Revision 6804faa0 htools/Ganeti/HTools/Cluster.hs

b/htools/Ganeti/HTools/Cluster.hs
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    , tryAlloc
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    , tryMGAlloc
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    , tryReloc
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    , tryEvac
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    , tryNodeEvac
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    , tryChangeGroup
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    , collapseFailures
......
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                                \destinations required (" ++ show reqn ++
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                                                  "), only one supported"
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-- | Change an instance's secondary node.
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evacInstance :: (Monad m) =>
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                [Ndx]                      -- ^ Excluded nodes
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             -> Instance.List              -- ^ The current instance list
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             -> (Node.List, AllocSolution) -- ^ The current state
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             -> Idx                        -- ^ The instance to evacuate
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             -> m (Node.List, AllocSolution)
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evacInstance ex_ndx il (nl, old_as) idx = do
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  -- FIXME: hardcoded one node here
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  -- Longer explanation: evacuation is currently hardcoded to DRBD
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  -- instances (which have one secondary); hence, even if the
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  -- IAllocator protocol can request N nodes for an instance, and all
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  -- the message parsing/loading pass this, this implementation only
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  -- supports one; this situation needs to be revisited if we ever
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  -- support more than one secondary, or if we change the storage
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  -- model
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  new_as <- tryReloc nl il idx 1 ex_ndx
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  case asSolutions new_as of
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    -- an individual relocation succeeded, we kind of compose the data
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    -- from the two solutions
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    csol@(nl', _, _, _):_ ->
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        return (nl', new_as { asSolutions = csol:asSolutions old_as })
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    -- this relocation failed, so we fail the entire evac
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    _ -> fail $ "Can't evacuate instance " ++
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         Instance.name (Container.find idx il) ++
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             ": " ++ describeSolution new_as
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-- | Try to evacuate a list of nodes.
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tryEvac :: (Monad m) =>
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            Node.List       -- ^ The node list
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         -> Instance.List   -- ^ The instance list
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         -> [Idx]           -- ^ Instances to be evacuated
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         -> [Ndx]           -- ^ Restricted nodes (the ones being evacuated)
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         -> m AllocSolution -- ^ Solution list
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tryEvac nl il idxs ex_ndx = do
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  (_, sol) <- foldM (evacInstance ex_ndx il) (nl, emptyAllocSolution) idxs
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  return sol
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-- | Function which fails if the requested mode is change secondary.
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--
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-- This is useful since except DRBD, no other disk template can

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