refactor: deduplicate host resolution logic and observations

Replaces the "API server listening on unix socket" with simpler
"API server listening on " observation. This allows refactoring
redundant code.

Signed-off-by: Taimoor Zaeem <taimoorzaeem@gmail.com>

src/PostgREST/Admin.hs

@@ -1,5 +1,3 @@
-{-# LANGUAGE NamedFieldPuns #-}
-
 module PostgREST.Admin
   ( runAdmin
   ) where
@@ -9,16 +7,14 @@ import qualified Network.HTTP.Types.Status as HTTP
 import qualified Network.Wai               as Wai
 import qualified Network.Wai.Handler.Warp  as Warp
 
-import Control.Monad.Extra (whenJust)
-
-import Network.Socket
+import Control.Monad.Extra       (whenJust)
+import Network.Socket            hiding (addrFamily)
 import Network.Socket.ByteString
 
 import PostgREST.AppState    (AppState)
-import PostgREST.Config      (AppConfig (..))
 import PostgREST.MediaType   (MediaType (..), toContentType)
 import PostgREST.Metrics     (metricsToText)
-import PostgREST.Network     (resolveHost)
+import PostgREST.Network     (resolveSocketToAddress)
 import PostgREST.Observation (Observation (..))
 
 import qualified PostgREST.AppState as AppState
@@ -27,10 +23,9 @@ import Protolude
 
 runAdmin :: AppState -> Warp.Settings -> IO ()
 runAdmin appState settings = do
-  AppConfig{configAdminServerPort} <- AppState.getConfig appState
   whenJust (AppState.getSocketAdmin appState) $ \adminSocket -> do
-    host <- resolveHost adminSocket
-    observer $ AdminStartObs host configAdminServerPort
+    address <- resolveSocketToAddress adminSocket
+    observer $ AdminStartObs address
     void . forkIO $ Warp.runSettingsSocket settings adminSocket adminApp
   where
     adminApp = admin appState

src/PostgREST/App.hs

@@ -46,7 +46,7 @@ import PostgREST.Auth.Types           (AuthResult (..))
 import PostgREST.Config               (AppConfig (..), LogLevel (..),
                                        LogQuery (..))
 import PostgREST.Error                (Error)
-import PostgREST.Network              (resolveHost)
+import PostgREST.Network              (resolveSocketToAddress)
 import PostgREST.Observation          (Observation (..))
 import PostgREST.Response.Performance (ServerTiming (..),
                                        serverTimingHeader)
@@ -56,7 +56,6 @@ import PostgREST.Version              (docsVersion, prettyVersion)
 import qualified Data.ByteString.Char8 as BS
 import qualified Data.List             as L
 import qualified Network.HTTP.Types    as HTTP
-import qualified Network.Socket        as NS
 import           Protolude             hiding (Handler)
 import           System.TimeIt         (timeItT)
 
@@ -76,13 +75,9 @@ run appState = do
 
   let app = postgrest configLogLevel appState (AppState.schemaCacheLoader appState)
 
-  case configServerUnixSocket of
-    Just path -> do
-      observer $ AppServerUnixObs path
-    Nothing   -> do
-      port <- NS.socketPort $ AppState.getSocketREST appState
-      host <- resolveHost $ AppState.getSocketREST appState
-      observer $ AppServerPortObs (fromJust host) port
+  do
+    address <- resolveSocketToAddress (AppState.getSocketREST appState)
+    observer $ AppServerAddressObs address
 
   Warp.runSettingsSocket (serverSettings conf) (AppState.getSocketREST appState) app
 

src/PostgREST/Network.hs

@@ -1,21 +1,37 @@
 module PostgREST.Network
-  ( resolveHost
+  ( resolveSocketToAddress
   ) where
 
-import           Data.IP        (fromHostAddress, fromHostAddress6)
 import           Data.String    (IsString (..))
 import qualified Network.Socket as NS
 
 import Protolude
 
-resolveHost :: NS.Socket -> IO (Maybe Text)
-resolveHost sock = do
+-- | Resolves the socket to an address depending on the socket type. The Show
+--   instance of the socket types automatically resolves it to the correct
+--   address. Example resolution:
+-- -----------------------------------------------------
+-- | IPv4         | IPv6             | Unix            |
+-- -----------------------------------------------------
+-- | 127.0.0.1:80 | [2001:db8::1]:80 | /tmp/pgrst.sock |
+-- -----------------------------------------------------
+resolveSocketToAddress :: NS.Socket -> IO Text
+resolveSocketToAddress sock = do
   sn <- NS.getSocketName sock
-  case sn of
-    NS.SockAddrInet _ hostAddr ->  pure $ Just $ fromString $ show $ fromHostAddress hostAddr
-    -- The IPv6 addresses are wrapped in [] brackets. This is done in accordance
-    -- to RFC 3986 (https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.2).
-    -- In short, we did this to have a clear separation between the port and host
-    -- because the components of an IPv6 are separated with the ':' character.
-    NS.SockAddrInet6 _ _ hostAddr6 _ -> pure $ Just $ fromString $ "[" ++ show (fromHostAddress6 hostAddr6) ++ "]"
-    _ -> pure Nothing
+  return $ showSocketAddr sn
+
+-- |
+-- >>> let addr_ipv4 = NS.SockAddrInet 80 (NS.tupleToHostAddress (127,0,0,1))
+-- >>> let addr_ipv6 = NS.SockAddrInet6 80 0 (0,0,0,1) 0
+-- >>> let addr_unix = NS.SockAddrUnix "/tmp/pgrst.sock"
+--
+-- >>> showSocketAddr addr_ipv4
+-- "127.0.0.1:80"
+
+-- >>> showSocketAddr addr_ipv6
+-- "[::1]:80"
+--
+-- >>> showSocketAddr addr_unix
+-- "/tmp/pgrst.sock"
+showSocketAddr :: NS.SockAddr -> Text
+showSocketAddr = fromString . show

src/PostgREST/Observation.hs

@@ -21,19 +21,16 @@ import qualified Hasql.Connection           as SQL
 import qualified Hasql.Pool                 as SQL
 import qualified Hasql.Pool.Observation     as SQL
 import           Network.HTTP.Types.Status  (Status)
-import qualified Network.Socket             as NS
 import           Numeric                    (showFFloat)
 import           PostgREST.Config.PgVersion
 import qualified PostgREST.Error            as Error
 
-import Protolude         hiding (toList)
-import Protolude.Partial (fromJust)
+import Protolude hiding (toList)
 
 data Observation
-  = AdminStartObs (Maybe Text) (Maybe Int)
+  = AdminStartObs Text
   | AppStartObs ByteString
-  | AppServerPortObs Text NS.PortNumber
-  | AppServerUnixObs FilePath
+  | AppServerAddressObs Text
   | ExitUnsupportedPgVersion PgVersion PgVersion
   | ExitDBNoRecoveryObs
   | ExitDBFatalError ObsFatalError SQL.UsageError
@@ -69,14 +66,12 @@ type ObservationHandler = Observation -> IO ()
 
 observationMessage :: Observation -> Text
 observationMessage = \case
-  AdminStartObs host port ->
-    "Admin server listening on " <> fromJust host <> ":" <> show (fromIntegral (fromJust port) :: Integer)
+  AdminStartObs address ->
+    "Admin server listening on " <> address
   AppStartObs ver ->
     "Starting PostgREST " <> T.decodeUtf8 ver <> "..."
-  AppServerPortObs host port ->
-    "API server listening on " <> host <> ":" <> show port
-  AppServerUnixObs sock ->
-    "API server listening on unix socket " <> show sock
+  AppServerAddressObs address ->
+    "API server listening on " <> address
   DBConnectedObs ver ->
     "Successfully connected to " <> ver
   ExitUnsupportedPgVersion pgVer minPgVer ->

test/doc/Main.hs

@@ -18,6 +18,7 @@ main =
     , "src/PostgREST/Config.hs"
     , "src/PostgREST/Error.hs"
     , "src/PostgREST/MediaType.hs"
+    , "src/PostgREST/Network.hs"
     , "src/PostgREST/Plan.hs"
     , "src/PostgREST/Query/SqlFragment.hs"
     , "src/PostgREST/Response.hs"

test/io/test_io.py

@@ -1378,7 +1378,7 @@ def test_log_postgrest_host_and_port(host, defaultenv):
         output = postgrest.read_stdout(nlines=10)
 
         if is_unix:
-            re.match(r'API server listening on unix socket "/tmp/.*\.sock"', output[2])
+            re.match(r'API server listening on "/tmp/.*\.sock"', output[2])
         elif is_ipv6(host):
             assert f"API server listening on [{host}]:{port}" in output[2]
         else:  # IPv4