Adds metrics helper test fixture

tests/conftest.py

@@ -8,6 +8,7 @@
 import requests
 import yaml
 
+from metrics import MetricsClient
 from server import FileActivityService
 
 
@@ -132,6 +133,13 @@ def fact_config(request, monitored_dir, logs_dir):
     config_file.close()
 
 
+@pytest.fixture
+def metrics(fact_config):
+    """Client for taking metrics snapshots from the FACT endpoint."""
+    config, _ = fact_config
+    return MetricsClient(config['endpoint']['address'])
+
+
 @pytest.fixture
 def test_container(request, docker_client, monitored_dir, ignored_dir):
     """

tests/metrics.py

@@ -0,0 +1,112 @@
+import re
+
+import requests
+
+
+class MetricsSnapshot:
+    """
+    A parsed snapshot of Prometheus/OpenMetrics metrics.
+
+    Supports querying by metric name and labels:
+
+        ss = metrics.snapshot()
+        assert ss.get("rate_limiter_events", label="Dropped") == 5
+        assert ss.get("bpf_events", label="Added") > 0
+
+    Metric names are matched without the "stackrox_fact_" prefix and
+    "_total" counter suffix, so "rate_limiter_events" matches
+    "stackrox_fact_rate_limiter_events_total".
+    """
+
+    _PREFIX = "stackrox_fact_"
+    _TOTAL_SUFFIX = "_total"
+    _LINE_RE = re.compile(
+        r'^(?P<name>\S+?)(?:\{(?P<labels>[^}]*)\})?\s+(?P<value>\S+)$'
+    )
+    _LABEL_RE = re.compile(r'(\w+)="([^"]*)"')
+
+    def __init__(self, text):
+        self._entries = []
+        for line in text.splitlines():
+            if line.startswith('#') or not line.strip():
+                continue
+
+            m = self._LINE_RE.match(line)
+            if not m:
+                continue
+
+            name, raw, labels = m.group('name', 'value', 'labels')
+
+            value = float(raw) if '.' in raw else int(raw)
+            labels = dict(self._LABEL_RE.findall(labels or ''))
+
+            self._entries.append((name, labels, value))
+
+    @classmethod
+    def _normalize(cls, name):
+        if name.startswith(cls._PREFIX):
+            name = name[len(cls._PREFIX):]
+        if name.endswith(cls._TOTAL_SUFFIX):
+            name = name[:-len(cls._TOTAL_SUFFIX)]
+        return name
+
+    def get(self, metric, **labels):
+        """
+        Get the value of a metric, optionally filtered by labels.
+
+        Args:
+            metric: Metric name, with or without the "stackrox_fact_"
+                prefix and "_total" suffix.
+            **labels: Label key=value pairs to match.
+
+        Returns:
+            The metric value as int or float.
+
+        Raises:
+            KeyError: If no matching metric is found.
+            ValueError: If multiple metrics match.
+        """
+        target = self._normalize(metric)
+        matches = []
+        for name, entry_labels, value in self._entries:
+            if self._normalize(name) != target:
+                continue
+            if all(entry_labels.get(k) == v for k, v in labels.items()):
+                matches.append(value)
+
+        if not matches:
+            label_desc = ', '.join(f'{k}="{v}"' for k, v in labels.items())
+            key = f'{metric}{{{label_desc}}}' if label_desc else metric
+            available = '\n  '.join(
+                f'{n} {ls} = {v}' for n, ls, v in self._entries
+            )
+            raise KeyError(
+                f'metric {key!r} not found. Available:\n  {available}'
+            )
+        if len(matches) > 1:
+            raise ValueError(
+                f'{metric} matched {len(matches)} entries; use labels to '
+                f'narrow the result'
+            )
+        return matches[0]
+
+    def get_all(self, metric, **labels):
+        """Like get(), but returns a list of all matching values."""
+        target = self._normalize(metric)
+        return [
+            value for name, entry_labels, value in self._entries
+            if self._normalize(name) == target
+            and all(entry_labels.get(k) == v for k, v in labels.items())
+        ]
+
+
+class MetricsClient:
+    """Fetches metrics snapshots from a FACT endpoint."""
+
+    def __init__(self, address):
+        self._url = f'http://{address}/metrics'
+
+    def snapshot(self, timeout=30):
+        resp = requests.get(self._url, timeout=timeout)
+        resp.raise_for_status()
+        return MetricsSnapshot(resp.text)

tests/test_rate_limit.py

@@ -3,11 +3,11 @@
 from time import sleep
 
 import pytest
-import requests
 import yaml
 
 from event import Event, EventType, Process
 
+
 @pytest.fixture
 def rate_limited_config(fact, fact_config, monitored_dir):
     """
@@ -23,11 +23,10 @@ def rate_limited_config(fact, fact_config, monitored_dir):
     sleep(0.1)
     return config, config_file
 
-def test_rate_limit_drops_events(rate_limited_config, monitored_dir, server):
+def test_rate_limit_drops_events(rate_limited_config, monitored_dir, server, metrics):
     """
     Test that the rate limiter drops events when the rate limit is exceeded.
     """
-    config, _ = rate_limited_config
     num_files = 100
     start_time = time.time()
 
@@ -51,31 +50,19 @@ def test_rate_limit_drops_events(rate_limited_config, monitored_dir, server):
     assert received_count < num_files, \
         f'Expected rate limiting to drop some events, but received all {received_count}'
 
-    metrics_response = requests.get(f'http://{config["endpoint"]["address"]}/metrics')
-    assert metrics_response.status_code == 200
-
-    metrics_text = metrics_response.text
-    assert 'rate_limiter_events' in metrics_text, 'rate_limiter_events metric not found'
-
-    dropped_count = 0
-    for line in metrics_text.split('\n'):
-        if 'rate_limiter_events' in line and 'label="Dropped"' in line:
-            parts = line.split()
-            if len(parts) >= 2:
-                dropped_count = int(parts[1])
-                break
+    ss = metrics.snapshot()
+    dropped_count = ss.get("rate_limiter_events", label="Dropped")
 
     assert dropped_count > 0, 'Expected rate limiter to report dropped events in metrics'
 
     total_accounted = received_count + dropped_count
 
     assert total_accounted == num_files, 'Expected rate limiter to see all events'
 
-def test_rate_limit_unlimited(monitored_dir, server, fact_config):
+def test_rate_limit_unlimited(monitored_dir, server, metrics):
     """
     Test that the default config (rate_limit=0) allows all events through.
     """
-    config, _ = fact_config
     num_files = 20
     events = []
     process = Process.from_proc()
@@ -90,18 +77,8 @@ def test_rate_limit_unlimited(monitored_dir, server, fact_config):
 
     server.wait_events(events)
 
-    metrics_response = requests.get(f'http://{config["endpoint"]["address"]}/metrics')
-    assert metrics_response.status_code == 200
-
-    metrics_text = metrics_response.text
-
-    dropped_count = 0
-    for line in metrics_text.split('\n'):
-        if 'rate_limiter_events' in line and 'label="Dropped"' in line:
-            parts = line.split()
-            if len(parts) >= 2:
-                dropped_count = int(parts[1])
-                break
+    ss = metrics.snapshot()
+    dropped_count = ss.get("rate_limiter_events", label="Dropped")
 
     assert dropped_count == 0, \
         f'Expected no dropped events with unlimited rate limiting, but got {dropped_count}'