Fix: health-check pooled DB connections and close the pool on worker shutdown (#12977)

src/documents/signals/handlers.py

@@ -15,6 +15,7 @@ from celery.signals import task_postrun
 from celery.signals import task_prerun
 from celery.signals import task_revoked
 from celery.signals import worker_process_init
+from celery.signals import worker_process_shutdown
 from django.conf import settings
 from django.contrib.auth.models import Group
 from django.contrib.auth.models import User
@@ -1339,6 +1340,20 @@ def close_connection_pool_on_worker_init(**kwargs) -> None:
             conn.close_pool()
 
 
+@worker_process_shutdown.connect
+def close_connection_pool_on_worker_shutdown(**kwargs) -> None:  # pragma: no cover
+    """
+    Close the DB connection pool when a Celery child process exits.
+
+    With CELERY_WORKER_MAX_TASKS_PER_CHILD=1 each child is replaced after a
+    single task. Without closing the pool on shutdown, its connections linger
+    on the server until TCP keepalive reaps them, accumulating over time.
+    """
+    for conn in connections.all(initialized_only=True):
+        if conn.alias == "default" and hasattr(conn, "pool") and conn.pool:
+            conn.close_pool()
+
+
 def add_or_update_document_in_llm_index(sender, document, **kwargs):
     """
     Add or update a document in the LLM index when it is created or updated.

src/paperless/settings/custom.py

@@ -252,6 +252,9 @@ def parse_db_settings(data_dir: Path) -> dict[str, dict[str, Any]]:
                 "NAME": os.getenv("PAPERLESS_DBNAME", "paperless"),
                 "USER": os.getenv("PAPERLESS_DBUSER", "paperless"),
                 "PASSWORD": os.getenv("PAPERLESS_DBPASS", "paperless"),
+                # Validate pooled connections so a connection closed server-side
+                # is replaced rather than handed out as "the connection is closed".
+                "CONN_HEALTH_CHECKS": True,
             }
 
             base_options = {

src/paperless/tests/settings/test_custom_parsers.py

@@ -398,6 +398,7 @@ class TestParseDbSettings:
                 {
                     "default": {
                         "ENGINE": "django.db.backends.postgresql",
+                        "CONN_HEALTH_CHECKS": True,
                         "HOST": "localhost",
                         "NAME": "paperless",
                         "USER": "paperless",
@@ -426,6 +427,7 @@ class TestParseDbSettings:
                 {
                     "default": {
                         "ENGINE": "django.db.backends.postgresql",
+                        "CONN_HEALTH_CHECKS": True,
                         "HOST": "paperless-db-host",
                         "PORT": 1111,
                         "NAME": "customdb",
@@ -455,6 +457,7 @@ class TestParseDbSettings:
                 {
                     "default": {
                         "ENGINE": "django.db.backends.postgresql",
+                        "CONN_HEALTH_CHECKS": True,
                         "HOST": "pghost",
                         "NAME": "paperless",
                         "USER": "paperless",
@@ -485,6 +488,7 @@ class TestParseDbSettings:
                 {
                     "default": {
                         "ENGINE": "django.db.backends.postgresql",
+                        "CONN_HEALTH_CHECKS": True,
                         "HOST": "pghost",
                         "NAME": "paperless",
                         "USER": "paperless",