背景

在linode上买了最低配的主机，将自己的个人博客站点搭建在上面，博客是用 WordPress 搭建的，对应的在服务器上部署了 Nginx + MySQL + php-fpm。

具体过程可参见之前的文章：

但最近一段时间站点总是莫名奇妙的离线，Jetpack 插件隔三差五给我发送监控邮件，告诉我我的站点没有响应了。之前几次在机器上看发现是 mariadb 数据库进程挂掉了，一直以为是我的数据库配置有问题，导致系统kill掉了它。所以每次都只是简单的重启了mariadb服务，也没有深究。后来将数据库的连接数调低，内存使用量也调低，但是还是会出现这个问题。才觉得这个不是数据库的问题，看下 top，发现php-fpm进程一大堆，内存基本都是被他们这些吃掉的，于是开始修改 php-fpm 的相关配置，修改后果然没有再出现之前的问题，top看起来负载也低了很多。

这里记录下这个过程。

参数优化

需要优化这样几个参数，pm，pm.max_children，pm.start_servers，pm.min_spare_servers，pm.max_spare_servers，pm.process_idle_timeout。

分别解释下这几个参数的含义：

  • pm

    Process Manager，进程管理器，不同的选项会使用不同的策略管理子进程数量。可选的值有三个：

    • static

      静态方式管理，这种模式下，只有 pm.max_children 会起作用，其他参数会被忽略。

    • dynmic

      动态方式管理，这种模式下，pm.max_children，pm.start_servers，pm.min_spare_servers ，pm.max_spare_servers这四个参数共同起作用，来控制决定子进程。

    • ondemand

      按需启动，这个模式下， pm.max_children，pm.process_idle_timeout 这两个参数共同起作用。

  • pm.max_children

    这个参数指定了当pm设置为“static”时要创建的子进程数，以及pm设置为“dynamic”或“ondemand”时的最大子进程数。

  • pm.start_servers

    该参数指定了主进程启动时创建的子进程数。这个参数的默认值是 min_spare_servers + (max_spare_servers – min_spare_servers) / 2。

  • pm.min_spare_servers

    该参数指定了最小的空闲进程数量。如果“空闲”进程的数量小于此数量，则将创建一些子进程。

  • pm.max_spare_servers

    该参数指定了最大的空闲进程数量。如果空闲进程的数量大于此数量，则会 kill 一些子进程。

  • pm.process_idle_timeout

    该参数指定了空闲进程可存活的最大秒数。

static or dynamic ？

我的linode 主机配置比较低，1CPU，1RAM, 25G存储。小内存的服务器适合 dynamic 模式，动态模式下灵活分配进程，省内存。而 static 模式适合内存比较大的主机，因为动态的创建回收对服务器资源也是一种消耗。

一般设置时，可按一个 php-fpm 进程 20M 算，进程数量还是根据自己主机的内存进行设置。

至于 ondemand 这个模式，没有研究过具体的使用场景。有时间研究下再来补充。

附上www.conf中的注释：

; Choose how the process manager will control the number of child processes.
; Possible Values:
;   static  - a fixed number (pm.max_children) of child processes;
;   dynamic - the number of child processes are set dynamically based on the
;             following directives. With this process management, there will be
;             always at least 1 children.
;             pm.max_children      - the maximum number of children that can
;                                    be alive at the same time.
;             pm.start_servers     - the number of children created on startup.
;             pm.min_spare_servers - the minimum number of children in 'idle'
;                                    state (waiting to process). If the number
;                                    of 'idle' processes is less than this
;                                    number then some children will be created.
;             pm.max_spare_servers - the maximum number of children in 'idle'
;                                    state (waiting to process). If the number
;                                    of 'idle' processes is greater than this
;                                    number then some children will be killed.
;  ondemand - no children are created at startup. Children will be forked when
;             new requests will connect. The following parameter are used:
;             pm.max_children           - the maximum number of children that
;                                         can be alive at the same time.
;             pm.process_idle_timeout   - The number of seconds after which
;                                         an idle process will be killed.
; Note: This value is mandatory.
pm = dynamic

; 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 = 5

; 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 = 2

; 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 = 1

; 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 = 3

; 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 = 500

参考链接