feat: add persistent json cache with background updates

Co-authored-by: aider (openrouter/thinkingmachines/inkling-small:free) <aider@aider.chat>

backend/main.py

@@ -4,6 +4,7 @@ import subprocess
 import time
 import json
 import threading
+import os
 
 app = FastAPI()
 
@@ -15,10 +16,38 @@ app.add_middleware(
     allow_headers=["*"],
 )
 
-cache = {}
+CACHE_FILE = "cache.json"
 CACHE_TTL = 300  # 5 minutes
+cache = {}
 cache_lock = threading.Lock()
 
+def load_persistent_cache():
+    global cache
+    if not os.path.exists(CACHE_FILE):
+        return
+    try:
+        with open(CACHE_FILE, "r") as f:
+            data = json.load(f)
+        loaded = {}
+        for k, v in data.items():
+            if isinstance(v, list) and len(v) == 2:
+                loaded[k] = (v[0], v[1])
+        with cache_lock:
+            cache = loaded
+    except Exception:
+        pass
+
+def save_persistent_cache():
+    try:
+        with cache_lock:
+            data = {}
+            for k, v in cache.items():
+                data[k] = [v[0], v[1]]
+        with open(CACHE_FILE, "w") as f:
+            json.dump(data, f)
+    except Exception:
+        pass
+
 def run_kubectl(args, context=None):
     cmd = ["kubectl"]
     if context:
@@ -43,6 +72,7 @@ def set_cached_items(resource, namespace, context, items):
     key = get_cache_key(resource, namespace, context)
     with cache_lock:
         cache[key] = (time.time(), items)
+    save_persistent_cache()
 
 def refresh_worker(resource, namespace, context, kubectl_args, item_mapper):
     while True:
@@ -61,7 +91,7 @@ def refresh_worker(resource, namespace, context, kubectl_args, item_mapper):
 
 @app.on_event("startup")
 def start_background_refresh():
-    # Background renewal for common default namespace / no context
+    load_persistent_cache()
     workers = [
         ("pods", "default", None, ["get", "pods", "-n", "default", "-o", "json"], lambda i: {"name": i.get("metadata", {}).get("name", "unknown"), "namespace": i.get("metadata", {}).get("namespace", "default")}),
         ("nodes", "default", None, ["get", "nodes", "-o", "json"], lambda i: {"name": i.get("metadata", {}).get("name", "unknown"), "namespace": "-"}),