Handle maintenance message

qiskit_ibm_runtime/api/session.py

@@ -35,7 +35,6 @@
 STATUS_FORCELIST = (
     500,  # General server error
     502,  # Bad Gateway
-    503,  # Service Unavailable
     504,  # Gateway Timeout
     520,  # Cloudflare general error
     521,  # Cloudflare web server is down
@@ -348,6 +347,12 @@ def request(  # type: ignore[override]
                     message += f". {ex.response.text}"
             if status_code == 401:
                 raise IBMNotAuthorizedError(message) from ex
+            if status_code == 503:  # Planned maintenance outage
+                raise RequestsApiError(
+                    "Unexpected response received from server. Please check if the service "
+                    "is in maintenance mode "
+                    f"https://docs.quantum.ibm.com/announcements/service-alerts {message}"
+                )
             raise RequestsApiError(message, status_code) from ex
 
         return response

qiskit_ibm_runtime/qiskit_runtime_service.py

@@ -12,7 +12,6 @@
 
 """Qiskit runtime service."""
 
-import json
 import logging
 import traceback
 import warnings
@@ -35,7 +34,7 @@
 from .api.exceptions import RequestsApiError
 from .constants import QISKIT_IBM_RUNTIME_API_URL
 from .exceptions import IBMNotAuthorizedError, IBMInputValueError, IBMAccountError
-from .exceptions import IBMRuntimeError, RuntimeProgramNotFound, RuntimeJobNotFound, IBMApiError
+from .exceptions import IBMRuntimeError, RuntimeProgramNotFound, RuntimeJobNotFound
 from .hub_group_project import HubGroupProject  # pylint: disable=cyclic-import
 from .utils.result_decoder import ResultDecoder
 from .runtime_job import RuntimeJob
@@ -161,14 +160,8 @@ def __init__(
             self._client_params.url = auth_client.current_service_urls()["services"]["runtime"]
             self._client_params.token = auth_client.current_access_token()
             self._api_client = RuntimeClient(self._client_params)
-            try:
-                self._hgps = self._initialize_hgps(auth_client)
-            except json.decoder.JSONDecodeError:
-                raise IBMApiError(
-                    "Unexpected response received from server. "
-                    "Please check if the service is in maintenance mode "
-                    "https://docs.quantum.ibm.com/announcements/service-alerts."
-                )
+            self._hgps = self._initialize_hgps(auth_client)
+
             self._backend_allowed_list = sorted(
                 set(sum([hgp.backends for hgp in self._hgps.values()], []))
             )
@@ -275,6 +268,7 @@ def _authenticate_ibm_quantum_account(self, client_params: ClientParameters) ->
             Authentication client.
         """
         version_info = self._check_api_version(client_params)
+
         # Check the URL is a valid authentication URL.
         if not version_info["new_api"] or "api-auth" not in version_info:
             raise IBMInputValueError(

release-notes/unreleased/2100.other.rst

@@ -0,0 +1,2 @@
+When there is a maintenance outage, an approproate error message will be raised when trying 
+to initialize the ``QiskitRuntimeService``.