache
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MAX_OBJECT_SIZE = 20 * 1024 * 1024
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TAG_PUT = 0
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TAG_DELETE = 1
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TAG_COMMIT = 2
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class Store(object):
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"""Filesystem based transactional key value store
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On disk layout:
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dir/README
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dir/config
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dir/data/<X / SEGMENTS_PER_DIR>/<X>
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dir/index.X
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dir/hints.X
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"""
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DEFAULT_MAX_SEGMENT_SIZE = 5 * 1024 * 1024
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DEFAULT_SEGMENTS_PER_DIR = 10000
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class DoesNotExist(KeyError):
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"""Requested key does not exist"""
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def __init__(self, path, create=False):
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if create:
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self.create(path)
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self.open(path)
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def create(self, path):
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"""Create a new empty store at `path`
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"""
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if os.path.exists(path) and (not os.path.isdir(path) or os.listdir(path)):
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raise Exception('Path "%s" already exists' % path)
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if not os.path.exists(path):
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os.mkdir(path)
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with open(os.path.join(path, 'README'), 'wb') as fd:
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fd.write('This is a DARC store')
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os.mkdir(os.path.join(path, 'data'))
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config = RawConfigParser()
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config.add_section('store')
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config.set('store', 'version', '1')
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config.set('store', 'segments_per_dir', self.DEFAULT_SEGMENTS_PER_DIR)
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config.set('store', 'max_segment_size', self.DEFAULT_MAX_SEGMENT_SIZE)
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config.set('store', 'id', os.urandom(32).encode('hex'))
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with open(os.path.join(path, 'config'), 'w') as fd:
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config.write(fd)
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def open(self, path):
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self.head = None
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self.path = path
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if not os.path.isdir(path):
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raise Exception('%s Does not look like a darc store' % path)
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self.lock_fd = open(os.path.join(path, 'README'), 'r+')
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fcntl.flock(self.lock_fd, fcntl.LOCK_EX)
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self.config = RawConfigParser()
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self.config.read(os.path.join(self.path, 'config'))
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if self.config.getint('store', 'version') != 1:
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raise Exception('%s Does not look like a darc store')
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self.max_segment_size = self.config.getint('store', 'max_segment_size')
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self.segments_per_dir = self.config.getint('store', 'segments_per_dir')
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self.id = self.config.get('store', 'id').decode('hex')
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self.rollback()
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def close(self):
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self.lock_fd.close()
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def commit(self, rollback=True):
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"""Commit transaction
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"""
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self.io.write_commit()
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self.compact_segments()
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self.write_index()
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self.rollback()
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def _available_indices(self, reverse=False):
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names = [int(name[6:]) for name in os.listdir(self.path) if re.match('index\.\d+', name)]
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names.sort(reverse=reverse)
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return names
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def open_index(self, head, read_only=False):
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if head is None:
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self.index = NSIndex.create(os.path.join(self.path, 'index.tmp'))
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self.segments = {}
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self.compact = set()
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else:
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if read_only:
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self.index = NSIndex(os.path.join(self.path, 'index.%d') % head)
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else:
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shutil.copy(os.path.join(self.path, 'index.%d' % head),
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os.path.join(self.path, 'index.tmp'))
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self.index = NSIndex(os.path.join(self.path, 'index.tmp'))
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hints = read_msgpack(os.path.join(self.path, 'hints.%d' % head))
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if hints['version'] != 1:
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raise ValueError('Unknown hints file version: %d' % hints['version'])
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self.segments = hints['segments']
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self.compact = set(hints['compact'])
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def write_index(self):
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hints = {'version': 1,
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'segments': self.segments,
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'compact': list(self.compact)}
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write_msgpack(os.path.join(self.path, 'hints.%d' % self.io.head), hints)
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self.index.flush()
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os.rename(os.path.join(self.path, 'index.tmp'),
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os.path.join(self.path, 'index.%d' % self.io.head))
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# Remove old indices
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current = '.%d' % self.io.head
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for name in os.listdir(self.path):
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if not name.startswith('index.') and not name.startswith('hints.'):
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continue
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if name.endswith(current):
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continue
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os.unlink(os.path.join(self.path, name))
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def compact_segments(self):
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"""Compact sparse segments by copying data into new segments
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"""
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if not self.compact:
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return
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def lookup(tag, key):
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return tag == TAG_PUT and self.index.get(key, (-1, -1))[0] == segment
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segments = self.segments
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for segment in self.compact:
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if segments[segment] > 0:
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for tag, key, data in self.io.iter_objects(segment, lookup, include_data=True):
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new_segment, offset = self.io.write_put(key, data)
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self.index[key] = new_segment, offset
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segments.setdefault(new_segment, 0)
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segments[new_segment] += 1
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segments[segment] -= 1
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assert segments[segment] == 0
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self.io.write_commit()
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for segment in self.compact:
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assert self.segments.pop(segment) == 0
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self.io.delete_segment(segment)
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self.compact = set()
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def recover(self, path):
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"""Recover missing index by replaying logs"""
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start = None
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available = self._available_indices()
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if available:
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start = available[-1]
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self.open_index(start)
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for segment, filename in self.io._segment_names():
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if start is not None and segment <= start:
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continue
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self.segments[segment] = 0
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for tag, key, offset in self.io.iter_objects(segment):
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if tag == TAG_PUT:
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try:
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s, _ = self.index[key]
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self.compact.add(s)
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self.segments[s] -= 1
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except KeyError:
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pass
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self.index[key] = segment, offset
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self.segments[segment] += 1
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elif tag == TAG_DELETE:
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try:
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s, _ = self.index.pop(key)
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self.segments[s] -= 1
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self.compact.add(s)
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self.compact.add(segment)
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except KeyError:
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pass
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if self.segments[segment] == 0:
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self.compact.add(segment)
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if self.io.head is not None:
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self.write_index()
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def rollback(self):
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"""
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"""
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self._active_txn = False
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self.io = LoggedIO(self.path, self.max_segment_size, self.segments_per_dir)
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if self.io.head is not None and not os.path.exists(os.path.join(self.path, 'index.%d' % self.io.head)):
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self.recover(self.path)
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self.open_index(self.io.head, read_only=True)
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@deferrable
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def get(self, id):
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try:
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segment, offset = self.index[id]
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return self.io.read(segment, offset, id)
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except KeyError:
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raise self.DoesNotExist
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@deferrable
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def put(self, id, data):
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if not self._active_txn:
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self._active_txn = True
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self.open_index(self.io.head)
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try:
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segment, _ = self.index[id]
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self.segments[segment] -= 1
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self.compact.add(segment)
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self.compact.add(self.io.write_delete(id))
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except KeyError:
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pass
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segment, offset = self.io.write_put(id, data)
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self.segments.setdefault(segment, 0)
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self.segments[segment] += 1
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self.index[id] = segment, offset
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@deferrable
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def delete(self, id):
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if not self._active_txn:
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self._active_txn = True
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self.open_index(self.io.head)
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try:
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segment, offset = self.index.pop(id)
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self.segments[segment] -= 1
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self.compact.add(segment)
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self.compact.add(self.io.write_delete(id))
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except KeyError:
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raise self.DoesNotExist
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def flush_rpc(self, *args):
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pass
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def add_callback(self, cb, data):
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cb(None, None, data)
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class LoggedIO(object):
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header_fmt = struct.Struct('<IIB')
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assert header_fmt.size == 9
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put_header_fmt = struct.Struct('<IIB32s')
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assert put_header_fmt.size == 41
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header_no_crc_fmt = struct.Struct('<IB')
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assert header_no_crc_fmt.size == 5
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crc_fmt = struct.Struct('<I')
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assert crc_fmt.size == 4
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_commit = header_no_crc_fmt.pack(9, TAG_COMMIT)
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COMMIT = crc_fmt.pack(crc32(_commit)) + _commit
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def __init__(self, path, limit, segments_per_dir, capacity=100):
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self.path = path
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self.fds = LRUCache(capacity)
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self.segment = None
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self.limit = limit
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self.segments_per_dir = segments_per_dir
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self.offset = 0
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self._write_fd = None
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self.head = None
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self.cleanup()
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def close(self):
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for segment in self.fds.keys():
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self.fds.pop(segment).close()
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self.close_segment()
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self.fds = None # Just to make sure we're disabled
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def _segment_names(self, reverse=False):
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for dirpath, dirs, filenames in os.walk(os.path.join(self.path, 'data')):
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dirs.sort(lambda a, b: cmp(int(a), int(b)), reverse=reverse)
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filenames.sort(lambda a, b: cmp(int(a), int(b)), reverse=reverse)
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for filename in filenames:
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yield int(filename), os.path.join(dirpath, filename)
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def cleanup(self):
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"""Delete segment files left by aborted transactions
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"""
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self.head = None
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self.segment = 0
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for segment, filename in self._segment_names(reverse=True):
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if self.is_complete_segment(filename):
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self.head = segment
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self.segment = self.head + 1
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return
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else:
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os.unlink(filename)
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def is_complete_segment(self, filename):
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with open(filename, 'rb') as fd:
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fd.seek(-self.header_fmt.size, 2)
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return fd.read(self.header_fmt.size) == self.COMMIT
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def segment_filename(self, segment):
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return os.path.join(self.path, 'data', str(segment / self.segments_per_dir), str(segment))
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def get_write_fd(self):
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if self.offset and self.offset > self.limit:
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self.close_segment()
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if not self._write_fd:
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if self.segment % self.segments_per_dir == 0:
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dirname = os.path.join(self.path, 'data', str(self.segment / self.segments_per_dir))
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if not os.path.exists(dirname):
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os.mkdir(dirname)
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self._write_fd = open(self.segment_filename(self.segment), 'ab')
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self._write_fd.write('DSEGMENT')
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self.offset = 8
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return self._write_fd
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def get_fd(self, segment):
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try:
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return self.fds[segment]
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except KeyError:
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fd = open(self.segment_filename(segment), 'rb')
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self.fds[segment] = fd
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return fd
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def delete_segment(self, segment):
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try:
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os.unlink(self.segment_filename(segment))
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except OSError:
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pass
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def iter_objects(self, segment, lookup=None, include_data=False):
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fd = self.get_fd(segment)
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fd.seek(0)
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if fd.read(8) != 'DSEGMENT':
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raise IntegrityError('Invalid segment header')
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offset = 8
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header = fd.read(self.header_fmt.size)
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while header:
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crc, size, tag = self.header_fmt.unpack(header)
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if size > MAX_OBJECT_SIZE:
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raise IntegrityError('Invalid segment object size')
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rest = fd.read(size - self.header_fmt.size)
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if crc32(rest, crc32(buffer(header, 4))) & 0xffffffff != crc:
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raise IntegrityError('Segment checksum mismatch')
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if tag not in (TAG_PUT, TAG_DELETE, TAG_COMMIT):
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raise IntegrityError('Invalid segment entry header')
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key = None
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if tag in (TAG_PUT, TAG_DELETE):
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key = rest[:32]
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if not lookup or lookup(tag, key):
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if include_data:
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yield tag, key, rest[32:]
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else:
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yield tag, key, offset
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offset += size
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header = fd.read(self.header_fmt.size)
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def read(self, segment, offset, id):
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if segment == self.segment:
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self._write_fd.flush()
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fd = self.get_fd(segment)
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fd.seek(offset)
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header = fd.read(self.put_header_fmt.size)
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crc, size, tag, key = self.put_header_fmt.unpack(header)
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if size > MAX_OBJECT_SIZE:
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raise IntegrityError('Invalid segment object size')
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data = fd.read(size - self.put_header_fmt.size)
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if crc32(data, crc32(buffer(header, 4))) & 0xffffffff != crc:
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raise IntegrityError('Segment checksum mismatch')
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if tag != TAG_PUT or id != key:
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raise IntegrityError('Invalid segment entry header')
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return data
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def write_put(self, id, data):
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size = len(data) + self.put_header_fmt.size
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fd = self.get_write_fd()
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offset = self.offset
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header = self.header_no_crc_fmt.pack(size, TAG_PUT)
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crc = self.crc_fmt.pack(crc32(data, crc32(id, crc32(header))) & 0xffffffff)
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fd.write(''.join((crc, header, id, data)))
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self.offset += size
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return self.segment, offset
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def write_delete(self, id):
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fd = self.get_write_fd()
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header = self.header_no_crc_fmt.pack(self.put_header_fmt.size, TAG_DELETE)
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crc = self.crc_fmt.pack(crc32(id, crc32(header)) & 0xffffffff)
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fd.write(''.join((crc, header, id)))
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self.offset += self.put_header_fmt.size
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return self.segment
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def write_commit(self):
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fd = self.get_write_fd()
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header = self.header_no_crc_fmt.pack(self.header_fmt.size, TAG_COMMIT)
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crc = self.crc_fmt.pack(crc32(header) & 0xffffffff)
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fd.write(''.join((crc, header)))
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self.head = self.segment
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self.close_segment()
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def close_segment(self):
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if self._write_fd:
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self.segment += 1
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self.offset = 0
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os.fsync(self._write_fd)
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self._write_fd.close()
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self._write_fd = None
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class StoreTestCase(unittest.TestCase):
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def setUp(self):
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self.tmppath = tempfile.mkdtemp()
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self.store = Store(os.path.join(self.tmppath, 'store'), create=True)
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def tearDown(self):
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shutil.rmtree(self.tmppath)
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def test1(self):
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for x in range(100):
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self.store.put('%-32d' % x, 'SOMEDATA')
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key50 = '%-32d' % 50
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self.assertEqual(self.store.get(key50), 'SOMEDATA')
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self.store.delete(key50)
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self.assertRaises(self.store.DoesNotExist, lambda: self.store.get(key50))
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self.store.commit()
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self.store.close()
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store2 = Store(os.path.join(self.tmppath, 'store'))
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self.assertRaises(store2.DoesNotExist, lambda: store2.get(key50))
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for x in range(100):
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if x == 50:
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continue
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self.assertEqual(self.store.get('%-32d' % x), 'SOMEDATA')
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def test2(self):
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"""Test multiple sequential transactions
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"""
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self.store.put('00000000000000000000000000000000', 'foo')
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self.store.put('00000000000000000000000000000001', 'foo')
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self.store.commit()
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self.store.delete('00000000000000000000000000000000')
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self.store.put('00000000000000000000000000000001', 'bar')
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self.store.commit()
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self.assertEqual(self.store.get('00000000000000000000000000000001'), 'bar')
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def suite():
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return unittest.TestLoader().loadTestsFromTestCase(StoreTestCase)
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if __name__ == '__main__':
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unittest.main()
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