A brief analysis of several timeout configurations in PHP configuration files

This article will talk about the PHP configuration file and analyze several timeout-related configurations in the configuration file (php.ini and php-fpm.conf). I hope it can help you!

1. Overview

There are many timeout-related configurations in php.ini and php-fpm.conf, so what exactly do these configurations do? How is it implemented in the source code? This article will talk about the following timeout configurations:

php.ini

• max_execution_time
• max_input_time

php- fpm.conf

• process_control_timeout
• request_terminate_timeout
• request_slowlog_timeout

##Running environment: Mac 10.14.2 PHP 7.3.7

2. Configure parsing rules

Parsing rules

The parsing of php.ini is completed in the

php_module_startup() stage, ini_entry is in The parsing rules defined for each php.ini configuration in main.c are in the following format:

ZEND_INI_ENTRY3_EX(name, default_value, modifiable, on_modify, arg1, arg2, arg3, displayer)

PHP defines many macros for different types of configurations,

ZEND_INI_ENTRY3_EX is The final macro after they are expanded, such as PHP_INI_ENTRYMacro

PHP_INI_ENTRY(name, default_value, modifiable, on_modify)

Parameter explanation

name: Configuration name

default_value: Configure the default value

modifiable: The configurable range of the configuration

These modes determine when and where a PHP command can be Whether it can be set. Each instruction in the manual has a mode to which it belongs. For example, some commands can be set in PHP scripts using ini_set(), while others can only be set in php.ini or httpd.conf.

For example, the output_buffering directive belongs to

PHP_INI_PERDIR, so it cannot be set with ini_set(). But the display_errors directive belongs to PHP_INI_ALL and can be set anywhere, including ini_set().

ModeMeaning##PHP_INI_USERPHP_INI_PERDIRPHP_INI_SYSTEMPHP_INI_ALL

on_modify： 配置修改函数

三、max_input_time、max_execution_time

因为max_input_time 和 max_execution_time 联系比较密切，所以放在一起来讲。

php.ini 解释

max_input_time

; Maximum amount of time each script may spend parsing request data. It's a good
; idea to limit this time on productions servers in order to eliminate unexpectedly
; long running scripts.
; Note: This directive is hardcoded to -1 for the CLI SAPI
; http://php.net/max-input-time

翻译过来就是：max_input_time是每个脚本可以花在解析请求数据上的最大时间。在生产服务器上通过限制max_input_time可以清除掉长时间运行的脚本。在CLI模式下会硬编码为-1，即无限制。

max_execution_time

; Maximum execution time of each script, in seconds
; http://php.net/max-execution-...
; Note: This directive is hardcoded to 0 for the CLI SAPI

翻译：max_execution_time是每个脚本的最大可执行时间。在CLI模式下硬编码为0

配置解析规则

// max_input_time，默认值为无限制
STD_PHP_INI_ENTRY("max_input_time", "-1",    PHP_INI_SYSTEM|PHP_INI_PERDIR, OnUpdateLong, max_input_time, php_core_globals, core_globals)
  
// max_execution_time，默认值为30s，修改函数为OnUpdateTimeout
PHP_INI_ENTRY("max_execution_time", "30",    PHP_INI_ALL, OnUpdateTimeout)

OnUpdateTimeout()函数如下，由第二节可知配置解析发生在php_module_startup()阶段，此时EG(timeout_seconds)被赋值为了max_execution_time，但还没有设置定时器。

// main.c
static PHP_INI_MH(OnUpdateTimeout)
{
    if (stage==PHP_INI_STAGE_STARTUP) {
        /* Don't set a timeout on startup, only per-request */
    /* EG(timeout_seconds) = max_execution_time */
        ZEND_ATOL(EG(timeout_seconds), ZSTR_VAL(new_value));
        return SUCCESS;
    }
    zend_unset_timeout();
    ZEND_ATOL(EG(timeout_seconds), ZSTR_VAL(new_value));
    zend_set_timeout(EG(timeout_seconds), 0);
    return SUCCESS;
}

设置超时定时器

// main.c
int php_request_startup(void) 
{
  ......
  if (PG(max_input_time) == -1) {
    zend_set_timeout(EG(timeout_seconds), 1);
  } else {
  zend_set_timeout(PG(max_input_time), 1);
  }
  ......
}

int php_execute_script(zend_file_handle *primary_file)
{
  ......
    if (PG(max_input_time) != -1) {
    zend_set_timeout(INI_INT("max_execution_time"), 0);
  }  
  ......
}

从上面代码可以看到，如果设置了max_input_time（即值不等于-1，-1可以认为是在CLI模式下），在php_request_startup()阶段会设置一个定时器，超时时间为max_input_time；在php_execute_script()阶段会重新设置一个定时器，超时时间为max_execution_time。那么整个PHP脚本执行的最大执行时间就等于max_input_time + max_execution_time。

如果没有设置max_input_time的话（即值等于-1），在php_request_startup()阶段也会设置一个定时器，但超时时间被设为了EG(timeout_seconds)，而EG(timeout_seconds)已经在php_module_startup()阶段被赋值为max_execution_time，所以此时的超时时间就是max_execution_time；在php_execute_script()阶段不会重新设置定时器，前一阶段设置的max_execution_time定时器仍然生效着。那么整个PHP脚本的最大执行时间就是max_execution_time。

zend_set_time() 使用setitimer(ITIMER_PROF, &t_r, NULL); 来实现定时器，ITIMER_PROF会统计包括用户态和内核态下所花费的时间，而像sleep()这样的系统调用会让进程挂起，不占用cpu时间片，所以这俩超时时间是不包括sleep()时间的。

当定时器到时间后，ZendVM会抛出E_ERROR，即Fatal error错误。

四、process_control_timeout

php-fpm.conf 解释

; Time limit for child processes to wait for a reaction on signals from master.
; Available units: s(econds), m(inutes), h(ours), or d(ays)
; Default Unit: seconds

翻译：process_control_timeout是留给子进程处理来自master进程信号的时间限制。

分析

当master进程接收到SIGINT、SIGTERM、SIGQUIT、SIGUSR2这些信号时，会调用fpm_pctl()来进行处理。

首先master进程会根据 接收到的信号 和 当前fpm的运行状态 来决定发送给worker进程的是SIGQUIT还是SIGTERM信号，同时注册时间为process_control_timeout的定时事件。

如果在process_control_timeout时间内子进程没有退出，那么master进程会升级SIGQUIT为SIGTERM，SIGTERM为SIGKILL，并注册1s的定时事件。SIGKILL就直接终止worker进程了，SIGTERM还能再给worker进程1s的时间。

综上，process_control_timeout可以理解为master进程留给worker进程结束自己的时间，要是到时间worker还没搞定那就开始master自己的策略了。

五、request_terminate_timeout、request_slowlog_timeout

因为request_terminate_timeout 和 request_slowlog_timeout 联系比较密切，所以放在一起来讲。

php-fpm.conf Explanation

request_terminate_timeout

; The timeout for serving a single request after which the worker process will
; be killed. This option should be used when the 'max_execution_time' ini option
; does not stop script execution for some reason. A value of '0' means 'off'.
; Available units: s(econds)(default), m(inutes ), h(ours), or d(ays)
; Default Value: 0

Translation: The timeout period for executing a request, after which the worker process will be terminated. This option should be used when max_execution_time this ini option cannot stop script execution for some reason.

request_slowlog_timeout

; The timeout for serving a single request after which a PHP backtrace will be
; dumped to the 'slowlog' file. A value of '0s' means 'off' .
; Available units: s(econds)(default), m(inutes), h(ours), or d(ays)
; Default Value: 0

Translation: Execute a request timeout, after which a PHP backtrace will be output to the slowlog file.

Analysis

request_slowlog_timeout and request_terminate_timeout are used in the heartbeat detection of the master process (fpm_pctl_heartbeat()) , the heartbeat time heartbeat The simplified algorithm is

• When request_terminate_timeout is turned on: request_terminate_timeout/1000*3

• When request_terminate_timeout is not enabled: request_slowlog_timeout/1000*3 or 0

• request_terminate_timeout >= request_slowlog_timeout

##The third rule is to ensure that slowlog does not affect normal requests,

heartbeat takes 1 of the timeout time /3 should be to avoid too frequent heartbeat detection, because each heartbeat detection needs to traverse all worker processes.

If a timeout event occurs, the worker process will be killed directly,

kill(child_pid, SIGTERM);, and then the kernel will recycle resources and close the client_socket, and nginx will return a 502 error to the browser.

Recommended learning: "

PHP Video Tutorial"

Can be set in a user script (e.g. ini_set()) or in the Windows registry (since PHP 5.3) and in .user.ini
Can be set in php.ini, .htaccess or httpd.conf
Can be set in php .ini or httpd.conf set
can be set anywhere

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