[fix] Graceful fallback to default timezone for invalid inputs

Modified MonitoringApiViewMixin to handle UnknownTimeZoneError by falling back to the system default timezone. Added strict regression tests in device and monitoring modules to verify chart data availability on fallback.

Author: UltraBot05

openwisp_monitoring/device/tests/test_api.py

@@ -640,7 +640,7 @@ def test_get_device_metrics_empty(self):
         self.assertEqual(response.status_code, 200)
         self.assertEqual(response.data["charts"], [])
 
-    def test_get_device_metrics_400_bad_timezone(self):
+    def test_get_device_metrics_bad_timezone_fallback(self):
         dd = self.create_test_data(no_resources=True)
         d = self.device_model.objects.get(pk=dd.pk)
         wrong_timezone_values = (
@@ -650,9 +650,10 @@ def test_get_device_metrics_400_bad_timezone(self):
         )
         for tz_value in wrong_timezone_values:
             url = "{0}&timezone={1}".format(self._url(d.pk, d.key), tz_value)
-            r = self.client.get(url)
-            self.assertEqual(r.status_code, 400)
-            self.assertIn("Unkown Time Zone", r.data)
+            response = self.client.get(url)
+            self.assertEqual(response.status_code, 200)
+            self.assertIn("charts", response.data)
+            self.assertGreater(len(response.data["charts"]), 0)
 
     def test_device_metrics_received_signal(self):
         d = self._create_device(organization=self._create_org())

openwisp_monitoring/monitoring/tests/test_api.py

@@ -679,6 +679,32 @@ def test_group_by_time(self):
             response = self.client.get(path, {"time": "3w"})
             self.assertEqual(response.status_code, 400)
 
+    def test_legacy_timezone_fallback(self):
+        """
+        Pass a legacy timezone, without crashing the API
+        with a 500 error when OS zoneinfo is missing. fix for monitoring#728
+        """
+        admin = self._create_admin()
+        self.client.force_login(admin)
+        path = reverse("monitoring_general:api_dashboard_timeseries")
+
+        # Test with a legacy timezone that isn't in modern tzdata
+        with self.subTest("Test legacy timezone normalization (Asia/Calcutta)"):
+            response = self.client.get(
+                path, {"timezone": "Asia/Calcutta", "time": "7d"}
+            )
+            self.assertEqual(response.status_code, 200)
+            self.assertIsInstance(response.data.get("charts"), list)
+
+        # Test with an invalid timezone to see if fallback works.
+        with self.subTest("Test invalid timezone fallback (Antarctica/Banana)"):
+            response = self.client.get(
+                path, {"timezone": "Antarctica/Banana", "time": "7d"}
+            )
+            self.assertEqual(response.status_code, 200)
+            self.assertIn("charts", response.data)
+            self.assertGreater(len(response.data["charts"]), 0)
+
     def test_organizations_list(self):
         path = reverse("monitoring_general:api_dashboard_timeseries")
         Organization.objects.all().delete()

openwisp_monitoring/utils.py

@@ -1,7 +1,9 @@
 import logging
-from functools import wraps
+from functools import lru_cache, wraps
 from time import sleep
+from zoneinfo import ZoneInfo, ZoneInfoNotFoundError
 
+from django.conf import settings
 from django.db import transaction
 
 from .settings import MONITORING_TIMESERIES_RETRY_OPTIONS
@@ -33,3 +35,42 @@ def wrapper(*args, **kwargs):
                     raise err
 
     return wrapper
+
+
+@lru_cache(maxsize=128)
+def normalize_timezone(tz_name):
+    """
+    Normalizes legacy timezones and verifies availability via zoneinfo.
+    """
+    if not tz_name:
+        return getattr(settings, "TIME_ZONE", "UTC")
+
+    # Mapping of legacy timezones
+    legacy_map = {
+        "Asia/Calcutta": "Asia/Kolkata",
+        "Asia/Saigon": "Asia/Ho_Chi_Minh",
+        "Asia/Katmandu": "Asia/Kathmandu",
+        "US/Eastern": "America/New_York",
+        "US/Pacific": "America/Los_Angeles",
+    }
+
+    normalized_tz = legacy_map.get(tz_name, tz_name)
+
+    # Verify timezone existence in a cross-platform way.
+    try:
+        ZoneInfo(normalized_tz)
+        if normalized_tz != tz_name:
+            logger.info(
+                f"Normalized deprecated timezone '{tz_name}' to '{normalized_tz}'"
+            )
+        return normalized_tz
+    except ZoneInfoNotFoundError:
+        pass
+
+    # Fallback if above is false
+    fallback = getattr(settings, "TIME_ZONE", "UTC")
+    logger.warning(
+        f"Timezone '{normalized_tz}' (original: '{tz_name}') not found in OS zoneinfo. "
+        f"Falling back to system TIME_ZONE '{fallback}'."
+    )
+    return fallback

openwisp_monitoring/views.py

@@ -14,6 +14,7 @@
 from swapper import load_model
 
 from .monitoring.exceptions import InvalidChartConfigException
+from .utils import normalize_timezone
 
 logger = logging.getLogger(__name__)
 
@@ -54,7 +55,8 @@ def get(self, request, *args, **kwargs):
         start_date = request.query_params.get("start", None)
         end_date = request.query_params.get("end", None)
         # try to read timezone
-        timezone = request.query_params.get("timezone", settings.TIME_ZONE)
+        raw_timezone = request.query_params.get("timezone", settings.TIME_ZONE)
+        timezone = normalize_timezone(raw_timezone)
         try:
             tz(timezone)
         except UnknownTimeZoneError: