About process number management of php-fpm

This article mainly introduces the process number management of php-fpm, which has certain reference value. Now I share it with everyone. Friends in need can refer to it

PHP-FPM

Let’s first understand some noun concepts:

CGI is Common Gateway Interface (Common Network Management Protocol), used to allow interactive programs and Web The protocol for server communication. It is responsible for processing URL requests, starting a process, taking the data sent by the client as input, and the web server collects the output of the program and adds appropriate headers, and then sends it back to the client.

FastCGI is an enhanced version of the protocol based on CGI. Instead of creating a new process to serve requests, it uses persistent processes and created child processes to handle a series of Processes, these processes are managed by the FastCGI server, with less overhead and higher efficiency.

PHP-FPM is an implementation of PHP FastCGI Process Manager (FastCGI Process Manager), used to replace PHP FastCGI Most of the additional features are suitable for high-load websites. Supported functions such as:

1. Advanced process management function for smooth stop/start

2. Slow logging script

3. Dynamic/static sub-process generation

4. Configuration file based on php.ini

PHP-FPM It has been integrated into the PHP source code after 5.4, providing a better PHP process management method, which can effectively control memory and processes, and smoothly reload PHP configuration. If you need to use it, just bring the -enable-fpm parameter when ./configure, and use PHP-FPM to control FastCGIProcess:

// 支持start/stop/quit/restart/reload/logrotate参数
// quit/reload是平滑终止和平滑重新加载，即等现有的服务完成
./php-fpm --start

PHP-FPM Configuration

PHP-FPMThe configuration file is php-fpm.conf, In this configuration file we need to know some parameters. All the sub-processes below refer to the php-fpm process, which can be viewed on the terminal via ps aux | grep php.

• Displayphp-fpm: pool www represents the work sub-process (actually processing the request)

• Displayphp-fpm: process master represents the master main process (responsible for managing the work sub-process)

Global configuration

Look firstPHP-FPM The most important global configuration part:

emergency_restart_threshold

If the number of parameter settings is received within the emergency_restart_intervalset time SIGSEGV or SIGBUS exit signal, FPM will restart. The default value is 0, which means turning off this function.

emergency_restart_interval

Set the smooth restart interval to help solve the problem of shared memory usage in the accelerator. Available units are s (default)/m/h/d, and the default value is 0, which means off.

process.max

FPMThe maximum number of child processes that can be created, it is using multiple pm = dynamic When configuring the php-fpm pool process pool, control the global number of child processes. The default value is 0, which means no limit.

Process Pool Configuration

The rest of the configuration of PHP-FPM is an area named Pool Definitions. The configuration settings in this area are each PHP-FPMProcess pool, the process pool is a series of related sub-processes. This part starts with [process pool name], such as [www].

It can be explained that ps aux | grep php shows php-fpm: pool www.

#pm

##pm refers to process manager, which specifies how the process manager controls the number of child processes. It is required and supports 3 values:

• static: Use a fixed number of child processes, specified by pm.max_children

• dynamic: Dynamically adjust the number of child processes based on the following parameters. There must be at least one child process

• pm.max_chidren: The maximum number of child processes that can survive at the same time

• pm.start_servers: The number of child processes created at startup, default The value is min_spare_servers max_spare_servers - min_spare_servers) / 2

• ##pm.min_spare_servers

  : The minimum number of idle child processes, if not enough, new The child processes will be automatically created

• pm.max_spare_servers

  : The maximum number of idle child processes. If exceeded, some child processes will be killed

• ondemand

  : The child process will not be created at startup and will only be created when a new request arrives. The following two parameters will be used:

• pm.max_children

• pm.process_idle_timeou

  t The idle timeout of the child process. If no new requests can be served after the timeout, it will be killed

pm.max_requests

每一个子进程的最大请求服务数量，如果超过了这个值，该子进程会被自动重启。在解决第三方库的内存泄漏问题时，这个参数会很有用。默认值为0，指子进程可以持续不断的服务请求。

PHP-FPM配置优化

PHP-FPM管理的方式是一个master主进程，多个pool进程池，多个worker子进程。其中每个进程池监听一个socket套接字。具体的图示：

其中的worker子进程实际处理连接请求，master主进程负责管理子进程：

1. `master`进程，设置1s定时器，通过`socket`文件监听
2. 在`pm=dynamic`时，如果`idle worker`数量`pm.max_spare_servers`，杀死多余的空闲子进程
4. 在`pm=ondemand`时，如果`idle worker`空闲时间>`pm.process_idle_timeout`，杀死该空闲进程
5. 当连接到达时，检测如果`worker`数量>`pm.max_children`，打印`warning`日志，退出；如果无异常，使用`idle worker`服务，或者新建`worker`服务

保障基本安全

我们为了避免PHP-FPM主进程由于某些糟糕的PHP代码挂掉，需要设置重启的全局配置：

; 如果在1min内有10个子进程被中断失效，重启主进程
emergency_restart_threshold = 10
emergency_restart_interval = 1m

进程数调优

每一个子进程同时只能服务一次连接，所以控制同时存在多少个进程数就很重要，如果过少会导致很多不必要的重建和销毁的开销，如果过多又会占用过多的内存，影响其他服务使用。

我们应该测试自己的PHP进程使用多少内存，一般来说刚启动时是8M左右，运行一段时间由于内存泄漏和缓存会上涨到30M左右，所以你需要根据自己的预期内存大小设定进程的数量。同时根据进程池的数量来看一个进程管理器的子进程数量限制。

测试平均PHP子进程占用的内存：

$ps auxf | grep php | grep -v grep
work     26829  0.0  0.0 715976  4712 ?        Ss   Jul11   0:00 php-fpm: master process (./etc/php-fpm.conf)
work     21889  0.0  0.0 729076 29668 ?        S    03:12   0:20  \_ php-fpm: pool www         
work     21273  0.0  0.0 728928 31380 ?        S    03:25   0:21  \_ php-fpm: pool www         
work     15114  0.0  0.0 728052 29084 ?        S    03:40   0:19  \_ php-fpm: pool www         
work     17072  0.0  0.0 728800 34240 ?        S    03:54   0:22  \_ php-fpm: pool www         
work     22763  0.0  0.0 727904 20352 ?        S    11:29   0:04  \_ php-fpm: pool www         
work     38545  0.0  0.0 727796 19484 ?        S    12:34   0:01  \_ php-fpm: pool www

// 共占用的内存数量
$ps auxf | grep php | grep -v grep | grep -v master | awk '{sum+=$6} END {print sum}'
162712

// 所有的子进程数量
$ ps auxf | grep php | grep -v grep | grep -v master | wc -l 
6

可以看到第6列，每一个子进程的内存占用大概在19-34M之间（单位为KB）。平均的内存占用为162712KB/6 = 27.1M。

查看服务器总的内存大小

$ free -g
             total       used       free     shared    buffers     cached
Mem:           157        141         15          0          4        123
-/+ buffers/cache:         13        143
Swap:            0          0          0

可以看出我的服务器总得内存大小是157G（-g采用了G的单位）。

进程数限制

此时如果我们分配全部的内存给PHP-FPM使用，那么进程数可以限制在157000/27 = 5814,但是由于我的服务器同时服务了很多内容，所以我们可以向下调整到512个进程数：

process.max = 512
pm = dynamic
pm.max_children = 512
pm.start_servers = 16
pm.min_spare_servers = 8
pm.max_spare_serveres = 30

防止内存泄漏

由于糟糕的插件和库，内存泄漏时有发生，所以我们需要对每一个子进程服务的请求数量做限制，防止无限制的内存泄漏：

pm.max_requests = 1000

重启

如果上面的配置都按照你的实际需求和环境配置好了，不要忘记重启PHP-FPM服务。

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