Add database connection health check (baserow#5170)

Author: bram2w

backend/src/baserow/config/celery.py

@@ -27,8 +27,30 @@ def clear_local(*args, **kwargs):
     clear_db_state()
 
 
+def close_old_db_connections(sender, **kwargs):
+    """
+    Close old or unusable database connections around each Celery task.
+
+    Calling `close_old_connections()` on both `task_prerun` and `task_postrun`
+    ensures Django's own connection lifecycle is applied to Celery tasks, matching the
+    documented recommendation for long-running processes.
+
+    Eager tasks (used in tests) are skipped because they run inside the
+    caller's process and share its database connection/transaction.
+    """
+
+    if getattr(sender.request, "is_eager", False):
+        return
+
+    from django.db import close_old_connections
+
+    close_old_connections()
+
+
 signals.task_prerun.connect(clear_local)
+signals.task_prerun.connect(close_old_db_connections)
 signals.task_postrun.connect(clear_local)
+signals.task_postrun.connect(close_old_db_connections)
 
 
 @signals.worker_process_init.connect

backend/src/baserow/config/settings/base.py

@@ -283,6 +283,12 @@
 
         DATABASE_READ_REPLICAS.append(db_key)
 
+# Enable connection health checks for all database connections. This makes Django
+# verify that a database connection is still usable before each request/task, which
+# prevents "connection already closed" errors when connections are dropped by the
+# server, a load balancer, or a connection pooler.
+for _db_key in DATABASES:
+    DATABASES[_db_key].setdefault("CONN_HEALTH_CHECKS", True)
 
 DATABASE_ROUTERS = ["baserow.config.db_routers.ReadReplicaRouter"]
 

changelog/entries/unreleased/bug/add_database_connection_health_check.json

@@ -0,0 +1,9 @@
+{
+  "type": "bug",
+  "message": "Add database connection health check.",
+  "issue_origin": "github",
+  "issue_number": null,
+  "domain": "core",
+  "bullet_points": [],
+  "created_at": "2026-04-12"
+}