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# (c) 2005 Ian Bicking and contributors; written for Paste (http://pythonpaste.org) # Licensed under the MIT license: http://www.opensource.org/licenses/mit-license.php # (c) 2005 Clark C. Evans # This module is part of the Python Paste Project and is released under # the MIT License: http://www.opensource.org/licenses/mit-license.php """ Middleware related to transactions and database connections. At this time it is very basic; but will eventually sprout all that two-phase commit goodness that I don't need. .. note:: This is experimental, and will change in the future. """ from paste.httpexceptions import HTTPException from wsgilib import catch_errors class TransactionManagerMiddleware(object): def __init__(self, application): self.application = application def __call__(self, environ, start_response): environ['paste.transaction_manager'] = manager = Manager() # This makes sure nothing else traps unexpected exceptions: environ['paste.throw_errors'] = True return catch_errors(self.application, environ, start_response, error_callback=manager.error, ok_callback=manager.finish) class Manager(object): def __init__(self): self.aborted = False self.transactions = [] def abort(self): self.aborted = True def error(self, exc_info): self.aborted = True self.finish() def finish(self): for trans in self.transactions: if self.aborted: trans.rollback() else: trans.commit() class ConnectionFactory(object): """ Provides a callable interface for connecting to ADBAPI databases in a WSGI style (using the environment). More advanced connection factories might use the REMOTE_USER and/or other environment variables to make the connection returned depend upon the request. """ def __init__(self, module, *args, **kwargs): #assert getattr(module,'threadsaftey',0) > 0 self.module = module self.args = args self.kwargs = kwargs # deal with database string quoting issues self.quote = lambda s: "'%s'" % s.replace("'","''") if hasattr(self.module,'PgQuoteString'): self.quote = self.module.PgQuoteString def __call__(self, environ=None): conn = self.module.connect(*self.args, **self.kwargs) conn.__dict__['module'] = self.module conn.__dict__['quote'] = self.quote return conn def BasicTransactionHandler(application, factory): """ Provides a simple mechanism for starting a transaction based on the factory; and for either committing or rolling back the transaction depending on the result. It checks for the response's current status code either through the latest call to start_response; or through a HTTPException's code. If it is a 100, 200, or 300; the transaction is committed; otherwise it is rolled back. """ def basic_transaction(environ, start_response): conn = factory(environ) environ['paste.connection'] = conn should_commit = [500] def finalizer(exc_info=None): if exc_info: if isinstance(exc_info[1], HTTPException): should_commit.append(exc_info[1].code) if should_commit.pop() < 400: conn.commit() else: try: conn.rollback() except: # TODO: check if rollback has already happened return conn.close() def basictrans_start_response(status, headers, exc_info = None): should_commit.append(int(status.split(" ")[0])) return start_response(status, headers, exc_info) return catch_errors(application, environ, basictrans_start_response, finalizer, finalizer) return basic_transaction __all__ = ['ConnectionFactory', 'BasicTransactionHandler'] if '__main__' == __name__ and False: from pyPgSQL import PgSQL factory = ConnectionFactory(PgSQL, database="testing") conn = factory() curr = conn.cursor() curr.execute("SELECT now(), %s" % conn.quote("B'n\\'gles")) (time, bing) = curr.fetchone() print bing, time