On 01/07/2016 05:44 PM, Mike Bayer wrote:
On 01/07/2016 07:39 AM, Clayton O'Neill wrote:
On Thu, Jan 7, 2016 at 2:49 AM, Roman Podoliaka <rpodoly...@mirantis.com> wrote:
Linux gurus please correct me here, but my understanding is that Linux
kernel queues up to $backlog number of connections *per socket*. In
our case child processes inherited the FD of the socket, so they will
accept() connections from the same queue in the kernel, i.e. the
backlog value is for *all* child processes, not *per* process.
Yes, it will be shared across all children.
In each child process eventlet WSGI server calls accept() in a loop to
get a client socket from the kernel and then puts into a greenlet from
a pool for processing:
It’s worse than that. What I’ve seen (via strace) is that eventlet actually
converts socket into a non-blocking socket, then converts that accept() into a
epoll()/accept() pair in every child. Then when a connection comes in, every
child process wakes up out of poll and races to try to accept on the the
non-blocking socket, and all but one of them fails.
is that eventlet-specific or would we see the same thing in gevent ?
If you've got multiple processes all doing select()/poll()/epoll()/etc on a
single socket that has become readable, you're going to run into this sort of
thundering herd problem unless you have a separate mechanism to serialize things.
Chris
__________________________________________________________________________
OpenStack Development Mailing List (not for usage questions)
Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe
http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
