fix(startup): ping real endpoints in warmup/keepalive (#3641)

_warmup_endpoints called model_discovery.get_endpoints(), which does not exist
on ModelDiscovery. It raised AttributeError on every startup and on every 60s
keepalive tick, was swallowed by the outer except, and pinged nothing, so the
cold-start prevention the loop exists for never ran.

Add ModelDiscovery.warmup_ping_urls(), which resolves the /models probe URLs
from the real discover_models() output, and call it from the warmup loop via
asyncio.to_thread (discovery does a blocking port scan, so keep it off the event
loop).

Adds tests/test_warmup_ping_urls.py: resolves /models URLs from discovered
items, honors the limit, degrades to [] on discovery failure, and documents that
get_endpoints never existed.

app.py

@@ -946,16 +946,21 @@ async def _startup_event():
     async def _warmup_endpoints():
         try:
             import httpx
-            endpoints = model_discovery.get_endpoints() if model_discovery else []
-            for ep in endpoints[:5]:
-                url = ep.get("url", "").replace("/chat/completions", "/models")
-                if url:
-                    try:
-                        async with httpx.AsyncClient(timeout=5.0) as client:
-                            await client.get(url)
-                        logger.info(f"Warmup ping OK: {url}")
-                    except Exception as e:
-                        logger.debug(f"Warmup ping failed for endpoint: {e}")
+            # model_discovery has no get_endpoints(); that call raised
+            # AttributeError every run and silently disabled warmup/keepalive.
+            # Resolve the /models probe URLs via the real discovery API, off the
+            # event loop since discovery does a blocking port scan.
+            urls = (
+                await asyncio.to_thread(model_discovery.warmup_ping_urls)
+                if model_discovery else []
+            )
+            for url in urls:
+                try:
+                    async with httpx.AsyncClient(timeout=5.0) as client:
+                        await client.get(url)
+                    logger.info(f"Warmup ping OK: {url}")
+                except Exception as e:
+                    logger.debug(f"Warmup ping failed for endpoint: {e}")
         except Exception as e:
             logger.debug(f"Warmup ping skipped: {e}")
 

src/model_discovery.py

@@ -223,6 +223,25 @@ class ModelDiscovery:
         )
         return {"hosts": hosts, "items": items}
 
+    def warmup_ping_urls(self, limit: int = 5) -> List[str]:
+        """The ``/models`` URLs of up to ``limit`` discovered endpoints.
+
+        Used by the startup warmup / keepalive loop to prime connections. Each
+        discovered item already carries a ``/v1/chat/completions`` url; swap the
+        suffix for the cheap ``/models`` probe. Failures degrade to an empty list
+        so warmup never crashes the caller.
+        """
+        try:
+            items = (self.discover_models() or {}).get("items", [])
+        except Exception:
+            return []
+        urls: List[str] = []
+        for ep in items[:limit]:
+            url = (ep.get("url") or "").replace("/chat/completions", "/models")
+            if url:
+                urls.append(url)
+        return urls
+
     def get_providers(self) -> Dict[str, Any]:
         """Get all available providers"""
         discovery = self.discover_models()

tests/test_warmup_ping_urls.py

@@ -0,0 +1,47 @@
+"""Startup warmup must resolve real endpoint URLs.
+
+The warmup/keepalive loop called `model_discovery.get_endpoints()`, which does
+not exist on ModelDiscovery, so it raised AttributeError every run and pinged
+nothing. `ModelDiscovery.warmup_ping_urls()` resolves the /models probe URLs
+from the real discovery API.
+"""
+from src.model_discovery import ModelDiscovery
+
+
+def _md():
+    return ModelDiscovery.__new__(ModelDiscovery)
+
+
+def test_old_method_never_existed():
+    # Documents why the old warmup was a silent no-op.
+    assert not hasattr(ModelDiscovery, "get_endpoints")
+
+
+def test_resolves_models_urls_from_discovered_items():
+    md = _md()
+    md.discover_models = lambda: {"items": [
+        {"url": "http://host:8000/v1/chat/completions", "models": ["a"]},
+        {"url": "http://host:1234/v1/chat/completions", "models": ["b"]},
+    ]}
+    assert md.warmup_ping_urls() == [
+        "http://host:8000/v1/models",
+        "http://host:1234/v1/models",
+    ]
+
+
+def test_limit_caps_results():
+    md = _md()
+    md.discover_models = lambda: {"items": [
+        {"url": f"http://h:{8000 + i}/v1/chat/completions"} for i in range(10)
+    ]}
+    assert len(md.warmup_ping_urls(limit=3)) == 3
+
+
+def test_discovery_failure_degrades_to_empty():
+    md = _md()
+
+    def boom():
+        raise RuntimeError("port scan failed")
+
+    md.discover_models = boom
+    assert md.warmup_ping_urls() == []