Memcached is a high-performance distributed memory object caching system used in dynamic web applications to reduce database load. It improves the speed of dynamic, database-driven websites by caching data and objects in memory to reduce the number of database reads. Memcached is based on a hashmap that stores key/value pairs. Its daemon is written in C, but the client can be written in any language and communicates with the daemon through the memcached protocol.
Memcached is a high-performance distributed memory object caching system for dynamic web applications to reduce database load. It improves the speed of dynamic, database-driven websites by caching data and objects in memory to reduce the number of database reads. We have collected the "Boolean Education Yan 18 Memcached Video Tutorial", hoping to help everyone better learn Memcached distributed clusters.
Video playback address: http://www.php.cn/course/314.html
1. memcached Basic settings
1) Start the server side of Memcache
# /usr/local/bin/memcached -d -m 10 -u root -l 192.168.0.200 -p 12000 -c 256 -P /tmp/memcached. The pid
-d option is to start a daemon process,
-m is the amount of memory allocated to Memcache, in MB, here it is 10MB,
-u is the user running Memcache, I am root here,
-l is the IP address of the listening server, if there are multiple addresses, I have specified the IP address of the server 192.168.0.200,
-p is the port where Memcache is set to listen, here I am 12000 is set, preferably a port above 1024. The
-c option is the maximum number of concurrent connections. The default is 1024. I set 256 here. Set it according to the load of your server.
- P is the pid file that is set to save Memcache. I save it in /tmp/memcached.pid.
2) If you want to end the Memcache process, execute:
# kill `cat /tmp/ memcached.pid`
The hash algorithm maps a binary value of any length into a smaller binary value of a fixed length. This small binary value is called a hash value. A hash value is a unique and extremely compact numerical representation of a piece of data. If you hash a piece of plaintext and change even one letter of the
paragraph, subsequent hashes will produce different values. It is computationally impossible to find two different inputs that hash to the same value.
2. The purpose of the consistent Hash algorithm is twofold: first, after the node changes, other nodes are affected as little as possible; second, after the node changes, the data redistribution is as balanced as possible.
3. Why run memcached?
If the website has high traffic and most visits will cause a high load on the database, using memcached can reduce the pressure on the database.
4. What business scenarios are memcached suitable for?
1) If the website contains dynamic web pages with high traffic, the load on the database will be very high. Since most database requests are read operations, memcached can significantly reduce database load.
2) If the load of the database server is relatively low but the CPU usage is high, the calculated results (computed objects) and rendered web page templates (rendered templates) can be cached.
3) Memcached can be used to cache session data and temporary data to reduce database write operations for them.
4) Cache some small but frequently accessed files.
5) Caching the results of Web 'services' (not Web Services promoted by IBM, translator's note) or RSS feeds.
5. Business scenarios where memcached is not applicable?
1) The size of the cache object is greater than 1MB
Memcached itself is not designed to handle large multimedia (large media) and huge binary blocks (streaming huge blobs).
2) The key length is greater than 250 characters
3) The virtual host does not allow memcached service to be run
If the application itself is hosted on a low-end virtual private server, like vmware , virtualization technologies such as xen are not suitable for running memcached. Memcached needs to take over and control large blocks of memory. If the memory managed by memcached is swapped out by the OS or hypervisor, the performance of memcached will be greatly reduced.
4) The application runs in an unsafe environment
Memcached can provide no security policy, and you can access memcached only through telnet. If the application is running on a shared system, security issues need to be considered.
5) The business itself needs persistent data or a database
6. Can all items in memcached be traversed?
No, this operation is relatively slow and blocks other operations (the slowness here is compared to other memcached commands). All non-debug commands of memcached, such as add, set, get, fulsh, etc., no matter how much data is stored in
memcached, their execution only consumes constant time. The time taken to execute any command that traverses all items will increase as the amount of data in memcached increases. When other commands are waiting (traversing all
The command with item has been executed) but cannot be executed, so blocking will occur.
The above is the detailed content of Boolean Education Yan 18 Memcached video data sharing. For more information, please follow other related articles on the PHP Chinese website!

MySQL's position in databases and programming is very important. It is an open source relational database management system that is widely used in various application scenarios. 1) MySQL provides efficient data storage, organization and retrieval functions, supporting Web, mobile and enterprise-level systems. 2) It uses a client-server architecture, supports multiple storage engines and index optimization. 3) Basic usages include creating tables and inserting data, and advanced usages involve multi-table JOINs and complex queries. 4) Frequently asked questions such as SQL syntax errors and performance issues can be debugged through the EXPLAIN command and slow query log. 5) Performance optimization methods include rational use of indexes, optimized query and use of caches. Best practices include using transactions and PreparedStatemen

MySQL is suitable for small and large enterprises. 1) Small businesses can use MySQL for basic data management, such as storing customer information. 2) Large enterprises can use MySQL to process massive data and complex business logic to optimize query performance and transaction processing.

InnoDB effectively prevents phantom reading through Next-KeyLocking mechanism. 1) Next-KeyLocking combines row lock and gap lock to lock records and their gaps to prevent new records from being inserted. 2) In practical applications, by optimizing query and adjusting isolation levels, lock competition can be reduced and concurrency performance can be improved.

MySQL is not a programming language, but its query language SQL has the characteristics of a programming language: 1. SQL supports conditional judgment, loops and variable operations; 2. Through stored procedures, triggers and functions, users can perform complex logical operations in the database.

MySQL is an open source relational database management system, mainly used to store and retrieve data quickly and reliably. Its working principle includes client requests, query resolution, execution of queries and return results. Examples of usage include creating tables, inserting and querying data, and advanced features such as JOIN operations. Common errors involve SQL syntax, data types, and permissions, and optimization suggestions include the use of indexes, optimized queries, and partitioning of tables.

MySQL is an open source relational database management system suitable for data storage, management, query and security. 1. It supports a variety of operating systems and is widely used in Web applications and other fields. 2. Through the client-server architecture and different storage engines, MySQL processes data efficiently. 3. Basic usage includes creating databases and tables, inserting, querying and updating data. 4. Advanced usage involves complex queries and stored procedures. 5. Common errors can be debugged through the EXPLAIN statement. 6. Performance optimization includes the rational use of indexes and optimized query statements.

MySQL is chosen for its performance, reliability, ease of use, and community support. 1.MySQL provides efficient data storage and retrieval functions, supporting multiple data types and advanced query operations. 2. Adopt client-server architecture and multiple storage engines to support transaction and query optimization. 3. Easy to use, supports a variety of operating systems and programming languages. 4. Have strong community support and provide rich resources and solutions.

InnoDB's lock mechanisms include shared locks, exclusive locks, intention locks, record locks, gap locks and next key locks. 1. Shared lock allows transactions to read data without preventing other transactions from reading. 2. Exclusive lock prevents other transactions from reading and modifying data. 3. Intention lock optimizes lock efficiency. 4. Record lock lock index record. 5. Gap lock locks index recording gap. 6. The next key lock is a combination of record lock and gap lock to ensure data consistency.


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

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.

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

EditPlus Chinese cracked version
Small size, syntax highlighting, does not support code prompt function

SublimeText3 Linux new version
SublimeText3 Linux latest version

SublimeText3 Chinese version
Chinese version, very easy to use