Nginx & php-fpm - Unix Socket or TCP/IP for fastcgi_pass?
Dear all,
I was always running Nginx in combination with PHP-FPM listening via TCP/IP (fastcgi_pass 127.0.0.1:9000;).
Then I tried to let it listen to a Unix Socket instead (fastcgi_pass unix:fastcgi.socket;). Even though the latter combination is often recommended for being generally faster, I do not see any significant boost in performance. I did not run any artificial test to be honest: It is just the impression that I have from observing a live website under some load with both combinations. Not only that the Unix Socket variation does not seem to be noticeable faster, the general server load is also higher compared to the TCP/IP solution. I have the impression that it adds around 0.3-0.5 to the load.
I wonder what your experiences with both solutions are: Maybe I just did something wrong so I am very much looking forward to your opinions...
Cheers
Amitz
Comments
By using TCP sockets instead of Unix sockets, you're technically adding unnecessary overhead to every connection, but it seems like the overhead is pretty neglibile: http://i.amniels.com/nginx-fast-cgi-performance-unix-socket-vs-tcp-ip
Yes, from a technical point of view, the Socket Connection should be a lot faster with lower latency than the TCP/IP Connection. The thing is: I do not see this "in real life". What I see instead are higher server loads and no noticeable (from a human perception) speed-up.
Thanks for sharing your live website experience. I always use tcp/ip because it's default and I'm too lazy to change.
There is literally no way it should be contributing to a higher server load unless your hosting environment is so bad that it can't handle the measly I/O.
I agree. This is how it should be in theory. But it isn't in (my) reality. That makes me wonder whether I did anything wrong. The thing is: There is not much that one can do wrong when configuring php-fpm to either listen on socket or TCP/IP port.
The general environment is well tuned. The website handles around 2,000,000 - 3,000,000 hits from 6,000 - 8,000 unique visitors each day. Everything is smooth, server load is seldom above 0.4-0.6. But as soon as I switch to Unix Sockets, it goes up to 0.8-1.1 and stays in that range. Really strange.
It's literally one line change to each of your fpm pool and site file. I don't notice a huge difference though since my site only gets 100 uniques per day.
Can this be handled by a VPS?
To be honest: Not by every VPS, as it seems. I have tried nearly every provider here on LET/LEB and even some of the bigger players like FutureHosting, WiredTree and Knownhost. Let's put it like this: A cPanel VPS in its standard configuration had big trouble with it. Furthermore, neighbors on a badly oversold node give you headaches too. A fine-tuned nginx + php-fpm + apc setup on a VPS from a good provider makes it well possible however.
The site is running simply GREAT on a Prometeus SSD-VPS and has a failover backup on a SSD-cached VPS from RamNode. I tested it live on both of them and it is running VERY smooth with server loads as mentioned above and CPU usage of less than half a core most of the time.
Nice. thanks for the info!
I changed my "fine" to "great" after you quoted me... ;-)
Indeed, I never had a better (and cheaper) VPS in every aspect than the ones from Prometeus and RamNode. And, as said, I nearly tried "them all". However, this was not planned to be a review thread... ;-)
Indeed, I never had a better (and cheaper) VPS in every aspect than the ones from Prometeus and RamNode. However, this was not planned to be a review thread... ;-)
If the prometeus is down, can your ramnode VPS handle those numbers?
Yes, as said - I tested it on both. I mainly use the Prometeus VPS as primary location because of the higher BW allocation and because it is geographically closer to me.
I use the VZSSD7 plan at @Prometeus and the 512MB CVZ plan at @Nick_A. Those two VPS under $10 helped me replace the cPanel server with a $90 price tag that I have used before for the site without any failover solution. Makes me happy. :-)
However - Back to the Socket vs. TCP/IP thing...
Wow, thats just under 7 bucks a month for that traffic
One simply HAS TO LOVE cheap virtualization done right. ;-)
I was in fear that my site and usage could harm the neighbors on my Node, but after looking at my Munin graphs, @Maounique (working @Prometeus) told me that they would be glad if every user would have such a reasonable usage like me. So obviously I am no menace to others.
What PHP version are you running @Amitz ?
https://github.com/perusio/php-fpm-example-config
I am using 5.3.19 in that setup.
Strange then, but very interesting.
EDIT:
/dev/shm/php-fpm.sock@Amitz ?If that is what you wanted to know...
Cheers @Amitz
Would moving
php5-fpm-name_of_virtual_host_user.sockto ramdisk make a difference for you then @Amitz ?Ah! Now I got the point... ;-)
Will try that today!
/var/run might already be a tmpfs.
Edit: doh, not on OpenVZ, and it depends on the distro.
Still a good thought process @lbft
@Zen, you're so sexy when you talk like that. My knickers are drenched !
This is not #frantech, Ladies! ;-)
@Amitz & @Zen - Haha
When I moved to a new VPS and had to reinstall php5-fpm I noticed they switched by default to the socket config.
@Amitz what are you serving? Static? Php/mysql?
It's a PHP/XML driven gallery. No MySQL.
As a little follow-up and not to spread wrong information:
The higher server load had nothing to do with switching from TCP/IP to Unix socket. There was another process going wild - Unfortunately exactly at the same time when I did my test.
I can say now that the switch has no (or just a very, very, very small) influence on the load. The predicted PRO for letting it listen on a socket instead of a TCP/IP connection, namely less latency, is not noticeable for me as a human being without doing benchmarks.
So the conclusion is: I (personally) do not feel any difference between the two configurations. I will keep an eye on the general server load during the next 24 hours, but it seems as if it does not matter which solution you choose as long as you are not running a very high traffic site with thousands of connections at the same time.
Cheers and thank you for the fish,
Amitz
I never test using socket though. But i love using nginx.
Love nginx also with cache