Fixed bug when connections are acquired from the pool with a different

class than the pool itself.

doc/src/release_notes.rst

@@ -35,6 +35,9 @@ Thin Mode Changes
     by a 16-byte unique identifier converted to base64 encoding.
 #)  Fixed bug when a dynamically sized pool is created with an ``increment``
     of zero and the pool needs to grow.
+#)  Fixed bug affecting connection reuse when connections were acquired from
+    the connection pool with a ``cclass`` different to the one used to
+    create the pool.
 #)  Fixed bug when a connection is discarded from the pool during
     :meth:`ConnectionPool.acquire()` and the ping check fails due to the
     connection being dead.

src/oracledb/impl/base/connect_params.pyx

@@ -785,12 +785,13 @@ cdef class Description:
             temp_parts.append(f"(SID={self.sid})")
         if self.server_type is not None:
             temp_parts.append(f"(SERVER={self.server_type})")
+        if cid is not None:
+            temp_parts.append(f"(CID={cid})")
+        else:
             if self.cclass is not None:
                 temp_parts.append(f"(POOL_CONNECTION_CLASS={self.cclass})")
             if self.purity != 0:
                 temp_parts.append(f"(POOL_PURITY={self.purity})")
-        if cid is not None:
-            temp_parts.append(f"(CID={cid})")
         if self.connection_id is not None:
             temp_parts.append(f"(CONNECTION_ID={self.connection_id})")
         if temp_parts:

src/oracledb/impl/thin/connection.pyx

@@ -68,6 +68,7 @@ cdef class ThinConnImpl(BaseConnImpl):
         int _dbobject_type_cache_num
         bytes _combo_key
         str _connection_id
+        bint _is_pool_extra
 
     def __init__(self, str dsn, ConnectParamsImpl params):
         if not HAS_CRYPTOGRAPHY:

src/oracledb/impl/thin/pool.pyx

@@ -36,12 +36,14 @@ cdef class ThinPoolImpl(BasePoolImpl):
         list _free_used_conn_impls
         list _busy_conn_impls
         list _conn_impls_to_drop
+        list _extra_conn_impls
         uint32_t _getmode
         uint32_t _stmt_cache_size
         uint32_t _timeout
         uint32_t _max_lifetime_session
         uint32_t _num_waiters
         uint32_t _auth_mode
+        uint32_t _num_to_create
         int _ping_interval
         object _wait_timeout
         object _bg_exc
@@ -72,6 +74,7 @@ cdef class ThinPoolImpl(BasePoolImpl):
         self._free_used_conn_impls = []
         self._busy_conn_impls = []
         self._conn_impls_to_drop = []
+        self._extra_conn_impls = []
         self._auth_mode = constants.AUTH_MODE_DEFAULT
         self._open = True
         self._condition = threading.Condition()
@@ -105,32 +108,34 @@ cdef class ThinPoolImpl(BasePoolImpl):
         needed. The thread terminates automatically when the pool is closed.
         """
         cdef:
-            uint32_t num_conns, open_count
+            uint32_t open_count, num_to_create
             list conn_impls_to_drop
             bint wait
 
         # create connections and close connections as needed
         while True:
             conn_impls_to_drop = []
-            num_conns = 0
             wait = True
 
             # determine if there is any work to do
             with self._condition:
                 open_count = self.get_open_count()
-                if self._open and \
+                if self._open and self._num_to_create == 0:
-                        (self._num_waiters > 0 or open_count < self.min):
+                    if open_count < self.min:
-                    num_conns = max(self.min - open_count,
+                        self._num_to_create = self.min - open_count
-                                    min(self.increment, self.max - open_count))
+                    elif self._num_waiters > 0:
+                        self._num_to_create = min(self.increment,
+                                              self.max - open_count)
                 if not self._open or self._bg_exc is None:
                     conn_impls_to_drop = self._conn_impls_to_drop
                     self._conn_impls_to_drop = []
 
             # create connections, if needed
-            if num_conns > 0:
+            if self._num_to_create > 0:
                 wait = False
-                self._create_conn_impls_helper(num_conns)
+                num_to_create = self._num_to_create
-                if num_conns > 1:
+                self._create_conn_impls_helper()
+                if num_to_create > 1:
                     self._check_timeout()
 
             # close connections, if needed
@@ -161,7 +166,7 @@ cdef class ThinPoolImpl(BasePoolImpl):
                                                  self._process_timeout)
             self._timer_thread.start()
 
-    cdef int _create_conn_impls_helper(self, uint32_t num_conns) except -1:
+    cdef int _create_conn_impls_helper(self) except -1:
         """
         Helper method which creates the specified number of connections. In
         order to prevent the thread from dying, exceptions are captured and
@@ -171,8 +176,7 @@ cdef class ThinPoolImpl(BasePoolImpl):
         cdef:
             ThinConnImpl conn_impl
             object exc
-            uint32_t i
+        while self._num_to_create > 0:
-        for i in range(num_conns):
             conn_impl = None
             try:
                 conn_impl = self._create_conn_impl()
@@ -182,6 +186,7 @@ cdef class ThinPoolImpl(BasePoolImpl):
                 if conn_impl is not None:
                     if self._open:
                         self._free_new_conn_impls.append(conn_impl)
+                        self._num_to_create -= 1
                     else:
                         conn_impl._force_close()
                         break
@@ -215,7 +220,7 @@ cdef class ThinPoolImpl(BasePoolImpl):
                     self._bg_exc = e
 
     cdef object _get_connection(self, bint wants_new, bint cclass_matches,
-                                str cclass):
+                                str cclass, bint* must_reconnect):
         """
         Returns a connection from the pool if one is available. If one is not
         available and a new connection needs to be created, the value True is
@@ -223,6 +228,7 @@ cdef class ThinPoolImpl(BasePoolImpl):
         """
         cdef:
             ThinConnImpl conn_impl
+            uint32_t open_count
             object exc
             ssize_t i
 
@@ -233,45 +239,51 @@ cdef class ThinPoolImpl(BasePoolImpl):
             raise exc
 
         # check for an available used connection (only permitted if a new
-        # connection is not required); in addition, if the cclass does not
+        # connection is not required); in addition, ensure that the cclass
-        # match, a new connection will be forced if one cannot be found
+        # matches
         if not wants_new and self._free_used_conn_impls:
-            if cclass_matches:
+            for i, conn_impl in enumerate(reversed(self._free_used_conn_impls)):
-                conn_impl = self._free_used_conn_impls.pop()
+                if cclass is None or conn_impl._cclass == cclass:
-                self._busy_conn_impls.append(conn_impl)
+                    i = len(self._free_used_conn_impls) - i - 1
-                return conn_impl
-            i = len(self._free_used_conn_impls) - 1
-            while i >= 0:
-                conn_impl = self._free_used_conn_impls[i]
-                if conn_impl._cclass == cclass:
                     self._free_used_conn_impls.pop(i)
-                    self._busy_conn_impls.append(conn_impl)
                     return conn_impl
-                i -= 1
 
         # check for an available new connection (only permitted if the cclass
         # matches)
         if cclass_matches and self._free_new_conn_impls:
-            conn_impl = self._free_new_conn_impls.pop()
+            return self._free_new_conn_impls.pop()
-            self._busy_conn_impls.append(conn_impl)
-            return conn_impl
 
-        # no connections are immediately available; if a brand new connection
+        # no matching connections are available; if the pool is full, see if
-        # is desired, the cclass doesn't match, or the pool is full and a
+        # any connections are available and if so, return one of them (but let
-        # getmode of FORCE has been specified, force the creation of a new
+        # the caller know that it must be discarded and a new connection
-        # connection
+        # created); if no connections are available to replace but the force
-        if wants_new or not cclass_matches \
+        # get flag is set, return True which signals that a new "extra"
-                or (self._force_get and self.get_open_count() >= self.max):
+        # connection will be created; a new "extra" connection is also created
+        # if the connection class doesn't match, since the background thread
+        # will only create connections with the pool's connection class
+        open_count = self.get_open_count() + self._num_to_create
+        if open_count >= self.max:
+            if self._free_new_conn_impls:
+                must_reconnect[0] = True
+                return self._free_new_conn_impls.pop()
+            elif self._free_used_conn_impls:
+                must_reconnect[0] = True
+                return self._free_used_conn_impls.pop()
+            elif self._force_get:
+                return True
+        elif not cclass_matches:
             return True
 
-        # wake up the background thread to create a connection
+        # wake up the background thread to create a connection if the pool
+        # is not already full
+        if open_count < self.max:
             with self._bg_thread_condition:
                 self._bg_thread_condition.notify()
 
     cdef ThinConnImpl _acquire_helper(self, ConnectParamsImpl params):
         cdef:
             ConnectParamsImpl creation_params = self.connect_params
-            bint wants_new, cclass_matches
+            bint wants_new, cclass_matches, must_reconnect = False
             object result, predicate
             str pool_cclass, cclass
             ThinConnImpl conn_impl
@@ -284,7 +296,7 @@ cdef class ThinPoolImpl(BasePoolImpl):
         wants_new = (params._default_description.purity == PURITY_NEW)
         cclass_matches = (cclass is None or cclass == pool_cclass)
         predicate = lambda: self._get_connection(wants_new, cclass_matches,
-                                                 cclass)
+                                                 cclass, &must_reconnect)
 
         # get a connection from the pool; if one is not immediately available,
         # wait as long as requested for one to be made available.
@@ -298,19 +310,20 @@ cdef class ThinPoolImpl(BasePoolImpl):
             if result is None:
                 errors._raise_err(errors.ERR_POOL_NO_CONNECTION_AVAILABLE)
             if isinstance(result, ThinConnImpl):
+                self._busy_conn_impls.append(result)
+                if not must_reconnect:
                     return result
 
         # no connection was returned from the pool so a new connection needs to
         # be created
         conn_impl = self._create_conn_impl(params=params)
         with self._condition:
-            if self.get_open_count() < self.max:
+            if must_reconnect:
-                self._busy_conn_impls.append(conn_impl)
+                self._busy_conn_impls.remove(result)
-            elif self._free_used_conn_impls:
-                self._drop_conn_impl(self._free_used_conn_impls.pop(0))
                 self._busy_conn_impls.append(conn_impl)
             else:
-                conn_impl._pool = None
+                conn_impl._is_pool_extra = True
+                self._extra_conn_impls.append(conn_impl)
         return conn_impl
 
     def _process_timeout(self):
@@ -328,20 +341,37 @@ cdef class ThinPoolImpl(BasePoolImpl):
         """
         Returns the connection to the pool. If the connection was closed for
         some reason it will be dropped; otherwise, it will be returned to the
-        list of connections available for further use.
+        list of connections available for further use. If an "extra" connection
+        was created (because the pool has a mode of "force" get or because a
+        different connection class than that used by the pool was requested)
+        then it will be added to the pool or will replace an unused new
+        connection or will be discarded depending on the current pool size.
         """
         cdef:
+            bint is_open = conn_impl._protocol._socket is not None
             ThinDbObjectTypeCache type_cache
+            uint32_t open_count
             int cache_num
         with self._condition:
             if conn_impl._dbobject_type_cache_num > 0:
                 cache_num = conn_impl._dbobject_type_cache_num
                 type_cache = get_dbobject_type_cache(cache_num)
                 type_cache._clear_meta_cursor()
-            if conn_impl._protocol._socket is not None:
+            if conn_impl._is_pool_extra:
+                self._extra_conn_impls.remove(conn_impl)
+                conn_impl._is_pool_extra = False
+                open_count = self.get_open_count() + self._num_to_create
+                if is_open and open_count >= self.max:
+                    if self._free_new_conn_impls and open_count == self.max:
+                        self._drop_conn_impl(self._free_new_conn_impls.pop(0))
+                    else:
+                        self._drop_conn_impl(conn_impl)
+                        is_open = False
+            else:
+                self._busy_conn_impls.remove(conn_impl)
+            if is_open:
                 self._free_used_conn_impls.append(conn_impl)
                 conn_impl._time_in_pool = time.monotonic()
-            self._busy_conn_impls.remove(conn_impl)
             self._check_timeout()
             self._condition.notify()
 
@@ -436,7 +466,8 @@ cdef class ThinPoolImpl(BasePoolImpl):
             self._open = False
             for lst in (self._free_used_conn_impls,
                         self._free_new_conn_impls,
-                        self._busy_conn_impls):
+                        self._busy_conn_impls,
+                        self._extra_conn_impls):
                 self._conn_impls_to_drop.extend(lst)
                 for conn_impl in lst:
                     conn_impl._pool = None

tests/test_2400_pool.py

@@ -754,5 +754,34 @@ class TestCase(test_env.BaseTestCase):
         self.assertEqual(pool.increment, 0)
         conn = pool.acquire()
 
+    def test_2435_acquire_with_different_cclass(self):
+        "2435 - verify that connection with different cclass is reused"
+        cclass = "cclass2435"
+        pool = test_env.get_pool(min=1, max=1)
+        # ignore the first acquire which, depending on the speed with which the
+        # minimum connections are created, may create a connection that is
+        # discarded; instead, use the second acquire which should remain in the
+        # pool
+        with pool.acquire(cclass=cclass) as conn:
+            pass
+        with pool.acquire(cclass=cclass) as conn:
+            with conn.cursor() as cursor:
+                cursor.execute("""
+                    select
+                        dbms_debug_jdwp.current_session_id || ',' ||
+                        dbms_debug_jdwp.current_session_serial
+                    from dual""")
+                sid_serial, = cursor.fetchone()
+        with pool.acquire(cclass=cclass) as conn:
+            with conn.cursor() as cursor:
+                cursor.execute("""
+                    select
+                        dbms_debug_jdwp.current_session_id || ',' ||
+                        dbms_debug_jdwp.current_session_serial
+                    from dual""")
+                next_sid_serial, = cursor.fetchone()
+                self.assertEqual(next_sid_serial, sid_serial)
+        self.assertEqual(pool.opened, 1)
+
 if __name__ == "__main__":
     test_env.run_test_cases()