module System.Metrics.Json
(
sampleToJson
, valueToJson
, Sample(..)
, Value(..)
) where
import Data.Aeson ((.=))
import qualified Data.Aeson.Encode as A
import qualified Data.Aeson.Types as A
import qualified Data.HashMap.Strict as M
import Data.Int (Int64)
import qualified Data.Text as T
import qualified System.Metrics as Metrics
import qualified System.Metrics.Distribution as Distribution
sampleToJson :: Metrics.Sample -> A.Value
sampleToJson metrics =
buildOne metrics $ A.emptyObject
where
buildOne :: M.HashMap T.Text Metrics.Value -> A.Value -> A.Value
buildOne m o = M.foldlWithKey' build o m
build :: A.Value -> T.Text -> Metrics.Value -> A.Value
build m name val = go m (T.splitOn "." name) val
go :: A.Value -> [T.Text] -> Metrics.Value -> A.Value
go (A.Object m) [str] val = A.Object $ M.insert str metric m
where metric = valueToJson val
go (A.Object m) (str:rest) val = case M.lookup str m of
Nothing -> A.Object $ M.insert str (go A.emptyObject rest val) m
Just m' -> A.Object $ M.insert str (go m' rest val) m
go v _ _ = typeMismatch "Object" v
typeMismatch :: String
-> A.Value
-> a
typeMismatch expected actual =
error $ "when expecting a " ++ expected ++ ", encountered " ++ name ++
" instead"
where
name = case actual of
A.Object _ -> "Object"
A.Array _ -> "Array"
A.String _ -> "String"
A.Number _ -> "Number"
A.Bool _ -> "Boolean"
A.Null -> "Null"
valueToJson :: Metrics.Value -> A.Value
valueToJson (Metrics.Counter n) = scalarToJson n CounterType
valueToJson (Metrics.Gauge n) = scalarToJson n GaugeType
valueToJson (Metrics.Label l) = scalarToJson l LabelType
valueToJson (Metrics.Distribution l) = distrubtionToJson l
scalarToJson :: A.ToJSON a => a -> MetricType -> A.Value
scalarToJson val ty = A.object
["val" .= val, "type" .= metricType ty]
data MetricType =
CounterType
| GaugeType
| LabelType
| DistributionType
metricType :: MetricType -> T.Text
metricType CounterType = "c"
metricType GaugeType = "g"
metricType LabelType = "l"
metricType DistributionType = "d"
distrubtionToJson :: Distribution.Stats -> A.Value
distrubtionToJson stats = A.object
[ "mean" .= Distribution.mean stats
, "variance" .= Distribution.variance stats
, "count" .= Distribution.count stats
, "sum" .= Distribution.sum stats
, "min" .= Distribution.min stats
, "max" .= Distribution.max stats
, "type" .= metricType DistributionType
]
newtype Sample = Sample Metrics.Sample
deriving Show
instance A.ToJSON Sample where
toJSON (Sample s) = sampleToJson s
newtype Value = Value Metrics.Value
deriving Show
instance A.ToJSON Value where
toJSON (Value v) = valueToJson v