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369 lines
13 KiB
Python
369 lines
13 KiB
Python
from __future__ import with_statement
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from ConfigParser import RawConfigParser
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import errno
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import fcntl
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import os
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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, BandIndex
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from .helpers import IntegrityError, read_set, write_set, deferrable
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from .lrucache import LRUCache
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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/bands/<X / BANDS_PER_DIR>/<X>
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dir/indexes/<NS>
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"""
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DEFAULT_MAX_BAND_SIZE = 5 * 1024 * 1024
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DEFAULT_BANDS_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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self.txn_active = 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, 'bands'))
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os.mkdir(os.path.join(path, 'indexes'))
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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', 'id', os.urandom(32).encode('hex'))
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config.set('store', 'bands_per_dir', self.DEFAULT_BANDS_PER_DIR)
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config.set('store', 'max_band_size', self.DEFAULT_MAX_BAND_SIZE)
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config.add_section('state')
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config.set('state', 'next_band', '0')
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config.set('state', 'tid', '0')
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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.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.rollback()
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self.config = RawConfigParser()
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self.config.read(os.path.join(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.id = self.config.get('store', 'id').decode('hex')
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self.tid = self.config.getint('state', 'tid')
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next_band = self.config.getint('state', 'next_band')
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max_band_size = self.config.getint('store', 'max_band_size')
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bands_per_dir = self.config.getint('store', 'bands_per_dir')
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self.io = BandIO(self.path, next_band, max_band_size, bands_per_dir)
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self.io.cleanup()
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def delete_bands(self):
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delete_path = os.path.join(self.path, 'indexes', 'delete')
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if os.path.exists(delete_path):
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bands = self.get_index('bands')
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for band in read_set(delete_path):
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assert bands.pop(band, 0) == 0
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self.io.delete_band(band, missing_ok=True)
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os.unlink(delete_path)
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def begin_txn(self):
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txn_dir = os.path.join(self.path, 'txn.tmp')
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# Initialize transaction snapshot
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os.mkdir(txn_dir)
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shutil.copytree(os.path.join(self.path, 'indexes'),
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os.path.join(txn_dir, 'indexes'))
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shutil.copy(os.path.join(self.path, 'config'), txn_dir)
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os.rename(os.path.join(self.path, 'txn.tmp'),
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os.path.join(self.path, 'txn.active'))
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self.compact = set()
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self.txn_active = True
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def close(self):
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self.rollback()
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self.lock_fd.close()
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def commit(self):
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"""Commit transaction, `tid` will be increased by 1
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"""
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self.compact_bands()
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self.io.close()
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self.tid += 1
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self.config.set('state', 'tid', self.tid)
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self.config.set('state', 'next_band', self.io.band + 1)
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with open(os.path.join(self.path, 'config'), 'w') as fd:
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self.config.write(fd)
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for i in self.indexes.values():
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i.flush()
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# If we crash before this line, the transaction will be
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# rolled back by open()
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os.rename(os.path.join(self.path, 'txn.active'),
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os.path.join(self.path, 'txn.commit'))
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self.rollback()
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def compact_bands(self):
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"""Compact sparse bands by copying data into new bands
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"""
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if not self.compact:
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return
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self.io.close_band()
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def lookup(ns, key):
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return key in self.get_index(ns)
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bands = self.get_index('bands')
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for band in self.compact:
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if bands[band] > 0:
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for ns, key, data in self.io.iter_objects(band, lookup):
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new_band, offset = self.io.write(ns, key, data)
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self.indexes[ns][key] = new_band, offset
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bands[band] -= 1
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bands.setdefault(new_band, 0)
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bands[new_band] += 1
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write_set(self.compact, os.path.join(self.path, 'indexes', 'delete'))
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def rollback(self):
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"""
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"""
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# Commit any half committed transaction
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if os.path.exists(os.path.join(self.path, 'txn.commit')):
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self.delete_bands()
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os.rename(os.path.join(self.path, 'txn.commit'),
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os.path.join(self.path, 'txn.tmp'))
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# Roll back active transaction
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txn_dir = os.path.join(self.path, 'txn.active')
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if os.path.exists(txn_dir):
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shutil.rmtree(os.path.join(self.path, 'indexes'))
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shutil.copytree(os.path.join(txn_dir, 'indexes'),
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os.path.join(self.path, 'indexes'))
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shutil.copy(os.path.join(txn_dir, 'config'), self.path)
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os.rename(txn_dir, os.path.join(self.path, 'txn.tmp'))
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# Remove partially removed transaction
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if os.path.exists(os.path.join(self.path, 'txn.tmp')):
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shutil.rmtree(os.path.join(self.path, 'txn.tmp'))
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self.indexes = {}
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self.txn_active = False
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def get_index(self, ns):
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try:
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return self.indexes[ns]
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except KeyError:
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if ns == 'bands':
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filename = os.path.join(self.path, 'indexes', 'bands')
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cls = BandIndex
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else:
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filename = os.path.join(self.path, 'indexes', 'ns%d' % ns)
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cls = NSIndex
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if os.path.exists(filename):
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self.indexes[ns] = cls(filename)
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else:
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self.indexes[ns] = cls.create(filename)
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return self.indexes[ns]
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@deferrable
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def get(self, ns, id):
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try:
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band, offset = self.get_index(ns)[id]
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return self.io.read(band, offset, ns, 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, ns, id, data):
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if not self.txn_active:
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self.begin_txn()
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band, offset = self.io.write(ns, id, data)
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bands = self.get_index('bands')
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bands.setdefault(band, 0)
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bands[band] += 1
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self.get_index(ns)[id] = band, offset
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@deferrable
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def delete(self, ns, id):
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if not self.txn_active:
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self.begin_txn()
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try:
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band, offset = self.get_index(ns).pop(id)
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self.get_index('bands')[band] -= 1
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self.compact.add(band)
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except KeyError:
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raise self.DoesNotExist
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@deferrable
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def list(self, ns, marker=None, limit=1000000):
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return [key for key, value in self.get_index(ns).iteritems(marker=marker, limit=limit)]
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def flush_rpc(self, *args):
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pass
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class BandIO(object):
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header_fmt = struct.Struct('<IBIB32s')
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assert header_fmt.size == 42
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def __init__(self, path, nextband, limit, bands_per_dir, capacity=100):
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self.path = path
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self.fds = LRUCache(capacity)
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self.band = nextband
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self.limit = limit
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self.bands_per_dir = bands_per_dir
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self.offset = 0
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def close(self):
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for band in self.fds.keys():
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self.fds.pop(band).close()
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def cleanup(self):
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"""Delete band files left by aborted transactions
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"""
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band = self.band
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while True:
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filename = self.band_filename(band)
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if not os.path.exists(filename):
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break
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os.unlink(filename)
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band += 1
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def band_filename(self, band):
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return os.path.join(self.path, 'bands', str(band / self.bands_per_dir), str(band))
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def get_fd(self, band, write=False):
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try:
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return self.fds[band]
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except KeyError:
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if write and band % 1000 == 0:
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dirname = os.path.join(self.path, 'bands', str(band / self.bands_per_dir))
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if not os.path.exists(dirname):
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os.mkdir(dirname)
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fd = open(self.band_filename(band), write and 'w+' or 'rb')
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self.fds[band] = fd
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return fd
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def delete_band(self, band, missing_ok=False):
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try:
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os.unlink(self.band_filename(band))
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except OSError, e:
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if not missing_ok or e.errno != errno.ENOENT:
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raise
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def read(self, band, offset, ns, id):
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fd = self.get_fd(band)
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fd.seek(offset)
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data = fd.read(self.header_fmt.size)
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size, magic, hash, ns_, id_ = self.header_fmt.unpack(data)
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if magic != 0 or ns != ns_ or id != id_:
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raise IntegrityError('Invalid band entry header')
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data = fd.read(size - self.header_fmt.size)
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if crc32(data) & 0xffffffff != hash:
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raise IntegrityError('Band checksum mismatch')
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return data
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def iter_objects(self, band, lookup):
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fd = self.get_fd(band)
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fd.seek(0)
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if fd.read(8) != 'DARCBAND':
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raise IntegrityError('Invalid band header')
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offset = 8
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data = fd.read(self.header_fmt.size)
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while data:
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size, magic, hash, ns, key = self.header_fmt.unpack(data)
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if magic != 0:
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raise IntegrityError('Unknown band entry header')
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offset += size
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if lookup(ns, key):
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data = fd.read(size - self.header_fmt.size)
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if crc32(data) & 0xffffffff != hash:
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raise IntegrityError('Band checksum mismatch')
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yield ns, key, data
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else:
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fd.seek(offset)
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data = fd.read(self.header_fmt.size)
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def write(self, ns, id, data):
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size = len(data) + self.header_fmt.size
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if self.offset and self.offset + size > self.limit:
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self.close_band()
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fd = self.get_fd(self.band, write=True)
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fd.seek(self.offset)
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if self.offset == 0:
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fd.write('DARCBAND')
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self.offset = 8
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offset = self.offset
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hash = crc32(data) & 0xffffffff
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fd.write(self.header_fmt.pack(size, 0, hash, ns, id))
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fd.write(data)
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self.offset += size
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return self.band, offset
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def close_band(self):
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self.band += 1
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self.offset = 0
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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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self.assertEqual(self.store.tid, 0)
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for x in range(100):
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self.store.put(0, '%-32d' % x, 'SOMEDATA')
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key50 = '%-32d' % 50
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self.assertEqual(self.store.get(0, key50), 'SOMEDATA')
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self.store.delete(0, key50)
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self.assertRaises(self.store.DoesNotExist, lambda: self.store.get(0, key50))
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self.store.commit()
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self.assertEqual(self.store.tid, 1)
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self.store.close()
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store2 = Store(os.path.join(self.tmppath, 'store'))
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self.assertEqual(store2.tid, 1)
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keys = list(store2.list(0))
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for x in range(50):
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key = '%-32d' % x
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self.assertEqual(store2.get(0, key), 'SOMEDATA')
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self.assertRaises(store2.DoesNotExist, lambda: store2.get(0, key50))
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assert key50 not in keys
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for x in range(51, 100):
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key = '%-32d' % x
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assert key in keys
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self.assertEqual(store2.get(0, key), 'SOMEDATA')
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self.assertEqual(len(keys), 99)
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for x in range(50):
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key = '%-32d' % x
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store2.delete(0, key)
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self.assertEqual(len(list(store2.list(0))), 49)
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for x in range(51, 100):
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key = '%-32d' % x
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store2.delete(0, key)
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self.assertEqual(len(list(store2.list(0))), 0)
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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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