Need to increase the number of concurrent HTTP connections to 85000

Question

I have a setup with 2 machines. I am using one as the server and the other as client. They are connected directly using a 1Ghz link. Both the machines have 4 cores, 8Gb ram and almost 100Gb disk space. I need to tune the Nginx server ( its the one im trying with but i can use any other as well) to handle 85000 concurrent connections. I have a 1kb file on the server and i am using curl on the client to get the same file over all the connections. After trying various tuning settings, i have 1500 established connections and around 30000 TIME_WAIT connections when i call the curl around 40000 times. Is there a way i can make the TIME_WAITs ESTABLISHED? Any help in tuning both the server and client will be much appreciated. I am pretty new to using Linux and trying to get the hang of it. The version of linux on both machines is Fedora 20.

Answer 1

Besides of tuning Nginx, you will also need to tune your Linux installation in respect to limits in number of tcp connections, sockets, open files, etc.

These two links should give you a great overview:

https://www.nginx.com/blog/tuning-nginx/

https://mrotaru.wordpress.com/2013/10/10/scaling-to-12-million-concurrent-connections-how-migratorydata-did-it/

Answer 2

You might want to check how much memory TCP buffers etc are using for all those connections.

See this SO thread: How much memory is consumed by the Linux kernel per TCP/IP network connection?

Also, this page is good: http://www.psc.edu/index.php/networking/641-tcp-tune

Given that your two machines are one the same physical network and delays are very low, you can use fairly small TCP window buffer sizes. Modern Linuxes (you didn't mention what kernel you're using) have TCP Autotuning that automatically adjusts these buffers, so you should not have to worry about this unless you're using an old kernel.

Regardless, however, the application(s) can allocate send- and receive buffers separately, which disables TCP Autotuning, so if you're running an application that does this, you might want to limit how much buffer space an application can request per connection (the net.core.wmem_max and net.core.rmem_max variables mentioned in the SO article).

Answer 3

我建议使用https://github.com/eunyoung14/mtcp来实现100万个并发连接，我对mtcp进行了一些调整，并在使用过的具有32G ram和8核的Dell PowerEdge R210上进行了测试，以实现100万个并发连接。