root / snf-common / synnefo / lib / db / xctx.py @ 26e15cff
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# Copyright 2013 GRNET S.A. All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or
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# without modification, are permitted provided that the following
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# conditions are met:
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#
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# 1. Redistributions of source code must retain the above
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# copyright notice, this list of conditions and the following
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# disclaimer.
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#
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# 2. Redistributions in binary form must reproduce the above
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# copyright notice, this list of conditions and the following
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# disclaimer in the documentation and/or other materials
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# provided with the distribution.
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#
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# THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS
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# OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR
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# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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# POSSIBILITY OF SUCH DAMAGE.
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#
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# The views and conclusions contained in the software and
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# documentation are those of the authors and should not be
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# interpreted as representing official policies, either expressed
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# or implied, of GRNET S.A.
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from django.db import transaction |
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# USAGE
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# =====
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# @transaction_context()
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# def a_view(args, ctx=None):
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# ...
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# if ctx:
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# ctx.mark_rollback()
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# ...
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# return http response
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#
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# OR (more cleanly)
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#
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# def a_view(args):
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# with transaction_context() as ctx:
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# ...
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# ctx.mark_rollback()
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# ...
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# return http response
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def transaction_context(**kwargs): |
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return TransactionHandler(ctx=TransactionContext, **kwargs)
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class TransactionContext(object): |
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def __init__(self, **kwargs): |
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self._rollback = False |
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def mark_rollback(self): |
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self._rollback = True |
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def is_marked_rollback(self): |
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return self._rollback |
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def postprocess(self): |
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pass
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class TransactionHandler(object): |
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def __init__(self, ctx=None, allow_postprocess=True, using=None, **kwargs): |
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self.using = using
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self.db = (using if using is not None |
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else transaction.DEFAULT_DB_ALIAS)
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self.ctx_class = ctx
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self.ctx_kwargs = kwargs
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self.allow_postprocess = allow_postprocess
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def __call__(self, func): |
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def wrap(*args, **kwargs): |
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ctx = self.__enter__()
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kwargs['ctx'] = ctx
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typ = value = trace = None
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result = None
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try:
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result = func(*args, **kwargs) |
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except Exception as e: |
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typ = type(e)
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value = e |
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trace = None
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finally:
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silent = self.__exit__(typ, value, trace)
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if not silent and value: |
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raise value
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return result
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return wrap
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def __enter__(self): |
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db = self.db
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transaction.enter_transaction_management(using=db) |
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transaction.managed(True, using=db)
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self.ctx = self.ctx_class(self.ctx_kwargs) |
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return self.ctx |
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def __exit__(self, type, value, traceback): |
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db = self.db
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trigger_postprocess = False
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try:
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if value is not None: # exception |
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if transaction.is_dirty(using=db):
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transaction.rollback(using=db) |
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else:
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if transaction.is_dirty(using=db):
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if self.ctx.is_marked_rollback(): |
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transaction.rollback(using=db) |
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else:
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try:
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transaction.commit(using=db) |
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except:
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transaction.rollback(using=db) |
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raise
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else:
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trigger_postprocess = True
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else:
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# postprocess,
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# even if there was nothing to commit
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trigger_postprocess = True
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finally:
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transaction.leave_transaction_management(using=db) |
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# checking allow_postprocess is needed
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# in order to avoid endless recursion
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if trigger_postprocess and self.allow_postprocess: |
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with TransactionHandler(ctx=self.ctx_class, |
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allow_postprocess=False,
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using=self.using,
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**self.ctx_kwargs):
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self.ctx.postprocess()
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