procrastinate/aiopg_connector.py

@@ -42,9 +42,17 @@ async def wrapped(*args, **kwargs):
 
 def wrap_query_exceptions(coro: CoroutineFunction) -> CoroutineFunction:
     """
-    Detect psycopg2 OperationalError's with a "server closed the connection
-    unexpectedly" message and retry a number of times.
+    Detect aiopg OperationalError's with a "server closed the connection unexpectedly"
+    message and retry a number of times.
 
+    This is to handle the case where the database connection (obtained from the pool)
+    was actually closed by the server. In this case, aiopg raises an OperationalError
+    with a "server closed the connection unexpectedly" message (and no pgcode) when the
+    connection is used for issuing a query. What we do is retry when an OperationalError
+    is raised, and until max_tries is reached.
+
+    max_tries is set to the max pool size + 1 (maxsize + 1) to handle the case where all
+    the connections we have in the pool were closed by the server.
     """
 
     @functools.wraps(coro)

procrastinate/psycopg2_connector.py

@@ -39,6 +39,14 @@ def wrap_query_exceptions(func: Callable) -> Callable:
     Detect psycopg2 InterfaceError's with a "connection already closed" message and
     retry a number of times.
 
+    This is to handle the case where the database connection (obtained from the pool)
+    was actually closed by the server. In this case, pyscopg2 raises an InterfaceError
+    with a "connection already closed" message (and no pgcode) when the connection is
+    used for issuing a query. What we do is retry when an InterfaceError is raised, and
+    until max_tries is reached.
+
+    max_tries is set to the max pool size + 1 (maxconn + 1) to handle the case where
+    all the connections we have in the pool were closed by the server.
     """
 
     @functools.wraps(func)