feat(api): complete Phase 2 - framework-less asyncio Ingestion API with backpressure and metrics

app/api/stats.py

@@ -0,0 +1,72 @@
+import asyncio
+import json
+import urllib.request
+import urllib.error
+from typing import Any, Dict
+
+from app.api.metrics import api_metrics
+from app.common.logging import setup_logger
+
+logger = setup_logger("ingestion-api")
+
+
+def _sync_fetch_worker_stats(url: str, timeout: float = 2.0) -> Dict[str, Any]:
+    req = urllib.request.Request(url, headers={"Accept": "application/json"})
+    with urllib.request.urlopen(req, timeout=timeout) as response:
+        if response.status == 200:
+            content = response.read().decode("utf-8")
+            return json.loads(content)
+        raise ValueError(f"Worker returned status {response.status}")
+
+
+async def get_aggregated_pipeline_stats(worker_stats_url: str) -> Dict[str, Any]:
+    """
+    Combines local Ingestion API statistics with remote runtime statistics
+    from the Processing Worker.
+    """
+    total_received = api_metrics.total_received
+
+    try:
+        loop = asyncio.get_running_loop()
+        worker_stats = await loop.run_in_executor(
+            None, _sync_fetch_worker_stats, worker_stats_url
+        )
+
+        pipeline_data = worker_stats.get("pipeline", {})
+        breakdown_data = worker_stats.get("breakdown", {})
+
+        return {
+            "pipeline": {
+                "total_received": total_received,
+                "total_processed": pipeline_data.get("total_processed", 0),
+                "total_dlq": pipeline_data.get("total_dlq", 0),
+                "in_flight_buffer": pipeline_data.get("in_flight_buffer", 0),
+                "last_flush_at": pipeline_data.get("last_flush_at"),
+            },
+            "breakdown": {
+                "by_service_type": breakdown_data.get("by_service_type", {}),
+                "by_radio_access_type": breakdown_data.get("by_radio_access_type", {}),
+                "dlq_by_reason": breakdown_data.get("dlq_by_reason", {}),
+            },
+        }
+    except Exception as e:
+        logger.warning(
+            f"Unable to fetch worker stats from {worker_stats_url}: {e}",
+            extra={"event": "worker_stats_fetch_failed"},
+        )
+        # Fallback when worker is temporarily unreachable
+        return {
+            "pipeline": {
+                "total_received": total_received,
+                "total_processed": 0,
+                "total_dlq": 0,
+                "in_flight_buffer": 0,
+                "last_flush_at": None,
+                "worker_status": "unreachable",
+            },
+            "breakdown": {
+                "by_service_type": {},
+                "by_radio_access_type": {},
+                "dlq_by_reason": {},
+            },
+        }