Welcome! Log In Create A New Profile

Advanced

TCP connection problems (FIN_WAIT2/LAST_ACK) when upstream server is keepalived

August 16, 2010 09:14AM
Have a strange problem. We have a configuration (this is only a part of the configuration) that has problems if the upstream server is a load-balanced server using ipvs/keepalived.

Here is the relevant part of the configuration:

upstream fb_server {
server foobar:8080;
}
server {
listen 80;
server_name f.b.com;
location /fb/ {
proxy_pass http://fb_server;
}
}

The hostname "foobar" resolves to an IP address that is load-balanced over 2 physical servers ("foo" and "bar") using ipvs/keepalived.

What we see is that on the 2 upstream servers "foo" and "bar" there are a lot of connections in FIN_WAIT2 state and on the machine where nginx is running we see an increasing number of connections in LAST_ACK state. This would imply that nginx is not managing the upstream connection shutdown properly.

In order to prove that the problem is related to the load-balancing, if we change the upstream server to either "foo" or "bar" the problem goes away.

Now I realize that we can also use nginx to do the load-balancing and not use ipvs/keepalived, but I'd like to know why this doesn't work properly in this configuration. It is also probably a useful thing for the nginx authors and users to know as well.

If anyone has any idea why this is behaving like this I'd love to hear from you.
Subject Author Posted

TCP connection problems (FIN_WAIT2/LAST_ACK) when upstream server is keepalived

dwass August 16, 2010 09:14AM

Re: TCP connection problems (FIN_WAIT2/LAST_ACK) when upstream server is keepalived

sridhar basam August 16, 2010 10:06AM

Re: TCP connection problems (FIN_WAIT2/LAST_ACK) when upstream server is keepalived

dwass August 18, 2010 03:52AM



Sorry, only registered users may post in this forum.

Click here to login

Online Users

Guests: 107
Record Number of Users: 6 on February 13, 2018
Record Number of Guests: 421 on December 02, 2018
Powered by nginx      Powered by FreeBSD      PHP Powered      Powered by MariaDB      ipv6 ready