root / src / Ganeti / Locking / Types.hs @ 80004e70
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{-| Ganeti lock-related types and type classes |
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-} |
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{- |
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Copyright (C) 2014 Google Inc. |
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This program is free software; you can redistribute it and/or modify |
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it under the terms of the GNU General Public License as published by |
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the Free Software Foundation; either version 2 of the License, or |
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(at your option) any later version. |
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This program is distributed in the hope that it will be useful, but |
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WITHOUT ANY WARRANTY; without even the implied warranty of |
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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General Public License for more details. |
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You should have received a copy of the GNU General Public License |
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along with this program; if not, write to the Free Software |
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
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02110-1301, USA. |
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-} |
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module Ganeti.Locking.Types |
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( Lock |
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, lockImplications |
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) where |
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{-| The type class of being a lock |
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As usual, locks need to come with an order, the lock order, and |
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be an instance of Show, so that malformed requests can meaningfully |
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be reported. |
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Additionally, in Ganeti we also have group locks, like a lock for all |
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nodes. While those group locks contain infinitely many locks, the set |
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of locks a single lock is included in is always finite, and usually |
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very small. So we take this association from a lock to the locks it |
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is (strictly) included in as additional data of the type class. |
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It is a prerequisite that whenever 'a' is implied in 'b', then all locks |
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that are in the lock order between 'a' and 'b' are also implied in 'b'. |
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-} |
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class (Ord a, Show a) => Lock a where |
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lockImplications :: a -> [a] |