2 files changed, 117 insertions, 0 deletions
diff --git a/shared/src/shared/healthcheck.py b/shared/src/shared/healthcheck.py
new file mode 100644
index 0000000..8294294
--- /dev/null
+++ b/shared/src/shared/healthcheck.py
@@ -0,0 +1,76 @@
+"""Health check HTTP server with Prometheus metrics endpoint."""
+from __future__ import annotations
+
+import time
+from typing import Any, Callable, Awaitable
+
+from aiohttp import web
+from prometheus_client import CollectorRegistry, REGISTRY, generate_latest, CONTENT_TYPE_LATEST
+
+
+class HealthCheckServer:
+    """Lightweight aiohttp server exposing /health and /metrics."""
+
+    def __init__(
+        self,
+        service_name: str,
+        port: int = 8080,
+        *,
+        registry: CollectorRegistry | None = None,
+    ) -> None:
+        self.service_name = service_name
+        self.port = port
+        self._checks: dict[str, Callable[[], Awaitable[bool]]] = {}
+        self._start_time = time.monotonic()
+        self._registry = registry or REGISTRY
+
+    def register_check(self, name: str, check_fn: Callable[[], Awaitable[bool]]) -> None:
+        """Register a named async health check function."""
+        self._checks[name] = check_fn
+
+    async def run_checks(self) -> dict[str, Any]:
+        """Execute all registered checks and return a status dict."""
+        checks: dict[str, str] = {}
+        all_ok = True
+
+        for name, fn in self._checks.items():
+            try:
+                result = await fn()
+                if result:
+                    checks[name] = "ok"
+                else:
+                    checks[name] = "fail"
+                    all_ok = False
+            except Exception as exc:
+                checks[name] = f"fail: {exc}"
+                all_ok = False
+
+        return {
+            "status": "ok" if all_ok else "degraded",
+            "service": self.service_name,
+            "uptime_seconds": round(time.monotonic() - self._start_time, 2),
+            "checks": checks,
+        }
+
+    async def _handle_health(self, request: web.Request) -> web.Response:
+        """GET /health — JSON health status."""
+        result = await self.run_checks()
+        status_code = 200 if result["status"] == "ok" else 503
+        return web.json_response(result, status=status_code)
+
+    async def _handle_metrics(self, request: web.Request) -> web.Response:
+        """GET /metrics — Prometheus text exposition."""
+        output = generate_latest(self._registry)
+        return web.Response(body=output, content_type=CONTENT_TYPE_LATEST)
+
+    async def start(self) -> web.AppRunner:
+        """Create and start the aiohttp application, returning the runner."""
+        app = web.Application()
+        app.router.add_get("/health", self._handle_health)
+        app.router.add_get("/metrics", self._handle_metrics)
+
+        runner = web.AppRunner(app)
+        await runner.setup()
+        site = web.TCPSite(runner, "0.0.0.0", self.port)
+        await site.start()
+        return runner
diff --git a/shared/src/shared/metrics.py b/shared/src/shared/metrics.py
new file mode 100644
index 0000000..3b00c5d
--- /dev/null
+++ b/shared/src/shared/metrics.py
@@ -0,0 +1,41 @@
+"""Prometheus metrics for trading platform services."""
+from __future__ import annotations
+
+from prometheus_client import Counter, Gauge, Histogram, CollectorRegistry, REGISTRY
+
+
+class ServiceMetrics:
+    """Creates Prometheus metrics with a service-name prefix."""
+
+    def __init__(self, service_name: str, *, registry: CollectorRegistry | None = None) -> None:
+        self.service_name = service_name.replace("-", "_")
+        reg = registry or REGISTRY
+        prefix = self.service_name
+
+        self.errors_total = Counter(
+            f"{prefix}_errors_total",
+            "Total error count",
+            labelnames=["service", "error_type"],
+            registry=reg,
+        )
+
+        self.events_processed = Counter(
+            f"{prefix}_events_processed_total",
+            "Total events processed",
+            labelnames=["service", "event_type"],
+            registry=reg,
+        )
+
+        self.processing_seconds = Histogram(
+            f"{prefix}_processing_seconds",
+            "Processing duration in seconds",
+            labelnames=["service"],
+            registry=reg,
+        )
+
+        self.service_up = Gauge(
+            f"{prefix}_service_up",
+            "Whether the service is up (1) or down (0)",
+            labelnames=["service"],
+            registry=reg,
+        )