feat(shared): add health checks and Prometheus metrics

1 files changed, 51 insertions, 0 deletions

diff --git a/shared/tests/test_metrics.py b/shared/tests/test_metrics.py
new file mode 100644
index 0000000..079f01c
--- /dev/null
+++ b/shared/tests/test_metrics.py
@@ -0,0 +1,51 @@
+"""Tests for Prometheus metrics utilities."""
+import pytest
+from prometheus_client import CollectorRegistry
+
+
+def make_metrics(service_name="test-service", registry=None):
+    from shared.metrics import ServiceMetrics
+    return ServiceMetrics(service_name, registry=registry)
+
+
+def test_metrics_creates_with_prefix():
+    """ServiceMetrics stores sanitized service name prefix."""
+    registry = CollectorRegistry()
+    m = make_metrics("my-service", registry=registry)
+    assert m.service_name == "my_service"
+
+
+def test_errors_total_increment():
+    """errors_total counter can be incremented with labels."""
+    registry = CollectorRegistry()
+    m = make_metrics("test-svc", registry=registry)
+    m.errors_total.labels(service="test_svc", error_type="timeout").inc()
+    assert m.errors_total.labels(service="test_svc", error_type="timeout")._value.get() == 1.0
+
+
+def test_events_processed_increment():
+    """events_processed counter can be incremented with labels."""
+    registry = CollectorRegistry()
+    m = make_metrics("test-svc", registry=registry)
+    m.events_processed.labels(service="test_svc", event_type="candle").inc(5)
+    assert m.events_processed.labels(service="test_svc", event_type="candle")._value.get() == 5.0
+
+
+def test_processing_seconds_observe():
+    """processing_seconds histogram can observe values."""
+    registry = CollectorRegistry()
+    m = make_metrics("test-svc", registry=registry)
+    m.processing_seconds.labels(service="test_svc").observe(0.5)
+    m.processing_seconds.labels(service="test_svc").observe(1.5)
+    # Sum should be 2.0
+    assert m.processing_seconds.labels(service="test_svc")._sum.get() == 2.0
+
+
+def test_service_up_gauge():
+    """service_up gauge can be set."""
+    registry = CollectorRegistry()
+    m = make_metrics("test-svc", registry=registry)
+    m.service_up.labels(service="test_svc").set(1)
+    assert m.service_up.labels(service="test_svc")._value.get() == 1.0
+    m.service_up.labels(service="test_svc").set(0)
+    assert m.service_up.labels(service="test_svc")._value.get() == 0.0