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New object store implementation.
This commit is contained in:
Jonas Borgström
parent
1d76aab21e
commit
1e2ecae4e4
1 changed files with 206 additions and 0 deletions
206
dedupstore/store.py
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206
dedupstore/store.py
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#!/usr/bin/env python
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import os
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import fcntl
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import hashlib
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import tempfile
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import shutil
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import unittest
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import uuid
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class Store(object):
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"""
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"""
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IDLE = 'Idle'
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OPEN = 'Open'
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ACTIVE = 'Active'
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VERSION = 'DEDUPSTORE VERSION 1'
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def __init__(self, path):
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self.tid = -1
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self.state = Store.IDLE
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if not os.path.exists(path):
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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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os.mkdir(path)
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open(os.path.join(path, 'version'), 'wb').write(self.VERSION)
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open(os.path.join(path, 'uuid'), 'wb').write(str(uuid.uuid4()))
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open(os.path.join(path, 'tid'), 'wb').write('0')
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os.mkdir(os.path.join(path, 'data'))
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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 store')
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version_path = os.path.join(path, 'version')
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if not os.path.exists(version_path) or open(version_path, 'rb').read() != self.VERSION:
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raise Exception('%s Does not look like a store2')
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self.uuid = open(os.path.join(path, 'uuid'), 'rb').read()
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self.lock_fd = open(os.path.join(path, 'lock'), 'w')
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fcntl.flock(self.lock_fd, fcntl.LOCK_EX)
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self.tid = int(open(os.path.join(path, 'tid'), 'r').read())
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self.recover()
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def recover(self):
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if os.path.exists(os.path.join(self.path, 'txn-active')):
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shutil.rmtree(os.path.join(self.path, 'txn-active'))
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if os.path.exists(os.path.join(self.path, 'txn-commit')):
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self.apply_txn()
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if os.path.exists(os.path.join(self.path, 'txn-applied')):
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shutil.rmtree(os.path.join(self.path, 'txn-applied'))
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self.state = Store.OPEN
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self.txn_delete = []
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self.txn_write = []
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def close(self):
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self.recover()
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self.lock_fd.close()
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self.state = Store.IDLE
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def commit(self):
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"""
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"""
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if self.state == Store.OPEN:
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return
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assert self.state == Store.ACTIVE
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with open(os.path.join(self.path, 'txn-active', 'delete_index'), 'wb') as fd:
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fd.write('\n'.join(self.txn_delete))
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with open(os.path.join(self.path, 'txn-active', 'write_index'), 'wb') as fd:
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fd.write('\n'.join(self.txn_write))
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with open(os.path.join(self.path, 'txn-active', 'tid'), 'wb') as fd:
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fd.write(str(self.tid + 1))
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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.recover()
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def apply_txn(self):
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assert os.path.isdir(os.path.join(self.path, 'txn-commit'))
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tid = int(open(os.path.join(self.path, 'txn-commit', 'tid'), 'rb').read())
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assert tid == self.tid + 1
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delete_list = [line.strip() for line in
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open(os.path.join(self.path, 'txn-commit', 'delete_index'), 'rb').readlines()]
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for name in delete_list:
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path = os.path.join(self.path, 'objects', name)
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os.unlink(path)
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write_list = [line.strip() for line in
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open(os.path.join(self.path, 'txn-commit', 'write_index'), 'rb').readlines()]
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for name in write_list:
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destname = os.path.join(self.path, 'objects', name)
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if not os.path.exists(os.path.dirname(destname)):
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os.makedirs(os.path.dirname(destname))
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os.rename(os.path.join(self.path, 'txn-commit', 'write', name), destname)
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with open(os.path.join(self.path, 'tid'), 'wb') as fd:
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fd.write(str(tid))
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os.rename(os.path.join(self.path, 'txn-commit'),
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os.path.join(self.path, 'txn-applied'))
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shutil.rmtree(os.path.join(self.path, 'txn-applied'))
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self.tid = tid
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def rollback(self):
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"""
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"""
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self.recover()
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def prepare_txn(self):
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if self.state == Store.ACTIVE:
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return os.path.join(self.path, 'txn-active')
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elif self.state == Store.OPEN:
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os.mkdir(os.path.join(self.path, 'txn-active'))
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os.mkdir(os.path.join(self.path, 'txn-active', 'write'))
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self.state = Store.ACTIVE
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def _filename(self, sha, base=''):
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hex = sha.encode('hex')
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return os.path.join(base, hex[:2], hex[2:4], hex[4:])
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def get(self, sha):
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"""
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"""
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path = self._filename(sha)
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if path in self.txn_write:
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filename = os.path.join(self.path, 'txn-active', 'write', path)
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return open(filename, 'rb').read()
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filename = self._filename(sha, os.path.join(self.path, 'objects'))
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if os.path.exists(filename):
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return open(filename, 'rb').read()
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else:
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raise Exception('Object %s does not exist' % sha.encode('hex'))
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def put(self, data, sha=None):
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"""
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"""
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if not sha:
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sha = hashlib.sha1(data).digest()
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self.prepare_txn()
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path = self._filename(sha)
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filename = self._filename(sha, os.path.join(self.path, 'objects'))
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if (path in self.txn_write or
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(path not in self.txn_delete and os.path.exists(filename))):
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raise Exception('Object already exists: %s' % sha.encode('hex'))
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if path in self.txn_delete:
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self.txn_delete.remove(path)
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if path not in self.txn_write:
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self.txn_write.append(path)
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filename = self._filename(sha, os.path.join(self.path, 'txn-active', 'write'))
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if not os.path.exists(os.path.dirname(filename)):
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os.makedirs(os.path.dirname(filename))
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with open(filename, 'wb') as fd:
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fd.write(data)
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return sha
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def delete(self, sha):
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"""
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"""
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self.prepare_txn()
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path = self._filename(sha)
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if path in self.txn_write:
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self.txn_write.remove(path)
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os.unlink(filename)
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else:
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filename = os.path.join(self.path, 'objects', path)
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if os.path.exists(filename):
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self.txn_delete.append(path)
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else:
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raise Exception('Object does not exist: %s' % sha.encode('hex'))
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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'))
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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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self.assertEqual(self.store.state, Store.OPEN)
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SOMEDATA_sha = self.store.put('SOMEDATA')
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self.assertRaises(Exception, lambda: self.store.put('SOMEDATA'))
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self.assertEqual(self.store.get(SOMEDATA_sha), 'SOMEDATA')
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self.store.rollback()
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self.assertRaises(Exception, lambda: self.store.get('SOMEDATA'))
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self.assertEqual(self.store.tid, 0)
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def test2(self):
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self.assertEqual(self.store.tid, 0)
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self.assertEqual(self.store.state, Store.OPEN)
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SOMEDATA_sha = self.store.put('SOMEDATA')
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self.assertEqual(self.store.get(SOMEDATA_sha), 'SOMEDATA')
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self.store.commit()
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self.assertEqual(self.store.get(SOMEDATA_sha), 'SOMEDATA')
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self.assertEqual(self.store.tid, 1)
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self.store.delete(SOMEDATA_sha)
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self.assertRaises(Exception, lambda: self.store.get('SOMEDATA'))
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self.store.rollback()
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self.assertEqual(self.store.get(SOMEDATA_sha), 'SOMEDATA')
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self.store.delete(SOMEDATA_sha)
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self.assertRaises(Exception, lambda: self.store.get('SOMEDATA'))
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self.store.commit()
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self.assertRaises(Exception, lambda: self.store.get('SOMEDATA'))
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if __name__ == '__main__':
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unittest.main()
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