1 .. -*- coding: utf-8 -*-

     2 

     3 Repository operations

     4 ======================

     5 

     6 When one needs to perform operations (real world operations like mail

     7 notifications, file operations, real-world side-effects) at

     8 transaction commit time, Operations are the way to go.

     9 

    10 Possible events are:

    11 

    12 * precommit: the pool is preparing to commit. You shouldn't do

    13   anything things which has to be reverted if the commit fail at this

    14   point, but you can freely do any heavy computation or raise an

    15   exception if the commit can't go.  You can add some new operation

    16   during this phase but their precommit event won't be triggered

    17 

    18 * commit: the pool is preparing to commit. You should avoid to do to

    19   expensive stuff or something that may cause an exception in this

    20   event

    21 

    22 * revertcommit: if an operation failed while commited, this event is

    23   triggered for all operations which had their commit event already to

    24   let them revert things (including the operation which made fail the

    25   commit)

    26 

    27 * rollback: the transaction has been either rollbacked either

    28 

    29   - intentionaly

    30   - a precommit event failed, all operations are rollbacked

    31   - a commit event failed, all operations which are not been triggered

    32     for commit are rollbacked

    33 

    34 Exceptions signaled from within a rollback are logged and swallowed.

    35 

    36 The order of operations may be important, and is controlled according

    37 to operation's class (see : Operation, LateOperation, SingleOperation,

    38 SingleLastOperation).