chore(rename): move llama_stack.distribution to llama_stack.core (#2975)

We would like to rename the term `template` to `distribution`. To
prepare for that, this is a precursor.

cc @leseb

llama_stack/core/server/quota.py

@@ -0,0 +1,110 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.
+
+import json
+import time
+from datetime import UTC, datetime, timedelta
+
+from starlette.types import ASGIApp, Receive, Scope, Send
+
+from llama_stack.log import get_logger
+from llama_stack.providers.utils.kvstore.api import KVStore
+from llama_stack.providers.utils.kvstore.config import KVStoreConfig, SqliteKVStoreConfig
+from llama_stack.providers.utils.kvstore.kvstore import kvstore_impl
+
+logger = get_logger(name=__name__, category="quota")
+
+
+class QuotaMiddleware:
+    """
+    ASGI middleware that enforces separate quotas for authenticated and anonymous clients
+    within a configurable time window.
+
+    - For authenticated requests, it reads the client ID from the
+      `Authorization: Bearer <client_id>` header.
+    - For anonymous requests, it falls back to the IP address of the client.
+    Requests are counted in a KV store (e.g., SQLite), and HTTP 429 is returned
+    once a client exceeds its quota.
+    """
+
+    def __init__(
+        self,
+        app: ASGIApp,
+        kv_config: KVStoreConfig,
+        anonymous_max_requests: int,
+        authenticated_max_requests: int,
+        window_seconds: int = 86400,
+    ):
+        self.app = app
+        self.kv_config = kv_config
+        self.kv: KVStore | None = None
+        self.anonymous_max_requests = anonymous_max_requests
+        self.authenticated_max_requests = authenticated_max_requests
+        self.window_seconds = window_seconds
+
+        if isinstance(self.kv_config, SqliteKVStoreConfig):
+            logger.warning(
+                "QuotaMiddleware: Using SQLite backend. Expiry/TTL is not enforced; cleanup is manual. "
+                f"window_seconds={self.window_seconds}"
+            )
+
+    async def _get_kv(self) -> KVStore:
+        if self.kv is None:
+            self.kv = await kvstore_impl(self.kv_config)
+        return self.kv
+
+    async def __call__(self, scope: Scope, receive: Receive, send: Send):
+        if scope["type"] == "http":
+            # pick key & limit based on auth
+            auth_id = scope.get("authenticated_client_id")
+            if auth_id:
+                key_id = auth_id
+                limit = self.authenticated_max_requests
+            else:
+                # fallback to IP
+                client = scope.get("client")
+                key_id = client[0] if client else "anonymous"
+                limit = self.anonymous_max_requests
+
+            current_window = int(time.time() // self.window_seconds)
+            key = f"quota:{key_id}:{current_window}"
+
+            try:
+                kv = await self._get_kv()
+                prev = await kv.get(key) or "0"
+                count = int(prev) + 1
+
+                if int(prev) == 0:
+                    # Set with expiration datetime when it is the first request in the window.
+                    expiration = datetime.now(UTC) + timedelta(seconds=self.window_seconds)
+                    await kv.set(key, str(count), expiration=expiration)
+                else:
+                    await kv.set(key, str(count))
+            except Exception:
+                logger.exception("Failed to access KV store for quota")
+                return await self._send_error(send, 500, "Quota service error")
+
+            if count > limit:
+                logger.warning(
+                    "Quota exceeded for client %s: %d/%d",
+                    key_id,
+                    count,
+                    limit,
+                )
+                return await self._send_error(send, 429, "Quota exceeded")
+
+        return await self.app(scope, receive, send)
+
+    async def _send_error(self, send: Send, status: int, message: str):
+        await send(
+            {
+                "type": "http.response.start",
+                "status": status,
+                "headers": [[b"content-type", b"application/json"]],
+            }
+        )
+        body = json.dumps({"error": {"message": message}}).encode()
+        await send({"type": "http.response.body", "body": body})