基础环境
其实基于PHP扩展的Memcache客户端实际上早已经实现,而且非常稳定。先解释一些名词,Memcache是danga.com的一个开源项目,可以类比于MySQL这样的服务,而PHP扩展的Memcache实际上是连接Memcache的方式。
首先,进行Memcache被安装具体可查看博客里的其它几篇文章;
其次,进行PHP扩展的安装,官方地址是http://pecl.php.net/package/memcache
最后,启动Memcache服务,比如这样,通过不同端口启动多个进程模拟分布式:
/usr/local/bin/memcached -d -p 11213 -u root -m 10 -c 1024 -t 8 -P /tmp/memcached.pid
/usr/local/bin/memcached -d -p 11214 -u root -m 10 -c 1024 -t 8 -P /tmp/memcached.pid
启动三个只使用10M内存以方便测试。
参数说明:
-d选项是启动一个守护进程,
-m 是分配给Memcache使用的内存数量,单位是MB,我这里是512MB,
-u是运行Memcache的用户,我这里是root,
-l 是监听的服务器IP地址,如果有多个地址的话,我这里指定了服务器的IP地址192.168.0.1,
-p是设置Memcache监听的端口,我 这里设置了11211,最好是1024以上的端口,
-c选项是最大运行的并发连接数,默认是1024,我这里设置了512,按照你服务器的负载量 来设定,
-P是设置保存Memcache的pid文件,我这里是保存
分布式部署
PHP的PECL扩展中的memcache实际上在2.0.0的版本中就已经实现多服务器支持,现在都已经2.2.5了。请看如下代码
$memcache = new Memcache; $memcache->addServer('localhost', 11211); $memcache->addServer('localhost', 11213); $memcache->addServer('localhost', 11214); $memStats = $memcache->getExtendedStats(); print_r($memStats);
通过上例就已经实现Memcache的分布式部署,是不是非常简单。
分布式系统的良性运行
在Memcache的实际使用中,遇到的最严重的问题,就是在增减服务器的时候,会导致大范围的缓存丢失,从而可能会引导数据库的性能瓶颈。测试时可以通过关闭一个memcached进程,来测试数据是否存在,实例:
<?php //第一次设置值后再作注释 $memcache = new Memcache; $memcache->addServer('localhost', 11211); //$memcache->set("mykey", "这个值在11213添加前添加的"); $memcache->addServer('localhost', 11213); if (!$memcache) echo "Connection to memcached failed"; /* $memcache->set("str_key", "String to store in memcached"); $memcache->set("num_key", 123); $object = new StdClass; $object->attribute = 'test'; $memcache->set("obj_key", $object); $array = Array('assoc'=>123, 345, 567); $memcache->set("arr_key", $array); */ var_dump($memcache->get('mykey')); var_dump($memcache->get('str_key')); var_dump($memcache->get('num_key')); var_dump($memcache->get('obj_key')); $memStats = $memcache->getExtendedStats(); var_dump($memStats); ?>
测试时关闭其中一台,可能会导致数据丢失:
string '这个值在11213添加前添加的' (length=35) string 'String to store in memcached' (length=28) boolean false boolean false
为了避免出现这种情况,请先看Consistent hashing算法,中文的介绍可以参考memcached全面剖析--4. memcached的分布式算法,通过存取时选定服务器算法的改变,来实现。
memcached虽然称为“分布式”缓存服务器,但服务器端并没有“分布式”功能。
修改PHP的Memcache扩展memcache.c的源代码中的
"memcache.hash_strategy" = standard
为
"memcache.hash_strategy" = consistent
重新编译,这时候就是使用Consistent hashing算法来寻找服务器存取数据了。
有效测试数据表明,使用Consistent hashing可以极大的改善增删Memcache时缓存大范围丢失的情况。
NonConsistentHash: 92% of lookups changed after adding a target to the existing 10 NonConsistentHash: 90% of lookups changed after removing 1 of 10 targets ConsistentHash: 6% of lookups changed after adding a target to the existing 10 ConsistentHash: 9% of lookups changed after removing 1 of 10 targets
安全配置
Memcache服务器端都是直接通过客户端连接后直接操作,没有任何的验证过程,这样如果服务器是直接暴露在互联网上的话是比较危险,轻则数据泄露被其他无关人员查看,重则服务器被入侵,因为Mecache是以root权限运行的,况且里面可能存在一些我们未知的bug或者是缓冲区溢出的情况,这些都是我们未知的,所以危险性是可以预见的。
内网访问
最好把两台服务器之间的访问是内网形态的,一般是Web服务器跟Memcache服务器之间。普遍的服务器都是有两块网卡,一块指向互联网,一块指向内网,那么就让Web服务器通过内网的网卡来访问Memcache服务器,我们Memcache的服务器上启动的时候就监听内网的IP地址和端口,内网间的访问能够有效阻止其他非法的访问。
Memcache服务器端设置监听通过内网的192.168.0.200的ip的11211端口,占用1024MB内存,并且允许最大1024个并发连接
设置防火墙
防火墙是简单有效的方式,如果却是两台服务器都是挂在网的,并且需要通过外网IP来访问Memcache的话,那么可以考虑使用防火墙或者代理程序来过滤非法访问。 一般我们在Linux下可以使用iptables或者FreeBSD下的ipfw来指定一些规则防止一些非法的访问,比如我们可以设置只允许我们的Web服务器来访问我们Memcache服务器,同时阻止其他的访问。
# iptables -F # iptables -P INPUT DROP # iptables -A INPUT -p tcp -s 192.168.0.2 --dport 11211 -j ACCEPT # iptables -A INPUT -p udp -s 192.168.0.2 --dport 11211 -j ACCEPT
上面的iptables规则就是只允许192.168.0.2这台Web服务器对Memcache服务器的访问,能够有效的阻止一些非法访问,相应的也可以增加一些其他的规则来加强安全性,这个可以根据自己的需要来做。

PHP is a server-side scripting language used for dynamic web development and server-side applications. 1.PHP is an interpreted language that does not require compilation and is suitable for rapid development. 2. PHP code is embedded in HTML, making it easy to develop web pages. 3. PHP processes server-side logic, generates HTML output, and supports user interaction and data processing. 4. PHP can interact with the database, process form submission, and execute server-side tasks.

PHP has shaped the network over the past few decades and will continue to play an important role in web development. 1) PHP originated in 1994 and has become the first choice for developers due to its ease of use and seamless integration with MySQL. 2) Its core functions include generating dynamic content and integrating with the database, allowing the website to be updated in real time and displayed in personalized manner. 3) The wide application and ecosystem of PHP have driven its long-term impact, but it also faces version updates and security challenges. 4) Performance improvements in recent years, such as the release of PHP7, enable it to compete with modern languages. 5) In the future, PHP needs to deal with new challenges such as containerization and microservices, but its flexibility and active community make it adaptable.

The core benefits of PHP include ease of learning, strong web development support, rich libraries and frameworks, high performance and scalability, cross-platform compatibility, and cost-effectiveness. 1) Easy to learn and use, suitable for beginners; 2) Good integration with web servers and supports multiple databases; 3) Have powerful frameworks such as Laravel; 4) High performance can be achieved through optimization; 5) Support multiple operating systems; 6) Open source to reduce development costs.

PHP is not dead. 1) The PHP community actively solves performance and security issues, and PHP7.x improves performance. 2) PHP is suitable for modern web development and is widely used in large websites. 3) PHP is easy to learn and the server performs well, but the type system is not as strict as static languages. 4) PHP is still important in the fields of content management and e-commerce, and the ecosystem continues to evolve. 5) Optimize performance through OPcache and APC, and use OOP and design patterns to improve code quality.

PHP and Python have their own advantages and disadvantages, and the choice depends on the project requirements. 1) PHP is suitable for web development, easy to learn, rich community resources, but the syntax is not modern enough, and performance and security need to be paid attention to. 2) Python is suitable for data science and machine learning, with concise syntax and easy to learn, but there are bottlenecks in execution speed and memory management.

PHP is used to build dynamic websites, and its core functions include: 1. Generate dynamic content and generate web pages in real time by connecting with the database; 2. Process user interaction and form submissions, verify inputs and respond to operations; 3. Manage sessions and user authentication to provide a personalized experience; 4. Optimize performance and follow best practices to improve website efficiency and security.

PHP uses MySQLi and PDO extensions to interact in database operations and server-side logic processing, and processes server-side logic through functions such as session management. 1) Use MySQLi or PDO to connect to the database and execute SQL queries. 2) Handle HTTP requests and user status through session management and other functions. 3) Use transactions to ensure the atomicity of database operations. 4) Prevent SQL injection, use exception handling and closing connections for debugging. 5) Optimize performance through indexing and cache, write highly readable code and perform error handling.

Using preprocessing statements and PDO in PHP can effectively prevent SQL injection attacks. 1) Use PDO to connect to the database and set the error mode. 2) Create preprocessing statements through the prepare method and pass data using placeholders and execute methods. 3) Process query results and ensure the security and performance of the code.


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

Zend Studio 13.0.1
Powerful PHP integrated development environment

SublimeText3 Linux new version
SublimeText3 Linux latest version

DVWA
Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software

VSCode Windows 64-bit Download
A free and powerful IDE editor launched by Microsoft

MinGW - Minimalist GNU for Windows
This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.