If you ever encounter problems on your Nginx-PHP FPM server with all of the sudden increased load, very slow page load, PHP processes being filled for no particular reason… check php-fpm logs:<\/p>\n
root@webserver:~# tail \/var\/log\/php5-fpm\/php-fpm.log\r\n[19-Dec-2012 13:53:07] 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 33 total children\r\n[19-Dec-2012 13:53:08] WARNING: [pool www] seems busy (you may need to increase pm.start_servers, or pm.min\/max_spare_servers), spawning 16 children, there are 0 idle, and 38 total children\r\n[19-Dec-2012 13:53:09] WARNING: [pool www] server reached pm.max_children setting (40), consider raising it<\/pre>\nIf you have server monitoring\/google anayltics on your site, and you see no increase of visitors, pages\/second or hits\/second… then there’s probably one or another bot crawling your site (I’ve noticed that robots.txt is not always working…), or in my case somebody requesting 500 or more pages in 3 seconds from 1 specific IP address. Not accusing anybody from attacking my servers…<\/p>\n
This mass page requests thingie, caused my nginx to throw 499 error to my webserver’s clients.<\/p>\n
I’ve resolved this by enabled rate limiting inside Nginx.<\/p>\n
This is how:<\/p>\n
Add the following line to your \/etc\/nginx\/nginx.conf:<\/p>\n
limit_req_zone $binary_remote_addr zone=onerps:10m rate=1r\/s;<\/pre>\nThis area is called\u00a0onerps and is allocated 10MB of storage.Using the $binary_remote_addr variable reduces the size of the states to 64 bytes. Since there can be about 16,000 states in a 1MB zone,10MB allows for about 160000 states. This should be sufficient your your visitors.<\/p>\n
The connection rate is limited to one request per second. You can also use something like 30r\/m, which putts a rate limit in place of 30 requests per minute.<\/p>\n
Works if not finished yet: To put this limit to work, we use the\u00a0limit_req\u00a0directive. You can use this directive in\u00a0http {},\u00a0server {}, and\u00a0location {}\u00a0containers.<\/p>\n
However the best option is to use this in the location {}\u00a0containers that pass requests to your app servers, eg PHP-FPM. because otherwise, if you load a single page with lots of images, CSS, and JavaScript files, you would probably exceed the given rate limit with a single page request :-p<\/p>\n
So let’s put this in a\u00a0location ~ \\.php$ {}\u00a0container:<\/p>\n
limit_req zone=onerps burst=5;<\/pre>\nIf your visitor is doing more than 1 request per second (or 5 in burst mode), the next request will be queued and executed the next second.\u00a0If the number of waiting requests exceed burst, the request is completed with the code 503 “Service Temporarily Unavailable”. By default, the burst is zero.<\/p>\n
If delaying excess requests within a burst is not necessary, you should use the option\u00a0nodelay:<\/p>\n
limit_req zone=onerps burst=5 nodelay;<\/pre>\n