Raise exception when num circuits exceeds backend max_circuits (#668)

* Added check that number of circuits does not exceed max_circuits of backend

* Release note

* Changed error message

* fix lint

---------

Co-authored-by: kevin-tian <kevin.tian@ibm.com>

qiskit_ibm_provider/ibm_backend.py

@@ -820,6 +820,11 @@ def _check_circuits_attributes(self, circuits: List[QuantumCircuit]) -> None:
             "https://qiskit.org/documentation/tutorials/circuits_advanced/05_pulse_gates.html` "
             "on how to use pulse gates."
         )
+        if len(circuits) > self._max_circuits:
+            raise IBMBackendValueError(
+                f"Number of circuits, {len(circuits)} exceeds the "
+                f"maximum for this backend, {self._max_circuits})"
+            )
         for circ in circuits:
             if isinstance(circ, Schedule):
                 raise IBMBackendValueError(schedule_error_msg)

releasenotes/notes/max_circuits-066b5eeebfe537a4.yaml

@@ -0,0 +1,5 @@
+---
+features:
+  - |
+    Raise an exception if the number of circuits passed to IBMBackend.run() exceeds
+    IBMBackend._max_circuits.

test/unit/test_backend.py

@@ -21,6 +21,7 @@
 from qiskit.providers.models import BackendStatus, BackendProperties
 
 from qiskit_ibm_provider.ibm_backend import IBMBackend
+from qiskit_ibm_provider.exceptions import IBMBackendValueError
 
 from ..ibm_test_case import IBMTestCase
 
@@ -324,3 +325,26 @@ def test_deepcopy(self):
         backend = self._create_dc_test_backend()
         backend_copy = copy.deepcopy(backend)
         self.assertEqual(backend_copy.name, backend.name)
+
+    def test_too_many_circuits(self):
+        """Test exception when number of circuits exceeds backend._max_circuits"""
+        model_backend = FakeManila()
+        backend = IBMBackend(
+            configuration=model_backend.configuration(),
+            provider=mock.MagicMock(),
+            api_client=None,
+            instance=None,
+        )
+        max_circs = backend.configuration().max_experiments
+
+        circs = []
+        for _ in range(max_circs + 1):
+            circ = QuantumCircuit(1)
+            circ.x(0)
+            circs.append(circ)
+        with self.assertRaises(IBMBackendValueError) as err:
+            backend.run(circs)
+        self.assertIn(
+            f"Number of circuits {max_circs+1} exceeds backend._max_circuits",
+            str(err.exception),
+        )