PHP-FPM Process Manager: ondemand, dynamic, or static

I noticed the default setting for "pm" in php-fpm.conf is "ondemand".

According to this post, "ondemand" is best for shared hosting environments which will have a high number of low-load pools.

I am running a single high-traffic site on my server in one pool (I think), and that post indicates "static" would be the best for me, presumably because this means the processes always exist and don't have to be created "on demand".

Is this a setting I should modify or should I just leave it as is?

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Thanks!

 

Thanks so much for the links, @eva2000...those shortcuts are awesome, too. Good idea to reduce the max_execution_time (and yes, that's my thread at XenForo).

I have a good amount of RAM (16GB) and decided to go with a static process manager config, then bumped my pm.max_children to 70. Immediately, it felt like I had just hit the TURBO button on my server, and my XenForo install felt faster than ever (and it was already very quick!). Benchmarks from loader.io testing also showed that the site was able to handle many more simultaneous connections than before.

There does seem to be some conflicting advice out there regarding how to calculate the optimal max_children setting for your server, though, so I'm not sure if I have done the right thing there. This guy offers a nice formula to go by (I calculated mine with conservative RAM usage relative to what I actually have), but then I've also read here and elsewhere that you don't really benefit from having more children than cores available in your system (I have 8), which obviously makes a lot of sense.

Nevertheless, I do seem to be using a fair amount of the children according to my phpstats.

Code:

pool: www
process manager: static
start time: 29/Aug/2014:21:07:06 -0400
start since: 57112
accepted conn: 745579
listen queue: 0
max listen queue: 1
listen queue len: 128
idle processes: 66
active processes: 4
total processes: 70
max active processes: 54
max children reached: 0

 

Yeah, I think it might be...like I said I read a lot of conflicting advice on this during my research on optimal max_children settings. Here are two links which promote a formula that can make some pretty high numbers, but it may be bad advice!

Optimize nginx and PHP-FPM (max_children)
Adjusting child processes for PHP-FPM (Nginx) | MYSHELL.CO.UK

I definitely trust the experts around here a lot more, though.

 

Thanks so much for sharing that link, I'm convinced.

I've updated my configuration and will see how it goes.

Code:

pm = static
pm.max_children = 8
; Default Value: min_spare_servers + (max_spare_servers - min_spare_servers) / 2
pm.start_servers = 8
pm.min_spare_servers = 8
pm.max_spare_servers = 8
pm.max_requests = 100

No specific reason for keeping it static, although nobody else seems to be using it. I don't know, it's kind of depressing. I wish there was a better way to learn about this.

 

After experiencing lots of issues with the Image Proxy after moving to SSL/SPDY, I have since had to change these values and abandon a static configuration. It's been running great since. For XenForo with the image proxy, I definitely recommend a dynamic value with a high max_children setting like what you're using, BamaStangGuy.

My new settings and theory for why SPDY caused the problem are here: XF 1.4 - Image Proxy crashing PHP-FPM after moving to SSL | XenForo Community

 

Here's what I'm running on my new dedicated server (specs here):

Code:

pm = dynamic
pm.max_children = 32
pm.start_servers = 6
pm.min_spare_servers = 6
pm.max_spare_servers = 10
pm.max_requests = 500

It's been running great (no downtime caused by the image proxy that I can see), but I just noticed I'm getting a few of the these errors each day in /var/log/php-fpm/www-error.log so it's time to adjust some values...

Code:

[20-May-2015 14:41:55] WARNING: [pool www] seems busy (you may need to increase pm.start_servers, or pm.min/max_spare_servers), spawning 8 children, there are 0 idle, and 15 total children