Hello!

On Mon, Jul 25, 2016 at 05:24:46PM -0700, Charles Lawrence wrote:

> I'm in the process of setting up a new server built on ubuntu 16.04
> using nginx 1.10.0.
>
> The specific issue is that while my new configuration essentially
> matches my old nginx configuration from an ubuntu 13.10 server using
> nginx 1.4.4, nginx 1.10.0 is only creating either ipv4 or ipv6
> workers, but not both. This behavior is not present on the old server.
> Not sure what else to try at this point.

Workers are not bound to IPv6 / IPv4. Instead, all workers listen
on all listening sockets configured.

[...]

> > include /etc/nginx/conf.d/*.conf;
> > include /etc/nginx/sites-enabled/*;
> > }

Note: such configurations are very error-prone, as all files from
a directory are included without any filtering. This is known to
cause unintended inclusion of various "swap", "temp" and "backup"
files.

For proper testing you may want to comment out the "include"
directives, and use server{} blocks directly written in
nginx.conf.

> Lastly, the weird thing is whether the workers get bound to ipv4 or
> ipv6 entirely depends on the order in which the listen directives are
> placed. In the following data, I've switched the order and tried
> different configurations multiple times. After each change to
> /etc/nginx/sites-enabled/blog I did sudo service nginx stop; sudo
> service nginx start; sudo lsof -i;to get the data.
>
> Also note that I changed the workers count to 8 after performing these
> steps. However while the number of workers increased, the same
> behavior was seen where all workers were either ipv4 or ipv6.
>
> > listen [::]:80;
> > listen 80;
> > nginx 27675 root 6u IPv4 204423 0t0 TCP *:http (LISTEN)
> > nginx 27676 www-data 6u IPv4 204423 0t0 TCP *:http (LISTEN)
> >
> > listen 80;
> > listen [::]:80;
> > nginx 27747 root 6u IPv6 205134 0t0 TCP *:http (LISTEN)
> > nginx 27748 www-data 6u IPv6 205134 0t0 TCP *:http (LISTEN)
> >
> > listen 80;
> > listen [::]:80 default ipv6only=on;
> > nginx 27819 root 6u IPv6 205849 0t0 TCP *:http (LISTEN)
> > nginx 27820 www-data 6u IPv6 205849 0t0 TCP *:http (LISTEN)
> >
> > listen 80;
> > listen [::]:80 default ipv6only=off;
> > nginx 27885 root 6u IPv6 206495 0t0 TCP *:http (LISTEN)
> > nginx 27886 www-data 6u IPv6 206495 0t0 TCP *:http (LISTEN)

Note: such a configuration is not expected to start at all on Linux,
as IPv6 socket [::]:80 with IPV6_V6ONLY option set to "off" will
conflict with IPv4 socket *:80.

That is, "sudo service nginx start" is expected to fail. If it
doesn't - this indicate that you are testing something different.

To further debug what's going on, consider:

- using a minimal config directly in nginx.conf, see above;

- starting nginx yourself by hand instead of using startup
scripts, this will ensure that this isn't something caused by
startup scripts;

- make sure to examine all sockets as printed by lsopt, and very
the results using other tools (e.g., "ss -nlt").

--
Maxim Dounin
http://nginx.org/

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