Support ignoring instance tags

datadog_checks_base/datadog_checks/base/checks/openmetrics/mixins.py

@@ -318,6 +318,19 @@ def create_scraper_configuration(self, instance=None):
         # Custom tags that will be sent with each metric
         config['custom_tags'] = instance.get('tags', [])
 
+        # Some tags can be ignored to reduce the cardinality.
+        # This can be useful for cost optimization in containerized environments when the openmetrics check is configured to collect custom metrics.
+        # Even when the Agent's Tagger is configured to add low-cardinality tags only, some tags can still generate unwanted metric contexts (e.g pod annotations as tags).
+        ignore_tags = instance.get('ignore_tags', default_instance.get('ignore_tags', []))
+        if ignore_tags:
+            ignored_tag_patterns = set()
+            for ignored_tag in ignore_tags:
+                ignored_tag_patterns.add(translate(ignored_tag))
+
+            if ignored_tag_patterns:
+                ignored_tags_re = compile('|'.join(ignored_tag_patterns))
+                config['custom_tags'] = [tag for tag in config['custom_tags'] if not ignored_tags_re.search(tag)]
+
         # Additional tags to be sent with each metric
         config['_metric_tags'] = []
 

datadog_checks_base/tests/test_openmetrics.py

@@ -2781,3 +2781,19 @@ def test_empty_namespace(aggregator, mocked_prometheus_check, text_data, ref_gau
     check.process_metric(ref_gauge, config)
 
     aggregator.assert_metric('process.vm.bytes', count=1)
+
+def test_ignore_tags(aggregator, mocked_prometheus_check, ref_gauge):
+    """
+    Test that tags matching ignored tag patterns are properly discarded.
+    """
+    check = mocked_prometheus_check
+    instance = copy.deepcopy(PROMETHEUS_CHECK_INSTANCE)
+    instance['tags'] = ['foo', 'foofoo', 'bar', 'bar:baz']
+    instance['ignore_tags'] = ['foo*', 'bar:baz']
+
+    config = check.get_scraper_config(instance)
+    config['_dry_run'] = False
+
+    check.process_metric(ref_gauge, config)
+
+    aggregator.assert_metric('prometheus.process.vm.bytes', tags=['bar'], count=1)