Synnefo » snf-ganeti » ganeti-local

{-| Implementation of cluster-wide logic.

This module holds all pure cluster-logic; I\/O related functionality

goes into the "Main" module for the individual binaries.

-}

{-

Copyright (C) 2009 Google Inc.

This program is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2 of the License, or

(at your option) any later version.

This program is distributed in the hope that it will be useful, but

WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

General Public License for more details.

You should have received a copy of the GNU General Public License

along with this program; if not, write to the Free Software

Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301, USA.

-}

module Ganeti.HTools.Cluster

    (

     -- * Types

      AllocSolution

    , Table(..)

    , CStats(..)

    -- * Generic functions

    , totalResources

    -- * First phase functions

    , computeBadItems

    -- * Second phase functions

    , printSolution

    , printSolutionLine

    , formatCmds

    , involvedNodes

    , splitJobs

    -- * Display functions

    , printNodes

    , printInsts

    -- * Balacing functions

    , checkMove

    , doNextBalance

    , tryBalance

    , compCV

    , printStats

    , iMoveToJob

    -- * IAllocator functions

    , tryAlloc

    , tryReloc

    , collapseFailures

    ) where

import Data.List

import Text.Printf (printf)

import Data.Function

import Control.Monad

import qualified Ganeti.HTools.Container as Container

import qualified Ganeti.HTools.Instance as Instance

import qualified Ganeti.HTools.Node as Node

import Ganeti.HTools.Types

import Ganeti.HTools.Utils

import qualified Ganeti.OpCodes as OpCodes

-- * Types

-- | Allocation\/relocation solution.

type AllocSolution = ([FailMode], Int, Maybe (Score, AllocElement))

-- | Allocation\/relocation element.

type AllocElement = (Node.List, Instance.Instance, [Node.Node])

-- | The complete state for the balancing solution

data Table = Table Node.List Instance.List Score [Placement]

             deriving (Show)

data CStats = CStats { csFmem :: Int    -- ^ Cluster free mem

                     , csFdsk :: Int    -- ^ Cluster free disk

                     , csAmem :: Int    -- ^ Cluster allocatable mem

                     , csAdsk :: Int    -- ^ Cluster allocatable disk

                     , csAcpu :: Int    -- ^ Cluster allocatable cpus

                     , csMmem :: Int    -- ^ Max node allocatable mem

                     , csMdsk :: Int    -- ^ Max node allocatable disk

                     , csMcpu :: Int    -- ^ Max node allocatable cpu

                     , csImem :: Int    -- ^ Instance used mem

                     , csIdsk :: Int    -- ^ Instance used disk

                     , csIcpu :: Int    -- ^ Instance used cpu

                     , csTmem :: Double -- ^ Cluster total mem

                     , csTdsk :: Double -- ^ Cluster total disk

                     , csTcpu :: Double -- ^ Cluster total cpus

                     , csXmem :: Int    -- ^ Unnacounted for mem

                     , csNmem :: Int    -- ^ Node own memory

                     , csScore :: Score -- ^ The cluster score

                     , csNinst :: Int   -- ^ The total number of instances

                     }

-- * Utility functions

-- | Verifies the N+1 status and return the affected nodes.

verifyN1 :: [Node.Node] -> [Node.Node]

verifyN1 = filter Node.failN1

{-| Computes the pair of bad nodes and instances.

The bad node list is computed via a simple 'verifyN1' check, and the

bad instance list is the list of primary and secondary instances of

those nodes.

-}

computeBadItems :: Node.List -> Instance.List ->

                   ([Node.Node], [Instance.Instance])

computeBadItems nl il =

  let bad_nodes = verifyN1 $ getOnline nl

      bad_instances = map (\idx -> Container.find idx il) .

                      sort . nub $

                      concatMap (\ n -> Node.sList n ++ Node.pList n) bad_nodes

  in

    (bad_nodes, bad_instances)

-- | Zero-initializer for the CStats type

emptyCStats :: CStats

emptyCStats = CStats 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

-- | Update stats with data from a new node

updateCStats :: CStats -> Node.Node -> CStats

updateCStats cs node =

    let CStats { csFmem = x_fmem, csFdsk = x_fdsk,

                 csAmem = x_amem, csAcpu = x_acpu, csAdsk = x_adsk,

                 csMmem = x_mmem, csMdsk = x_mdsk, csMcpu = x_mcpu,

                 csImem = x_imem, csIdsk = x_idsk, csIcpu = x_icpu,

                 csTmem = x_tmem, csTdsk = x_tdsk, csTcpu = x_tcpu,

                 csXmem = x_xmem, csNmem = x_nmem, csNinst = x_ninst

               }

            = cs

        inc_amem = Node.fMem node - Node.rMem node

        inc_amem' = if inc_amem > 0 then inc_amem else 0

        inc_adsk = Node.availDisk node

        inc_imem = truncate (Node.tMem node) - Node.nMem node

                   - Node.xMem node - Node.fMem node

        inc_icpu = Node.uCpu node

        inc_idsk = truncate (Node.tDsk node) - Node.fDsk node

    in cs { csFmem = x_fmem + Node.fMem node

          , csFdsk = x_fdsk + Node.fDsk node

          , csAmem = x_amem + inc_amem'

          , csAdsk = x_adsk + inc_adsk

          , csAcpu = x_acpu

          , csMmem = max x_mmem inc_amem'

          , csMdsk = max x_mdsk inc_adsk

          , csMcpu = x_mcpu

          , csImem = x_imem + inc_imem

          , csIdsk = x_idsk + inc_idsk

          , csIcpu = x_icpu + inc_icpu

          , csTmem = x_tmem + Node.tMem node

          , csTdsk = x_tdsk + Node.tDsk node

          , csTcpu = x_tcpu + Node.tCpu node

          , csXmem = x_xmem + Node.xMem node

          , csNmem = x_nmem + Node.nMem node

          , csNinst = x_ninst + length (Node.pList node)

          }

-- | Compute the total free disk and memory in the cluster.

totalResources :: Node.List -> CStats

totalResources nl =

    let cs = foldl' updateCStats emptyCStats . Container.elems $ nl

    in cs { csScore = compCV nl }

-- | The names of the individual elements in the CV list

detailedCVNames :: [String]

detailedCVNames = [ "free_mem_cv"

                  , "free_disk_cv"

                  , "n1_cnt"

                  , "reserved_mem_cv"

                  , "offline_all_cnt"

                  , "offline_pri_cnt"

                  , "vcpu_ratio_cv"

                  , "cpu_load_cv"

                  , "mem_load_cv"

                  , "disk_load_cv"

                  , "net_load_cv"

                  , "pri_tags_score"

                  ]

-- | Compute the mem and disk covariance.

compDetailedCV :: Node.List -> [Double]

compDetailedCV nl =

    let

        all_nodes = Container.elems nl

        (offline, nodes) = partition Node.offline all_nodes

        mem_l = map Node.pMem nodes

        dsk_l = map Node.pDsk nodes

        -- metric: memory covariance

        mem_cv = varianceCoeff mem_l

        -- metric: disk covariance

        dsk_cv = varianceCoeff dsk_l

        n1_l = length $ filter Node.failN1 nodes

        -- metric: count of failN1 nodes

        n1_score = fromIntegral n1_l::Double

        res_l = map Node.pRem nodes

        -- metric: reserved memory covariance

        res_cv = varianceCoeff res_l

        -- offline instances metrics

        offline_ipri = sum . map (length . Node.pList) $ offline

        offline_isec = sum . map (length . Node.sList) $ offline

        -- metric: count of instances on offline nodes

        off_score = fromIntegral (offline_ipri + offline_isec)::Double

        -- metric: count of primary instances on offline nodes (this

        -- helps with evacuation/failover of primary instances on

        -- 2-node clusters with one node offline)

        off_pri_score = fromIntegral offline_ipri::Double

        cpu_l = map Node.pCpu nodes

        -- metric: covariance of vcpu/pcpu ratio

        cpu_cv = varianceCoeff cpu_l

        -- metrics: covariance of cpu, memory, disk and network load

        (c_load, m_load, d_load, n_load) = unzip4 $

            map (\n ->

                     let DynUtil c1 m1 d1 n1 = Node.utilLoad n

                         DynUtil c2 m2 d2 n2 = Node.utilPool n

                     in (c1/c2, m1/m2, d1/d2, n1/n2)

                ) nodes

        -- metric: conflicting instance count

        pri_tags_inst = sum $ map Node.conflictingPrimaries nodes

        pri_tags_score = fromIntegral pri_tags_inst::Double

    in [ mem_cv, dsk_cv, n1_score, res_cv, off_score, off_pri_score, cpu_cv

       , varianceCoeff c_load, varianceCoeff m_load

       , varianceCoeff d_load, varianceCoeff n_load

       , pri_tags_score ]

-- | Compute the /total/ variance.

compCV :: Node.List -> Double

compCV = sum . compDetailedCV

-- | Compute online nodes from a Node.List

getOnline :: Node.List -> [Node.Node]

getOnline = filter (not . Node.offline) . Container.elems

-- * hbal functions

-- | Compute best table. Note that the ordering of the arguments is important.

compareTables :: Table -> Table -> Table

compareTables a@(Table _ _ a_cv _) b@(Table _ _ b_cv _ ) =

    if a_cv > b_cv then b else a

-- | Applies an instance move to a given node list and instance.

applyMove :: Node.List -> Instance.Instance

          -> IMove -> OpResult (Node.List, Instance.Instance, Ndx, Ndx)

-- Failover (f)

applyMove nl inst Failover =

    let old_pdx = Instance.pNode inst

        old_sdx = Instance.sNode inst

        old_p = Container.find old_pdx nl

        old_s = Container.find old_sdx nl

        int_p = Node.removePri old_p inst

        int_s = Node.removeSec old_s inst

        new_nl = do -- Maybe monad

          new_p <- Node.addPri int_s inst

          new_s <- Node.addSec int_p inst old_sdx

          let new_inst = Instance.setBoth inst old_sdx old_pdx

          return (Container.addTwo old_pdx new_s old_sdx new_p nl,

                  new_inst, old_sdx, old_pdx)

    in new_nl

-- Replace the primary (f:, r:np, f)

applyMove nl inst (ReplacePrimary new_pdx) =

    let old_pdx = Instance.pNode inst

        old_sdx = Instance.sNode inst

        old_p = Container.find old_pdx nl

        old_s = Container.find old_sdx nl

        tgt_n = Container.find new_pdx nl

        int_p = Node.removePri old_p inst

        int_s = Node.removeSec old_s inst

        new_nl = do -- Maybe monad

          -- check that the current secondary can host the instance

          -- during the migration

          tmp_s <- Node.addPri int_s inst

          let tmp_s' = Node.removePri tmp_s inst

          new_p <- Node.addPri tgt_n inst

          new_s <- Node.addSec tmp_s' inst new_pdx

          let new_inst = Instance.setPri inst new_pdx

          return (Container.add new_pdx new_p $

                  Container.addTwo old_pdx int_p old_sdx new_s nl,

                  new_inst, new_pdx, old_sdx)

    in new_nl

-- Replace the secondary (r:ns)

applyMove nl inst (ReplaceSecondary new_sdx) =

    let old_pdx = Instance.pNode inst

        old_sdx = Instance.sNode inst

        old_s = Container.find old_sdx nl

        tgt_n = Container.find new_sdx nl

        int_s = Node.removeSec old_s inst

        new_inst = Instance.setSec inst new_sdx

        new_nl = Node.addSec tgt_n inst old_pdx >>=

                 \new_s -> return (Container.addTwo new_sdx

                                   new_s old_sdx int_s nl,

                                   new_inst, old_pdx, new_sdx)

    in new_nl

-- Replace the secondary and failover (r:np, f)

applyMove nl inst (ReplaceAndFailover new_pdx) =

    let old_pdx = Instance.pNode inst

        old_sdx = Instance.sNode inst

        old_p = Container.find old_pdx nl

        old_s = Container.find old_sdx nl

        tgt_n = Container.find new_pdx nl

        int_p = Node.removePri old_p inst

        int_s = Node.removeSec old_s inst

        new_nl = do -- Maybe monad

          new_p <- Node.addPri tgt_n inst

          new_s <- Node.addSec int_p inst new_pdx

          let new_inst = Instance.setBoth inst new_pdx old_pdx

          return (Container.add new_pdx new_p $

                  Container.addTwo old_pdx new_s old_sdx int_s nl,

                  new_inst, new_pdx, old_pdx)

    in new_nl

-- Failver and replace the secondary (f, r:ns)

applyMove nl inst (FailoverAndReplace new_sdx) =

    let old_pdx = Instance.pNode inst

        old_sdx = Instance.sNode inst

        old_p = Container.find old_pdx nl

        old_s = Container.find old_sdx nl

        tgt_n = Container.find new_sdx nl

        int_p = Node.removePri old_p inst

        int_s = Node.removeSec old_s inst

        new_nl = do -- Maybe monad

          new_p <- Node.addPri int_s inst

          new_s <- Node.addSec tgt_n inst old_sdx

          let new_inst = Instance.setBoth inst old_sdx new_sdx

          return (Container.add new_sdx new_s $

                  Container.addTwo old_sdx new_p old_pdx int_p nl,

                  new_inst, old_sdx, new_sdx)

    in new_nl

-- | Tries to allocate an instance on one given node.

allocateOnSingle :: Node.List -> Instance.Instance -> Node.Node

                 -> OpResult AllocElement

allocateOnSingle nl inst p =

    let new_pdx = Node.idx p

        new_inst = Instance.setBoth inst new_pdx Node.noSecondary

        new_nl = Node.addPri p inst >>= \new_p ->

                 return (Container.add new_pdx new_p nl, new_inst, [new_p])

    in new_nl

-- | Tries to allocate an instance on a given pair of nodes.

allocateOnPair :: Node.List -> Instance.Instance -> Node.Node -> Node.Node

               -> OpResult AllocElement

allocateOnPair nl inst tgt_p tgt_s =

    let new_pdx = Node.idx tgt_p

        new_sdx = Node.idx tgt_s

        new_nl = do -- Maybe monad

          new_p <- Node.addPri tgt_p inst

          new_s <- Node.addSec tgt_s inst new_pdx

          let new_inst = Instance.setBoth inst new_pdx new_sdx

          return (Container.addTwo new_pdx new_p new_sdx new_s nl, new_inst,

                 [new_p, new_s])

    in new_nl

-- | Tries to perform an instance move and returns the best table

-- between the original one and the new one.

checkSingleStep :: Table -- ^ The original table

                -> Instance.Instance -- ^ The instance to move

                -> Table -- ^ The current best table

                -> IMove -- ^ The move to apply

                -> Table -- ^ The final best table

checkSingleStep ini_tbl target cur_tbl move =

    let

        Table ini_nl ini_il _ ini_plc = ini_tbl

        tmp_resu = applyMove ini_nl target move

    in

      case tmp_resu of

        OpFail _ -> cur_tbl

        OpGood (upd_nl, new_inst, pri_idx, sec_idx) ->

            let tgt_idx = Instance.idx target

                upd_cvar = compCV upd_nl

                upd_il = Container.add tgt_idx new_inst ini_il

                upd_plc = (tgt_idx, pri_idx, sec_idx, move, upd_cvar):ini_plc

                upd_tbl = Table upd_nl upd_il upd_cvar upd_plc

            in

              compareTables cur_tbl upd_tbl

-- | Given the status of the current secondary as a valid new node and

-- the current candidate target node, generate the possible moves for

-- a instance.

possibleMoves :: Bool      -- ^ Whether the secondary node is a valid new node

              -> Ndx       -- ^ Target node candidate

              -> [IMove]   -- ^ List of valid result moves

possibleMoves True tdx =

    [ReplaceSecondary tdx,

     ReplaceAndFailover tdx,

     ReplacePrimary tdx,

     FailoverAndReplace tdx]

possibleMoves False tdx =

    [ReplaceSecondary tdx,

     ReplaceAndFailover tdx]

-- | Compute the best move for a given instance.

checkInstanceMove :: [Ndx]             -- ^ Allowed target node indices

                  -> Bool              -- ^ Whether disk moves are allowed

                  -> Table             -- ^ Original table

                  -> Instance.Instance -- ^ Instance to move

                  -> Table             -- ^ Best new table for this instance

checkInstanceMove nodes_idx disk_moves ini_tbl target =

    let

        opdx = Instance.pNode target

        osdx = Instance.sNode target

        nodes = filter (\idx -> idx /= opdx && idx /= osdx) nodes_idx

        use_secondary = elem osdx nodes_idx

        aft_failover = if use_secondary -- if allowed to failover

                       then checkSingleStep ini_tbl target ini_tbl Failover

                       else ini_tbl

        all_moves = if disk_moves

                    then concatMap (possibleMoves use_secondary) nodes

                    else []

    in

      -- iterate over the possible nodes for this instance

      foldl' (checkSingleStep ini_tbl target) aft_failover all_moves

-- | Compute the best next move.

checkMove :: [Ndx]               -- ^ Allowed target node indices

          -> Bool                -- ^ Whether disk moves are allowed

          -> Table               -- ^ The current solution

          -> [Instance.Instance] -- ^ List of instances still to move

          -> Table               -- ^ The new solution

checkMove nodes_idx disk_moves ini_tbl victims =

    let Table _ _ _ ini_plc = ini_tbl

        -- iterate over all instances, computing the best move

        best_tbl =

            foldl'

            (\ step_tbl em ->

                 compareTables step_tbl $

                 checkInstanceMove nodes_idx disk_moves ini_tbl em)

            ini_tbl victims

        Table _ _ _ best_plc = best_tbl

    in if length best_plc == length ini_plc

       then ini_tbl -- no advancement

       else best_tbl

-- | Check if we are allowed to go deeper in the balancing

doNextBalance :: Table       -- ^ The starting table

              -> Int         -- ^ Remaining length

              -> Score       -- ^ Score at which to stop

              -> Bool -- ^ The resulting table and commands

doNextBalance ini_tbl max_rounds min_score =

    let Table _ _ ini_cv ini_plc = ini_tbl

        ini_plc_len = length ini_plc

    in (max_rounds < 0 || ini_plc_len < max_rounds) && ini_cv > min_score

-- | Run a balance move

tryBalance :: Table       -- ^ The starting table

           -> Bool        -- ^ Allow disk moves

           -> Bool        -- ^ Only evacuate moves

           -> Maybe Table -- ^ The resulting table and commands

tryBalance ini_tbl disk_moves evac_mode =

    let Table ini_nl ini_il ini_cv _ = ini_tbl

        all_inst = Container.elems ini_il

        all_inst' = if evac_mode

                    then let bad_nodes = map Node.idx . filter Node.offline $

                                         Container.elems ini_nl

                         in filter (\e -> Instance.sNode e `elem` bad_nodes ||

                                          Instance.pNode e `elem` bad_nodes)

                            all_inst

                    else all_inst

        reloc_inst = filter (\e -> Instance.sNode e /= Node.noSecondary)

                     all_inst'

        node_idx = map Node.idx . filter (not . Node.offline) $

                   Container.elems ini_nl

        fin_tbl = checkMove node_idx disk_moves ini_tbl reloc_inst

        (Table _ _ fin_cv _) = fin_tbl

    in

      if fin_cv < ini_cv

      then Just fin_tbl -- this round made success, return the new table

      else Nothing

-- * Allocation functions

-- | Build failure stats out of a list of failures

collapseFailures :: [FailMode] -> FailStats

collapseFailures flst =

    map (\k -> (k, length $ filter ((==) k) flst)) [minBound..maxBound]

-- | Update current Allocation solution and failure stats with new

-- elements

concatAllocs :: AllocSolution -> OpResult AllocElement -> AllocSolution

concatAllocs (flst, cntok, sols) (OpFail reason) = (reason:flst, cntok, sols)

concatAllocs (flst, cntok, osols) (OpGood ns@(nl, _, _)) =

    let nscore = compCV nl

        -- Choose the old or new solution, based on the cluster score

        nsols = case osols of

                  Nothing -> Just (nscore, ns)

                  Just (oscore, _) ->

                      if oscore < nscore

                      then osols

                      else Just (nscore, ns)

        nsuc = cntok + 1

    -- Note: we force evaluation of nsols here in order to keep the

    -- memory profile low - we know that we will need nsols for sure

    -- in the next cycle, so we force evaluation of nsols, since the

    -- foldl' in the caller will only evaluate the tuple, but not the

    -- elements of the tuple

    in nsols `seq` nsuc `seq` (flst, nsuc, nsols)

-- | Try to allocate an instance on the cluster.

tryAlloc :: (Monad m) =>

            Node.List         -- ^ The node list

         -> Instance.List     -- ^ The instance list

         -> Instance.Instance -- ^ The instance to allocate

         -> Int               -- ^ Required number of nodes

         -> m AllocSolution   -- ^ Possible solution list

tryAlloc nl _ inst 2 =

    let all_nodes = getOnline nl

        all_pairs = liftM2 (,) all_nodes all_nodes

        ok_pairs = filter (\(x, y) -> Node.idx x /= Node.idx y) all_pairs

        sols = foldl' (\cstate (p, s) ->

                           concatAllocs cstate $ allocateOnPair nl inst p s

                      ) ([], 0, Nothing) ok_pairs

    in return sols

tryAlloc nl _ inst 1 =

    let all_nodes = getOnline nl

        sols = foldl' (\cstate ->

                           concatAllocs cstate . allocateOnSingle nl inst

                      ) ([], 0, Nothing) all_nodes

    in return sols

tryAlloc _ _ _ reqn = fail $ "Unsupported number of allocation \

                             \destinations required (" ++ show reqn ++

                                               "), only two supported"

-- | Try to allocate an instance on the cluster.

tryReloc :: (Monad m) =>

            Node.List       -- ^ The node list

         -> Instance.List   -- ^ The instance list

         -> Idx             -- ^ The index of the instance to move

         -> Int             -- ^ The number of nodes required

         -> [Ndx]           -- ^ Nodes which should not be used

         -> m AllocSolution -- ^ Solution list

tryReloc nl il xid 1 ex_idx =

    let all_nodes = getOnline nl

        inst = Container.find xid il

        ex_idx' = Instance.pNode inst:ex_idx

        valid_nodes = filter (not . flip elem ex_idx' . Node.idx) all_nodes

        valid_idxes = map Node.idx valid_nodes

        sols1 = foldl' (\cstate x ->

                            let em = do

                                  (mnl, i, _, _) <-

                                      applyMove nl inst (ReplaceSecondary x)

                                  return (mnl, i, [Container.find x mnl])

                            in concatAllocs cstate em

                       ) ([], 0, Nothing) valid_idxes

    in return sols1

tryReloc _ _ _ reqn _  = fail $ "Unsupported number of relocation \

                                \destinations required (" ++ show reqn ++

                                                  "), only one supported"

-- * Formatting functions

-- | Given the original and final nodes, computes the relocation description.

computeMoves :: Instance.Instance -- ^ The instance to be moved

             -> String -- ^ The instance name

             -> IMove  -- ^ The move being performed

             -> String -- ^ New primary

             -> String -- ^ New secondary

             -> (String, [String])

                -- ^ Tuple of moves and commands list; moves is containing

                -- either @/f/@ for failover or @/r:name/@ for replace

                -- secondary, while the command list holds gnt-instance

                -- commands (without that prefix), e.g \"@failover instance1@\"

computeMoves i inam mv c d =

    case mv of

      Failover -> ("f", [mig])

      FailoverAndReplace _ -> (printf "f r:%s" d, [mig, rep d])

      ReplaceSecondary _ -> (printf "r:%s" d, [rep d])

      ReplaceAndFailover _ -> (printf "r:%s f" c, [rep c, mig])

      ReplacePrimary _ -> (printf "f r:%s f" c, [mig, rep c, mig])

    where morf = if Instance.running i then "migrate" else "failover"

          mig = printf "%s -f %s" morf inam::String

          rep n = printf "replace-disks -n %s %s" n inam

-- | Converts a placement to string format.

printSolutionLine :: Node.List     -- ^ The node list

                  -> Instance.List -- ^ The instance list

                  -> Int           -- ^ Maximum node name length

                  -> Int           -- ^ Maximum instance name length

                  -> Placement     -- ^ The current placement

                  -> Int           -- ^ The index of the placement in

                                   -- the solution

                  -> (String, [String])

printSolutionLine nl il nmlen imlen plc pos =

    let

        pmlen = (2*nmlen + 1)

        (i, p, s, mv, c) = plc

        inst = Container.find i il

        inam = Instance.name inst

        npri = Container.nameOf nl p

        nsec = Container.nameOf nl s

        opri = Container.nameOf nl $ Instance.pNode inst

        osec = Container.nameOf nl $ Instance.sNode inst

        (moves, cmds) =  computeMoves inst inam mv npri nsec

        ostr = printf "%s:%s" opri osec::String

        nstr = printf "%s:%s" npri nsec::String

    in

      (printf "  %3d. %-*s %-*s => %-*s %.8f a=%s"

       pos imlen inam pmlen ostr

       pmlen nstr c moves,

       cmds)

-- | Return the instance and involved nodes in an instance move.

involvedNodes :: Instance.List -> Placement -> [Ndx]

involvedNodes il plc =

    let (i, np, ns, _, _) = plc

        inst = Container.find i il

        op = Instance.pNode inst

        os = Instance.sNode inst

    in nub [np, ns, op, os]

-- | Inner function for splitJobs, that either appends the next job to

-- the current jobset, or starts a new jobset.

mergeJobs :: ([JobSet], [Ndx]) -> MoveJob -> ([JobSet], [Ndx])

mergeJobs ([], _) n@(ndx, _, _, _) = ([[n]], ndx)

mergeJobs (cjs@(j:js), nbuf) n@(ndx, _, _, _)

    | null (ndx `intersect` nbuf) = ((n:j):js, ndx ++ nbuf)

    | otherwise = ([n]:cjs, ndx)

-- | Break a list of moves into independent groups. Note that this

-- will reverse the order of jobs.

splitJobs :: [MoveJob] -> [JobSet]

splitJobs = fst . foldl mergeJobs ([], [])

-- | Given a list of commands, prefix them with @gnt-instance@ and

-- also beautify the display a little.

formatJob :: Int -> Int -> (Int, MoveJob) -> [String]

formatJob jsn jsl (sn, (_, _, _, cmds)) =

    let out =

            printf "  echo job %d/%d" jsn sn:

            printf "  check":

            map ("  gnt-instance " ++) cmds

    in if sn == 1

       then ["", printf "echo jobset %d, %d jobs" jsn jsl] ++ out

       else out

-- | Given a list of commands, prefix them with @gnt-instance@ and

-- also beautify the display a little.

formatCmds :: [JobSet] -> String

formatCmds =

    unlines .

    concatMap (\(jsn, js) -> concatMap (formatJob jsn (length js))

                             (zip [1..] js)) .

    zip [1..]

-- | Converts a solution to string format.

printSolution :: Node.List

              -> Instance.List

              -> [Placement]

              -> ([String], [[String]])

printSolution nl il sol =

    let

        nmlen = Container.maxNameLen nl

        imlen = Container.maxNameLen il

    in

      unzip $ zipWith (printSolutionLine nl il nmlen imlen) sol [1..]

-- | Print the node list.

printNodes :: Node.List -> [String] -> String

printNodes nl fs =

    let fields = if null fs

                 then Node.defaultFields

                 else fs

        snl = sortBy (compare `on` Node.idx) (Container.elems nl)

        (header, isnum) = unzip $ map Node.showHeader fields

    in unlines . map ((:) ' ' .  intercalate " ") $

       formatTable (header:map (Node.list fields) snl) isnum

-- | Print the instance list.

printInsts :: Node.List -> Instance.List -> String

printInsts nl il =

    let sil = sortBy (compare `on` Instance.idx) (Container.elems il)

        helper inst = [ if Instance.running inst then "R" else " "

                      , Instance.name inst

                      , Container.nameOf nl (Instance.pNode inst)

                      , (let sdx = Instance.sNode inst

                         in if sdx == Node.noSecondary

                            then  ""

                            else Container.nameOf nl sdx)

                      , printf "%3d" $ Instance.vcpus inst

                      , printf "%5d" $ Instance.mem inst

                      , printf "%5d" $ Instance.dsk inst `div` 1024

                      , printf "%5.3f" lC

                      , printf "%5.3f" lM

                      , printf "%5.3f" lD

                      , printf "%5.3f" lN

                      ]

            where DynUtil lC lM lD lN = Instance.util inst

        header = [ "F", "Name", "Pri_node", "Sec_node", "vcpu", "mem"

                 , "dsk", "lCpu", "lMem", "lDsk", "lNet" ]

        isnum = False:False:False:False:repeat True

    in unlines . map ((:) ' ' . intercalate " ") $

       formatTable (header:map helper sil) isnum

-- | Shows statistics for a given node list.

printStats :: Node.List -> String

printStats nl =

    let dcvs = compDetailedCV nl

        hd = zip (detailedCVNames ++ repeat "unknown") dcvs

        formatted = map (\(header, val) ->

                             printf "%s=%.8f" header val::String) hd

    in intercalate ", " formatted

-- | Convert a placement into a list of OpCodes (basically a job).

iMoveToJob :: String -> Node.List -> Instance.List

          -> Idx -> IMove -> [OpCodes.OpCode]

iMoveToJob csf nl il idx move =

    let inst = Container.find idx il

        iname = Instance.name inst ++ csf

        lookNode n = Just (Container.nameOf nl n ++ csf)

        opF = if Instance.running inst

              then OpCodes.OpMigrateInstance iname True False

              else OpCodes.OpFailoverInstance iname False

        opR n = OpCodes.OpReplaceDisks iname (lookNode n)

                OpCodes.ReplaceNewSecondary [] Nothing

    in case move of

         Failover -> [ opF ]

         ReplacePrimary np -> [ opF, opR np, opF ]

         ReplaceSecondary ns -> [ opR ns ]

         ReplaceAndFailover np -> [ opR np, opF ]

         FailoverAndReplace ns -> [ opF, opR ns ]