[ADD] server: allow env variable to control HTTP socket timeout

As indicated in the comment, it's much preferred to perform response
buffering at the reverse proxy level than to increase the socket
timeout. It will free up HTTP workers for other requests faster, while
the proxy does the work of buffering the stream on disk as needed.

/!\ The timeout is also used to protect from accidental DoS effects
in situations of low worker availability, due to idle connections
caused e.g. by wkhtmltopdf's connection pooling.
Setting a high timeout will make the protection less effective, so
ensuring you have enough free HTTP workers at all times becomes critical.

In our tests with nginx's defaut buffering on a typical hardware with
SSD storage, buffering up to 1GB responses did not require any change
of the socket timeout on the Odoo side, though your mileage may vary.
See also nginx's `proxy_buffering` and `proxy_max_temp_file_size` config
directives.

OPW-2247730
See also: odoo#20158

closes odoo#51824

Signed-off-by: Olivier Dony (odo) <odo@openerp.com>

odoo/service/server.py

@@ -869,9 +869,20 @@ def _runloop(self):
 
 class WorkerHTTP(Worker):
     """ HTTP Request workers """
+    def __init__(self, multi):
+        super(WorkerHTTP, self).__init__(multi)
+
+        # The ODOO_HTTP_SOCKET_TIMEOUT environment variable allows to control socket timeout for
+        # extreme latency situations. It's generally better to use a good buffering reverse proxy
+        # to quickly free workers rather than increasing this timeout to accomodate high network
+        # latencies & b/w saturation. This timeout is also essential to protect against accidental
+        # DoS due to idle HTTP connections.
+        sock_timeout = os.environ.get("ODOO_HTTP_SOCKET_TIMEOUT")
+        self.sock_timeout = float(sock_timeout) if sock_timeout else 2
+
     def process_request(self, client, addr):
         client.setblocking(1)
-        client.settimeout(2)
+        client.settimeout(self.sock_timeout)
         client.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
         # Prevent fd inherientence close_on_exec
         flags = fcntl.fcntl(client, fcntl.F_GETFD) | fcntl.FD_CLOEXEC