[loop-cycle-1658] feat: provider health history endpoint (#457) (#611)

src/infrastructure/router/__init__.py

@@ -2,6 +2,7 @@
 
 from .api import router
 from .cascade import CascadeRouter, Provider, ProviderStatus, get_router
+from .history import HealthHistoryStore, get_history_store
 
 __all__ = [
     "CascadeRouter",
@@ -9,4 +10,6 @@ __all__ = [
     "ProviderStatus",
     "get_router",
     "router",
+    "HealthHistoryStore",
+    "get_history_store",
 ]

src/infrastructure/router/api.py

@@ -8,6 +8,7 @@ from fastapi import APIRouter, Depends, HTTPException
 from pydantic import BaseModel
 
 from .cascade import CascadeRouter, get_router
+from .history import HealthHistoryStore, get_history_store
 
 logger = logging.getLogger(__name__)
 router = APIRouter(prefix="/api/v1/router", tags=["router"])
@@ -199,6 +200,17 @@ async def reload_config(
         raise HTTPException(status_code=500, detail=f"Reload failed: {exc}") from exc
 
 
+@router.get("/history")
+async def get_history(
+    hours: int = 24,
+    store: Annotated[HealthHistoryStore, Depends(get_history_store)] = None,
+) -> list[dict[str, Any]]:
+    """Get provider health history for the last N hours."""
+    if store is None:
+        store = get_history_store()
+    return store.get_history(hours=hours)
+
+
 @router.get("/config")
 async def get_config(
     cascade: Annotated[CascadeRouter, Depends(get_cascade_router)],

src/infrastructure/router/history.py

@@ -0,0 +1,152 @@
+"""Provider health history — time-series snapshots for dashboard visualization."""
+
+import asyncio
+import logging
+import sqlite3
+from datetime import UTC, datetime, timedelta
+from pathlib import Path
+
+logger = logging.getLogger(__name__)
+
+_store: "HealthHistoryStore | None" = None
+
+
+class HealthHistoryStore:
+    """Stores timestamped provider health snapshots in SQLite."""
+
+    def __init__(self, db_path: str = "data/router_history.db") -> None:
+        self.db_path = db_path
+        if db_path != ":memory:":
+            Path(db_path).parent.mkdir(parents=True, exist_ok=True)
+        self._conn = sqlite3.connect(db_path, check_same_thread=False)
+        self._conn.row_factory = sqlite3.Row
+        self._init_schema()
+        self._bg_task: asyncio.Task | None = None
+
+    def _init_schema(self) -> None:
+        self._conn.execute("""
+            CREATE TABLE IF NOT EXISTS snapshots (
+                id INTEGER PRIMARY KEY AUTOINCREMENT,
+                timestamp TEXT NOT NULL,
+                provider_name TEXT NOT NULL,
+                status TEXT NOT NULL,
+                error_rate REAL NOT NULL,
+                avg_latency_ms REAL NOT NULL,
+                circuit_state TEXT NOT NULL,
+                total_requests INTEGER NOT NULL
+            )
+        """)
+        self._conn.execute("""
+            CREATE INDEX IF NOT EXISTS idx_snapshots_ts
+            ON snapshots(timestamp)
+        """)
+        self._conn.commit()
+
+    def record_snapshot(self, providers: list[dict]) -> None:
+        """Record a health snapshot for all providers."""
+        ts = datetime.now(UTC).isoformat()
+        rows = [
+            (
+                ts,
+                p["name"],
+                p["status"],
+                p["error_rate"],
+                p["avg_latency_ms"],
+                p["circuit_state"],
+                p["total_requests"],
+            )
+            for p in providers
+        ]
+        self._conn.executemany(
+            """INSERT INTO snapshots
+               (timestamp, provider_name, status, error_rate,
+                avg_latency_ms, circuit_state, total_requests)
+               VALUES (?, ?, ?, ?, ?, ?, ?)""",
+            rows,
+        )
+        self._conn.commit()
+
+    def get_history(self, hours: int = 24) -> list[dict]:
+        """Return snapshots from the last N hours, grouped by timestamp."""
+        cutoff = (datetime.now(UTC) - timedelta(hours=hours)).isoformat()
+        rows = self._conn.execute(
+            """SELECT timestamp, provider_name, status, error_rate,
+                      avg_latency_ms, circuit_state, total_requests
+               FROM snapshots WHERE timestamp >= ? ORDER BY timestamp""",
+            (cutoff,),
+        ).fetchall()
+
+        # Group by timestamp
+        snapshots: dict[str, list[dict]] = {}
+        for row in rows:
+            ts = row["timestamp"]
+            if ts not in snapshots:
+                snapshots[ts] = []
+            snapshots[ts].append(
+                {
+                    "name": row["provider_name"],
+                    "status": row["status"],
+                    "error_rate": row["error_rate"],
+                    "avg_latency_ms": row["avg_latency_ms"],
+                    "circuit_state": row["circuit_state"],
+                    "total_requests": row["total_requests"],
+                }
+            )
+
+        return [{"timestamp": ts, "providers": providers} for ts, providers in snapshots.items()]
+
+    def prune(self, keep_hours: int = 168) -> int:
+        """Remove snapshots older than keep_hours. Returns rows deleted."""
+        cutoff = (datetime.now(UTC) - timedelta(hours=keep_hours)).isoformat()
+        cursor = self._conn.execute("DELETE FROM snapshots WHERE timestamp < ?", (cutoff,))
+        self._conn.commit()
+        return cursor.rowcount
+
+    def close(self) -> None:
+        """Close the database connection."""
+        if self._bg_task and not self._bg_task.done():
+            self._bg_task.cancel()
+        self._conn.close()
+
+    def _capture_snapshot(self, cascade_router) -> None:  # noqa: ANN001
+        """Capture current provider state as a snapshot."""
+        providers = []
+        for p in cascade_router.providers:
+            providers.append(
+                {
+                    "name": p.name,
+                    "status": p.status.value,
+                    "error_rate": round(p.metrics.error_rate, 4),
+                    "avg_latency_ms": round(p.metrics.avg_latency_ms, 2),
+                    "circuit_state": p.circuit_state.value,
+                    "total_requests": p.metrics.total_requests,
+                }
+            )
+        self.record_snapshot(providers)
+
+    async def start_background_task(
+        self,
+        cascade_router,
+        interval_seconds: int = 60,  # noqa: ANN001
+    ) -> None:
+        """Start periodic snapshot capture."""
+
+        async def _loop() -> None:
+            while True:
+                try:
+                    self._capture_snapshot(cascade_router)
+                    logger.debug("Recorded health snapshot")
+                except Exception:
+                    logger.exception("Failed to record health snapshot")
+                await asyncio.sleep(interval_seconds)
+
+        self._bg_task = asyncio.create_task(_loop())
+        logger.info("Health history background task started (interval=%ds)", interval_seconds)
+
+
+def get_history_store() -> HealthHistoryStore:
+    """Get or create the singleton history store."""
+    global _store  # noqa: PLW0603
+    if _store is None:
+        _store = HealthHistoryStore()
+    return _store