Config.hs

-- | Configuration for the metrics web server.
module Shibuya.Metrics.Config
  ( MetricsServerConfig (..),
    defaultConfig,
  )
where

import Data.Text (Text)
import Data.Time.Clock (NominalDiffTime)
import GHC.Generics (Generic)

-- | Configuration for the metrics web server.
data MetricsServerConfig = MetricsServerConfig
  { -- | Host to listen on (default: loopback only, @127.0.0.1@).
    --
    -- Set this to @*@ only behind an authentication and authorization boundary;
    -- metrics and terminal failure details are operationally sensitive.
    host :: !String,
    -- | Port to listen on (default: 9090)
    port :: !Int,
    -- | Enable JSON endpoints (default: True)
    enableJSON :: !Bool,
    -- | Enable Prometheus endpoint (default: True)
    enablePrometheus :: !Bool,
    -- | Enable WebSocket endpoint (default: True)
    enableWebSocket :: !Bool,
    -- | Enable reversible control POSTs (default False). The server performs
    -- no authentication; use a trusted network or authenticating reverse proxy.
    enableControl :: !Bool,
    -- | Exact browser Origins allowed for HTTP CORS and WebSocket upgrades.
    -- An empty list disables the policy (default). Entries must be serialized
    -- @scheme://host[:port]@ origins without whitespace, paths or trailing slashes.
    -- Origins are compared byte-for-byte; the wildcard @*@ is refused.
    corsAllowedOrigins :: ![Text],
    -- | WebSocket push interval in microseconds (default: 100_000 = 100ms)
    wsPushIntervalUs :: !Int,
    -- | Maximum WebSocket connections (default: 100)
    wsMaxConnections :: !Int,
    -- | Maximum retained processor identifiers per WebSocket connection
    -- (default: 1,000). A client exceeding this policy is disconnected.
    wsMaxSubscriptions :: !Int,
    -- | Maximum retained outbound frames, including required frames (default: 64; minimum: 2).
    wsMaxQueuedFrames :: !Int,
    -- | Maximum retained encoded outbound bytes (default: 1 MiB).
    -- At most one popped frame and a transient encoding are outside this budget.
    wsMaxQueuedBytes :: !Int,
    -- | Deadline for a send and the entire orderly close flush (default: 5 seconds).
    wsSendTimeoutUs :: !Int,
    -- | Timeout for liveness check in microseconds (default: 1_000_000 = 1s)
    livenessTimeoutMicros :: !Int,
    -- | Timeout for each dependency readiness check in microseconds (default: 1s)
    dependencyTimeoutMicros :: !Int,
    -- | How long a processor can be in Processing state before considered stuck (default: 60s)
    stuckThreshold :: !NominalDiffTime
  }
  deriving stock (Eq, Show, Generic)

-- | Default configuration.
defaultConfig :: MetricsServerConfig
defaultConfig =
  MetricsServerConfig
    { host = "127.0.0.1",
      port = 9090,
      enableJSON = True,
      enablePrometheus = True,
      enableWebSocket = True,
      enableControl = False,
      corsAllowedOrigins = [],
      wsPushIntervalUs = 100_000, -- 100ms
      wsMaxConnections = 100,
      wsMaxSubscriptions = 1_000,
      wsMaxQueuedFrames = 64,
      wsMaxQueuedBytes = 1_048_576,
      wsSendTimeoutUs = 5_000_000,
      livenessTimeoutMicros = 1_000_000, -- 1 second
      dependencyTimeoutMicros = 1_000_000, -- 1 second per dependency
      stuckThreshold = 60 -- 60 seconds
    }