Use BaseStatMonitor to implement built-in downloader exception monitor

spidermon/contrib/scrapy/monitors.py

@@ -12,7 +12,6 @@
 SPIDERMON_MAX_ITEM_VALIDATION_ERRORS = "SPIDERMON_MAX_ITEM_VALIDATION_ERRORS"
 SPIDERMON_MAX_EXECUTION_TIME = "SPIDERMON_MAX_EXECUTION_TIME"
 SPIDERMON_MAX_RETRIES = "SPIDERMON_MAX_RETRIES"
-SPIDERMON_MAX_DOWNLOADER_EXCEPTIONS = "SPIDERMON_MAX_DOWNLOADER_EXCEPTIONS"
 SPIDERMON_MIN_SUCCESSFUL_REQUESTS = "SPIDERMON_MIN_SUCCESSFUL_REQUESTS"
 SPIDERMON_MAX_REQUESTS_ALLOWED = "SPIDERMON_MAX_REQUESTS_ALLOWED"
 
@@ -302,24 +301,26 @@ def test_check_unwanted_http_codes(self):
 
 
 @monitors.name("Downloader Exceptions monitor")
-class DownloaderExceptionMonitor(BaseScrapyMonitor):
-    """Check the amount of downloader exceptions (timeouts, rejected
-    connections, etc.).
-
-    You can configure it using the ``SPIDERMON_MAX_DOWNLOADER_EXCEPTIONS`` setting.
-    The default is ``-1`` which disables the monitor.
+class DownloaderExceptionMonitor(BaseStatMonitor):
+    """This monitor checks if the amount of downloader
+    exceptions (timeouts, rejected connections, etc.) is
+    lesser or equal to a specified threshold.
+
+    This amount is provided by ``downloader/exception_count``
+    value of your job statistics. If the value is not available
+    in the statistics (i.e., no exception was raised), the monitor
+    will pass.
+
+    Configure the threshold using the ``SPIDERMON_MAX_DOWNLOADER_EXCEPTIONS``
+    setting. There's **NO** default value for this setting.
+    If you try to use this monitor without a value specified, a
+    ``NotConfigured`` exception will be raised.
     """
 
-    @monitors.name("Should not hit the limit of downloader exceptions")
-    def test_maximum_downloader_exceptions(self):
-        exception_count = self.stats.get("downloader/exception_count", 0)
-        threshold = self.crawler.settings.getint(
-            SPIDERMON_MAX_DOWNLOADER_EXCEPTIONS, -1
-        )
-        if threshold < 0:
-            return
-        msg = "Too many downloader exceptions ({})".format(exception_count)
-        self.assertLessEqual(exception_count, threshold, msg=msg)
+    stat_name = "downloader/exception_count"
+    threshold_setting = "SPIDERMON_MAX_DOWNLOADER_EXCEPTIONS"
+    assert_type = "<="
+    fail_if_stat_missing = False
 
 
 @monitors.name("Retry Count monitor")

tests/contrib/scrapy/monitors/test_downloader_exception_monitor.py

@@ -1,55 +1,48 @@
+import pytest
+
 from spidermon.contrib.scrapy.monitors import (
     DownloaderExceptionMonitor,
-    SPIDERMON_MAX_DOWNLOADER_EXCEPTIONS,
 )
 from spidermon import MonitorSuite
+from spidermon.exceptions import NotConfigured
+from spidermon import settings
 
 
-def new_suite():
+@pytest.fixture
+def downloader_exception_suite():
     return MonitorSuite(monitors=[DownloaderExceptionMonitor])
 
 
-def test_downloader_exception_monitor_should_fail(make_data):
-    """Downloader Exceptions should fail if the downloader exceptions count is higher than expected"""
-
-    data = make_data({SPIDERMON_MAX_DOWNLOADER_EXCEPTIONS: 10})
-    runner = data.pop("runner")
-    suite = new_suite()
-    data["stats"]["downloader/exception_count"] = 12
-    runner.run(suite, **data)
-    assert (
-        "Too many downloader exceptions (12)" in runner.result.monitor_results[0].error
-    )
-
-
-def test_downloader_exception_monitor_should_pass_disabled(make_data):
-    """Downloader Exceptions should pass if the limit is negative"""
-
-    data = make_data({SPIDERMON_MAX_DOWNLOADER_EXCEPTIONS: -1})
-    runner = data.pop("runner")
-    suite = new_suite()
-    data["stats"]["downloader/exception_count"] = 99999
-    runner.run(suite, **data)
-    assert runner.result.monitor_results[0].error is None
-
-
-def test_downloader_exception_monitor_should_pass_default(make_data):
-    """Downloader Exceptions should pass if the limit is not set"""
-
+def test_needs_to_configure_downloader_exception_monitor(
+    make_data, downloader_exception_suite
+):
     data = make_data()
     runner = data.pop("runner")
-    suite = new_suite()
-    data["stats"]["downloader/exception_count"] = 99999
-    runner.run(suite, **data)
-    assert runner.result.monitor_results[0].error is None
+    data["crawler"].stats.set_value(DownloaderExceptionMonitor.stat_name, 10)
+    with pytest.raises(NotConfigured):
+        runner.run(downloader_exception_suite, **data)
+
+
+@pytest.mark.parametrize(
+    "value,threshold,expected_status",
+    [
+        (0, 100, settings.MONITOR.STATUS.SUCCESS),
+        (50, 100, settings.MONITOR.STATUS.SUCCESS),
+        (99, 100, settings.MONITOR.STATUS.SUCCESS),
+        (100, 100, settings.MONITOR.STATUS.SUCCESS),
+        (101, 100, settings.MONITOR.STATUS.FAILURE),
+        (1000, 1, settings.MONITOR.STATUS.FAILURE),
+    ],
+)
+def test_downloader_exception_monitor_validation(
+    make_data, downloader_exception_suite, value, threshold, expected_status
+):
+    data = make_data({DownloaderExceptionMonitor.threshold_setting: threshold})
+    runner = data.pop("runner")
 
+    data["stats"][DownloaderExceptionMonitor.stat_name] = value
 
-def test_downloader_exception_monitor_should_pass_under_limit(make_data):
-    """Downloader Exceptions should pass if the downloader exceptions count is not higher than expected"""
+    runner.run(downloader_exception_suite, **data)
 
-    data = make_data({SPIDERMON_MAX_DOWNLOADER_EXCEPTIONS: 10})
-    runner = data.pop("runner")
-    suite = new_suite()
-    data["stats"]["downloader/exception_count"] = 3
-    runner.run(suite, **data)
-    assert runner.result.monitor_results[0].error is None
+    assert len(runner.result.monitor_results) == 1
+    assert runner.result.monitor_results[0].status == expected_status