From ee8b3ef8fee8560ae224dbcbdadb229dce76c972 Mon Sep 17 00:00:00 2001
From: steve-chavez <stevechavezast@gmail.com>
Date: Tue, 19 Mar 2024 00:46:43 -0500
Subject: [PATCH] fix: log on LISTEN notification

---
 CHANGELOG.md                 |  2 +-
 src/PostgREST/AppState.hs    | 12 +++++++-----
 src/PostgREST/Observation.hs |  8 +++++++-
 test/io/test_io.py           |  2 ++
 4 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 26f1d7eb6..355fc872f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -24,7 +24,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
  - #3237, Dump media handlers and timezones with --dump-schema - @wolfgangwalther
  - #3323, #3324, Don't hide error on LISTEN channel failure - @steve-chavez
  - #3330, Incorrect admin server `/ready` response on slow schema cache loads - @steve-chavez
- - #3327, Fix slow responses on schema cache reloads - @steve-chavez
+ - #3340, Log when the LISTEN channel gets a notification - @steve-chavez
 
 ### Deprecated
 
diff --git a/src/PostgREST/AppState.hs b/src/PostgREST/AppState.hs
index 4ec78f692..29059c073 100644
--- a/src/PostgREST/AppState.hs
+++ b/src/PostgREST/AppState.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE LambdaCase      #-}
+{-# LANGUAGE MultiWayIf      #-}
 {-# LANGUAGE NamedFieldPuns  #-}
 {-# LANGUAGE RecordWildCards #-}
 
@@ -501,6 +502,7 @@ listener appState observer = do
         putIsListenerOn appState True
         SQL.listen db $ SQL.toPgIdentifier dbChannel
         SQL.waitForNotifications handleNotification db
+
       Left err -> do
         observer $ DBListenerFail dbChannel err
         exitFailure
@@ -517,11 +519,11 @@ listener appState observer = do
       -- retry the listener
       listener appState observer
 
-    handleNotification _ msg
-      | BS.null msg            = cacheReloader
-      | msg == "reload schema" = cacheReloader
-      | msg == "reload config" = reReadConfig False appState observer
-      | otherwise              = pure () -- Do nothing if anything else than an empty message is sent
+    handleNotification channel msg =
+      if | BS.null msg            -> observer (DBListenerGotSCacheMsg channel) >> cacheReloader
+         | msg == "reload schema" -> observer (DBListenerGotSCacheMsg channel) >> cacheReloader
+         | msg == "reload config" -> observer (DBListenerGotConfigMsg channel) >> reReadConfig False appState observer
+         | otherwise              -> pure () -- Do nothing if anything else than an empty message is sent
 
     cacheReloader =
       -- reloads the schema cache + restarts pool connections
diff --git a/src/PostgREST/Observation.hs b/src/PostgREST/Observation.hs
index 98370ef98..de0396539 100644
--- a/src/PostgREST/Observation.hs
+++ b/src/PostgREST/Observation.hs
@@ -40,6 +40,8 @@ data Observation
   | DBListenerStart Text
   | DBListenerFail Text SQL.ConnectionError
   | DBListenerFailRecoverObs Bool Text (Either SomeException ())
+  | DBListenerGotSCacheMsg ByteString
+  | DBListenerGotConfigMsg ByteString
   | ConfigReadErrorObs
   | ConfigReadErrorFatalObs SQL.UsageError Text
   | ConfigReadErrorNotFatalObs SQL.UsageError
@@ -82,11 +84,15 @@ observationMessage = \case
   ConnectionPgVersionErrorObs usageErr ->
     jsonMessage usageErr
   DBListenerStart channel -> do
-    "Listening for notifications on the " <> channel <> " channel"
+    "Listening for notifications on the " <> show channel <> " channel"
   DBListenerFail channel err -> do
     "Could not listen for notifications on the " <> channel <> " channel. " <> show err
   DBListenerFailRecoverObs recover channel err ->
     "Could not listen for notifications on the " <> channel <> " channel. " <> showListenerError err <> (if recover then " Retrying listening for notifications.." else mempty)
+  DBListenerGotSCacheMsg channel ->
+    "Received a schema cache reload message on the " <> show channel <> " channel"
+  DBListenerGotConfigMsg channel ->
+    "Received a config reload message on the " <> show channel <> " channel"
   ConfigReadErrorObs ->
     "An error ocurred when trying to query database settings for the config parameters"
   ConfigReadErrorFatalObs usageErr hint ->
diff --git a/test/io/test_io.py b/test/io/test_io.py
index ca4211502..d35fdb6b8 100644
--- a/test/io/test_io.py
+++ b/test/io/test_io.py
@@ -421,6 +421,8 @@ def test_invalid_role_claim_key_notify_reload(defaultenv):
     with run(env=env) as postgrest:
         postgrest.session.post("/rpc/invalid_role_claim_key_reload")
 
+        output = postgrest.read_stdout()
+        assert 'Received a config reload message on the "pgrst" channel' in output[0]
         output = postgrest.read_stdout()
         assert "failed to parse role-claim-key value" in output[0]