# HG changeset patch
# User Jun Wu <quark@fb.com>
# Date 1500089181 25200
# Node ID 27d23fe32887279db649eccae244f261452be7ac
# Parent  5d0c0c8d2929be8fb23c722ec2df21b149dc8fc2
commandserver: use selectors2

Previously, commandserver was using select.select. That could have issue if
_sock.fileno() >= FD_SETSIZE (usually 1024), which raises:

  ValueError: filedescriptor out of range in select()

We got that in production today, although it's the code opening that many
files to blame, it seems better for commandserver to work in this case.
There are multiple way to "solve" it, like preserving a fd with a small
number and swap it with sock using dup2(). But upgrading to a modern
selector supported by the system seems to be the most correct way.

diff -r 5d0c0c8d2929 -r 27d23fe32887 mercurial/commandserver.py
--- a/mercurial/commandserver.py	Fri Jul 14 20:19:46 2017 -0700
+++ b/mercurial/commandserver.py	Fri Jul 14 20:26:21 2017 -0700
@@ -22,6 +22,7 @@
     encoding,
     error,
     pycompat,
+    selectors2,
     util,
 )
 
@@ -476,6 +477,8 @@
     def _mainloop(self):
         exiting = False
         h = self._servicehandler
+        selector = selectors2.DefaultSelector()
+        selector.register(self._sock, selectors2.EVENT_READ)
         while True:
             if not exiting and h.shouldexit():
                 # clients can no longer connect() to the domain socket, so
@@ -486,7 +489,7 @@
                 self._unlinksocket()
                 exiting = True
             try:
-                ready = select.select([self._sock], [], [], h.pollinterval)[0]
+                ready = selector.select(timeout=h.pollinterval)
                 if not ready:
                     # only exit if we completed all queued requests
                     if exiting: