add queue

app/main.py

@@ -4,6 +4,7 @@ from collections import deque
 from pathlib import Path
 from typing import Optional, Tuple, List, Dict, Any
 from dataclasses import dataclass, field
+from contextlib import contextmanager
 
 from fastapi import FastAPI, HTTPException, Response
 from fastapi.middleware.cors import CORSMiddleware
@@ -88,6 +89,25 @@ class RateLimiter:
 
 limiter = RateLimiter(10)
 storyboard_limiter = RateLimiter(30)
+RENDER_LOCK = threading.Lock()
+
+
+@contextmanager
+def acquire_render_slot(timeout: Optional[float] = None):
+    """
+    Global render queue: only one Manim render runs at a time.
+    Blocks until the lock is available (optional timeout).
+    """
+    if timeout is None:
+        acquired = RENDER_LOCK.acquire()
+    else:
+        acquired = RENDER_LOCK.acquire(timeout=timeout)
+    if not acquired:
+        raise RuntimeError("Render queue is busy; try again shortly.")
+    try:
+        yield
+    finally:
+        RENDER_LOCK.release()
 
 def _to_chat_content_item(item: Any) -> Any:
     if isinstance(item, str):
@@ -1236,7 +1256,12 @@ class EmailIn(BaseModel):
 
 @app.get("/")
 def health():
-    return {"ok": True, "model": MODEL, "has_gemini": bool(API_KEY)}
+    return {
+        "ok": True,
+        "model": MODEL,
+        "has_gemini": bool(gemini_client),
+        "has_gpt": bool(gpt_client),
+    }
 
 @app.post("/generate-code")
 def generate_code(inp: GenerateCodeIn):
@@ -1247,7 +1272,16 @@ def generate_code(inp: GenerateCodeIn):
 @app.post("/generate-and-render")
 def generate_and_render(inp: PromptIn):
     try:
-        mp4 = refine_loop(inp.prompt, settings=inp.settings, max_error_refines=3, do_visual_refine=False)
+        with acquire_render_slot():
+            mp4 = refine_loop(inp.prompt, settings=inp.settings, max_error_refines=3, do_visual_refine=False)
+    except RuntimeError:
+        raise HTTPException(
+            status_code=503,
+            detail={
+                "error": "queue_busy",
+                "message": "Another render is already running. Please wait a moment and try again.",
+            },
+        )
     except Exception:
         raise HTTPException(500, "Failed to produce video after refinement")
     return Response(
@@ -1261,49 +1295,59 @@ def generate_and_render(inp: PromptIn):
 def render_code(inp: RenderCodeIn):
     quality = _quality_from_settings(inp.settings)
     try:
-        mp4_bytes, _ = _run_manim(inp.code, run_id="manual", quality=quality)
-        return Response(
-            content=mp4_bytes,
-            media_type="video/mp4",
-            headers={"Content-Disposition": 'inline; filename="result.mp4"'}
-        )
-    except RenderError as exc:
-        log = exc.log or ""
-        if not inp.auto_fix:
-            raise HTTPException(
-                status_code=400,
-                detail={
-                    "error": "Render failed",
-                    "message": "Render failed. Attempting automatic fix...",
-                },
-            )
-        fixed_code, fixed_video, final_log = _auto_fix_render(
-            user_prompt=inp.prompt or "User-edited Manim code",
-            code=inp.code,
-            settings=inp.settings,
-            initial_log=log,
-        )
-        if fixed_code and fixed_video:
-            payload = {
-                "auto_fixed": True,
-                "message": "Your code triggered a Manim error, so I applied the smallest possible fix (keeping your edits) and reran the render.",
-                "code": fixed_code,
-                "video_base64": base64.b64encode(fixed_video).decode("utf-8"),
-                "video_mime_type": "video/mp4",
-                "files": [
-                    {"filename": "scene.py", "contents": fixed_code}
-                ],
-                "meta": {"resolution": inp.settings.get("resolution") if inp.settings else None},
-                "log_tail": (log or "")[-600:]
-            }
-            return Response(
-                content=json.dumps(payload),
-                media_type="application/json",
-            )
-        detail_log = (final_log or log)[-6000:]
+        with acquire_render_slot():
+            try:
+                mp4_bytes, _ = _run_manim(inp.code, run_id="manual", quality=quality)
+                return Response(
+                    content=mp4_bytes,
+                    media_type="video/mp4",
+                    headers={"Content-Disposition": 'inline; filename="result.mp4"'}
+                )
+            except RenderError as exc:
+                log = exc.log or ""
+                if not inp.auto_fix:
+                    raise HTTPException(
+                        status_code=400,
+                        detail={
+                            "error": "Render failed",
+                            "message": "Render failed. Attempting automatic fix...",
+                        },
+                    )
+                fixed_code, fixed_video, final_log = _auto_fix_render(
+                    user_prompt=inp.prompt or "User-edited Manim code",
+                    code=inp.code,
+                    settings=inp.settings,
+                    initial_log=log,
+                )
+                if fixed_code and fixed_video:
+                    payload = {
+                        "auto_fixed": True,
+                        "message": "Your code triggered a Manim error, so I applied the smallest possible fix (keeping your edits) and reran the render.",
+                        "code": fixed_code,
+                        "video_base64": base64.b64encode(fixed_video).decode("utf-8"),
+                        "video_mime_type": "video/mp4",
+                        "files": [
+                            {"filename": "scene.py", "contents": fixed_code}
+                        ],
+                        "meta": {"resolution": inp.settings.get("resolution") if inp.settings else None},
+                        "log_tail": (log or "")[-600:]
+                    }
+                    return Response(
+                        content=json.dumps(payload),
+                        media_type="application/json",
+                    )
+                detail_log = (final_log or log)[-6000:]
+                raise HTTPException(
+                    status_code=400,
+                    detail={"error": "Render failed", "log": detail_log, "code": inp.code},
+                )
+    except RuntimeError:
         raise HTTPException(
-            status_code=400,
-            detail={"error": "Render failed", "log": detail_log, "code": inp.code},
+            status_code=503,
+            detail={
+                "error": "queue_busy",
+                "message": "Another render is already running. Please wait a moment and try again.",
+            },
         )
     except Exception as exc:
         raise HTTPException(status_code=500, detail={"error": "Unexpected render failure", "log": str(exc)})