On Wed, Jul 11, 2018 at 12:37:28PM +0530, Numan Siddique wrote: > On Wed, Jul 11, 2018 at 2:08 AM Ben Pfaff <[email protected]> wrote: > > > On Wed, Jul 11, 2018 at 12:56:39AM +0530, [email protected] wrote: > > > From: Numan Siddique <[email protected]> > > > > > > The python function ovs.socket_util.check_connection_completion() uses > > select() > > > (provided by python) to monitor the socket file descriptor. The select() > > > returns 1 when the file descriptor becomes ready. For error cases like - > > > 111 (Connection refused) and 113 (No route to host) (POLLERR), > > ovs.poller._SelectSelect.poll() > > > expects the exceptfds list to be set by select(). But that is not the > > case. > > > As per the select() man page, writefds list will be set for POLLERR. > > > Please see "Correspondence between select() and poll() notifications" > > section of select(2) > > > man page. > > > > > > Because of this behavior, ovs.socket_util.check_connection_completion() > > returns success > > > even if the remote is unreachable or not listening on the port. > > > > > > This patch fixes this issue by adding a wrapper function - > > check_connection_completion_status() > > > which calls sock.connect_ex() to get the status of the connection if > > > ovs.socket_util.check_connection_completion() returns success. > > > > > > The test cases added fails without the fix in this patch. > > > > > > Signed-off-by: Numan Siddique <[email protected]> > > > > Can we just code check_connection_completion() like we do in C, by > > directly using select() on Windows and poll() everywhere else? The > > approach in this patch seems a little indirect to me. > > > > > Thanks for the review. As per the comments here - > https://github.com/openvswitch/ovs/blob/master/python/ovs/poller.py#L51 > ***** > # eventlet/gevent doesn't support select.poll. If select.poll is used, > # python interpreter is blocked as a whole instead of switching from the > # current thread that is about to block to other runnable thread. > # So emulate select.poll by select.select because using python means that > # performance isn't so important. > ******* > > we cannot use poll() in python. I tried with this patch to test it out - > https://paste.fedoraproject.org/paste/YUhgVte-BOjgid-ojmHZJw > All the ovs python idl tests pass. But it doesn't work with openstack > networking-ovn. The whole neutron-server process just blocks. > > I don't see any other way for python. Once select() returns we have to use > some mechanism to get the error code. > Does calling sock.connect_ex() bother you ?
I don't mean to change what poller.py does. I mean to implement ovs.socket_util.check_connection_completion in terms of select.poll and select.select directly. The comment in python/ovs/poller.py should not be relevant because the use of select.poll in check_connection_completion would never block (it would use a timeout of 0). Thanks, Ben. _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
