add: Log pg version details of listener connection

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

CHANGELOG.md

@@ -6,7 +6,7 @@ All notable changes to this project will be documented in this file. From versio
 
 ### Added
 
-- Log the actual host and port of listener database connection by @mkleczek in #4617
+- Log host, port and pg version of listener database connection by @mkleczek in #4617 #4618
 
 ## [14.8] - 2026-04-03
 

src/PostgREST/Listener.hs

@@ -21,6 +21,9 @@ 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 pgFullName dbChannel
-          observer $ DBListenStart pqHost pqPort 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
+  DBListenStart host port fullName channel -> do
-    "Listener connected to " <> show (fold $ host <> fmap (":" <>) port) <> " and listening for database notifications on the " <> show channel <> " channel"
+    "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

test/io/test_io.py

@@ -1667,9 +1667,11 @@ def test_log_listener_connection_start(defaultenv):
     }
 
     with run(env=env, no_startup_stdout=False, wait_for_readiness=True) as postgrest:
-        output = postgrest.read_stdout(nlines=5)
+        output = postgrest.read_stdout(nlines=10)
+        # Check for the listener start message containing host and port
+        # Do not check if pg version is displayed properly as it is tricky to test it
         assert any(
-            f'Listener connected to "{defaultenv["PGHOST"]}:5432" and listening for database notifications on the "pgrst" channel'
+            f'"{defaultenv["PGHOST"]}:5432" and listening for database notifications on the "pgrst" channel'
             in line
             for line in output
         )

test/observability/ObsHelper.hs

@@ -206,5 +206,5 @@ waitForObs (ObsChan orig copy) t msg f =
 obsDiagMessage :: Observation -> Text
 obsDiagMessage = \case
   (HasqlPoolObs o) -> show o
-  o@(DBListenStart host port channel) -> constrName o <> show (host, port, channel)
+  o@(DBListenStart host port name channel) -> constrName o <> show (host, port, name, channel)
   o -> constrName o