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import logging
import weakref
from threading import Event
from threading import Thread
try:
from Queue import Queue
except ImportError:
from queue import Queue
try:
import gevent
from gevent import Greenlet as GThread
from gevent.event import Event as GEvent
from gevent.queue import Queue as GQueue
except ImportError:
GThread = GQueue = GEvent = None
from playhouse.sqlite_ext import SqliteExtDatabase
logger = logging.getLogger('peewee.sqliteq')
class ResultTimeout(Exception):
pass
class AsyncCursor(object):
__slots__ = ('sql', 'params', 'commit', 'timeout',
'_event', '_cursor', '_exc', '_idx', '_rows')
def __init__(self, event, sql, params, commit, timeout):
self._event = event
self.sql = sql
self.params = params
self.commit = commit
self.timeout = timeout
self._cursor = self._exc = self._idx = self._rows = None
def set_result(self, cursor, exc=None):
self._cursor = cursor
self._exc = exc
self._idx = 0
self._rows = cursor.fetchall() if exc is None else []
self._event.set()
return self
def _wait(self, timeout=None):
timeout = timeout if timeout is not None else self.timeout
if not self._event.wait(timeout=timeout) and timeout:
raise ResultTimeout('results not ready, timed out.')
if self._exc is not None:
raise self._exc
def __iter__(self):
self._wait()
if self._exc is not None:
raise self._exec
return self
def next(self):
try:
obj = self._rows[self._idx]
except IndexError:
raise StopIteration
else:
self._idx += 1
return obj
__next__ = next
@property
def lastrowid(self):
self._wait()
return self._cursor.lastrowid
@property
def rowcount(self):
self._wait()
return self._cursor.rowcount
@property
def description(self):
return self._cursor.description
def close(self):
self._cursor.close()
def fetchall(self):
return list(self) # Iterating implies waiting until populated.
def fetchone(self):
self._wait()
try:
return next(self)
except StopIteration:
return None
THREADLOCAL_ERROR_MESSAGE = ('threadlocals cannot be set to True when using '
'the Sqlite thread / queue database. All queries '
'are serialized through a single connection, so '
'allowing multiple threads to connect defeats '
'the purpose of this database.')
WAL_MODE_ERROR_MESSAGE = ('SQLite must be configured to use the WAL journal '
'mode when using this feature. WAL mode allows '
'one or more readers to continue reading while '
'another connection writes to the database.')
class SqliteQueueDatabase(SqliteExtDatabase):
def __init__(self, database, use_gevent=False, autostart=False, readers=1,
queue_max_size=None, results_timeout=None, *args, **kwargs):
if kwargs.get('threadlocals'):
raise ValueError(THREADLOCAL_ERROR_MESSAGE)
kwargs['threadlocals'] = False
kwargs['check_same_thread'] = False
# Ensure that journal_mode is WAL. This value is passed to the parent
# class constructor below.
pragmas = self._validate_journal_mode(
kwargs.pop('journal_mode', None),
kwargs.pop('pragmas', None))
# Reference to execute_sql on the parent class. Since we've overridden
# execute_sql(), this is just a handy way to reference the real
# implementation.
Parent = super(SqliteQueueDatabase, self)
self.__execute_sql = Parent.execute_sql
# Call the parent class constructor with our modified pragmas.
Parent.__init__(database, pragmas=pragmas, *args, **kwargs)
self._autostart = autostart
self._results_timeout = results_timeout
self._num_readers = readers
self._is_stopped = True
self._thread_helper = self.get_thread_impl(use_gevent)(queue_max_size)
self._create_queues_and_workers()
if self._autostart:
self.start()
def get_thread_impl(self, use_gevent):
return GreenletHelper if use_gevent else ThreadHelper
def _validate_journal_mode(self, journal_mode=None, pragmas=None):
if journal_mode and journal_mode.lower() != 'wal':
raise ValueError(WAL_MODE_ERROR_MESSAGE)
if pragmas:
pdict = dict((k.lower(), v) for (k, v) in pragmas)
if pdict.get('journal_mode', 'wal').lower() != 'wal':
raise ValueError(WAL_MODE_ERROR_MESSAGE)
return [(k, v) for (k, v) in pragmas
if k != 'journal_mode'] + [('journal_mode', 'wal')]
else:
return [('journal_mode', 'wal')]
def _create_queues_and_workers(self):
self._write_queue = self._thread_helper.queue()
self._read_queue = self._thread_helper.queue()
target = self._run_worker_loop
self._writer = self._thread_helper.thread(target, self._write_queue)
self._readers = [self._thread_helper.thread(target, self._read_queue)
for _ in range(self._num_readers)]
def _run_worker_loop(self, queue):
while True:
async_cursor = queue.get()
if async_cursor is StopIteration:
logger.info('worker shutting down.')
return
logger.debug('received query %s', async_cursor.sql)
self._process_execution(async_cursor)
def _process_execution(self, async_cursor):
try:
cursor = self.__execute_sql(async_cursor.sql, async_cursor.params,
async_cursor.commit)
except Exception as exc:
cursor = None
else:
exc = None
return async_cursor.set_result(cursor, exc)
def queue_size(self):
return (self._write_queue.qsize(), self._read_queue.qsize())
def execute_sql(self, sql, params=None, require_commit=True, timeout=None):
cursor = AsyncCursor(
event=self._thread_helper.event(),
sql=sql,
params=params,
commit=require_commit,
timeout=self._results_timeout if timeout is None else timeout)
queue = self._write_queue if require_commit else self._read_queue
queue.put(cursor)
return cursor
def start(self):
with self._conn_lock:
if not self._is_stopped:
return False
self._writer.start()
for reader in self._readers:
reader.start()
logger.info('workers started.')
self._is_stopped = False
return True
def stop(self):
logger.debug('environment stop requested.')
with self._conn_lock:
if self._is_stopped:
return False
self._write_queue.put(StopIteration)
for _ in self._readers:
self._read_queue.put(StopIteration)
self._writer.join()
for reader in self._readers:
reader.join()
return True
def is_stopped(self):
with self._conn_lock:
return self._is_stopped
class ThreadHelper(object):
__slots__ = ('queue_max_size',)
def __init__(self, queue_max_size=None):
self.queue_max_size = queue_max_size
def event(self): return Event()
def queue(self, max_size=None):
max_size = max_size if max_size is not None else self.queue_max_size
return Queue(maxsize=max_size or 0)
def thread(self, fn, *args, **kwargs):
thread = Thread(target=fn, args=args, kwargs=kwargs)
thread.daemon = True
return thread
class GreenletHelper(ThreadHelper):
__slots__ = ('queue_max_size',)
def event(self): return GEvent()
def queue(self, max_size=None):
max_size = max_size if max_size is not None else self.queue_max_size
return GQueue(maxsize=max_size or 0)
def thread(self, fn, *args, **kwargs):
def wrap(*a, **k):
gevent.sleep()
return fn(*a, **k)
return GThread(wrap, *args, **kwargs)
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