[Operating] allow to identify DB connection "owner"

When having several different services running as part of a CRCon setup,
and trying to identify what component/service is using a particular
amount/number of DB connections is hard, apart from telling the total
number of open connections.

This commit aims to solve this issue by providing a proper
identification for a DB connection. It is composed out of the name of
the component that initiated the connection (e.g. gunicorn for the API
backend, auto_settings for the autosettings component, etc) together
with the server number.

The name is inferred from the application start commands to keep the API
for using the DB layer in the CRCon stable and to not bother callers to
provide any identification. If a component name cannot be inferred, a
generic "CRCon Generic" name is used.

The connection name will show up as the "application_name" in the
pg_stat_activity table of postgres, which can be quried with:
select * from pg_stat_activity;

Author: FlorianSW

rcon/models.py

@@ -1,10 +1,11 @@
 import logging
 import os
 import re
+import sys
 from collections import defaultdict
 from contextlib import contextmanager
 from datetime import datetime, timezone
-from typing import Any, Generator, List, Literal, Optional, Sequence, overload, TypedDict
+from typing import Any, Generator, List, Literal, Optional, Sequence, overload
 
 import pydantic
 from sqlalchemy import TIMESTAMP, Enum, ForeignKey, String, create_engine, select, text, JSON
@@ -73,6 +74,30 @@
 _ENGINE = None
 
 
+def _connection_name() -> str:
+    """
+    Identify what application component is using the SQLAlchemy session. This can be helpful when inspecting the connections
+    in Postgres to identify the purpose of a connection. The connection name will be used as the application_name connection
+    property and show up in the pg_stat_activity table:
+    select * from pg_stat_activity;
+
+    :return: str
+    """
+    args = sys.argv
+    name = 'CRCon Generic'
+    if "manage.py" not in args[0]:
+        # stuff like daphne, gunicorn (backend) etc
+        name = args[0]
+    elif len(args) > 1 and args[1] != "":
+        # Take whatever argument we passed to manage.py (for Supervisor services, such as log_loop, etc)
+        name = args[1]
+
+    name = (os.getenv("SERVER_NUMBER") or "") + name
+    # in the standard build (which we use in teh default docker setup) the name cannot exceed 63 chars (less than 64),
+    # see https://www.postgresql.org/docs/current/runtime-config-logging.html#GUC-APPLICATION-NAME
+    return name[:63]
+
+
 def get_engine():
     global _ENGINE
 
@@ -84,7 +109,7 @@ def get_engine():
         logger.error(msg)
         raise ValueError(msg)
 
-    _ENGINE = create_engine(url, echo=False)
+    _ENGINE = create_engine(url, echo=False, connect_args={"application_name":_connection_name()})
     return _ENGINE
 
 

rconweb/rconweb/settings.py

@@ -253,6 +253,9 @@
         "HOST": db_info["HOST"],
         "PORT": db_info["PORT"],
         "NAME": db_info["NAME"],
+        "OPTIONS": {
+            "application_name": (os.getenv("SERVER_NUMBER") or "") + "Django",
+        }
     }
 }