Make blocking threadpool size configurable to lift image concurrency

All blocking endpoints (image gen, text, content filter) run via
run_in_threadpool on anyio's default thread limiter, capped at 40. That
40 was the hard ceiling on simultaneous in-flight image generations
regardless of how many accounts (each accounts x image_account_concurrency
slot) the pool had.

Add config.blocking_threadpool_size (env BLOCKING_THREADPOOL_SIZE or
config.json, floor 40 / ceil 2048) and raise the limiter in the app
lifespan so it takes effect inside the event loop. Image gen is
I/O-bound, so a few hundred threads cost little on modest hardware; the
real ceiling then becomes accounts x concurrency and upstream rate
limits rather than the runtime.

Bake BLOCKING_THREADPOOL_SIZE=128 into the Space image as the default;
override via a Space Variable.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Dockerfile

@@ -22,7 +22,8 @@ ARG TARGETARCH
 ENV PYTHONDONTWRITEBYTECODE=1 \
     PYTHONUNBUFFERED=1 \
     UV_LINK_MODE=copy \
-    HOME=/app
+    HOME=/app \
+    BLOCKING_THREADPOOL_SIZE=128
 
 WORKDIR /app
 

api/app.py

@@ -3,6 +3,7 @@ from __future__ import annotations
 from contextlib import asynccontextmanager
 from threading import Event
 
+import anyio
 from fastapi import FastAPI, HTTPException
 from fastapi.middleware.cors import CORSMiddleware
 from fastapi.responses import FileResponse
@@ -12,6 +13,20 @@ from api import accounts, ai, image_tasks, openai_keys, register, system
 from api.support import resolve_web_asset, start_limited_account_watcher
 from services.backup_service import backup_service
 from services.config import config
+from utils.log import logger
+
+
+def _apply_blocking_threadpool_size() -> None:
+    # 抬高 anyio run_in_threadpool 线程池上限（默认 40），解除生图/文本接口的同时并发硬顶。
+    # 必须在事件循环内调用（limiter 绑定当前 async backend），故放在 lifespan 启动里。
+    size = config.blocking_threadpool_size
+    try:
+        limiter = anyio.to_thread.current_default_thread_limiter()
+        if limiter.total_tokens != size:
+            limiter.total_tokens = size
+        logger.info({"event": "blocking_threadpool_configured", "total_tokens": limiter.total_tokens})
+    except Exception as exc:
+        logger.warning({"event": "blocking_threadpool_config_failed", "error": str(exc)})
 
 
 def create_app() -> FastAPI:
@@ -19,6 +34,7 @@ def create_app() -> FastAPI:
 
     @asynccontextmanager
     async def lifespan(_: FastAPI):
+        _apply_blocking_threadpool_size()
         stop_event = Event()
         thread = start_limited_account_watcher(stop_event)
         backup_service.start()

services/config.py

@@ -224,6 +224,20 @@ class ConfigStore:
         except (TypeError, ValueError):
             return 3
 
+    @property
+    def blocking_threadpool_size(self) -> int:
+        # 所有阻塞型接口（生图/文本/内容过滤）都跑在 anyio 的 run_in_threadpool 线程池里，
+        # 默认只有 40，是生图同时并发的硬顶（见 conversation.stream_image_outputs_with_pool）。
+        # 这里允许通过 env BLOCKING_THREADPOOL_SIZE 或 config.json 抬高；I/O 密集，2C16G 抬到
+        # 一两百只占很少内存，真正天花板会让位给 账号数×image_account_concurrency 与上游限流。
+        raw = os.getenv("BLOCKING_THREADPOOL_SIZE") or self.data.get("blocking_threadpool_size") or 40
+        try:
+            value = int(raw)
+        except (TypeError, ValueError):
+            value = 40
+        # 不低于 anyio 默认 40（避免误降并发），上限防手滑打爆内存。
+        return max(40, min(2048, value))
+
     @property
     def auto_remove_invalid_accounts(self) -> bool:
         value = self.data.get("auto_remove_invalid_accounts", False)
@@ -310,6 +324,7 @@ class ConfigStore:
         data["image_retention_days"] = self.image_retention_days
         data["image_poll_timeout_secs"] = self.image_poll_timeout_secs
         data["image_account_concurrency"] = self.image_account_concurrency
+        data["blocking_threadpool_size"] = self.blocking_threadpool_size
         data["auto_remove_invalid_accounts"] = self.auto_remove_invalid_accounts
         data["auto_remove_rate_limited_accounts"] = self.auto_remove_rate_limited_accounts
         data["log_levels"] = self.log_levels