fix: Do not clear the schema cache during retries

retryingSchemaCacheLoad should not clear existing schema cache upon failure - there is no reason to do that. If there is a communication issue with the database server or db is down, clients are going to get 502 anyway. If it was a glitch when loading the schema cache - the clients are going to use old (stale) schema cache for some time until next retry re-loads it successfully.

Author: mkleczek

CHANGELOG.md

@@ -22,6 +22,7 @@ All notable changes to this project will be documented in this file. From versio
 - Remove automatic transaction retries on `40001 (serialization_failure)` errors to prevent replication lag by @laurenceisla in #3673
 - Fix unexpected results when embedding and filtering the same table more than once by @laurenceisla in #4075
 - Fix race condition in pool_available metric causing negative values during network instability by @mkleczek in #4622
+- PostgREST no longer returns voids schema cache during loading retries by @mkleczek in #4873 #4869
 
 ### Changed
 

src/PostgREST/AppState.hs

@@ -347,7 +347,6 @@ retryingSchemaCacheLoad appState@AppState{stateObserver=observer, stateMainThrea
       case result of
         Left e -> do
           markSchemaCachePending appState
-          putSchemaCache appState Nothing
           observer $ SchemaCacheErrorObs configDbSchemas configDbExtraSearchPath e
           return Nothing
 

test/io/fixtures/roles.sql

@@ -14,6 +14,8 @@ GRANT
   postgrest_test_serializable, postgrest_test_repeatable_read,
   postgrest_test_w_superuser_settings TO :"PGUSER";
 
+GRANT postgrest_test_anonymous TO timeout_authenticator;
+
 ALTER ROLE :"PGUSER" SET pgrst.db_anon_role = 'postgrest_test_anonymous';
 ALTER ROLE postgrest_test_serializable SET default_transaction_isolation = 'serializable';
 ALTER ROLE postgrest_test_repeatable_read SET default_transaction_isolation = 'REPEATABLE READ';

test/io/test_io.py

@@ -731,7 +731,7 @@ def test_admin_ready_includes_schema_cache_state(defaultenv, metapostgrest):
     env = {
         **defaultenv,
         "PGUSER": role,
-        "PGRST_DB_ANON_ROLE": role,
+        "PGRST_DB_ANON_ROLE": "postgrest_test_anonymous",
         "PGRST_INTERNAL_SCHEMA_CACHE_QUERY_SLEEP": "500",
     }
 
@@ -749,7 +749,7 @@ def test_admin_ready_includes_schema_cache_state(defaultenv, metapostgrest):
         assert response.status_code == 503
 
         response = postgrest.session.get("/projects", timeout=1)
-        assert response.status_code == 503
+        assert response.status_code == 200
 
     reset_statement_timeout(metapostgrest, role)