108 lines
3.3 KiB
Haskell
108 lines
3.3 KiB
Haskell
{-# LANGUAGE OverloadedStrings #-}
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module System.Remote.Json
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(
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encodeAll
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, encodeOne
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) where
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import qualified Data.Aeson.Encode as A
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import qualified Data.Aeson.Types as A
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import qualified Data.ByteString.Lazy as L
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import qualified Data.HashMap.Strict as M
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import Data.Int (Int64)
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import qualified Data.Text as T
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import Prelude hiding (read)
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import System.Metrics
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import qualified System.Metrics.Distribution as Distribution
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------------------------------------------------------------------------
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-- * JSON serialization
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data MetricType =
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CounterType
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| GaugeType
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| LabelType
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| DistributionType
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metricType :: MetricType -> T.Text
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metricType CounterType = "c"
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metricType GaugeType = "g"
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metricType LabelType = "l"
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metricType DistributionType = "d"
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-- | Encode metrics as nested JSON objects. Each "." in the metric
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-- name introduces a new level of nesting. For example, the metrics
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-- @[("foo.bar", 10), ("foo.baz", "label")]@ are encoded as
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--
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-- > {
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-- > "foo": {
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-- > "bar": {
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-- > "type:", "c",
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-- > "val": 10
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-- > },
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-- > "baz": {
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-- > "type": "l",
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-- > "val": "label"
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-- > }
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-- > }
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-- > }
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--
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encodeAll :: Sample -> L.ByteString
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encodeAll metrics =
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A.encode $ buildOne metrics $ A.emptyObject
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where
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buildOne :: M.HashMap T.Text Value -> A.Value -> A.Value
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buildOne m o = M.foldlWithKey' build o m
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build :: A.Value -> T.Text -> Value -> A.Value
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build m name val = go m (T.splitOn "." name) val
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go :: A.Value -> [T.Text] -> Value -> A.Value
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go (A.Object m) [str] val = A.Object $ M.insert str metric m
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where metric = buildOneM val
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go (A.Object m) (str:rest) val = case M.lookup str m of
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Nothing -> A.Object $ M.insert str (go A.emptyObject rest val) m
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Just m' -> A.Object $ M.insert str (go m' rest val) m
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go v _ _ = typeMismatch "Object" v
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buildOneM :: Value -> A.Value
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buildOneM (Counter n) = goOne n CounterType
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buildOneM (Gauge n) = goOne n GaugeType
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buildOneM (Label l) = goOne l LabelType
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buildOneM (Distribution l) = goDistribution l
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goDistribution :: Distribution.Stats -> A.Value
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goDistribution stats = A.object [
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("mean", A.toJSON $! Distribution.mean stats),
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("variance", A.toJSON $! Distribution.variance stats),
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("count", A.toJSON $! Distribution.count stats),
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("sum", A.toJSON $! Distribution.sum stats),
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("min", A.toJSON $! Distribution.min stats),
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("max", A.toJSON $! Distribution.max stats),
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("type", A.toJSON (metricType DistributionType))]
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goOne :: A.ToJSON a => a -> MetricType -> A.Value
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goOne val ty = A.object [
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("val", A.toJSON val), ("type", A.toJSON (metricType ty))]
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{-# SPECIALIZE goOne :: Int64 -> MetricType -> A.Value #-}
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{-# SPECIALIZE goOne :: T.Text -> MetricType -> A.Value #-}
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encodeOne :: Value -> L.ByteString
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encodeOne = A.encode . buildOneM
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typeMismatch :: String -- ^ The expected type
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-> A.Value -- ^ The actual value encountered
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-> a
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typeMismatch expected actual =
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error $ "when expecting a " ++ expected ++ ", encountered " ++ name ++
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" instead"
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where
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name = case actual of
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A.Object _ -> "Object"
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A.Array _ -> "Array"
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A.String _ -> "String"
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A.Number _ -> "Number"
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A.Bool _ -> "Boolean"
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A.Null -> "Null"
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