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OpenStack Study: db.py**** CubicPower OpenStack Study ****
# Copyright (c) 2010-2012 OpenStack Foundation # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or # implied. # See the License for the specific language governing permissions and # limitations under the License. """ Database code for Swift """ from contextlib import contextmanager, closing import hashlib import logging import os from uuid import uuid4 import sys import time import errno from swift import gettext_ as _ from tempfile import mkstemp from eventlet import sleep, Timeout import sqlite3 from swift.common.utils import json, normalize_timestamp, renamer, \ mkdirs, lock_parent_directory, fallocate from swift.common.exceptions import LockTimeout #: Whether calls will be made to preallocate disk space for database files. DB_PREALLOCATION = True #: Timeout for trying to connect to a DB BROKER_TIMEOUT = 25 #: Pickle protocol to use PICKLE_PROTOCOL = 2 #: Max number of pending entries PENDING_CAP = 131072
**** CubicPower OpenStack Study **** def utf8encode(*args): return [(s.encode('utf8') if isinstance(s, unicode) else s) for s in args]
**** CubicPower OpenStack Study **** def utf8encodekeys(metadata): uni_keys = [k for k in metadata if isinstance(k, unicode)] for k in uni_keys: sv = metadata[k] del metadata[k] metadata[k.encode('utf-8')] = sv
**** CubicPower OpenStack Study **** def _db_timeout(timeout, db_file, call): with LockTimeout(timeout, db_file): retry_wait = 0.001 while True: try: return call() except sqlite3.OperationalError as e: if 'locked' not in str(e): raise sleep(retry_wait) retry_wait = min(retry_wait * 2, 0.05)
**** CubicPower OpenStack Study **** class DatabaseConnectionError(sqlite3.DatabaseError): """More friendly error messages for DB Errors."""
**** CubicPower OpenStack Study **** def __init__(self, path, msg, timeout=0): self.path = path self.timeout = timeout self.msg = msg
**** CubicPower OpenStack Study **** def __str__(self): return 'DB connection error (%s, %s):\n%s' % ( self.path, self.timeout, self.msg)
**** CubicPower OpenStack Study **** class DatabaseAlreadyExists(sqlite3.DatabaseError): """More friendly error messages for DB Errors."""
**** CubicPower OpenStack Study **** def __init__(self, path): self.path = path
**** CubicPower OpenStack Study **** def __str__(self): return 'DB %s already exists' % self.path
**** CubicPower OpenStack Study **** class GreenDBConnection(sqlite3.Connection): """SQLite DB Connection handler that plays well with eventlet."""
**** CubicPower OpenStack Study **** def __init__(self, database, timeout=None, *args, **kwargs): if timeout is None: timeout = BROKER_TIMEOUT self.timeout = timeout self.db_file = database super(GreenDBConnection, self).__init__(database, 0, *args, **kwargs)
**** CubicPower OpenStack Study **** def cursor(self, cls=None): if cls is None: cls = GreenDBCursor return sqlite3.Connection.cursor(self, cls)
**** CubicPower OpenStack Study **** def commit(self): return _db_timeout( self.timeout, self.db_file, lambda: sqlite3.Connection.commit(self))
**** CubicPower OpenStack Study **** class GreenDBCursor(sqlite3.Cursor): """SQLite Cursor handler that plays well with eventlet."""
**** CubicPower OpenStack Study **** def __init__(self, *args, **kwargs): self.timeout = args[0].timeout self.db_file = args[0].db_file super(GreenDBCursor, self).__init__(*args, **kwargs)
**** CubicPower OpenStack Study **** def execute(self, *args, **kwargs): return _db_timeout( self.timeout, self.db_file, lambda: sqlite3.Cursor.execute( self, *args, **kwargs)) def dict_factory(crs, row): """ This should only be used when you need a real dict, i.e. when you're going to serialize the results. """ return dict( ((col[0], row[idx]) for idx, col in enumerate(crs.description))) def chexor(old, name, timestamp): """ Each entry in the account and container databases is XORed by the 128-bit hash on insert or delete. This serves as a rolling, order-independent hash of the contents. (check + XOR) :param old: hex representation of the current DB hash :param name: name of the object or container being inserted :param timestamp: timestamp of the new record :returns: a hex representation of the new hash value """ if name is None: raise Exception('name is None!') new = hashlib.md5(('%s-%s' % (name, timestamp)).encode('utf8')).hexdigest() return '%032x' % (int(old, 16) ^ int(new, 16)) def get_db_connection(path, timeout=30, okay_to_create=False): """ Returns a properly configured SQLite database connection. :param path: path to DB :param timeout: timeout for connection :param okay_to_create: if True, create the DB if it doesn't exist :returns: DB connection object """ try: connect_time = time.time() conn = sqlite3.connect(path, check_same_thread=False, factory=GreenDBConnection, timeout=timeout) if path != ':memory:' and not okay_to_create: # attempt to detect and fail when connect creates the db file stat = os.stat(path) if stat.st_size == 0 and stat.st_ctime >= connect_time: os.unlink(path) raise DatabaseConnectionError(path, 'DB file created by connect?') conn.row_factory = sqlite3.Row conn.text_factory = str with closing(conn.cursor()) as cur: cur.execute('PRAGMA synchronous = NORMAL') cur.execute('PRAGMA count_changes = OFF') cur.execute('PRAGMA temp_store = MEMORY') cur.execute('PRAGMA journal_mode = DELETE') conn.create_function('chexor', 3, chexor) except sqlite3.DatabaseError: import traceback raise DatabaseConnectionError(path, traceback.format_exc(), timeout=timeout) return conn
**** CubicPower OpenStack Study **** def dict_factory(crs, row): """ This should only be used when you need a real dict, i.e. when you're going to serialize the results. """ return dict( ((col[0], row[idx]) for idx, col in enumerate(crs.description)))
**** CubicPower OpenStack Study **** def chexor(old, name, timestamp): """ Each entry in the account and container databases is XORed by the 128-bit hash on insert or delete. This serves as a rolling, order-independent hash of the contents. (check + XOR) :param old: hex representation of the current DB hash :param name: name of the object or container being inserted :param timestamp: timestamp of the new record :returns: a hex representation of the new hash value """ if name is None: raise Exception('name is None!') new = hashlib.md5(('%s-%s' % (name, timestamp)).encode('utf8')).hexdigest() return '%032x' % (int(old, 16) ^ int(new, 16))
**** CubicPower OpenStack Study **** def get_db_connection(path, timeout=30, okay_to_create=False): """ Returns a properly configured SQLite database connection. :param path: path to DB :param timeout: timeout for connection :param okay_to_create: if True, create the DB if it doesn't exist :returns: DB connection object """ try: connect_time = time.time() conn = sqlite3.connect(path, check_same_thread=False, factory=GreenDBConnection, timeout=timeout) if path != ':memory:' and not okay_to_create: # attempt to detect and fail when connect creates the db file stat = os.stat(path) if stat.st_size == 0 and stat.st_ctime >= connect_time: os.unlink(path) raise DatabaseConnectionError(path, 'DB file created by connect?') conn.row_factory = sqlite3.Row conn.text_factory = str with closing(conn.cursor()) as cur: cur.execute('PRAGMA synchronous = NORMAL') cur.execute('PRAGMA count_changes = OFF') cur.execute('PRAGMA temp_store = MEMORY') cur.execute('PRAGMA journal_mode = DELETE') conn.create_function('chexor', 3, chexor) except sqlite3.DatabaseError: import traceback raise DatabaseConnectionError(path, traceback.format_exc(), timeout=timeout) return conn
**** CubicPower OpenStack Study **** class DatabaseBroker(object): """Encapsulates working with a database."""
**** CubicPower OpenStack Study **** def __init__(self, db_file, timeout=BROKER_TIMEOUT, logger=None, account=None, container=None, pending_timeout=None, stale_reads_ok=False): """Encapsulates working with a database.""" self.conn = None self.db_file = db_file self.pending_file = self.db_file + '.pending' self.pending_timeout = pending_timeout or 10 self.stale_reads_ok = stale_reads_ok self.db_dir = os.path.dirname(db_file) self.timeout = timeout self.logger = logger or logging.getLogger() self.account = account self.container = container self._db_version = -1
**** CubicPower OpenStack Study **** def __str__(self): """ Returns a string indentifying the entity under broker to a human. The baseline implementation returns a full pathname to a database. This is vital for useful diagnostics. """ return self.db_file
**** CubicPower OpenStack Study **** def initialize(self, put_timestamp=None): """ Create the DB :param put_timestamp: timestamp of initial PUT request """ if self.db_file == ':memory:': tmp_db_file = None conn = get_db_connection(self.db_file, self.timeout) else: mkdirs(self.db_dir) fd, tmp_db_file = mkstemp(suffix='.tmp', dir=self.db_dir) os.close(fd) conn = sqlite3.connect(tmp_db_file, check_same_thread=False, factory=GreenDBConnection, timeout=0) # creating dbs implicitly does a lot of transactions, so we # pick fast, unsafe options here and do a big fsync at the end. with closing(conn.cursor()) as cur: cur.execute('PRAGMA synchronous = OFF') cur.execute('PRAGMA temp_store = MEMORY') cur.execute('PRAGMA journal_mode = MEMORY') conn.create_function('chexor', 3, chexor) conn.row_factory = sqlite3.Row conn.text_factory = str conn.executescript(""" CREATE TABLE outgoing_sync ( remote_id TEXT UNIQUE, sync_point INTEGER, updated_at TEXT DEFAULT 0 ); CREATE TABLE incoming_sync ( remote_id TEXT UNIQUE, sync_point INTEGER, updated_at TEXT DEFAULT 0 ); CREATE TRIGGER outgoing_sync_insert AFTER INSERT ON outgoing_sync BEGIN UPDATE outgoing_sync SET updated_at = STRFTIME('%s', 'NOW') WHERE ROWID = new.ROWID; END; CREATE TRIGGER outgoing_sync_update AFTER UPDATE ON outgoing_sync BEGIN UPDATE outgoing_sync SET updated_at = STRFTIME('%s', 'NOW') WHERE ROWID = new.ROWID; END; CREATE TRIGGER incoming_sync_insert AFTER INSERT ON incoming_sync BEGIN UPDATE incoming_sync SET updated_at = STRFTIME('%s', 'NOW') WHERE ROWID = new.ROWID; END; CREATE TRIGGER incoming_sync_update AFTER UPDATE ON incoming_sync BEGIN UPDATE incoming_sync SET updated_at = STRFTIME('%s', 'NOW') WHERE ROWID = new.ROWID; END; """) if not put_timestamp: put_timestamp = normalize_timestamp(0) self._initialize(conn, put_timestamp) conn.commit() if tmp_db_file: conn.close() with open(tmp_db_file, 'r+b') as fp: os.fsync(fp.fileno()) with lock_parent_directory(self.db_file, self.pending_timeout): if os.path.exists(self.db_file): # It's as if there was a "condition" where different parts # of the system were "racing" each other. raise DatabaseAlreadyExists(self.db_file) renamer(tmp_db_file, self.db_file) self.conn = get_db_connection(self.db_file, self.timeout) else: self.conn = conn
**** CubicPower OpenStack Study **** def delete_db(self, timestamp): """ Mark the DB as deleted :param timestamp: delete timestamp """ timestamp = normalize_timestamp(timestamp) # first, clear the metadata cleared_meta = {} for k in self.metadata: cleared_meta[k] = ('', timestamp) self.update_metadata(cleared_meta) # then mark the db as deleted with self.get() as conn: self._delete_db(conn, timestamp) conn.commit()
**** CubicPower OpenStack Study **** def possibly_quarantine(self, exc_type, exc_value, exc_traceback): """ Checks the exception info to see if it indicates a quarantine situation (malformed or corrupted database). If not, the original exception will be reraised. If so, the database will be quarantined and a new sqlite3.DatabaseError will be raised indicating the action taken. """ if 'database disk image is malformed' in str(exc_value): exc_hint = 'malformed' elif 'file is encrypted or is not a database' in str(exc_value): exc_hint = 'corrupted' else: raise exc_type, exc_value, exc_traceback prefix_path = os.path.dirname(self.db_dir) partition_path = os.path.dirname(prefix_path) dbs_path = os.path.dirname(partition_path) device_path = os.path.dirname(dbs_path) quar_path = os.path.join(device_path, 'quarantined', self.db_type + 's', os.path.basename(self.db_dir)) try: renamer(self.db_dir, quar_path) except OSError as e: if e.errno not in (errno.EEXIST, errno.ENOTEMPTY): raise quar_path = "%s-%s" % (quar_path, uuid4().hex) renamer(self.db_dir, quar_path) detail = _('Quarantined %s to %s due to %s database') % \ (self.db_dir, quar_path, exc_hint) self.logger.error(detail) raise sqlite3.DatabaseError(detail) @contextmanager
**** CubicPower OpenStack Study **** def get(self): """Use with the "with" statement; returns a database connection.""" if not self.conn: if self.db_file != ':memory:' and os.path.exists(self.db_file): try: self.conn = get_db_connection(self.db_file, self.timeout) except (sqlite3.DatabaseError, DatabaseConnectionError): self.possibly_quarantine(*sys.exc_info()) else: raise DatabaseConnectionError(self.db_file, "DB doesn't exist") conn = self.conn self.conn = None try: yield conn conn.rollback() self.conn = conn except sqlite3.DatabaseError: try: conn.close() except Exception: pass self.possibly_quarantine(*sys.exc_info()) except (Exception, Timeout): conn.close() raise @contextmanager
**** CubicPower OpenStack Study **** def lock(self): """Use with the "with" statement; locks a database.""" if not self.conn: if self.db_file != ':memory:' and os.path.exists(self.db_file): self.conn = get_db_connection(self.db_file, self.timeout) else: raise DatabaseConnectionError(self.db_file, "DB doesn't exist") conn = self.conn self.conn = None orig_isolation_level = conn.isolation_level conn.isolation_level = None conn.execute('BEGIN IMMEDIATE') try: yield True except (Exception, Timeout): pass try: conn.execute('ROLLBACK') conn.isolation_level = orig_isolation_level self.conn = conn except (Exception, Timeout): logging.exception( _('Broker error trying to rollback locked connection')) conn.close()
**** CubicPower OpenStack Study **** def newid(self, remote_id): """ Re-id the database. This should be called after an rsync. :param remote_id: the ID of the remote database being rsynced in """ with self.get() as conn: row = conn.execute(''' UPDATE %s_stat SET id=? ''' % self.db_type, (str(uuid4()),)) row = conn.execute(''' SELECT ROWID FROM %s ORDER BY ROWID DESC LIMIT 1 ''' % self.db_contains_type).fetchone() sync_point = row['ROWID'] if row else -1 conn.execute(''' INSERT OR REPLACE INTO incoming_sync (sync_point, remote_id) VALUES (?, ?) ''', (sync_point, remote_id)) self._newid(conn) conn.commit()
**** CubicPower OpenStack Study **** def _newid(self, conn): # Override for additional work when receiving an rsynced db. pass
**** CubicPower OpenStack Study **** def merge_timestamps(self, created_at, put_timestamp, delete_timestamp): """ Used in replication to handle updating timestamps. :param created_at: create timestamp :param put_timestamp: put timestamp :param delete_timestamp: delete timestamp """ with self.get() as conn: conn.execute(''' UPDATE %s_stat SET created_at=MIN(?, created_at), put_timestamp=MAX(?, put_timestamp), delete_timestamp=MAX(?, delete_timestamp) ''' % self.db_type, (created_at, put_timestamp, delete_timestamp)) conn.commit()
**** CubicPower OpenStack Study **** def get_items_since(self, start, count): """ Get a list of objects in the database between start and end. :param start: start ROWID :param count: number to get :returns: list of objects between start and end """ self._commit_puts_stale_ok() with self.get() as conn: curs = conn.execute(''' SELECT * FROM %s WHERE ROWID > ? ORDER BY ROWID ASC LIMIT ? ''' % self.db_contains_type, (start, count)) curs.row_factory = dict_factory return [r for r in curs]
**** CubicPower OpenStack Study **** def get_sync(self, id, incoming=True): """ Gets the most recent sync point for a server from the sync table. :param id: remote ID to get the sync_point for :param incoming: if True, get the last incoming sync, otherwise get the last outgoing sync :returns: the sync point, or -1 if the id doesn't exist. """ with self.get() as conn: row = conn.execute( "SELECT sync_point FROM %s_sync WHERE remote_id=?" % ('incoming' if incoming else 'outgoing'), (id,)).fetchone() if not row: return -1 return row['sync_point']
**** CubicPower OpenStack Study **** def get_syncs(self, incoming=True): """ Get a serialized copy of the sync table. :param incoming: if True, get the last incoming sync, otherwise get the last outgoing sync :returns: list of {'remote_id', 'sync_point'} """ with self.get() as conn: curs = conn.execute(''' SELECT remote_id, sync_point FROM %s_sync ''' % 'incoming' if incoming else 'outgoing') result = [] for row in curs: result.append({'remote_id': row[0], 'sync_point': row[1]}) return result
**** CubicPower OpenStack Study **** def get_replication_info(self): """ Get information about the DB required for replication. :returns: dict containing keys: hash, id, created_at, put_timestamp, delete_timestamp, count, max_row, and metadata """ self._commit_puts_stale_ok() query_part1 = ''' SELECT hash, id, created_at, put_timestamp, delete_timestamp, %s_count AS count, CASE WHEN SQLITE_SEQUENCE.seq IS NOT NULL THEN SQLITE_SEQUENCE.seq ELSE -1 END AS max_row, ''' % \ self.db_contains_type query_part2 = ''' FROM (%s_stat LEFT JOIN SQLITE_SEQUENCE ON SQLITE_SEQUENCE.name == '%s') LIMIT 1 ''' % (self.db_type, self.db_contains_type) with self.get() as conn: try: curs = conn.execute(query_part1 + 'metadata' + query_part2) except sqlite3.OperationalError as err: if 'no such column: metadata' not in str(err): raise curs = conn.execute(query_part1 + "'' as metadata" + query_part2) curs.row_factory = dict_factory return curs.fetchone()
**** CubicPower OpenStack Study **** def _commit_puts(self, item_list=None): """ Scan for .pending files and commit the found records by feeding them to merge_items(). :param item_list: A list of items to commit in addition to .pending """ if self.db_file == ':memory:' or not os.path.exists(self.pending_file): return if item_list is None: item_list = [] with lock_parent_directory(self.pending_file, self.pending_timeout): self._preallocate() if not os.path.getsize(self.pending_file): if item_list: self.merge_items(item_list) return with open(self.pending_file, 'r+b') as fp: for entry in fp.read().split(':'): if entry: try: self._commit_puts_load(item_list, entry) except Exception: self.logger.exception( _('Invalid pending entry %(file)s: %(entry)s'), {'file': self.pending_file, 'entry': entry}) if item_list: self.merge_items(item_list) try: os.ftruncate(fp.fileno(), 0) except OSError as err: if err.errno != errno.ENOENT: raise
**** CubicPower OpenStack Study **** def _commit_puts_stale_ok(self): """ Catch failures of _commit_puts() if broker is intended for reading of stats, and thus does not care for pending updates. """ try: self._commit_puts() except LockTimeout: if not self.stale_reads_ok: raise
**** CubicPower OpenStack Study **** def _commit_puts_load(self, item_list, entry): """ Unmarshall the :param:entry and append it to :param:item_list. This is implemented by a particular broker to be compatible with its :func:`merge_items`. """ raise NotImplementedError
**** CubicPower OpenStack Study **** def merge_syncs(self, sync_points, incoming=True): """ Merge a list of sync points with the incoming sync table. :param sync_points: list of sync points where a sync point is a dict of {'sync_point', 'remote_id'} :param incoming: if True, get the last incoming sync, otherwise get the last outgoing sync """ with self.get() as conn: for rec in sync_points: try: conn.execute(''' INSERT INTO %s_sync (sync_point, remote_id) VALUES (?, ?) ''' % ('incoming' if incoming else 'outgoing'), (rec['sync_point'], rec['remote_id'])) except sqlite3.IntegrityError: conn.execute(''' UPDATE %s_sync SET sync_point=max(?, sync_point) WHERE remote_id=? ''' % ('incoming' if incoming else 'outgoing'), (rec['sync_point'], rec['remote_id'])) conn.commit()
**** CubicPower OpenStack Study **** def _preallocate(self): """ The idea is to allocate space in front of an expanding db. If it gets within 512k of a boundary, it allocates to the next boundary. Boundaries are 2m, 5m, 10m, 25m, 50m, then every 50m after. """ if not DB_PREALLOCATION or self.db_file == ':memory:': return MB = (1024 * 1024) def prealloc_points(): for pm in (1, 2, 5, 10, 25, 50): yield pm * MB while True: pm += 50 yield pm * MB stat = os.stat(self.db_file) file_size = stat.st_size allocated_size = stat.st_blocks * 512 for point in prealloc_points(): if file_size <= point - MB / 2: prealloc_size = point break if allocated_size < prealloc_size: with open(self.db_file, 'rb+') as fp: fallocate(fp.fileno(), int(prealloc_size)) @property
**** CubicPower OpenStack Study **** def prealloc_points(): for pm in (1, 2, 5, 10, 25, 50): yield pm * MB while True: pm += 50 yield pm * MB stat = os.stat(self.db_file) file_size = stat.st_size allocated_size = stat.st_blocks * 512 for point in prealloc_points(): if file_size <= point - MB / 2: prealloc_size = point break if allocated_size < prealloc_size: with open(self.db_file, 'rb+') as fp: fallocate(fp.fileno(), int(prealloc_size)) @property
**** CubicPower OpenStack Study **** def metadata(self): """ Returns the metadata dict for the database. The metadata dict values are tuples of (value, timestamp) where the timestamp indicates when that key was set to that value. """ with self.get() as conn: try: metadata = conn.execute('SELECT metadata FROM %s_stat' % self.db_type).fetchone()[0] except sqlite3.OperationalError as err: if 'no such column: metadata' not in str(err): raise metadata = '' if metadata: metadata = json.loads(metadata) utf8encodekeys(metadata) else: metadata = {} return metadata
**** CubicPower OpenStack Study **** def update_metadata(self, metadata_updates): """ Updates the metadata dict for the database. The metadata dict values are tuples of (value, timestamp) where the timestamp indicates when that key was set to that value. Key/values will only be overwritten if the timestamp is newer. To delete a key, set its value to ('', timestamp). These empty keys will eventually be removed by :func:`reclaim` """ old_metadata = self.metadata if set(metadata_updates).issubset(set(old_metadata)): for key, (value, timestamp) in metadata_updates.iteritems(): if timestamp > old_metadata[key][1]: break else: return with self.get() as conn: try: md = conn.execute('SELECT metadata FROM %s_stat' % self.db_type).fetchone()[0] md = json.loads(md) if md else {} utf8encodekeys(md) except sqlite3.OperationalError as err: if 'no such column: metadata' not in str(err): raise conn.execute(""" ALTER TABLE %s_stat ADD COLUMN metadata TEXT DEFAULT '' """ % self.db_type) md = {} for key, value_timestamp in metadata_updates.iteritems(): value, timestamp = value_timestamp if key not in md or timestamp > md[key][1]: md[key] = value_timestamp conn.execute('UPDATE %s_stat SET metadata = ?' % self.db_type, (json.dumps(md),)) conn.commit()
**** CubicPower OpenStack Study **** def reclaim(self, age_timestamp, sync_timestamp): """ Delete rows from the db_contains_type table that are marked deleted and whose created_at timestamp is < age_timestamp. Also deletes rows from incoming_sync and outgoing_sync where the updated_at timestamp is < sync_timestamp. In addition, this calls the DatabaseBroker's :func:`_reclaim` method. :param age_timestamp: max created_at timestamp of object rows to delete :param sync_timestamp: max update_at timestamp of sync rows to delete """ self._commit_puts() with self.get() as conn: conn.execute(''' DELETE FROM %s WHERE deleted = 1 AND %s < ? ''' % (self.db_contains_type, self.db_reclaim_timestamp), (age_timestamp,)) try: conn.execute(''' DELETE FROM outgoing_sync WHERE updated_at < ? ''', (sync_timestamp,)) conn.execute(''' DELETE FROM incoming_sync WHERE updated_at < ? ''', (sync_timestamp,)) except sqlite3.OperationalError as err: # Old dbs didn't have updated_at in the _sync tables. if 'no such column: updated_at' not in str(err): raise DatabaseBroker._reclaim(self, conn, age_timestamp) conn.commit()
**** CubicPower OpenStack Study **** def _reclaim(self, conn, timestamp): """ Removes any empty metadata values older than the timestamp using the given database connection. This function will not call commit on the conn, but will instead return True if the database needs committing. This function was created as a worker to limit transactions and commits from other related functions. :param conn: Database connection to reclaim metadata within. :param timestamp: Empty metadata items last updated before this timestamp will be removed. :returns: True if conn.commit() should be called """ try: md = conn.execute('SELECT metadata FROM %s_stat' % self.db_type).fetchone()[0] if md: md = json.loads(md) keys_to_delete = [] for key, (value, value_timestamp) in md.iteritems(): if value == '' and value_timestamp < timestamp: keys_to_delete.append(key) if keys_to_delete: for key in keys_to_delete: del md[key] conn.execute('UPDATE %s_stat SET metadata = ?' % self.db_type, (json.dumps(md),)) return True except sqlite3.OperationalError as err: if 'no such column: metadata' not in str(err): raise return False
**** CubicPower OpenStack Study **** def update_put_timestamp(self, timestamp): """ Update the put_timestamp. Only modifies it if it is greater than the current timestamp. :param timestamp: put timestamp """ with self.get() as conn: conn.execute( 'UPDATE %s_stat SET put_timestamp = ?' ' WHERE put_timestamp < ?' % self.db_type, (timestamp, timestamp)) conn.commit()
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