feat: add SIGHUP hot config reload

On SIGHUP, re-read the YAML config file and update mutable runtime
settings: timeout, retries, log_level, and pool config (sources,
intervals, thresholds). Pool triggers an immediate source re-fetch.
Listen address and chain require restart.

src/s5p/cli.py

@@ -62,6 +62,8 @@ def main(argv: list[str] | None = None) -> int:
     args = _parse_args(argv)
 
     config = load_config(args.config) if args.config else Config()
+    if args.config:
+        config.config_file = args.config
 
     if args.listen:
         if ":" in args.listen:

src/s5p/config.py

@@ -74,6 +74,7 @@ class Config:
     log_level: str = "info"
     proxy_source: ProxySourceConfig | None = None
     proxy_pool: ProxyPoolConfig | None = None
+    config_file: str = ""
 
 
 def parse_proxy_url(url: str) -> ChainHop:

src/s5p/pool.py

@@ -90,6 +90,13 @@ class ProxyPool:
         self._tasks.append(asyncio.create_task(self._refresh_loop()))
         self._tasks.append(asyncio.create_task(self._health_loop()))
 
+    async def reload(self, cfg: ProxyPoolConfig) -> None:
+        """Update pool config and trigger source re-fetch."""
+        self._cfg = cfg
+        logger.info("pool: config reloaded, re-fetching sources")
+        await self._fetch_all_sources()
+        self._save_state()
+
     async def stop(self) -> None:
         """Cancel background tasks and save state."""
         self._stop.set()

src/s5p/server.py

@@ -8,7 +8,7 @@ import signal
 import struct
 import time
 
-from .config import Config
+from .config import Config, load_config
 from .metrics import Metrics
 from .pool import ProxyPool
 from .proto import ProtoError, Socks5Reply, build_chain, read_socks5_address
@@ -253,6 +253,32 @@ async def serve(config: Config) -> None:
     for sig in (signal.SIGTERM, signal.SIGINT):
         loop.add_signal_handler(sig, lambda s=sig: stop.set_result(s))
 
+    # SIGHUP: hot-reload config (timeout, retries, log_level, pool settings)
+    async def _reload() -> None:
+        if not config.config_file:
+            logger.warning("reload: no config file specified, ignoring SIGHUP")
+            return
+        try:
+            new = load_config(config.config_file)
+        except Exception as e:
+            logger.warning("reload: failed to read config: %s", e)
+            return
+        config.timeout = new.timeout
+        config.retries = new.retries
+        if new.log_level != config.log_level:
+            config.log_level = new.log_level
+            logging.getLogger("s5p").setLevel(
+                getattr(logging, new.log_level.upper(), logging.INFO),
+            )
+        if isinstance(proxy_pool, ProxyPool) and new.proxy_pool:
+            await proxy_pool.reload(new.proxy_pool)
+        logger.info("reload: config reloaded")
+
+    def _on_sighup() -> None:
+        asyncio.ensure_future(_reload())
+
+    loop.add_signal_handler(signal.SIGHUP, _on_sighup)
+
     metrics_stop = asyncio.Event()
     pool_ref = proxy_pool if isinstance(proxy_pool, ProxyPool) else None
     metrics_task = asyncio.create_task(_metrics_logger(metrics, metrics_stop, pool_ref))