author | Julien Jehannet <julien.jehannet@logilab.fr> |
Wed, 30 Sep 2009 18:53:18 +0200 | |
branch | stable |
changeset 3537 | 73b5bec579ba |
parent 2765 | 5e2525d7b1b1 |
child 2835 | 04034421b072 |
child 3691 | ccd72f500daa |
permissions | -rw-r--r-- |
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"""CubicWeb server connections pool : |
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* the rql repository has a limited number of connections pools, each of them |
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dealing with a set of connections on each source used by the repository |
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* operation may be registered by hooks during a transaction, which will be |
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fired when the pool is commited or rollbacked |
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This module defined the `ConnectionsPool` class and a set of abstract classes |
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for operation. |
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:organization: Logilab |
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:copyright: 2001-2009 LOGILAB S.A. (Paris, FRANCE), license is LGPL v2. |
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:contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr |
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:license: GNU Lesser General Public License, v2.1 - http://www.gnu.org/licenses |
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""" |
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__docformat__ = "restructuredtext en" |
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import sys |
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class ConnectionsPool(object): |
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"""handle connections on a set of sources, at some point associated to a |
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user session |
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""" |
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def __init__(self, sources): |
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# dictionnary of (source, connection), indexed by sources'uri |
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self.source_cnxs = {} |
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for source in sources: |
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self.source_cnxs[source.uri] = (source, source.get_connection()) |
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if not 'system' in self.source_cnxs: |
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self.source_cnxs['system'] = self.source_cnxs[sources[0].uri] |
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self._cursors = {} |
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def __getitem__(self, uri): |
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"""subscription notation provide access to sources'cursors""" |
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try: |
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cursor = self._cursors[uri] |
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except KeyError: |
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cursor = self.source_cnxs[uri][1].cursor() |
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if cursor is not None: |
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# None possible on sources without cursor support such as ldap |
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self._cursors[uri] = cursor |
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return cursor |
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def commit(self): |
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"""commit the current transaction for this user""" |
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# FIXME: what happends if a commit fail |
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# would need a two phases commit or like, but I don't know how to do |
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# this using the db-api... |
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for source, cnx in self.source_cnxs.values(): |
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# let exception propagates |
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cnx.commit() |
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def rollback(self): |
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"""rollback the current transaction for this user""" |
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for source, cnx in self.source_cnxs.values(): |
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# catch exceptions, rollback other sources anyway |
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try: |
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cnx.rollback() |
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except: |
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source.critical('rollback error', exc_info=sys.exc_info()) |
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def close(self, i_know_what_i_do=False): |
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"""close all connections in the pool""" |
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if i_know_what_i_do is not True: # unexpected closing safety belt |
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raise RuntimeError('pool shouldn\'t be closed') |
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for cu in self._cursors.values(): |
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try: |
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cu.close() |
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except: |
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continue |
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for _, cnx in self.source_cnxs.values(): |
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try: |
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cnx.close() |
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except: |
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continue |
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# internals ############################################################### |
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def pool_set(self): |
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"""pool is being set""" |
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self.check_connections() |
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def pool_reset(self): |
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"""pool is being reseted""" |
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for source, cnx in self.source_cnxs.values(): |
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source.pool_reset(cnx) |
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def sources(self): |
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"""return the source objects handled by this pool""" |
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# implementation details of flying insert requires the system source |
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# first |
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yield self.source_cnxs['system'][0] |
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for uri, (source, cursor) in self.source_cnxs.items(): |
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if uri == 'system': |
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continue |
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yield source |
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#return [source_cnx[0] for source_cnx in self.source_cnxs.values()] |
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def source(self, uid): |
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"""return the source object with the given uri""" |
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return self.source_cnxs[uid][0] |
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def connection(self, uid): |
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"""return the connection on the source object with the given uri""" |
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return self.source_cnxs[uid][1] |
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def reconnect(self, source=None): |
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"""reopen a connection for this source or all sources if none specified |
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""" |
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if source is None: |
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sources = self.sources() |
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else: |
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sources = (source,) |
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for source in sources: |
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source.info('trying to reconnect') |
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self.source_cnxs[source.uri] = (source, source.get_connection()) |
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self._cursors.pop(source.uri, None) |
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def check_connections(self): |
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for source, cnx in self.source_cnxs.itervalues(): |
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newcnx = source.check_connection(cnx) |
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if newcnx is not None: |
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self.reset_connection(source, newcnx) |
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def reset_connection(self, source, cnx): |
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self.source_cnxs[source.uri] = (source, cnx) |
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self._cursors.pop(source.uri, None) |
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class Operation(object): |
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"""an operation is triggered on connections pool events related to |
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commit / rollback transations. Possible events are: |
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precommit: |
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the pool is preparing to commit. You shouldn't do anything things which |
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has to be reverted if the commit fail at this point, but you can freely |
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do any heavy computation or raise an exception if the commit can't go. |
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You can add some new operation during this phase but their precommit |
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event won't be triggered |
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commit: |
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the pool is preparing to commit. You should avoid to do to expensive |
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stuff or something that may cause an exception in this event |
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revertcommit: |
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if an operation failed while commited, this event is triggered for |
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all operations which had their commit event already to let them |
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revert things (including the operation which made fail the commit) |
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rollback: |
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the transaction has been either rollbacked either |
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* intentionaly |
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* a precommit event failed, all operations are rollbacked |
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* a commit event failed, all operations which are not been triggered for |
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commit are rollbacked |
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order of operations may be important, and is controlled according to: |
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* operation's class |
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""" |
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def __init__(self, session, **kwargs): |
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self.session = session |
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self.user = session.user |
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self.repo = session.repo |
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self.schema = session.repo.schema |
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self.config = session.repo.config |
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self.__dict__.update(kwargs) |
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self.register(session) |
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# execution information |
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self.processed = None # 'precommit', 'commit' |
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self.failed = False |
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def register(self, session): |
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session.add_operation(self, self.insert_index()) |
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def insert_index(self): |
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"""return the index of the lastest instance which is not a |
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LateOperation instance |
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""" |
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for i, op in enumerate(self.session.pending_operations): |
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if isinstance(op, (LateOperation, SingleLastOperation)): |
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return i |
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return None |
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def handle_event(self, event): |
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"""delegate event handling to the opertaion""" |
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getattr(self, event)() |
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def precommit_event(self): |
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"""the observed connections pool is preparing a commit""" |
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def revertprecommit_event(self): |
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"""an error went when pre-commiting this operation or a later one |
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should revert pre-commit's changes but take care, they may have not |
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been all considered if it's this operation which failed |
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""" |
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def commit_event(self): |
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"""the observed connections pool is commiting""" |
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raise NotImplementedError() |
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def revertcommit_event(self): |
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"""an error went when commiting this operation or a later one |
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should revert commit's changes but take care, they may have not |
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been all considered if it's this operation which failed |
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""" |
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def rollback_event(self): |
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"""the observed connections pool has been rollbacked |
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do nothing by default, the operation will just be removed from the pool |
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operation list |
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""" |
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class PreCommitOperation(Operation): |
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"""base class for operation only defining a precommit operation |
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""" |
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def precommit_event(self): |
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"""the observed connections pool is preparing a commit""" |
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raise NotImplementedError() |
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def commit_event(self): |
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"""the observed connections pool is commiting""" |
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class LateOperation(Operation): |
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"""special operation which should be called after all possible (ie non late) |
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operations |
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""" |
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def insert_index(self): |
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"""return the index of the lastest instance which is not a |
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SingleLastOperation instance |
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""" |
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for i, op in enumerate(self.session.pending_operations): |
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if isinstance(op, SingleLastOperation): |
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return i |
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return None |
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class SingleOperation(Operation): |
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"""special operation which should be called once""" |
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def register(self, session): |
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"""override register to handle cases where this operation has already |
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been added |
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""" |
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operations = session.pending_operations |
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index = self.equivalent_index(operations) |
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if index is not None: |
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equivalent = operations.pop(index) |
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else: |
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equivalent = None |
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session.add_operation(self, self.insert_index()) |
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return equivalent |
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def equivalent_index(self, operations): |
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"""return the index of the equivalent operation if any""" |
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equivalents = [i for i, op in enumerate(operations) |
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if op.__class__ is self.__class__] |
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if equivalents: |
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return equivalents[0] |
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return None |
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class SingleLastOperation(SingleOperation): |
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"""special operation which should be called once and after all other |
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operations |
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""" |
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def insert_index(self): |
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return None |
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from logging import getLogger |
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from cubicweb import set_log_methods |
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set_log_methods(Operation, getLogger('cubicweb.session')) |