Replace in-memory TTL cache with Redis

routers/overview.py

@@ -1,7 +1,7 @@
 import asyncio
 import logging
 
-from fastapi import APIRouter
+from fastapi import APIRouter, Response
 
 from models.schemas import (
     DriveHealthSummary,
@@ -22,7 +22,7 @@ router = APIRouter(prefix="/api/overview", tags=["overview"])
 
 
 @router.get("", response_model=Overview)
-async def get_overview():
+async def get_overview(response: Response):
     """Aggregate view of all enclosures, slots, and drive health."""
     enclosures_raw = discover_enclosures()
     pool_map = await get_zfs_pool_map()
@@ -53,12 +53,19 @@ async def get_overview():
         smart_results = await asyncio.gather(*smart_tasks, return_exceptions=True)
 
         smart_map: dict[str, dict] = {}
+        all_cache_hits = True
+        any_lookups = False
         for (slot_info, dev), result in zip(populated, smart_results):
             if isinstance(result, Exception):
                 logger.warning("SMART query failed for %s: %s", dev, result)
                 smart_map[dev] = {"device": dev, "smart_supported": False}
+                all_cache_hits = False
             else:
-                smart_map[dev] = result
+                data, hit = result
+                smart_map[dev] = data
+                any_lookups = True
+                if not hit:
+                    all_cache_hits = False
 
         slots_out: list[SlotWithDrive] = []
         for s in slots_raw:
@@ -170,6 +177,8 @@ async def get_overview():
                 warnings += 1
         host_drives_out.append(HostDrive(**hd))
 
+    response.headers["X-Cache"] = "HIT" if (any_lookups and all_cache_hits) else "MISS"
+
     return Overview(
         healthy=all_healthy and errors == 0,
         drive_count=total_drives,