


Analysis on how to use long connection of PHP extension module memcached, extension module memcached_PHP tutorial
Analysis on how to use long connection of PHP extension module memcached, extension module memcached
There is an article widely circulated on the Internet about the difference between memcache and memcached, the two extension modules of PHP. It specifically emphasizes that a big difference between memcached and memcached is that the memcached module does not support long connections. So for many years I thought that memcached did not support long connections. In fact, this is not the case. The memcached extension module has supported long connections since a very early version. We can see from the source code of the extension module:
/* {{{ Memcached::__construct([string persistent_id[, callback on_new[, string connection_str]]]))
Creates a Memcached object, optionally using persistent memcache connection */
static PHP_METHOD(Memcached, __construct)
{
From the PHP manual, we can see that the constructor provided by the memcached extension module provides an optional parameter persistent_id
, which is introduced in the manual:
By default, Memcached instances will be destroyed after the request ends. However, you can share instances between requests by specifying a unique ID for each instance by persistent_id
when creating it. All instances created with the same persistent_id
value share the same connection.
The meaning of this parameter is that if you pass a named id to the constructor, then a long connection will be established. Usually we use PHP-FPM mode, so that the PHP-FPM process will resume the memcached service A long connection channel. We can also understand that persistent_id is a connection pool name, and all php-fpm processes are members of this connection pool.
But what we need to pay attention to is that PHP is an interpreted language. When PHP establishes a long connection through the memached module for the first time, remember that subsequent PHP executions should not build long connections named with the same persistent_id through the constructor of memcached. Long connections with different persistent_id names can be established. If the same name is executed repeatedly by PHP, it will definitely cause the php-fpm process to be abnormal and cause the communication with memcached to become slower and slower. At the same time, depending on the version of libmemcached, it will also cause PHP to generate coredump. .
So how do we prevent a single php-fpm from repeatedly establishing a long connection after establishing a long connection named with persistent_id? In fact, it is explained in the PHP manual with comments, and the content is as follows:
When using persistent connections, it is important to not re-add servers.
This is what you do not want to do:
$mc = new Memcached('mc'); $mc->setOption(Memcached::OPT_LIBKETAMA_COMPATIBLE, true); $mc->addServers(array( array('mc1.example.com',11211), array('mc2.example.com',11211), ));
Every time the page is loaded those servers will be appended to the list resulting in many simultaneous open connections to the same server. The addServer/addServers functions to not check for existing references to the specified servers.
A better approach is something like:
$mc = new Memcached('mc'); $mc->setOption(Memcached::OPT_LIBKETAMA_COMPATIBLE, true); if (!count($mc->getServerList())) { $mc->addServers(array( array('mc1.example.com',11211), array('mc2.example.com',11211), )); }<br />
Use the getServerList() method to check whether a long connection resource with the same name already exists in the php-fpm process container currently used for execution. If it exists, do not repeatedly use the addServers() method to add a new connection configuration.

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.

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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.


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