503 lines
16 KiB
Python
503 lines
16 KiB
Python
# -*- test-case-name: twisted.test.test_adbapi -*-
|
|
# Copyright (c) Twisted Matrix Laboratories.
|
|
# See LICENSE for details.
|
|
|
|
"""
|
|
An asynchronous mapping to U{DB-API
|
|
2.0<http://www.python.org/topics/database/DatabaseAPI-2.0.html>}.
|
|
"""
|
|
|
|
import sys
|
|
|
|
from twisted.internet import threads
|
|
from twisted.python import reflect, log, compat
|
|
|
|
|
|
class ConnectionLost(Exception):
|
|
"""
|
|
This exception means that a db connection has been lost. Client code may
|
|
try again.
|
|
"""
|
|
|
|
|
|
|
|
class Connection(object):
|
|
"""
|
|
A wrapper for a DB-API connection instance.
|
|
|
|
The wrapper passes almost everything to the wrapped connection and so has
|
|
the same API. However, the L{Connection} knows about its pool and also
|
|
handle reconnecting should when the real connection dies.
|
|
"""
|
|
|
|
def __init__(self, pool):
|
|
self._pool = pool
|
|
self._connection = None
|
|
self.reconnect()
|
|
|
|
|
|
def close(self):
|
|
# The way adbapi works right now means that closing a connection is
|
|
# a really bad thing as it leaves a dead connection associated with
|
|
# a thread in the thread pool.
|
|
# Really, I think closing a pooled connection should return it to the
|
|
# pool but that's handled by the runWithConnection method already so,
|
|
# rather than upsetting anyone by raising an exception, let's ignore
|
|
# the request
|
|
pass
|
|
|
|
|
|
def rollback(self):
|
|
if not self._pool.reconnect:
|
|
self._connection.rollback()
|
|
return
|
|
|
|
try:
|
|
self._connection.rollback()
|
|
curs = self._connection.cursor()
|
|
curs.execute(self._pool.good_sql)
|
|
curs.close()
|
|
self._connection.commit()
|
|
return
|
|
except:
|
|
log.err(None, "Rollback failed")
|
|
|
|
self._pool.disconnect(self._connection)
|
|
|
|
if self._pool.noisy:
|
|
log.msg("Connection lost.")
|
|
|
|
raise ConnectionLost()
|
|
|
|
|
|
def reconnect(self):
|
|
if self._connection is not None:
|
|
self._pool.disconnect(self._connection)
|
|
self._connection = self._pool.connect()
|
|
|
|
|
|
def __getattr__(self, name):
|
|
return getattr(self._connection, name)
|
|
|
|
|
|
|
|
class Transaction:
|
|
"""
|
|
A lightweight wrapper for a DB-API 'cursor' object.
|
|
|
|
Relays attribute access to the DB cursor. That is, you can call
|
|
C{execute()}, C{fetchall()}, etc., and they will be called on the
|
|
underlying DB-API cursor object. Attributes will also be retrieved from
|
|
there.
|
|
"""
|
|
_cursor = None
|
|
|
|
def __init__(self, pool, connection):
|
|
self._pool = pool
|
|
self._connection = connection
|
|
self.reopen()
|
|
|
|
|
|
def close(self):
|
|
_cursor = self._cursor
|
|
self._cursor = None
|
|
_cursor.close()
|
|
|
|
|
|
def reopen(self):
|
|
if self._cursor is not None:
|
|
self.close()
|
|
|
|
try:
|
|
self._cursor = self._connection.cursor()
|
|
return
|
|
except:
|
|
if not self._pool.reconnect:
|
|
raise
|
|
else:
|
|
log.err(None, "Cursor creation failed")
|
|
|
|
if self._pool.noisy:
|
|
log.msg('Connection lost, reconnecting')
|
|
|
|
self.reconnect()
|
|
self._cursor = self._connection.cursor()
|
|
|
|
|
|
def reconnect(self):
|
|
self._connection.reconnect()
|
|
self._cursor = None
|
|
|
|
|
|
def __getattr__(self, name):
|
|
return getattr(self._cursor, name)
|
|
|
|
|
|
|
|
class ConnectionPool:
|
|
"""
|
|
Represent a pool of connections to a DB-API 2.0 compliant database.
|
|
|
|
@ivar connectionFactory: factory for connections, default to L{Connection}.
|
|
@type connectionFactory: any callable.
|
|
|
|
@ivar transactionFactory: factory for transactions, default to
|
|
L{Transaction}.
|
|
@type transactionFactory: any callable
|
|
|
|
@ivar shutdownID: L{None} or a handle on the shutdown event trigger which
|
|
will be used to stop the connection pool workers when the reactor
|
|
stops.
|
|
|
|
@ivar _reactor: The reactor which will be used to schedule startup and
|
|
shutdown events.
|
|
@type _reactor: L{IReactorCore} provider
|
|
"""
|
|
|
|
CP_ARGS = "min max name noisy openfun reconnect good_sql".split()
|
|
|
|
noisy = False # If true, generate informational log messages
|
|
min = 3 # Minimum number of connections in pool
|
|
max = 5 # Maximum number of connections in pool
|
|
name = None # Name to assign to thread pool for debugging
|
|
openfun = None # A function to call on new connections
|
|
reconnect = False # Reconnect when connections fail
|
|
good_sql = 'select 1' # A query which should always succeed
|
|
|
|
running = False # True when the pool is operating
|
|
connectionFactory = Connection
|
|
transactionFactory = Transaction
|
|
|
|
# Initialize this to None so it's available in close() even if start()
|
|
# never runs.
|
|
shutdownID = None
|
|
|
|
def __init__(self, dbapiName, *connargs, **connkw):
|
|
"""
|
|
Create a new L{ConnectionPool}.
|
|
|
|
Any positional or keyword arguments other than those documented here
|
|
are passed to the DB-API object when connecting. Use these arguments to
|
|
pass database names, usernames, passwords, etc.
|
|
|
|
@param dbapiName: an import string to use to obtain a DB-API compatible
|
|
module (e.g. C{'pyPgSQL.PgSQL'})
|
|
|
|
@param cp_min: the minimum number of connections in pool (default 3)
|
|
|
|
@param cp_max: the maximum number of connections in pool (default 5)
|
|
|
|
@param cp_noisy: generate informational log messages during operation
|
|
(default C{False})
|
|
|
|
@param cp_openfun: a callback invoked after every C{connect()} on the
|
|
underlying DB-API object. The callback is passed a new DB-API
|
|
connection object. This callback can setup per-connection state
|
|
such as charset, timezone, etc.
|
|
|
|
@param cp_reconnect: detect connections which have failed and reconnect
|
|
(default C{False}). Failed connections may result in
|
|
L{ConnectionLost} exceptions, which indicate the query may need to
|
|
be re-sent.
|
|
|
|
@param cp_good_sql: an sql query which should always succeed and change
|
|
no state (default C{'select 1'})
|
|
|
|
@param cp_reactor: use this reactor instead of the global reactor
|
|
(added in Twisted 10.2).
|
|
@type cp_reactor: L{IReactorCore} provider
|
|
"""
|
|
self.dbapiName = dbapiName
|
|
self.dbapi = reflect.namedModule(dbapiName)
|
|
|
|
if getattr(self.dbapi, 'apilevel', None) != '2.0':
|
|
log.msg('DB API module not DB API 2.0 compliant.')
|
|
|
|
if getattr(self.dbapi, 'threadsafety', 0) < 1:
|
|
log.msg('DB API module not sufficiently thread-safe.')
|
|
|
|
reactor = connkw.pop('cp_reactor', None)
|
|
if reactor is None:
|
|
from twisted.internet import reactor
|
|
self._reactor = reactor
|
|
|
|
self.connargs = connargs
|
|
self.connkw = connkw
|
|
|
|
for arg in self.CP_ARGS:
|
|
cpArg = 'cp_%s' % (arg,)
|
|
if cpArg in connkw:
|
|
setattr(self, arg, connkw[cpArg])
|
|
del connkw[cpArg]
|
|
|
|
self.min = min(self.min, self.max)
|
|
self.max = max(self.min, self.max)
|
|
|
|
# All connections, hashed on thread id
|
|
self.connections = {}
|
|
|
|
# These are optional so import them here
|
|
from twisted.python import threadpool
|
|
from twisted.python import threadable
|
|
|
|
self.threadID = threadable.getThreadID
|
|
self.threadpool = threadpool.ThreadPool(self.min, self.max)
|
|
self.startID = self._reactor.callWhenRunning(self._start)
|
|
|
|
|
|
def _start(self):
|
|
self.startID = None
|
|
return self.start()
|
|
|
|
|
|
def start(self):
|
|
"""
|
|
Start the connection pool.
|
|
|
|
If you are using the reactor normally, this function does *not*
|
|
need to be called.
|
|
"""
|
|
if not self.running:
|
|
self.threadpool.start()
|
|
self.shutdownID = self._reactor.addSystemEventTrigger(
|
|
'during', 'shutdown', self.finalClose)
|
|
self.running = True
|
|
|
|
|
|
def runWithConnection(self, func, *args, **kw):
|
|
"""
|
|
Execute a function with a database connection and return the result.
|
|
|
|
@param func: A callable object of one argument which will be executed
|
|
in a thread with a connection from the pool. It will be passed as
|
|
its first argument a L{Connection} instance (whose interface is
|
|
mostly identical to that of a connection object for your DB-API
|
|
module of choice), and its results will be returned as a
|
|
L{Deferred}. If the method raises an exception the transaction will
|
|
be rolled back. Otherwise, the transaction will be committed.
|
|
B{Note} that this function is B{not} run in the main thread: it
|
|
must be threadsafe.
|
|
|
|
@param *args: positional arguments to be passed to func
|
|
|
|
@param **kw: keyword arguments to be passed to func
|
|
|
|
@return: a L{Deferred} which will fire the return value of
|
|
C{func(Transaction(...), *args, **kw)}, or a
|
|
L{twisted.python.failure.Failure}.
|
|
"""
|
|
return threads.deferToThreadPool(self._reactor, self.threadpool,
|
|
self._runWithConnection,
|
|
func, *args, **kw)
|
|
|
|
|
|
def _runWithConnection(self, func, *args, **kw):
|
|
conn = self.connectionFactory(self)
|
|
try:
|
|
result = func(conn, *args, **kw)
|
|
conn.commit()
|
|
return result
|
|
except:
|
|
excType, excValue, excTraceback = sys.exc_info()
|
|
try:
|
|
conn.rollback()
|
|
except:
|
|
log.err(None, "Rollback failed")
|
|
compat.reraise(excValue, excTraceback)
|
|
|
|
|
|
def runInteraction(self, interaction, *args, **kw):
|
|
"""
|
|
Interact with the database and return the result.
|
|
|
|
The 'interaction' is a callable object which will be executed in a
|
|
thread using a pooled connection. It will be passed an L{Transaction}
|
|
object as an argument (whose interface is identical to that of the
|
|
database cursor for your DB-API module of choice), and its results will
|
|
be returned as a L{Deferred}. If running the method raises an
|
|
exception, the transaction will be rolled back. If the method returns a
|
|
value, the transaction will be committed.
|
|
|
|
NOTE that the function you pass is *not* run in the main thread: you
|
|
may have to worry about thread-safety in the function you pass to this
|
|
if it tries to use non-local objects.
|
|
|
|
@param interaction: a callable object whose first argument is an
|
|
L{adbapi.Transaction}.
|
|
|
|
@param *args: additional positional arguments to be passed to
|
|
interaction
|
|
|
|
@param **kw: keyword arguments to be passed to interaction
|
|
|
|
@return: a Deferred which will fire the return value of
|
|
C{interaction(Transaction(...), *args, **kw)}, or a
|
|
L{twisted.python.failure.Failure}.
|
|
"""
|
|
return threads.deferToThreadPool(self._reactor, self.threadpool,
|
|
self._runInteraction,
|
|
interaction, *args, **kw)
|
|
|
|
|
|
def runQuery(self, *args, **kw):
|
|
"""
|
|
Execute an SQL query and return the result.
|
|
|
|
A DB-API cursor which will be invoked with C{cursor.execute(*args,
|
|
**kw)}. The exact nature of the arguments will depend on the specific
|
|
flavor of DB-API being used, but the first argument in C{*args} be an
|
|
SQL statement. The result of a subsequent C{cursor.fetchall()} will be
|
|
fired to the L{Deferred} which is returned. If either the 'execute' or
|
|
'fetchall' methods raise an exception, the transaction will be rolled
|
|
back and a L{twisted.python.failure.Failure} returned.
|
|
|
|
The C{*args} and C{**kw} arguments will be passed to the DB-API
|
|
cursor's 'execute' method.
|
|
|
|
@return: a L{Deferred} which will fire the return value of a DB-API
|
|
cursor's 'fetchall' method, or a L{twisted.python.failure.Failure}.
|
|
"""
|
|
return self.runInteraction(self._runQuery, *args, **kw)
|
|
|
|
|
|
def runOperation(self, *args, **kw):
|
|
"""
|
|
Execute an SQL query and return L{None}.
|
|
|
|
A DB-API cursor which will be invoked with C{cursor.execute(*args,
|
|
**kw)}. The exact nature of the arguments will depend on the specific
|
|
flavor of DB-API being used, but the first argument in C{*args} will be
|
|
an SQL statement. This method will not attempt to fetch any results
|
|
from the query and is thus suitable for C{INSERT}, C{DELETE}, and other
|
|
SQL statements which do not return values. If the 'execute' method
|
|
raises an exception, the transaction will be rolled back and a
|
|
L{Failure} returned.
|
|
|
|
The C{*args} and C{*kw} arguments will be passed to the DB-API cursor's
|
|
'execute' method.
|
|
|
|
@return: a L{Deferred} which will fire with L{None} or a
|
|
L{twisted.python.failure.Failure}.
|
|
"""
|
|
return self.runInteraction(self._runOperation, *args, **kw)
|
|
|
|
|
|
def close(self):
|
|
"""
|
|
Close all pool connections and shutdown the pool.
|
|
"""
|
|
if self.shutdownID:
|
|
self._reactor.removeSystemEventTrigger(self.shutdownID)
|
|
self.shutdownID = None
|
|
if self.startID:
|
|
self._reactor.removeSystemEventTrigger(self.startID)
|
|
self.startID = None
|
|
self.finalClose()
|
|
|
|
|
|
def finalClose(self):
|
|
"""
|
|
This should only be called by the shutdown trigger.
|
|
"""
|
|
self.shutdownID = None
|
|
self.threadpool.stop()
|
|
self.running = False
|
|
for conn in self.connections.values():
|
|
self._close(conn)
|
|
self.connections.clear()
|
|
|
|
|
|
def connect(self):
|
|
"""
|
|
Return a database connection when one becomes available.
|
|
|
|
This method blocks and should be run in a thread from the internal
|
|
threadpool. Don't call this method directly from non-threaded code.
|
|
Using this method outside the external threadpool may exceed the
|
|
maximum number of connections in the pool.
|
|
|
|
@return: a database connection from the pool.
|
|
"""
|
|
|
|
tid = self.threadID()
|
|
conn = self.connections.get(tid)
|
|
if conn is None:
|
|
if self.noisy:
|
|
log.msg('adbapi connecting: %s' % (self.dbapiName,))
|
|
conn = self.dbapi.connect(*self.connargs, **self.connkw)
|
|
if self.openfun is not None:
|
|
self.openfun(conn)
|
|
self.connections[tid] = conn
|
|
return conn
|
|
|
|
|
|
def disconnect(self, conn):
|
|
"""
|
|
Disconnect a database connection associated with this pool.
|
|
|
|
Note: This function should only be used by the same thread which called
|
|
L{ConnectionPool.connect}. As with C{connect}, this function is not
|
|
used in normal non-threaded Twisted code.
|
|
"""
|
|
tid = self.threadID()
|
|
if conn is not self.connections.get(tid):
|
|
raise Exception("wrong connection for thread")
|
|
if conn is not None:
|
|
self._close(conn)
|
|
del self.connections[tid]
|
|
|
|
|
|
def _close(self, conn):
|
|
if self.noisy:
|
|
log.msg('adbapi closing: %s' % (self.dbapiName,))
|
|
try:
|
|
conn.close()
|
|
except:
|
|
log.err(None, "Connection close failed")
|
|
|
|
|
|
def _runInteraction(self, interaction, *args, **kw):
|
|
conn = self.connectionFactory(self)
|
|
trans = self.transactionFactory(self, conn)
|
|
try:
|
|
result = interaction(trans, *args, **kw)
|
|
trans.close()
|
|
conn.commit()
|
|
return result
|
|
except:
|
|
excType, excValue, excTraceback = sys.exc_info()
|
|
try:
|
|
conn.rollback()
|
|
except:
|
|
log.err(None, "Rollback failed")
|
|
compat.reraise(excValue, excTraceback)
|
|
|
|
|
|
def _runQuery(self, trans, *args, **kw):
|
|
trans.execute(*args, **kw)
|
|
return trans.fetchall()
|
|
|
|
|
|
def _runOperation(self, trans, *args, **kw):
|
|
trans.execute(*args, **kw)
|
|
|
|
|
|
def __getstate__(self):
|
|
return {'dbapiName': self.dbapiName,
|
|
'min': self.min,
|
|
'max': self.max,
|
|
'noisy': self.noisy,
|
|
'reconnect': self.reconnect,
|
|
'good_sql': self.good_sql,
|
|
'connargs': self.connargs,
|
|
'connkw': self.connkw}
|
|
|
|
|
|
def __setstate__(self, state):
|
|
self.__dict__ = state
|
|
self.__init__(self.dbapiName, *self.connargs, **self.connkw)
|
|
|
|
|
|
|
|
__all__ = ['Transaction', 'ConnectionPool']
|