Add setting to allow monitor not fail if stat is not present

spidermon/contrib/scrapy/monitors.py

@@ -74,7 +74,26 @@ class MyCustomStatMonitor(BaseStatMonitor):
 
             def get_threshold(self):
                 item_scraped_count = self.stats.get("item_scraped_count")
-                return item_scraped_count * 0.01"""
+                return item_scraped_count * 0.01
+
+    By default, if the stat can't be found in job statistics, the monitor will fail.
+    If you want the monitor to be skipped in that case, you should set ``fail_if_stat_missing``
+    attribute as ``False``.
+
+
+    The following monitor will not fail if the job doesn't have a ``numerical_job_statistic``
+    value in its statistics:
+
+    .. code-block:: python
+
+        class MyCustomStatMonitor(BaseStatMonitor):
+            stat_name = "numerical_job_statistic"
+            threshold_setting = "CUSTOM_STAT_THRESHOLD"
+            assert_type = ">="
+            fail_if_stat_missing = False
+    """
+
+    fail_if_stat_missing = True
 
     def run(self, result):
         has_threshold_config = any(
@@ -113,6 +132,14 @@ def test_stat_monitor(self):
             "!=": self.assertNotEqual,
         }
         threshold = self._get_threshold_value()
+
+        if self.stat_name not in self.stats:
+            message = f"Unable to find '{self.stat_name}' in job stats."
+            if self.fail_if_stat_missing:
+                self.fail(message)
+            else:
+                self.skipTest(message)
+
         value = self.stats.get(self.stat_name)
 
         assertion_method = assertions.get(self.assert_type)

spidermon/results/monitor.py

@@ -107,7 +107,7 @@ def addFailure(self, test, error):
     @monitors_step_required
     def addSkip(self, test, reason):
         super().addSkip(test, reason)
-        self.step[test].status = settings.MONITOR.STATUS.FAILURE
+        self.step[test].status = settings.MONITOR.STATUS.SKIPPED
         self.step[test].reason = reason
 
     @monitors_step_required

tests/contrib/scrapy/monitors/test_base_stat_monitor.py

@@ -115,3 +115,54 @@ class TestBaseStatMonitor(BaseStatMonitor):
         == f"Expecting '{TestBaseStatMonitor.stat_name}' to be '{TestBaseStatMonitor.assert_type}' "
         f"to '{expected_threshold}'. Current value: '{obtained_value}'",
     )
+
+
+def test_fail_if_stat_can_not_be_found(make_data):
+    class TestBaseStatMonitor(BaseStatMonitor):
+        stat_name = "test_statistic"
+        threshold_setting = "THRESHOLD_SETTING"
+        assert_type = ">="
+
+    data = make_data({"THRESHOLD_SETTING": 100})
+    runner = data.pop("runner")
+    data["stats"] = {"other_stats": 1}
+    monitor_suite = MonitorSuite(monitors=[TestBaseStatMonitor])
+
+    runner.run(monitor_suite, **data)
+    assert runner.result.monitor_results[0].status == settings.MONITOR.STATUS.FAILURE
+
+
+def test_success_if_stat_can_not_be_found_but_monitor_configured_to_not_ignore_it(
+    make_data,
+):
+    class TestBaseStatMonitor(BaseStatMonitor):
+        stat_name = "test_statistic"
+        threshold_setting = "THRESHOLD_SETTING"
+        assert_type = ">="
+        fail_if_stat_missing = True
+
+    data = make_data({"THRESHOLD_SETTING": 100})
+    runner = data.pop("runner")
+    data["stats"] = {"other_stats": 1}
+    monitor_suite = MonitorSuite(monitors=[TestBaseStatMonitor])
+
+    runner.run(monitor_suite, **data)
+    assert runner.result.monitor_results[0].status == settings.MONITOR.STATUS.FAILURE
+
+
+def test_skipped_if_stat_can_not_be_found_but_monitor_configured_to_be_ignore(
+    make_data,
+):
+    class TestBaseStatMonitor(BaseStatMonitor):
+        stat_name = "test_statistic"
+        threshold_setting = "THRESHOLD_SETTING"
+        assert_type = ">="
+        fail_if_stat_missing = False
+
+    data = make_data({"THRESHOLD_SETTING": 100})
+    runner = data.pop("runner")
+    data["stats"] = {"other_stats": 1}
+    monitor_suite = MonitorSuite(monitors=[TestBaseStatMonitor])
+
+    runner.run(monitor_suite, **data)
+    assert runner.result.monitor_results[0].status == settings.MONITOR.STATUS.SKIPPED