content: {-# LANGUAGE TupleSections, NamedFieldPuns, ScopedTypeVariables, Rank2Types,
               GADTs #-}
  {-| Filtering of jobs for the Ganeti job queue.
  
  -}
  
  {-
  
  Copyright (C) 2014 Google Inc.
  All rights reserved.
  
  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are
  met:
  
  1. Redistributions of source code must retain the above copyright notice,
  this list of conditions and the following disclaimer.
  
  2. Redistributions in binary form must reproduce the above copyright
  notice, this list of conditions and the following disclaimer in the
  documentation and/or other materials provided with the distribution.
  
  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
  IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  -}
  
  module Ganeti.JQScheduler.Filtering
    ( applyingFilter
    , jobFiltering
    -- * For testing only
    , matchPredicate
    , matches
    ) where
  
  import qualified Data.ByteString as BS
  import Data.List
  import Data.Maybe
  import qualified Data.Map as Map
  import Data.Set (Set)
  import qualified Data.Set as Set
  import qualified Text.JSON as J
  
  import Ganeti.BasicTypes
  import Ganeti.Errors
  import Ganeti.Lens hiding (chosen)
  import Ganeti.JQScheduler.Types
  import Ganeti.JQueue (QueuedJob(..))
  import Ganeti.JQueue.Lens
  import Ganeti.JSON (nestedAccessByKeyDotted)
  import Ganeti.Objects (FilterRule(..), FilterAction(..), FilterPredicate(..),
                         filterRuleOrder)
  import Ganeti.OpCodes (OpCode)
  import Ganeti.OpCodes.Lens
  import Ganeti.Query.Language
  import Ganeti.Query.Filter (evaluateFilterM, evaluateFilterJSON, Comparator,
                              FilterOp(..), toCompFun)
  import Ganeti.SlotMap
  import Ganeti.Types (JobId(..), ReasonElem)
  
  
  -- | Accesses a field of the JSON representation of an `OpCode` using a dotted
  -- accessor (like @"a.b.c"@).
  accessOpCodeField :: OpCode -> String -> ErrorResult J.JSValue
  accessOpCodeField opc s = case nestedAccessByKeyDotted s (J.showJSON opc) of
    J.Ok x    -> Ok x
    J.Error e -> Bad . ParameterError $ e
  
  
  -- | All `OpCode`s of a job.
  opCodesOf :: QueuedJob -> [OpCode]
  opCodesOf job =
    job ^.. qjOpsL . traverse . qoInputL . validOpCodeL . metaOpCodeL
  
  
  -- | All `ReasonElem`s of a job.
  reasonsOf :: QueuedJob -> [ReasonElem]
  reasonsOf job = job ^.. qjOpsL . traverse . qoInputL . validOpCodeL
                          . metaParamsL . opReasonL . traverse
  
  
  -- | Like `evaluateFilterM`, but allowing only `Comparator` operations;
  -- all other filter language operations are evaluated as `False`.
  --
  -- The passed function is supposed to return `Just True/False` depending
  -- on whether the comparing operation succeeds or not, and `Nothing` if
  -- the comparison itself is invalid (e.g. comparing to a field that doesn't
  -- exist).
  evaluateFilterComparator :: (Ord field)
                           => Filter field
                           -> (Comparator -> field -> FilterValue -> Maybe Bool)
                           -> Bool
  evaluateFilterComparator fil opFun =
    fromMaybe False $
      evaluateFilterM
        (\filterOp -> case filterOp of
           Comp cmp -> opFun (toCompFun cmp)
           _        -> \_ _ -> Nothing -- non-comparisons (become False)
        )
        fil
  
  
  -- | Whether a `FilterPredicate` is true for a job.
  matchPredicate :: QueuedJob
                 -> JobId            -- ^ the watermark to compare against
                                     --   if the predicate references it
                 -> FilterPredicate
                 -> Bool
  matchPredicate job watermark predicate = case predicate of
  
    FPJobId fil ->
      let jid    = qjId job
          jidInt = fromIntegral (fromJobId jid)
  
      in evaluateFilterComparator fil $ \comp field val -> case field of
           "id" -> case val of
             NumericValue i           -> Just $ jidInt `comp` i
             QuotedString "watermark" -> Just $ jid `comp` watermark
             QuotedString _           -> Nothing
           _    -> Nothing
  
    FPOpCode fil ->
      let opMatches opc = genericResult (const False) id $ do
            jsonFilter <- traverse (accessOpCodeField opc) fil
            evaluateFilterJSON jsonFilter
      in any opMatches (opCodesOf job)
  
    FPReason fil ->
      let reasonMatches (source, reason, timestamp) =
            evaluateFilterComparator fil $ \comp field val -> case field of
              "source"    -> Just $ QuotedString source `comp` val
              "reason"    -> Just $ QuotedString reason `comp` val
              "timestamp" -> Just $ NumericValue timestamp `comp` val
              _           -> Nothing
      in any reasonMatches (reasonsOf job)
  
  
  -- | Whether all predicates of the filter rule are true for the job.
  matches :: QueuedJob -> FilterRule -> Bool
  matches job FilterRule{ frPredicates, frWatermark } =
    all (matchPredicate job frWatermark) frPredicates
  
  
  -- | Filters need to be processed in the order as given by the spec;
  -- see `filterRuleOrder`.
  orderFilters :: Set FilterRule -> [FilterRule]
  orderFilters = sortBy filterRuleOrder . Set.toList
  
  
  -- | Finds the first filter whose predicates all match the job and whose
  -- action is not `Continue`. This is the /applying/ filter.
  applyingFilter :: Set FilterRule -> QueuedJob -> Maybe FilterRule
  applyingFilter filters job =
    -- Skip over all `Continue`s, to the first filter that matches.
    find ((Continue /=) . frAction)
      . filter (matches job)
      . orderFilters
      $ filters
  
  
  -- | SlotMap for filter rule rate limiting, having `FilterRule` UUIDs as keys.
  type RateLimitSlotMap = SlotMap BS.ByteString
  -- We would prefer FilterRule here but that has no Ord instance (yet).
  
  
  -- | State to be accumulated while traversing filters.
  data FilterChainState = FilterChainState
    { rateLimitSlotMap :: RateLimitSlotMap -- ^ counts
    } deriving (Eq, Ord, Show)
  
  
  -- | Update a `FilterChainState` if the given `CountMap` fits into its
  -- filtering SlotsMap.
  tryFitSlots :: FilterChainState
              -> CountMap BS.ByteString
              -> Maybe FilterChainState
  tryFitSlots st@FilterChainState{ rateLimitSlotMap = slotMap } countMap =
    if slotMap `hasSlotsFor` countMap
      then Just st{ rateLimitSlotMap = slotMap `occupySlots` countMap }
      else Nothing
  
  
  -- | For a given job queue and set of filters, calculates how many rate
  -- limiting filter slots are available and how many are taken by running jobs
  -- in the queue.
  queueRateLimitSlotMap :: Queue -> Set FilterRule -> RateLimitSlotMap
  queueRateLimitSlotMap queue filters =
    let -- Rate limiting slots for each filter, with 0 occupied count each
        -- (limits only).
        emptyFilterSlots =
          Map.fromList
            [ (uuid, Slot 0 n)
            | FilterRule{ frUuid   = uuid
                        , frAction = RateLimit n } <- Set.toList filters ]
  
        -- How many rate limiting slots are taken by the jobs currently running
        -- in the queue jobs (counts only).
        -- A job takes a slot of a RateLimit filter if that filter is the first
        -- one that matches for the job.
        runningJobSlots = Map.fromListWith (+)
          [ (frUuid, 1) | Just FilterRule{ frUuid, frAction = RateLimit _ } <-
                            map (applyingFilter filters . jJob)
                              $ qRunning queue ++ qManipulated queue ]
  
    in -- Fill limits from above with counts from above.
       emptyFilterSlots `occupySlots` runningJobSlots
  
  
  -- | Implements job filtering as specified in `doc/design-optables.rst`.
  --
  -- Importantly, the filter that *applies* is the first one of which all
  -- predicates match; this is implemented in `applyingFilter`.
  --
  -- The initial `FilterChainState` is currently not cached across
  -- `selectJobsToRun` invocations because the number of running jobs is
  -- typically small (< 100).
  jobFiltering :: Queue -> Set FilterRule -> [JobWithStat] -> [JobWithStat]
  jobFiltering queue filters =
    let
        processFilters :: FilterChainState
                       -> JobWithStat
                       -> (FilterChainState, Maybe JobWithStat)
        processFilters state job =
          case applyingFilter filters (jJob job) of
            Nothing -> (state, Just job) -- no filter applies, accept job
            Just FilterRule{ frUuid, frAction } -> case frAction of
              Accept      -> (state, Just job)
              Continue    -> (state, Just job)
              Pause       -> (state, Nothing)
              Reject      -> (state, Nothing)
              RateLimit _ -> -- A matching job takes 1 slot.
                             let jobSlots = Map.fromList [(frUuid, 1)]
                             in case tryFitSlots state jobSlots of
                                  Nothing     -> (state,  Nothing)
                                  Just state' -> (state', Just job)
  
    in catMaybes . snd . mapAccumL processFilters FilterChainState
         { rateLimitSlotMap = queueRateLimitSlotMap queue filters
         }
  