better support for 700+ connections

when there was more than ~700 active connections,
* sendfile (non-https downloads) could fail
* mdns and ssdp could fail to reinitialize on network changes

...because `select` can't handle FDs higher than 512 on windows
(1024 on linux/macos), so prefer `poll` where possible (linux/macos)

but apple keeps breaking and unbreaking `poll` in macos,
so use `--no-poll` if necessary to force `select` instead

copyparty/__main__.py

@@ -13,6 +13,7 @@ import base64
 import locale
 import os
 import re
+import select
 import socket
 import sys
 import threading
@@ -1335,6 +1336,8 @@ def add_debug(ap):
     ap2 = ap.add_argument_group('debug options')
     ap2.add_argument("--vc", action="store_true", help="verbose config file parser (explain config)")
     ap2.add_argument("--cgen", action="store_true", help="generate config file from current config (best-effort; probably buggy)")
+    if hasattr(select, "poll"):
+        ap2.add_argument("--no-poll", action="store_true", help="kernel-bug workaround: disable poll; use select instead (limits max num clients to ~700)")
     ap2.add_argument("--no-sendfile", action="store_true", help="kernel-bug workaround: disable sendfile; do a safe and slow read-send-loop instead")
     ap2.add_argument("--no-scandir", action="store_true", help="kernel-bug workaround: disable scandir; do a listdir + stat on each file instead")
     ap2.add_argument("--no-fastboot", action="store_true", help="wait for initial filesystem indexing before accepting client requests")
@@ -1545,7 +1548,7 @@ def main(argv: Optional[list[str]] = None, rsrc: Optional[str] = None) -> None:
         if hard > 0:  # -1 == infinite
             nc = min(nc, int(hard / 4))
     except:
-        nc = 512
+        nc = 486  # mdns/ssdp restart headroom; select() maxfd is 512 on windows
 
     retry = False
     for fmtr in [RiceFormatter, RiceFormatter, Dodge11874, BasicDodge11874]:
@@ -1638,6 +1641,9 @@ def main(argv: Optional[list[str]] = None, rsrc: Optional[str] = None) -> None:
     if not hasattr(os, "sendfile"):
         al.no_sendfile = True
 
+    if not hasattr(select, "poll"):
+        al.no_poll = True
+
     # signal.signal(signal.SIGINT, sighandler)
 
     SvcHub(al, dal, argv, "".join(printed)).run()

copyparty/httpcli.py

@@ -3193,7 +3193,14 @@ class HttpCli(object):
 
             sendfun = sendfile_kern if use_sendfile else sendfile_py
             remains = sendfun(
-                self.log, lower, upper, f, self.s, self.args.s_wr_sz, self.args.s_wr_slp
+                self.log,
+                lower,
+                upper,
+                f,
+                self.s,
+                self.args.s_wr_sz,
+                self.args.s_wr_slp,
+                not self.args.no_poll,
             )
 
         if remains > 0:

copyparty/mdns.py

@@ -292,6 +292,22 @@ class MDNS(MCast):
     def run2(self) -> None:
         last_hop = time.time()
         ihop = self.args.mc_hop
+
+        try:
+            if self.args.no_poll:
+                raise Exception()
+            fd2sck = {}
+            srvpoll = select.poll()
+            for sck in self.srv:
+                fd = sck.fileno()
+                fd2sck[fd] = sck
+                srvpoll.register(fd, select.POLLIN)
+        except Exception as ex:
+            srvpoll = None
+            if not self.args.no_poll:
+                t = "WARNING: failed to poll(), will use select() instead: %r"
+                self.log(t % (ex,), 3)
+
         while self.running:
             timeout = (
                 0.02 + random.random() * 0.07
@@ -300,8 +316,13 @@ class MDNS(MCast):
                 if self.unsolicited
                 else (last_hop + ihop if ihop else 180)
             )
+            if srvpoll:
+                pr = srvpoll.poll(timeout * 1000)
+                rx = [fd2sck[x[0]] for x in pr if x[1] & select.POLLIN]
+            else:
                 rdy = select.select(self.srv, [], [], timeout)
                 rx: list[socket.socket] = rdy[0]  # type: ignore
+
             self.rx4.cln()
             self.rx6.cln()
             buf = b""

copyparty/ssdp.py

@@ -141,9 +141,29 @@ class SSDPd(MCast):
         self.log("stopped", 2)
 
     def run2(self) -> None:
+        try:
+            if self.args.no_poll:
+                raise Exception()
+            fd2sck = {}
+            srvpoll = select.poll()
+            for sck in self.srv:
+                fd = sck.fileno()
+                fd2sck[fd] = sck
+                srvpoll.register(fd, select.POLLIN)
+        except Exception as ex:
+            srvpoll = None
+            if not self.args.no_poll:
+                t = "WARNING: failed to poll(), will use select() instead: %r"
+                self.log(t % (ex,), 3)
+
         while self.running:
+            if srvpoll:
+                pr = srvpoll.poll((self.args.z_chk or 180) * 1000)
+                rx = [fd2sck[x[0]] for x in pr if x[1] & select.POLLIN]
+            else:
                 rdy = select.select(self.srv, [], [], self.args.z_chk or 180)
                 rx: list[socket.socket] = rdy[0]  # type: ignore
+
             self.rxc.cln()
             buf = b""
             addr = ("0", 0)

copyparty/util.py

@@ -2517,6 +2517,7 @@ def sendfile_py(
     s: socket.socket,
     bufsz: int,
     slp: int,
+    use_poll: bool,
 ) -> int:
     remains = upper - lower
     f.seek(lower)
@@ -2545,15 +2546,23 @@ def sendfile_kern(
     s: socket.socket,
     bufsz: int,
     slp: int,
+    use_poll: bool,
 ) -> int:
     out_fd = s.fileno()
     in_fd = f.fileno()
     ofs = lower
     stuck = 0.0
+    if use_poll:
+        poll = select.poll()
+        poll.register(out_fd, select.POLLOUT)
+
     while ofs < upper:
         stuck = stuck or time.time()
         try:
             req = min(2 ** 30, upper - ofs)
+            if use_poll:
+                poll.poll(10000)
+            else:
                 select.select([], [out_fd], [], 10)
             n = os.sendfile(out_fd, in_fd, ofs, req)
             stuck = 0
@@ -2561,6 +2570,7 @@ def sendfile_kern(
             # client stopped reading; do another select
             d = time.time() - stuck
             if d < 3600 and ex.errno == errno.EWOULDBLOCK:
+                time.sleep(0.02)
                 continue
 
             n = 0