Table of Contents
问题
解决方案
第一种,代码中控制并发
第二种,使用linux的flock命令
Home Backend Development PHP Tutorial 解决crond脚本执行并发冲突问题

解决crond脚本执行并发冲突问题

Jun 23, 2016 am 09:09 AM

问题

在crond配置脚本执行后,经常会出现重复执行的情况。如下面的脚本:

<?phpsleep(70);?>
Copy after login

如果,在crond中的配置项如下:

*/1 * * * * root php ./test.php
Copy after login

就出出现,之前执行的test.php还未结束,新的test.php又被执行。如下:

[hailong@vhost ~]$ ps aux | grep tt.php56667     5280  0.0  0.0 103388  4432 pts/2    T    08:06   0:00 vim ./test.phproot      5455  0.0  0.1 225288  8812 ?        Ssl  08:08   0:00 /usr/bin/php /home/hailong/test.phproot      5665  5.0  0.1 225288  8748 ?        Ssl  08:09   0:00 /usr/bin/php /home/hailong/test.php56667     5675  0.0  0.0  69460   852 pts/2    S+   08:09   0:00 grep tt.php
Copy after login

进程一直堆积的话,可能会把系统资源给耗尽,导致系统宕机。

解决方案

解决方案有两种。各有利弊。

第一种,代码中控制并发

这种方法,就是对代码进行改造。增加是否有进程执行的判断。如下面的代码:

<?php  $lockfile = '/tmp/mytest.lock';    if(file_exists($lockfile)){      exit();  }file_put_contents($lockfile, date("Y-m-d H:i:s"));  sleep(70);unlink($lockfile);  ?>
Copy after login

代码逻辑很简单,这里就不再解释。这种判断文件是否不存在的方式,会有一个问题。那就是有可能程序未执行到最后,也就是没有删除之前创建的mytest.lock文件。这会导致,之后程序将不能正常执行。

为了解决这个问题,我们对代码进行下改造。不再使用文件是否存在的判断,而是判断进程是否存在。代码修改后如下:

$fp = popen("ps aux | grep 'test.php' | wc -l", "r");$proc_num = fgets($fp);if ($proc_num > 3) {    exit;}sleep(70);
Copy after login

这种方式有一个弊端,就是ps命令要写的精确。避免把不是执行test.php脚本的进程也统计到。如:

我们通过vim打开test.php文件。就会导致上面命令误统计。

另外,$proc_num 为什么要大于3而不是大于1,大家可以想想。如果,想不明白,可以加我微信 1798159444。

第二种,使用linux的flock命令

flock命令提供了文件锁的功能。命令参数如下:

[hailong@vhost ~]$ flock -hflock (util-linux 2.13-pre7)Usage: flock [-sxun][-w #] fd#       flock [-sxon][-w #] file [-c] command...  -s  --shared     Get a shared lock  -x  --exclusive  Get an exclusive lock  -u  --unlock     Remove a lock  -n  --nonblock   Fail rather than wait  -w  --timeout    Wait for a limited amount of time  -o  --close      Close file descriptor before running command  -c  --command    Run a single command string through the shell  -h  --help       Display this text  -V  --version    Display version
Copy after login

使用flock控制并发冲突,我们的crond配置如下:

*/1 * * * * root flock -xn /tmp/mytest.lock -c 'php ./test.php'
Copy after login

其实,使用flock也是有坑的。坑的详细信息,请查看 crond中使用flock命令的坑

原文链接: 解决crond脚本执行并发冲突问题,转载请注明来源!

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
2 weeks ago By 尊渡假赌尊渡假赌尊渡假赌
Repo: How To Revive Teammates
4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌
Hello Kitty Island Adventure: How To Get Giant Seeds
3 weeks ago By 尊渡假赌尊渡假赌尊渡假赌

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

11 Best PHP URL Shortener Scripts (Free and Premium) 11 Best PHP URL Shortener Scripts (Free and Premium) Mar 03, 2025 am 10:49 AM

Long URLs, often cluttered with keywords and tracking parameters, can deter visitors. A URL shortening script offers a solution, creating concise links ideal for social media and other platforms. These scripts are valuable for individual websites a

Introduction to the Instagram API Introduction to the Instagram API Mar 02, 2025 am 09:32 AM

Following its high-profile acquisition by Facebook in 2012, Instagram adopted two sets of APIs for third-party use. These are the Instagram Graph API and the Instagram Basic Display API.As a developer building an app that requires information from a

Working with Flash Session Data in Laravel Working with Flash Session Data in Laravel Mar 12, 2025 pm 05:08 PM

Laravel simplifies handling temporary session data using its intuitive flash methods. This is perfect for displaying brief messages, alerts, or notifications within your application. Data persists only for the subsequent request by default: $request-

Build a React App With a Laravel Back End: Part 2, React Build a React App With a Laravel Back End: Part 2, React Mar 04, 2025 am 09:33 AM

This is the second and final part of the series on building a React application with a Laravel back-end. In the first part of the series, we created a RESTful API using Laravel for a basic product-listing application. In this tutorial, we will be dev

Simplified HTTP Response Mocking in Laravel Tests Simplified HTTP Response Mocking in Laravel Tests Mar 12, 2025 pm 05:09 PM

Laravel provides concise HTTP response simulation syntax, simplifying HTTP interaction testing. This approach significantly reduces code redundancy while making your test simulation more intuitive. The basic implementation provides a variety of response type shortcuts: use Illuminate\Support\Facades\Http; Http::fake([ 'google.com' => 'Hello World', 'github.com' => ['foo' => 'bar'], 'forge.laravel.com' =>

cURL in PHP: How to Use the PHP cURL Extension in REST APIs cURL in PHP: How to Use the PHP cURL Extension in REST APIs Mar 14, 2025 am 11:42 AM

The PHP Client URL (cURL) extension is a powerful tool for developers, enabling seamless interaction with remote servers and REST APIs. By leveraging libcurl, a well-respected multi-protocol file transfer library, PHP cURL facilitates efficient execution of various network protocols, including HTTP, HTTPS, and FTP. This extension offers granular control over HTTP requests, supports multiple concurrent operations, and provides built-in security features.

12 Best PHP Chat Scripts on CodeCanyon 12 Best PHP Chat Scripts on CodeCanyon Mar 13, 2025 pm 12:08 PM

Do you want to provide real-time, instant solutions to your customers' most pressing problems? Live chat lets you have real-time conversations with customers and resolve their problems instantly. It allows you to provide faster service to your custom

Announcement of 2025 PHP Situation Survey Announcement of 2025 PHP Situation Survey Mar 03, 2025 pm 04:20 PM

The 2025 PHP Landscape Survey investigates current PHP development trends. It explores framework usage, deployment methods, and challenges, aiming to provide insights for developers and businesses. The survey anticipates growth in modern PHP versio

See all articles