Combating nginx 499 HTTP responses during flash traffic scenario

Hongli Lai hongli at
Mon Oct 29 21:06:43 UTC 2012

On Mon, Oct 29, 2012 at 8:41 PM, Eric Wong <normalperson at> wrote:
> I'm not sure, Tom can investigate further.
> I do recall haproxy having more intelligent load distribution than
> nginx, so it can send requests to less-busy machines, at least.

It is correct that HAProxy can do more intelligent load distribution.
The "maxconn 1" feature in HAProxy is a bit like global queuing in
Phusion Passenger, or the kernel socket queuing that Unicorn relies
on. Phusion Passenger sends the request to the first worker that
becomes available, and the kernel passes the connection to the first
Unicorn instance that accept()s the socket. Nginx's proxy_module
passes requests immediately and only does round robin.

So to solve this problem we need to add 2 features to the layer that
manages the queue:
1. It must be able to detect an early disconnect.
2. It must be able to remove a client from the queue.

The kernel obviously can't do this, but I'm very curious as to whether
HAProxy supports these two things. I also think it shouldn't be too
hard to implement this in Phusion Passenger 4's new architecture.

Phusion | Ruby & Rails deployment, scaling and tuning solutions

E-mail: info at
Chamber of commerce no: 08173483 (The Netherlands)

More information about the mongrel-unicorn mailing list