On 01/07/2016 09:49 AM, Roman Podoliaka wrote:
Actually we already do that in the parent process. The parent process:
1) starts and creates a socket
2) binds the socket and calls listen() on it passing the backlog value
(http://linux.die.net/man/2/listen)
3) passes the socket to the eventlet WSGI server
(https://github.com/openstack/oslo.service/blob/master/oslo_service/wsgi.py#L177-L192)
4) forks $*_workers times (child processes inherit all open file
descriptors including the socket one)
5) child processes call accept() in a loop
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.
I believe this is correct, the limit is on the (shared) socket and not the
individual processes.
Also, an interesting point from the listen man page above:
"If the backlog argument is greater than the value in
/proc/sys/net/core/somaxconn, then it is silently truncated to that value; the
default value in this file is 128."
Chris
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