twisted.enterprise.adbapi.ConnectionPool : API documentation

Represent a pool of connections to a DB-API 2.0 compliant database.

Instance Variables	connectionFactory	factory for connections, default to `Connection`. (type: any callable. )
	transactionFactory	factory for transactions, default to `Transaction`. (type: any callable )
	shutdownID	`None` or a handle on the shutdown event trigger which will be used to stop the connection pool workers when the reactor stops.
	_reactor	The reactor which will be used to schedule startup and shutdown events. (type: `IReactorCore` provider )

Method	__init__	Create a new ConnectionPool.
Method	start	Start the connection pool.
Method	runWithConnection	Execute a function with a database connection and return the result.
Method	runInteraction	Interact with the database and return the result.
Method	runQuery	Execute an SQL query and return the result.
Method	runOperation	Execute an SQL query and return None.
Method	close	Close all pool connections and shutdown the pool.
Method	finalClose	This should only be called by the shutdown trigger.
Method	connect	Return a database connection when one becomes available.
Method	disconnect	Disconnect a database connection associated with this pool.
Method	__getstate__	Undocumented
Method	__setstate__	Undocumented
Method	_start	Undocumented
Method	_runWithConnection	Undocumented
Method	_close	Undocumented
Method	_runInteraction	Undocumented
Method	_runQuery	Undocumented
Method	_runOperation	Undocumented

def __init__(self, dbapiName, *connargs, **connkw): (source)

Create a new 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.

Parameters	dbapiName	an import string to use to obtain a DB-API compatible module (e.g. 'pyPgSQL.PgSQL')
	cp_min	the minimum number of connections in pool (default 3)
	cp_max	the maximum number of connections in pool (default 5)
	cp_noisy	generate informational log messages during operation (default False)
	cp_openfun	a callback invoked after every 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.
	cp_reconnect	detect connections which have failed and reconnect (default False). Failed connections may result in ConnectionLost exceptions, which indicate the query may need to be re-sent.
	cp_good_sql	an sql query which should always succeed and change no state (default 'select 1')
	cp_reactor	use this reactor instead of the global reactor (added in Twisted 10.2). (type: `IReactorCore` provider )

def _start(self): (source)

Undocumented

def start(self): (source)

Start the connection pool.

If you are using the reactor normally, this function does *not* need to be called.

def runWithConnection(self, func, *args, **kw): (source)

Execute a function with a database connection and return the result.

Parameters	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 `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 Deferred. If the method raises an exception the transaction will be rolled back. Otherwise, the transaction will be committed. Note that this function is not run in the main thread: it must be threadsafe.
	*args	positional arguments to be passed to func
	**kw	keyword arguments to be passed to func
Returns	a Deferred which will fire the return value of `func(Transaction(...), args, *kw)`, or a Failure.

def _runWithConnection(self, func, *args, **kw): (source)

Undocumented

def runInteraction(self, interaction, *args, **kw): (source)

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 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 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.

Parameters	interaction	a callable object whose first argument is an `adbapi.Transaction`.
	*args	additional positional arguments to be passed to interaction
	**kw	keyword arguments to be passed to interaction
Returns	a Deferred which will fire the return value of 'interaction(Transaction(...), args, *kw)', or a Failure.

def runQuery(self, *args, **kw): (source)

Execute an SQL query and return the result.

A DB-API cursor will will be invoked with 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 *args be an SQL statement. The result of a subsequent cursor.fetchall() will be fired to the Deferred which is returned. If either the 'execute' or 'fetchall' methods raise an exception, the transaction will be rolled back and a Failure returned.

The *args and **kw arguments will be passed to the DB-API cursor's 'execute' method.

Returns a Deferred which will fire the return value of a DB-API cursor's 'fetchall' method, or a Failure.

def runOperation(self, *args, **kw): (source)

Execute an SQL query and return None.

A DB-API cursor will will be invoked with 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 *args will be an SQL statement. This method will not attempt to fetch any results from the query and is thus suitable for INSERT, 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 Failure returned.

The args and kw arguments will be passed to the DB-API cursor's 'execute' method.

return: a Deferred which will fire None or a Failure.

def close(self): (source)

Close all pool connections and shutdown the pool.

def finalClose(self): (source)

This should only be called by the shutdown trigger.

def connect(self): (source)

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.

Returns a database connection from the pool.

def disconnect(self, conn): (source)

Disconnect a database connection associated with this pool.

Note: This function should only be used by the same thread which called connect(). As with connect(), this function is not used in normal non-threaded twisted code.

t.e.a.ConnectionPool : class documentation