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Viewing changes to lib/lp/services/database/transaction_policy.py

  • Committer: Raphael Badin
  • Date: 2012-01-06 08:27:55 UTC
  • mfrom: (14513.5.4 builder-history-lfa)
  • mto: This revision was merged to the branch mainline in revision 14654.
  • Revision ID: raphael.badin@canonical.com-20120106082755-95a0eh6nakv5hj3b
Merge devel.

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lib/lp/services/database/transaction_policy.py
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    'DatabaseTransactionPolicy',
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    ]
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from functools import wraps
 
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from psycopg2.extensions import TRANSACTION_STATUS_IDLE
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import transaction
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from zope.component import getUtility
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        :raise TransactionInProgress: if a transaction was already ongoing.
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        """
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        self._checkNoTransaction(
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            "Entered DatabaseTransactionPolicy while in a transaction.")
 
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        # We must check the transaction status before checking the current
 
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        # policy because getting the policy causes a status change.
 
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        in_transaction = self._isInTransaction()
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        self.previous_policy = self._getCurrentPolicy()
 
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        # If the current transaction is read-write and we're moving to
 
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        # read-only then we should check for a transaction. If the current
 
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        # policy is read-only then we don't care if a transaction is in
 
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        # progress.
 
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        if in_transaction and self.read_only and not self.previous_policy:
 
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            raise TransactionInProgress(
 
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                "Attempting to enter a read-only transaction while holding "
 
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                "open a read-write transaction.")
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        self._setPolicy(self.read_only)
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        # Commit should include the policy itself.  If this breaks
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        # because the transaction was already in a failed state before
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    def _isInTransaction(self):
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        """Is our store currently in a transaction?"""
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        pg_connection = self.store._connection._raw_connection
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        status = pg_connection.get_transaction_status()
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        return status != TRANSACTION_STATUS_IDLE
 
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        if pg_connection is None:
 
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            return False
 
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        else:
 
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            status = pg_connection.get_transaction_status()
 
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            return status != TRANSACTION_STATUS_IDLE
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    def _checkNoTransaction(self, error_msg):
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        """Verify that no transaction is ongoing.
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        """
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        self.store.execute(
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            "SET %s TO %s" % (self.db_switch, quote(read_only)))
 
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    @classmethod
 
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    def readOnly(cls, func):
 
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        @wraps(func)
 
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        def wrapper(*args, **kwargs):
 
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            with cls(read_only=True):
 
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                return func(*args, **kwargs)
 
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        return wrapper
 
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    @classmethod
 
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    def readWrite(cls, func):
 
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        @wraps(func)
 
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        def wrapper(*args, **kwargs):
 
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            with cls(read_only=False):
 
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                return func(*args, **kwargs)
 
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        return wrapper