Added support for growing the pool back to the minimum number of

connections allowed in the pool when connections are killed or otherwise
become unusable; fixed bug when a dynamically sized pool is created with
an increment of zero and the pool needs to grow.

doc/src/release_notes.rst

@@ -18,6 +18,9 @@ Thin Mode Changes
 #)  Added support for shrinking the pool back to the minimum number of
     connections allowed in the pool when the pool is idle for
     :data:`ConnectionPool.timeout` seconds.
+#)  Added support for growing the pool back to the minimum number of
+    connections allowed in the pool when connections are killed or otherwise
+    made unusable.
 #)  Fixed bug using :attr:`Cursor.arraysize` for tuning data fetches from REF
     CURSORS.
 #)  Fixed bug connecting to databases with older 11g password verifiers
@@ -31,6 +34,8 @@ Thin Mode Changes
     listener redirects.
 #)  Fixed bug when executing PL/SQL with a large number of binds.
 #)  Fixed bug when using DRCP with Oracle Database 23c.
+#)  Fixed bug when a dynamically sized pool is created with an increment of
+    zero and the pool needs to grow.
 #)  Fixed bug when a connection is discarded from the pool during
     acquire() and the ping check fails due to the connection being dead.
 

src/oracledb/impl/base/pool_params.pyx

@@ -94,3 +94,8 @@ cdef class PoolParamsImpl(ConnectParamsImpl):
                                              &self.max_sessions_per_shard)
         _set_bool_param(args, "soda_metadata_cache", &self.soda_metadata_cache)
         _set_int_param(args, "ping_interval", &self.ping_interval)
+
+        # if the pool is dynamically sized (min != max) then ensure that the
+        # increment value is non-zero (as otherwise the pool would never grow!)
+        if self.max != self.min and self.increment == 0:
+            self.increment = 1

src/oracledb/impl/thin/pool.pyx

@@ -108,9 +108,6 @@ cdef class ThinPoolImpl(BasePoolImpl):
             list conn_impls_to_drop
             bint wait
 
-        # create the initial set of connections requested
-        self._create_conn_impls_helper(self.min)
-
         # create connections and close connections as needed
         while True:
             conn_impls_to_drop = []
@@ -119,9 +116,11 @@ cdef class ThinPoolImpl(BasePoolImpl):
 
             # determine if there is any work to do
             with self._condition:
-                if self._open and self._num_waiters > 0:
-                    open_count = self.get_open_count()
-                    num_conns = min(self.increment, self.max - open_count)
+                open_count = self.get_open_count()
+                if self._open and \
+                        (self._num_waiters > 0 or open_count < self.min):
+                    num_conns = max(self.min - open_count,
+                                    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 = []

tests/test_2400_pool.py

@@ -741,5 +741,18 @@ class TestCase(test_env.BaseTestCase):
         sid = conn.cursor().execute(sql).fetchone()[0]
         self.assertEqual(sid, sids[0], "not LIFO")
 
+    def test_2433_dynamic_pool_with_zero_increment(self):
+        "2433 - verify that dynamic pool cannot have an increment of zero"
+        pool = test_env.get_pool(min=1, max=3, increment=0)
+        self.assertEqual(pool.increment, 1)
+        conn1 = pool.acquire()
+        conn2 = pool.acquire()
+
+    def test_2434_static_pool_with_zero_increment(self):
+        "2434 - verify that static pool can have an increment of zero"
+        pool = test_env.get_pool(min=1, max=1, increment=0)
+        self.assertEqual(pool.increment, 0)
+        conn = pool.acquire()
+
 if __name__ == "__main__":
     test_env.run_test_cases()