Consider schema cache state on the ready check

* empty schema cache when it fails loading so the ready check can pick
  its new state

test/Main.hs

@@ -76,7 +76,7 @@ main = do
       let config = cfg testDbConn
       appState <- AppState.initWithPool pool config
       AppState.putPgVersion appState actualPgVersion
-      AppState.putDbStructure appState baseDbStructure
+      AppState.putDbStructure appState (Just baseDbStructure)
       when (isJust $ configDbRootSpec config) $
         AppState.putJsonDbS appState $ toS $ JSON.encode baseDbStructure
       return ((), postgrest LogCrit appState $ pure ())
@@ -91,7 +91,7 @@ main = do
           actualPgVersion
       appState <- AppState.initWithPool pool config
       AppState.putPgVersion appState actualPgVersion
-      AppState.putDbStructure appState customDbStructure
+      AppState.putDbStructure appState (Just customDbStructure)
       when (isJust $ configDbRootSpec config) $
         AppState.putJsonDbS appState $ toS $ JSON.encode baseDbStructure
       return ((), postgrest LogCrit appState $ pure ())

test/io-tests/db_config.sql

@@ -53,3 +53,11 @@ ALTER ROLE other_authenticator SET pgrst.db_pre_request = 'test.other_custom_hea
 ALTER ROLE other_authenticator SET pgrst.db_max_rows = '100';
 ALTER ROLE other_authenticator SET pgrst.db_extra_search_path = 'public, extensions, other';
 ALTER ROLE other_authenticator SET pgrst.openapi_mode = 'disabled';
+
+-- limited authenticator used for failed schema cache loads
+CREATE ROLE limited_authenticator LOGIN NOINHERIT;
+
+create or replace function no_schema_cache_for_limited_authenticator() returns void as $_$
+begin
+  ALTER ROLE limited_authenticator SET statement_timeout to 1;
+end $_$ volatile security definer language plpgsql ;

test/io-tests/test_io.py

@@ -768,6 +768,32 @@ def test_admin_ready_wo_channel(defaultenv):
         assert response.status_code == 200
 
 
+def test_admin_ready_includes_schema_cache_state(defaultenv):
+    "Should get a failed response from the admin server ready endpoint when the schema cache is not loaded"
+
+    db_uri = defaultenv["PGRST_DB_URI"].replace(
+        "postgrest_test_authenticator", "limited_authenticator"
+    )
+    env = {
+        **defaultenv,
+        "PGRST_DB_URI": db_uri,
+        "PGRST_DB_ANON_ROLE": "limited_authenticator",
+    }
+
+    with run(env=env, adminport=freeport()) as postgrest:
+
+        # make it impossible to load the schema cache
+        response = postgrest.session.post(
+            "/rpc/no_schema_cache_for_limited_authenticator"
+        )
+        assert response.status_code == 200
+        # force a reconnection so the new role setting is picked up
+        postgrest.process.send_signal(signal.SIGUSR1)
+        time.sleep(0.1)
+        response = postgrest.admin.get("/ready")
+        assert response.status_code == 503
+
+
 def test_admin_not_found(defaultenv):
     "Should get a not found from a undefined endpoint on the admin server"