add: Log pg version details of listener connection

Follow-up to #4617 adding more information to log entry produced upon successful listener connection establishement.

src/PostgREST/Listener.hs

@@ -17,10 +17,13 @@ import           PostgREST.Version     (prettyVersion)
 import qualified PostgREST.AppState as AppState
 import qualified PostgREST.Config   as Config
 
-import           Control.Arrow             ((&&&))
-import           Data.Bitraversable        (bisequence)
-import           Data.Either.Combinators   (whenRight)
-import qualified Database.PostgreSQL.LibPQ as LibPQ
+import           Control.Arrow              ((&&&))
+import           Data.Bitraversable         (bisequence)
+import           Data.Either.Combinators    (whenRight)
+import qualified Database.PostgreSQL.LibPQ  as LibPQ
+import qualified Hasql.Session              as SQL
+import           PostgREST.Config.Database  (queryPgVersion)
+import           PostgREST.Config.PgVersion (pgvFullName)
 import           Protolude
 
 -- | Starts the Listener in a thread
@@ -66,6 +69,9 @@ retryingListen appState = do
       \case
         Right db -> do
           SQL.listen db $ SQL.toPgIdentifier dbChannel
+          (pqHost, pqPort) <- SQL.withLibPQConnection db $ bisequence . (LibPQ.host &&& LibPQ.port)
+          pgFullName <- SQL.run (queryPgVersion False) db >>= either throwIO (pure . pgvFullName)
+
           AppState.putIsListenerOn appState True
 
           delay <- AppState.getNextListenerDelay appState
@@ -75,8 +81,8 @@ retryingListen appState = do
             -- reset the delay
             AppState.putNextListenerDelay appState 1
 
-          (pqHost, pqPort) <- SQL.withLibPQConnection db $ bisequence . (LibPQ.host &&& LibPQ.port)
-          observer $ DBListenStart pqHost pqPort dbChannel
+          observer $ DBListenStart pqHost pqPort pgFullName dbChannel
+
           -- wait for notifications
           -- this will never return, in case of an error it will throw and be caught by onError
           forever $ SQL.waitForNotifications handleNotification db

src/PostgREST/Observation.hs

@@ -45,7 +45,7 @@ data Observation
   | SchemaCacheSummaryObs Text
   | SchemaCacheLoadedObs Double
   | ConnectionRetryObs Int
-  | DBListenStart (Maybe ByteString) (Maybe ByteString) Text -- host, port, channel
+  | DBListenStart (Maybe ByteString) (Maybe ByteString) Text Text -- host, port, version string, channel
   | DBListenFail Text (Either SQL.ConnectionError SomeException)
   | DBListenRetry Int
   | DBListenBugHint -- https://github.com/PostgREST/postgrest/issues/3147
@@ -114,8 +114,8 @@ observationMessage = \case
     "Attempting to reconnect to the database in " <> (show delay::Text) <> " seconds..."
   QueryPgVersionError usageErr ->
     "Failed to query the PostgreSQL version. " <> jsonMessage usageErr
-  DBListenStart host port channel -> do
-    "Listener connected to " <> show (fold $ host <> fmap (":" <>) port) <> " and listening for database notifications on the " <> show channel <> " channel"
+  DBListenStart host port fullName channel -> do
+    "Listener connected to " <> fullName <> " on " <> show (fold $ host <> fmap (":" <>) port) <> " and listening for database notifications on the " <> show channel <> " channel"
   DBListenFail channel listenErr ->
     "Failed listening for database notifications on the " <> show channel <> " channel. " <>
       either showListenerConnError showListenerException listenErr