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{-# LANGUAGE OverloadedStrings, FlexibleContexts, FlexibleInstances #-}
module Logstat.Eval where
import Data.Fixed (mod')
import Data.Foldable (foldl',toList)
import qualified Data.ByteString as B
import qualified Data.Heap as Heap
import qualified Data.Map.Strict as Map
import Logstat.Types
import Logstat.Value
import Logstat.Regex
data State
= StNone
| StSortAscNum !(Heap.Heap (SortItem AscNum ))
| StSortAscBS !(Heap.Heap (SortItem AscBS ))
| StSortDescNum !(Heap.Heap (SortItem DescNum))
| StSortDescBS !(Heap.Heap (SortItem DescBS ))
| StGroup !(Map.Map [Val] ()) -- TODO: Should add more state than '()'
deriving Show
data SortItem a = SortItem !a !Event deriving Show
newtype AscNum = AscNum Double deriving (Show,Eq)
newtype AscBS = AscBS B.ByteString deriving (Show,Eq)
newtype DescNum = DescNum Double deriving (Show,Eq,Ord)
newtype DescBS = DescBS B.ByteString deriving (Show,Eq,Ord)
instance Ord AscNum where (AscNum a) <= (AscNum b) = a >= b
instance Ord AscBS where (AscBS a) <= (AscBS b) = a >= b
instance Eq a => Eq (SortItem a) where (SortItem a _) == (SortItem b _) = a == b
instance Ord a => Ord (SortItem a) where (SortItem a _) <= (SortItem b _) = a <= b
newState :: [Stmt] -> [State]
newState = map st
where
st s = case s of
SSort _ _ SortAscNum -> StSortAscNum mempty
SSort _ _ SortAscBS -> StSortAscBS mempty
SSort _ _ SortDescNum -> StSortDescNum mempty
SSort _ _ SortDescBS -> StSortDescBS mempty
SGroup _ -> StGroup mempty
_ -> StNone
getField :: Event -> Field -> Either EvalError Val
getField st n = maybe (Left (UnknownField n)) return $ Map.lookup n st
evalExpr :: Expr -> Event -> Either EvalError Val
evalExpr expr ev = case expr of
ELit e -> Right e
EField f -> getField ev f
ENot e -> bool . not . asBool <$> evalExpr e ev
EIf e t f-> evalExpr e ev >>= \b -> evalExpr (if asBool b then t else f) ev
ENeg e -> do
v <- evalExpr e ev >>= asNum
return $ num (- v)
EMatch r e -> do
v <- evalExpr e ev
return $ bool $ reMatch r (asBS v)
EExtract e r -> do
v <- asBS <$> evalExpr e ev
ma <- maybe (Left (NoExtract v)) return $ match r v
return $ bs $ ma !! 1
EReplace e r n ->
-- TODO: Support subpattern substitution
bs . gsub r (const n) . asBS <$> evalExpr e ev
EOp op a' b' ->
case op of
OEq -> bcmp (==)
ONeq -> bcmp (/=)
OLt -> bcmp (<)
OGt -> bcmp (>)
OLe -> bcmp (<=)
OGe -> bcmp (>=)
OIEq -> icmp (==)
OINeq -> icmp (/=)
OILt -> icmp (<)
OIGt -> icmp (>)
OILe -> icmp (<=)
OIGe -> icmp (>=)
OConcat -> withab (return . asBS) $ \a b -> return $ bs $ B.append a b
OPlus -> iop (+)
OMinus -> iop (-)
OMul -> iop (*)
ODiv -> idiv (/)
OMod -> idiv mod'
OPow -> iop (**)
OOr -> with a' return $ \a -> if asBool a then return a else with b' return return
OAnd -> with a' return $ \a -> if asBool a then with b' return return else return a
where
with v f p = evalExpr v ev >>= f >>= p
withab f p = with a' f $ \a -> with b' f $ \b -> p a b
-- ByteString comparison
bcmp f = withab (return . asBS) $ \a b -> return $ bool $ f a b
-- Numeric comparison
icmp f = withab asNum $ \a b -> return $ bool $ f a b
-- Numeric operations
iop f = withab asNum $ \a b -> return $ num $ f a b
-- Division with zero-check
idiv f = withab asNum $ \a b ->
if b == 0
then Left DivByZero
else return $ num $ f a b
-- The behavior of each statement is implemented in two functions:
--
-- step:
-- Process a single event. This function can update some internal state of
-- the statement and/or immediately return a (modified) event, to be
-- processed by the next statement in the chain.
--
-- final:
-- Return a list of aggregated/sorted events stored in the internal state of
-- the statement.
-- The sorting algorithm is optimized for the scenario where there are many
-- logs as input and we're only interested in the top n (100 or so) logs. This
-- isn't the most efficient algorithm for other scenarios, alternative
-- strategies could be added later.
-- The current algorithm uses a fixed size min-heap to efficiently filter out
-- all logs that would not make it to the top n. This heap is then sorted in
-- the final step.
step :: Stmt -> State -> Event -> (State, Either EvalError Event)
step stmt st ev = case stmt of
SShow _ -> undefined -- Should be handled by extractShow
SSet f e -> (,) st $ evalExpr e ev >>= \v -> return $ Map.insert f v ev
SFilter e -> (,) st $ evalExpr e ev >>= \v -> if asBool v then return ev else Left Filtered
SRegex f r p -> (,) st $ do
val <- asBS <$> getField ev f
ma <- maybe (Left (NoMatch f val)) return $ match r val
return $ foldl' ins ev $ zip ma p
where
ins s (_, Nothing) = s
ins s (v, Just n) = Map.insert n (bs v) s
SSort n e _ ->
case st of
StSortAscNum hp -> run StSortAscNum hp (\v -> AscNum <$> asNum v)
StSortAscBS hp -> run StSortAscBS hp (return . AscBS . asBS)
StSortDescNum hp -> run StSortDescNum hp (\v -> DescNum <$> asNum v)
StSortDescBS hp -> run StSortDescBS hp (return . DescBS . asBS)
_ -> error "Invalid state for sort"
where
run wrap hp f =
case evalExpr e ev >>= f of
Left err -> (st, Left err)
Right val -> (wrap (ins hp val), Left Filtered)
ins hp val =
let si = SortItem val ev in
if Heap.size hp < n
then Heap.insert si hp
else if Heap.minimum hp < si
then Heap.insert si $ Heap.deleteMin hp
else hp
SGroup f ->
let StGroup m = st in
case mapM (getField ev) f of
Left err -> (st, Left err)
Right v -> (StGroup $ Map.insert v () m, Left Filtered)
final :: Stmt -> State -> [Event]
final stmt st = case stmt of
SSort _ _ _ ->
case st of
StSortAscNum hp -> f hp
StSortAscBS hp -> f hp
StSortDescNum hp -> f hp
StSortDescBS hp -> f hp
_ -> error "Invalid state for sort"
where
f hp = map (\(SortItem _ ev) -> ev) $ reverse $ toList hp
SGroup f ->
let StGroup m = st in
map (\(k,_) -> Map.fromList $ zip f k) $ Map.toList m
_ -> []
type Step = [State] -> Event -> ([State], Either EvalError Event)
stepL :: [Stmt] -> Step
stepL stmts =
-- "materialize" the statements into a list of (State -> Event -> ..)
-- functions. This hopefully causes the pattern matching on the Stmt value to
-- be performed only once, thus speeding up evaluation. But I obviously need
-- to measure the effect of this optimization to see if it even works at all.
let fs = map step stmts in loop fs
where
loop (f:fns) (st:sts) ev =
case f st ev of
(st', Left err) -> (st':sts, Left err)
(st', Right e) -> let (sts', e') = loop fns sts e in (st':sts', e')
loop _ _ ev = ([], Right ev)
finalL :: [Stmt] -> [State] -> [Either EvalError Event]
finalL stmts =
-- Same thing as in stepL
let fns = zip (stepL' stmts) (map final stmts) in loop fns
where
stepL' :: [Stmt] -> [Step]
stepL' [] = []
stepL' (_:xs) = stepL xs : stepL' xs
loop (f:fns) (st:sts) =
let (sts', l1) = steps (fst f) sts (snd f st)
l2 = loop fns sts'
in l1 ++ l2
loop _ _ = []
steps :: Step -> [State] -> [Event] -> ([State], [Either EvalError Event])
steps _ st [] = (st, [])
steps f st (ev:evs) =
let (st', r) = f st ev
(st'', evs') = steps f st' evs
in (,) st'' $ case r of
Left Filtered -> evs'
_ -> r : evs'
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