php fpm 优化502,Nginx php-fpm出现502解决办法和调优心得
这几天web经常出现Nginx 502的问题，先开始也像很多人一样认为是Nginx的问题，从网上查了查原来是php-fpm在作怪。
web使用的是nginx+php的架构，网站上线还没多久，所以优化方面基本只是做了些初始的配置。
查看php-fpm.log发现有警告，这些警告和网站的挂了个时间基本吻合。我就从这里开始入手。
先开始也是找了些文档，但是第二天还是出现问题。后来查看配置文件并翻译了下(百度)，英文底子不好。pm模块类似apache的模块，是分静态和动态的。
网上说的很多调整都是基于动态居多，但是并没说么定义这个模块。所以大家用动态和静态还是要仔细看看配置文件
pm = static
; The number of child processes to be created when pm is set to 'static' and the
; maximum number of child processes when pm is set to 'dynamic' or 'ondemand'.
; This value sets the limit on the number of simultaneous requests that will be
; served. Equivalent to the ApacheMaxClients directive with mpm_prefork.
; Equivalent to the PHP_FCGI_CHILDREN environment variable in the original PHP
; CGI. The below defaults are based on a server without much resources. Don't
; forget to tweak pm.* to fit your needs.
; Note: Used when pm is set to 'static', 'dynamic' or 'ondemand'
; Note: This value is mandatory.
pm.max_children = 300
; The number of child processes created on startup.
; Note: Used only when pm is set to 'dynamic'
; Default Value: min_spare_servers + (max_spare_servers - min_spare_servers) / 2
;pm.start_servers = 50
; The desired minimum number of idle server processes.
; Note: Used only when pm is set to 'dynamic'
; Note: Mandatory when pm is set to 'dynamic'
;pm.min_spare_servers = 20
; The desired maximum number of idle server processes.
; Note: Used only when pm is set to 'dynamic'
; Note: Mandatory when pm is set to 'dynamic'
;pm.max_spare_servers = 500
; The number of seconds after which an idle process will be killed.
; Note: Used only when pm is set to 'ondemand'
; Default Value: 10s
pm.process_idle_timeout = 10s;
; The number of requests each child process should execute before respawning.
; This can be useful to work around memory leaks in 3rd party libraries. For
; endless request processing specify '0'. Equivalent to PHP_FCGI_MAX_REQUESTS.
; Default Value: 0
pm.max_requests = 10240
红色字段就是定义方式的，定义好这个再去根据服务器情况设置参数
假如使用静态 pm.max_children这个参数会起作用，其余不会。动态反之。
2G内存pm.max_children大概开启50左右，按照实际情况来调优，这个是很必要的。
如果哪里有不足希望大家提意见，502解决办法。