Memcached method for building cache server

Preface

Many web applications store data in a relational database management system (RDBMS), from which the application server reads the data and displays it in the browser.

However, as the amount of data increases and access becomes more concentrated, there will be major impacts such as increased burden on the RDBMS, deterioration of database response, and delays in website display.

Memcached/redis is a high-performance distributed memory cache server that caches database query results and reduces the number of database accesses to increase the speed and scalability of applications such as dynamic Web.

RDBMS stands for Relational Database Management System

1. Introduction

1. Nosql products: redis, mongodb, memcached.

NOSQL term explanation: non-relational database

(1) Storing data in the form of key-value pairs --- ( Key-Value )

(2) Cache database - The role of the cache server: speed up access and relieve database pressure

2. Advantages/Disadvantages of NoSQL

advantage:
- High scalability
- Distributed computing
- low cost
- Flexibility of architecture
- No complicated relationships
​
shortcoming:
- No standardization
- Limited query capabilities (so far)
- Eventually consistent programming is unintuitive

Cache server function: speed up access and relieve database pressure

3. The difference between relational database and non-relational database:---------High frequency interview question

1. First, let’s understand what a relational database is?
The most typical data structure of a relational database is a table, which is a data organization consisting of two-dimensional tables and the connections between them.
advantage:
1. Easy to maintain: all use table structure with consistent format;
2. Easy to use: SQL language is universal and can be used for complex queries;
3. Complex operations: Supports SQL and can be used for very complex queries within a table or between multiple tables.
shortcoming:
1. The reading and writing performance is relatively poor, especially the efficient reading and writing of massive data;
2. Fixed table structure, slightly less flexible;
3. High concurrent read and write requirements. For traditional relational databases, hard disk I/O is a big bottleneck

2. What is a non-relational database?

Non-relational data is a collection of structured data storage methods, which can be documents or key-value pairs.

advantage:
1. Flexible format: The format of stored data can be key, value, document, image, etc. It is flexible to use and has a wide range of application scenarios, while relational databases only support basic types.
2. Fast speed: NoSQL can use hard disk or random access memory as a carrier, while relational database can only use hard disk;
3. High scalability;
4. Low cost: NoSQL database is easy to deploy and is basically open source software.

shortcoming:
1. No SQL support is provided, and the learning and use costs are high;
2. No transaction processing;
3. The data structure is relatively complex, and it is slightly lacking in complex queries.

2. memcached

1. Features

1. Built-in memory storage method-----------In order to improve performance, the data saved in memcached is stored in the built-in memory storage space of memcache. Since the data only exists in the memory, restarting the operating system will cause all data to disappear.
2. Simple key/value storage--------------The server does not care about the meaning and structure of the data itself, as long as it is serializable data.

The storage item consists of four parts: "key, expiration time, optional flag and data";

2. Service Framework

principle

1. Check whether the client's request data is in memcached. If so, return the request data directly without performing any operations on the database. The path operations are ①②③⑦.

2. If the requested data is not in memcached, check the database and return the data obtained from the database to the client. At the same time, cache a copy of the data in memcached (the memcached client is not responsible and needs to be clearly implemented by the program). The path operation is ①②④⑤⑦⑥.

3. Keep the cache fresh. Whenever the data changes (for example, the data is modified or deleted), the cache information should be updated synchronously to ensure that users do not retrieve old data from the cache.

3. Configure and install Memcached

How much data memcache can store depends on how much memory the server itself has.

1. Installation--Prepare a server

[root@memcached ~]# yum install memcached -y
[root@memcached ~]# systemctl start memcached #Start

2. Modify the configuration file

[root@memcached ~]# vim /etc/sysconfig/memcached
PORT="11211" --- Listening port, default is 11211. Can be modified USER="memcached" ----- User MAXCONN="1024" ----- Default concurrency, can be modified CACHESIZE="64" ------ Given memory. The default is M
OPTIONS="" ----Listening network address

Then send the IP address to the developer, who will use the API interface to connect to memcached.
test:

[root@memcached ~]# yum install -y telnet #Install telent
[root@memcached ~]# telnet 192.168.246.188 11211
Trying 192.168.246.188...
Connected to 192.168.246.188.
Escape character is '^]'.
set name 0 60 9 #Set the key named name key mark bit (id number) expiration time size helloword #The value of name STORED #The appearance of stopped means that the storage has been successful.
get name #Query key value VALUE name 0 9
helloword
END
quit ---Exit

Parameter explanation:
name: The name of the key is defined by yourself
0: key id number, needs to be different from other keys
60: Cache expiration time, in seconds, 0 means forever
9: Maximum string length

Reasons for not using it: The type of data stored is single and the data can only be stored in memory. Data persistence cannot be achieved. If the server is restarted, the data will disappear.

=================================================================
Extension: Install PHP extension module to support memcached:
Install php7.0

[root@memcached ~]# rpm -Uvh https://mirror.webtatic.com/yum/el7/epel-release.rpm
[root@memcached ~]# rpm -Uvh https://mirror.webtatic.com/yum/el7/webtatic-release.rpm
[root@memcached ~]# yum -y install php70w.x86_64 php70w-cli.x86_64 php70w-common.x86_64 php70w-gd.x86_64 php70w-ldap.x86_64 php70w-mbstring.x86_64 php70w-mcrypt.x86_64 php70w-mysql.x86_64 php70w-pdo.x86_64 php70w-devel zlib-devel php70w-fpm libmemcached php70w-pecl-memcached
[root@memcached ~]# yum install -y make gcc zlib-devel libmemcached-devel git

Download PHP Memcache extension

Install nginx briefly and configure the yum source of nginx. Test access to PHP page.
[root@memcached ~]# vim /etc/nginx/conf.d/nginx.conf
server {
 listen 80;
 server_name localhost;
​
 location ~ \.php$ {
 root /usr/share/nginx/html;
 fastcgi_pass 127.0.0.1:9000;
 fastcgi_index index.php;
 fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
 include fastcgi_params;
 }
}
Edit php page [root@memcached html]# vim /usr/share/nginx/html/index.php
<?php
phpinfo();
?>
Restart nginx
Start php-fpm
Browser access 

This is the end of this article about how to build a cache server with Memcached. For more relevant Memcached cache server content, please search for previous articles on 123WORDPRESS.COM or continue to browse the following related articles. I hope everyone will support 123WORDPRESS.COM in the future!