Imported from SVN by Bitbucket

Paste-1.7.5.1-py2.6.egg/paste/transaction.py

@@ -0,0 +1,120 @@
+# (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
+