Try to fix the previous fix - once we've started working with a

connection in a transaction we can't just keep getting new connections,
this would be nonsensical ...

Author: ctheune

src/Products/ZPsycopgDA/db.py

@@ -45,6 +45,7 @@ class DB(TM):
     _p_oid = _p_changed = None
     _registered = False
     _sort_key = '1'
+    _conn = None
 
     def __init__(self, dsn, tilevel, typecasts, enc='utf-8'):
         self.dsn = dsn
@@ -59,6 +60,20 @@ def __init__(self, dsn, tilevel, typecasts, enc='utf-8'):
         self.make_mappings()
 
     def getconn(self, init='ignored'):
+        if self._conn:
+            # As the TM is a short-lived object, keep a reference to the connection - we really
+            # expect the pool's getconn() to reliably return the same connection anyway.
+            # This is needed to differentiate between an initial connection
+            # where its fine to keep going through the pool and fetching a new one
+            # versus an existing connection in a running transaction where e.g. a failure
+            # on the server side has aborted the transaction and we can't e.g. run `select 1`
+            # any longer but we also need the original connection to clean up correctly within
+            # Zope's transaction management.
+            # Theoretically this could be placed in `_register()` but I'm not 100% sure
+            # someone might be using getconn() without the TM integration thus going around
+            # `_register()` ...
+            return self._conn
+
         _pool = pool.getpool(self.dsn, create=True)
 
         # Loop to support cleaning up potentially all `maxconn` faulty
@@ -74,22 +89,21 @@ def getconn(self, init='ignored'):
             except (psycopg2.InterfaceError, psycopg2.OperationalError):
                 pool.putconn(self.dsn, conn, close=True)
 
-        if id(conn) in _pool._initialized:
-            return conn
+        if id(conn) not in _pool._initialized:
+            conn.set_session(isolation_level=int(self.tilevel))
+            conn.set_client_encoding(self.encoding)
+            for tc in self.typecasts:
+                register_type(tc, conn)
+            _pool._initialized.add(id(conn))
 
-        conn.set_session(isolation_level=int(self.tilevel))
-        conn.set_client_encoding(self.encoding)
-        for tc in self.typecasts:
-            register_type(tc, conn)
-        _pool._initialized.add(id(conn))
+        self._conn = conn
         return conn
 
     def putconn(self, close=False):
-        try:
-            conn = pool.getconn(self.dsn, False)
-        except AttributeError:
-            pass
-        pool.putconn(self.dsn, conn, close)
+        if not self._conn:
+            return
+        pool.putconn(self.dsn, self._conn, close)
+        self._conn = None
 
     def getcursor(self):
         conn = self.getconn()