Memcached (high performance memory object cache)

Case study ： High performance memory object cache

Memcached

Skill goal ：

understand Memcached The core concept

Will be carried out in Memcached Related deployment operations

Will be carried out in Memcached Primary primary replication operation

Will be carried out in Memcached Service high availability configuration

2.1 case analysis

2.1.1 Case Overview

Memcached It is an open source high-performance distributed memory object caching system , It stores all the data inside

In storage , Because the memory will maintain a huge Hash surface , Therefore, any storage type of data is supported . Many networks

Station use Memcached Improve the speed of website visit , Especially large websites that need to access data frequently .

Memcached Is a typical C/S framework , So you need to build Memcached Server side and Memcached API customer

Home end .Memcached The server side uses C language-written , and Memcached API The client can write in any language

Write , Such as PHP、Python、Perl etc. , And pass Memcached Deal with the Memcached Server side communication .

Typical architectures are shown in the figure 2.1 Shown .

chart 2.1 Memcache Common architecture

When Web The client sends a request to Web Server application , The application will call Memcached API

Client library interface to connect Memcached Server query data . If Web The data requested by the client is in

Memcached The server has been cached , be Memcached The server will return the data to Web client ; otherwise , Will Web Client requests are sent to MySQL database , The database queries and returns the requested data to Memcached as well as Web client , meanwhile Memcached The server will also save the data , Convenient for the next user request .

2.1.2 Case pre knowledge points

1. Data storage method and data expiration method

Memcached It has unique data storage mode and data expiration mode .

1） Data storage mode ：Slab Allocation

Slab Allocation That is, allocate memory by group , Assign one at a time Slab, Equivalent to a size of 1M

Page of . then , stay 1M The space is divided into the same size according to the data Chunk, Pictured 2.2 Shown . The method

It can effectively solve the problem of memory fragmentation , But it may also waste memory space .

chart 2.2 Slab Allocation 2） Data expiration method ：LRU、Laxzy Expiration

LRU and Laxzy Expiration There are two ways to expire data .

Ø LUR When the additional data space is insufficient , Will be based on LRU Eliminate the least recently used records .

Ø Laxzy Expiration That is, the inertia expires , Refers to the use of get View the record time when , So the inspection record is

No has expired .

2. Memcached Caching mechanisms

Cache is the data resident in memory , Can read quickly , and Memcached This is a very

Excellent caching software . When a program writes a cache data request ,Memcached Of API The interface will Key Input path

The algorithm module routes to a service in the cluster , After that by API Interface to communicate with the server , Complete one minute

Cloth cache write , Pictured 2.3 Shown .

chart 2.3 Memcached Caching mechanisms

3. Memcached Distributed

Memcached Distributed deployment mainly depends on Memcached Client side implementation of , Multiple Memcached

The server is independent . How distributed data is stored is determined by the routing algorithm .

When Count According to the To reach customer Household End cheng order library , customer Household End Of count Law Just In accordance with the According to the road from count Law Come on " set Protect save Of

Memcached The server . When reading data , The client selects and based on the same routing algorithm used to save data

When storing data, the same server reads the data , Pictured 2.4 Shown .

chart 2.4 Memcached Distributed

4. Memcached Routing algorithm

1） Mod hash Algorithm

Mod hash The algorithm starts with key do hash The operation results in an integer , Do it again hash Algorithm , according to

Remainder for routing , This algorithm is suitable for most data requirements . But it's not suitable for dynamic environment , Than

If a large number of machines are added or deleted , This will cause a large number of object storage locations to fail .

2） Uniformity hash Algorithm

Uniformity hash The algorithm is suitable for use in dynamic environment . The principle is based on hash The algorithm corresponds to

key Through certain hash After the algorithm is processed, the mapping forms a closed loop with head and tail connected , Then by using and

Like storage hash The algorithm also maps machines into rings , Clockwise calculation stores all objects in

In your nearest machine , Pictured 2.5 Shown .

chart 2.5 Uniformity hash Algorithm

 

2.1.3 Case environment

This case uses three CentOS 7.3 The system is complete , among ： Two are Memcached The server , The other is Ji

On LAMP Architecture Memcached Extended Memcached API client , The specific structure needs to be adjusted according to the needs of the enterprise . The case environment is shown in the table 2-1 Shown .

 

2.2.1 install Memcached The server

1. install Libevent

Libevent Is a cross platform event processing interface encapsulation , Event access that is compatible with multiple operating systems .

Memcached Installation of depends on Libevent, Therefore, it needs to be completed first Libevent Installation .

[[email protected] ~]# tar -zxvf libevent-2.1.8-stable.tar.gz -C /usr/src/

[[email protected] libevent-2.1.8-stable]# ./configure --prefix=/usr/local/libevent

[[email protected] libevent-2.1.8-stable]# make && make install

Here we are Libevent Installation completed , Next you can install Memcached.

2. install Memcached

Use the source code Memcached Build and install , During installation, you need to specify Libevent Installation

route .

[[email protected] ~]# tar -zxvf memcached-1.5.1.tar.gz -C /usr/src/ [[email protected] ~]# cd

/usr/src/memcached-1.5.1/

[[email protected] memcached-1.5.1]# ./configure --prefix=/usr/local/memcached

--with-libevent=/usr/local/libevent

[[email protected] memcached-1.5.1]# make && make install

3. Set up Memcached Service script

Memcached After the server is installed , You can use the... Under the installation directory bin/memcached To start the service

service . however , For more convenient management Memcached, Write scripts to manage Memcached service .

[[email protected] ~]# vim /usr/local/memcached/memcached_service.sh

#!/bin/bash

CMD="/usr/local/memcached/bin/memcached"

start(){

$CMD -d -m 128 -u root

}

stop(){

killall memcached;

}

ACTION=$1

case $ACTION in

'start')

start;;

'stop')

stop;;

'restart')

stop

sleep 2

start;;

*)

echo 'Usage:{start|stop|restart}'

esac Which starts Memcached when ,-d Option to run as a daemon Memcached service ,

-m Is for Memcached Distribute 128M Of memory , It should be adjusted according to the needs of the enterprise ,-u Specify the user account to run .

Then set script permissions , start-up Memcached service .

[[email protected] ~]# chmod 755 /usr/local/memcached/memcached_service.sh

[[email protected] ~]# /usr/local/memcached/memcached_service.sh start

After the service starts , monitor 11211/tcp port .

[[email protected] ~]# netstat -antp |grep memcached

tcp 0 0 0.0.0.0:11211 0.0.0.0:* LISTEN 10196/memcached

tcp6 0 0 :::11211 :::* LISTEN 10196/memcached

2.2.2 Memcached API client

So that the program can directly call Memcached Libraries and interfaces , have access to Memcached Extension components

take Memcache Added as PHP A module of . This extension uses Libmemcached Library provides the API And

Memcached The server interacts with each other .

The client needs to install apache And php To test memcache, about Apache And PHP Configuration process

It is omitted here .

1. Compilation and installation Libmemcached

Compiling Memcached When extending components , You need to specify the Libmemcached Location of the library , So install it first

Libmemcached library .

[[email protected] ~]# tar -xzvf libmemcached-1.0.18.tar.gz

[[email protected] ~]# cd libmemcached-1.0.18/

[[email protected] libmemcached-1.0.18]# ./configure --prefix=/usr/local/libmemcached

--with-memcached=/usr/local/memcached

[[email protected] libmemcached-1.0.18]# make && make install

2. Compilation and installation Memcached Expand

install Libmemcached Behind the library , You can do it PHP Of Memcached Extension component installation .

[[email protected] ~]# wget ​ ​http://pecl.php.net/get/memcached-2.2.0.tgz​​

[[email protected] ~]# tar -xzvf memcached-2.2.0.tgz

[[email protected] ~]# cd memcached-2.2.0/

Be careful ： To configure Memcached API when ,memcached-2.2.0.tgz By default, there is no... In the source package configure with

Set script , Need to use PHP Of phpize Script generation configuration script configure.

[[email protected] memcached-2.2.0]# /usr/local/php5/bin/phpize

Configuring for:

PHP Api Version: 20121113

Zend Module Api No: 20121212

Zend Extension Api No: 220121212

[[email protected] memcached-2.2.0]# cp -r /usr/local/php5/include/php/ext/ ./

[[email protected] memcached-2.2.0]# ./configure \

--enable-memcached --with-php-config=/usr/local/php5/bin/php-config \

--with-libmemcached-dir=/usr/local/libmemcached \

--disable-memcached-sasl

Be careful ： When configuring, use --disable-memcached-sasl Options , close Memcached Of SASL Authentication function ,

Otherwise, an error will be reported .

[[email protected] memcached-2.2.0]# make

[[email protected] memcached-2.2.0]# make test

[[email protected] memcached-2.2.0]# make install

[[email protected] memcached-2.2.0]# make install

Installing shared extensions: /usr/local/php5/lib/php/extensions/no-debug-zts-20121212/

// Share the location of the build

3. To configure PHP add to Memcached Components

edit PHP The configuration file php.ini, add to Memcached Component support .

[[email protected] ~]# cd /usr/local/php5/

[[email protected] php5]# vim php.ini

Add the following

extension_dir = "/usr/local/php5/lib/php/extensions/no-debug-zts-20121212/"

extension=memcached.so Can pass phpinfo, Check to see if you have added Memcached Extension module .

[[email protected] ~]# vim /usr/local/httpd/htdocs/index.php

<?php

phpinfo();

?>

Use a browser to access , The result is shown in Fig. 2.6 Shown , Added successfully .

chart 2.6 phpinfo Information

4. test Memcached-API function

By writing simple PHP Test code calls Memcache Program interface to test whether it is connected with Memcached The server

Working together , The code is as follows ：

[[email protected] ~]# vim /usr/local/httpd/htdocs/test.php

<?php

$memcache = new Memcached();

$memcache->addServer('192.168.9.200', 11211);

$memcache->set('key', 'Memcache test successful!', 0, 60);

$result = $memcache->get('key');

unset($memcache);

echo $result;

?>

The purpose of this code is to connect the client Memcached The server , Set the name to ‘key’ The value of the key of is

‘Memcache test successful!’, And read the display , Success indicates that the server and client work together normally , send

Access with a browser , The test results are shown in the figure 2.7 Shown .

chart 2.7 The test page

2.3 Memcached Database operation and management

Memcache The protocol is simple and can be used directly telnet Connect Memcached Of 11211 Port pair Memcached data

Library for operation and management .

[[email protected] ~]# telnet 127.0.0.1 11211

Trying 127.0.0.1...

Connected to 127.0.0.1.

Escape character is '^]'.

// Enter the operation instructions

Operation command format ：<command name> <key> <flags> <exptime> <bytes> <data block>

Here is Memcached Common operation instructions for databases .

1. Add a key value data

add username 0 0 7

example

STORED

among add username 0 0 7 Indicates that the key value is named username, The tag bit indicates that the custom information is 0, Be overdue

Time is 0（ Never expire , The unit is in seconds ）, The number of bytes is 7; example Key value , Note that the input length is 7 byte ,

Conform to the set value .

2. Query key data

get username

VALUE username 0 7

example

END

gets username

VALUE username 0 7 4

example

END

among get Followed by the key name , If checking for recent updates , have access to gets, The last one shows the update

factor , The number of update factors will be increased by one for each update .

3. Update a key data

set username 0 0 10

everything

STORED

get username

VALUE username 0 10

everything

END

among set Followed by the key name that needs to be updated 、 Marker bit 、 Expiration time 、 Number of bytes . If the key name does not exist ,set phase

When add add to . If you just want to simply update without adding functions , Use replace. The updated key name must be

There must be , If the key name does not exist, it will report NOT_STORED Error of .

replace username 0 0 7

lodging

STORED

gets username

VALUE username 0 7 6

lodging

END

replace username1 0 0 7

example

NOT_STORED

4. Clear a cache of data

delete username

DELETED

get username

END

Use delete Delete a key with a value of usernmame Cache data , Use get Check that no content exists .

5. Update after checking check and set

gets username

VALUE username 0 7 7

example

END

cas username 0 0 7 1

lodging

EXISTS

cas username 0 0 7 7

lodging

STORED

gets username

VALUE username 0 7 8

lodging

END

If cas The number of the last update factor of is the same as gets The number of update factors returned is equal , Update ; Otherwise return to

EXISTS.

6. Additional data

append username 0 0 7 // After adding 7 byte

example

STORED

get username

VALUE username 0 14

lodgingexample

END

In the key name username Add data after the original key value append.

prepend username 0 0 2 // Pre append 2 byte

un

STORED

get username

VALUE username 0 16

unlodgingexample

END

In the key name username Append data before the original key value prepend.

7. Clear all cached data

flush_all

OK

8. View server statistics

stats

stats items // Returns all key value pair Statistics

stats cachedump 1 0 // Returns the key value pair of the specified storage space

stats slabs // Display each slab Information about , Include chunk Size 、 number 、 Usage, etc

stats sizes // Output all item Size and number of

stats reset // Clear statistics

2.4 Memcached Ways to achieve primary replication and high availability

Memcached Primary primary replication refers to the replication of data on any computer Memcahed The modified data of the server will be synchronized to another server ,

however Memcahed API The client cannot determine which one to connect to Memcahed The server , So you need to set VIP

Address , Provide to Memcahed API Client connection . have access to keepalived produce VIP Address connection master Memcahed

The server , And provide high availability architecture .

2.4.1 Memcached Primary primary replication Architecture

Memcached The replication function of supports multiple Memcached Copy each other （ Two way replication , Both active and standby are readable

Written ）, Can solve Memcached Disaster recovery of .

To use Memcached Replication Architecture , Before uninstalling memcache1 On the machine 1.5.1 Version of memcached,

Re download the... That supports replication Memcached Installation package .

[[email protected] ~]# yum -y install psmisc

[[email protected] ~]# /usr/local/memcached/memcached_service.sh stop

[[email protected] ~]# netstat -lnupt | grep memcached

The installation process is the same as that of the previous installation Memcached In the same way , Here is a brief introduction .

1. Install with replication Memcached

installation is complete libevent after , Will download memcached-1.2.8-repcached-2.2.tar.gz Into the

Line unzip , After that, complete the configuration, compilation and installation .

[[email protected] ~]# cd memcached-1.2.8-repcached-2.2/

[[email protected] memcached-1.2.8-repcached-2.2]# ./configure

--prefix=/usr/local/memcached_replication --enable-replication

--with-libevent=/usr/local/libevent

modify memcached.c The configuration file

[[email protected] memcached-1.2.8-repcached-2.2]# vim memcached.c

#ifndef IOV_MAX

#if defined(__FreeBSD__) || defined(__APPLE__)

# define IOV_MAX 1024

#endif

#endif

Change to ：

/* FreeBSD 4.x doesn't have IOV_MAX exposed. */

#ifndef IOV_MAX

# define IOV_MAX 1024

#endif

Compilation and installation

[[email protected] memcached-1.2.8-repcached-2.2]# make && make install

2. start-up Memcached service

Copy the function of Memcached After installation , You need to compile and install libevent-2.1.so.6 model

Copy block to /usr/lib64 Under the table of contents , Otherwise, start the with replication function Memcached Service times are wrong .

[[email protected] ~]# ln -s /usr/local/libevent/lib/libevent-2.1.so.6 /usr/lib64/

When starting the service , Use -x Options point to the opposite end .

[[email protected] ~]# /usr/local/memcached_replication/bin/memcached -d -u root -m 128 -x

192.168.9.202

[[email protected] ~]# netstat -antp |grep memcached

tcp 0 0 0.0.0.0:11211 0.0.0.0:* LISTEN

16863/memcached

tcp 0 0 192.168.9.200:42786 192.168.9.202:11212 ESTABLISHED

16863/memcached

tcp6 0 0 :::11211 :::* LISTEN

16863/memcached

Also start memcached2 The server , Pay attention to start Memcached Service points to the opposite end .

3. Use telnet Simply verify the replication function

1） stay Memcached1 Insert a characteristic key value on the

install telnet Tools

[[email protected] ~]#yum -y install telnet*

Connect memcached

[[email protected] Memcached1 lib]# 192.168.9.200 11211

Trying 192.168.9.200...

Connected to 192.168.9.200.

Escape character is '^]'.

set username 0 0 8

20180523

STORED

get username

VALUE username 0 8

20180523

END

quit

Connection closed by foreign host. 2） stay Memcached2 To view the key value just inserted

[[email protected] ~]# elnet 192.168.9.202 11211

Trying 192.168.9.202...

Connected to 192.168.9.202.

Escape character is '^]'.

get username

VALUE username 0 8

20180523

END

get username2

END

Quit

Connection closed by foreign host. Same as The reason is , stay Memcached2 On insert Enter into Of Count According to the , stay Memcached1 also can With check see To . this Namely

Memcached Master copy of .

2.4.2 Memcached Master master copy + Keepalived High availability Architecture

because Memcached Master master replicates this architecture , When the program connects, it does not know which primary server it should connect to ,

the With need stay front End plus VIP The earth site , real present high You can use frame structure . this in use Keepalived real present , because and

Keepalived It's used to detect Memcached Whether the status of the server is normal , Pictured 2.8 Shown .

chart 2.8 Memcached High availability Architecture

keepalived through too No break check measuring Memcached Lord clothing service device Of 11211 End mouth , Such as fruit check measuring To

Memcached Service downtime or crash occurs , Will be VIP Move from master server to slave server , So as to realize

present Memcached High availability .

1. Installation configuration keepalived

[[email protected] ~]# yum install –y keepalived

1） Configuration master keepalived

[[email protected] ~]# vim /etc/keepalived/keepalived.conf

! Configuration File for keepalived

global_defs {

notification_email {

[email protected]

[email protected]

[email protected]

}

notification_email_from [email protected]

smtp_server 192.168.200.1

smtp_connect_timeout 30

router_id LVS_DEVEL // Route identification , Keep the master and the slave in line

vrrp_skip_check_adv_addr

vrrp_strict

vrrp_garp_interval 0

vrrp_gna_interval 0

}

vrrp_instance VI_1 {

state MASTER // Both active and standby status are MASTER

interface ens33

virtual_router_id 51 // Virtual routing ID, The master and the slave are the same

priority 100 // priority , The primary is superior to the standby

advert_int 1

nopreempt // Don't take the initiative to seize resources , Only in Master Or on a high priority server

authentication {

auth_type PASS

auth_pass 1111

}

virtual_ipaddress {

192.168.1.100 // Definition VIP Address

}

}

virtual_server 192.168.1.100 11211 { //VIP Fault detection

delay_loop 6

lb_algo rr

lb_kind NAT

persistence_timeout 20

protocol TCP

sorry_server 192.168.9.202 11211 // Opposite end

real_server 192.168.9.200 11211 { // This machine

weight 3

notify_down /root/memcached.sh // When memcached Downtime , stop it keepalived service

TCP_CHECK {

connect_timeout 3

nb_get_retry 3

delay_before_retry 3

connect_port 11211

}

}

}

Set the execution script ：

[[email protected] ~]# echo "/usr/bin/systemctl stop keepalived" > /root/memcached.sh

[[email protected] ~]# chmod +x memcached.sh

2） Configure the backup keepalived

Master-slave keepalived The content of the configuration file is similar , Copy directly to modify , Only the different ones are listed below

The place is sorted out .

[[email protected] ~]# scp /etc/keepalived/keepalived.conf 192.168.9.202:/etc/keepalived/

// Omit

vrrp_instance VI_1 {

state MASTER // The standby status is also MASTER

interface eth0

virtual_router_id 51 // Virtual routing ID, The master and the slave are the same

priority 99 // Low priority

advert_int 1

// Get rid of nopreempt

authentication {

auth_type PASS

auth_pass 1111

}

// Omit

virtual_server 192.168.1.100 11211 { //VIP Fault detection

delay_loop 6

lb_algo rr

lb_kind NAT

persistence_timeout 20

protocol TCP

sorry_server 192.168.9.200 11211 // Opposite end

real_server 192.168.9.202 11211 { // This machine

weight 3

notify_down /root/memcached.sh // When memcached Downtime , stop it keepalived service

// Omit

Also set the script ：

[[email protected] ~]# echo "/usr/bin/systemctl stop keepalived" > /root/memcached.sh

[[email protected] ~]# chmod +x memcached.sh

2. Test verification

Start the master and slave respectively keepalived service .

[[email protected] ~]# systemctl start keepalived

[[email protected] ~]# systemctl start keepalived

1） Validation master keepalived obtain VIP Address

Use ip address show Command view VIP Address （ Use ifconfig Can't view ）.

[[email protected] ~]# ip address

// Omit

2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000

link/ether 52:54:00:f0:23:a6 brd ff:ff:ff:ff:ff:ff

inet 192.168.9.200/24 brd 192.168.9.255 scope global dynamic eth0

valid_lft 7181sec preferred_lft 7181sec

inet 192.168.1.100/32 scope global eth0 // Have obtained VIP Address

valid_lft forever preferred_lft forever

inet6 fe80::dcdb:41a6:7a18:680b/64 scope link

valid_lft forever preferred_lft forever 2） Verify high availability

close Memcached1 Server's Memcached service , stay Memcached2 Check the address letter on the server

Rest .（ notes ： Be sure to shut down both machines selinux）

[[email protected] ~]#setenforce 0

[[email protected] ~]#setenforce 0

[[email protected] ~]# killall memcached

[[email protected] ~]# ip addr

// Omit

2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000

link/ether 52:54:00:ad:1e:2b brd ff:ff:ff:ff:ff:ff

inet 192.168.9.202/24 brd 192.168.9.255 scope global eth0

valid_lft forever preferred_lft forever

inet 192.168.1.100/32 scope global eth0 // Obtained VIP Address

valid_lft forever preferred_lft forever

inet6 fe80::5054:ff:fead:1e2b/64 scope link

valid_lft forever preferred_lft forever

3. The architecture features

Keepalived To be able to Memcached A... Is generated on the database VIP Address , The program connects to this fixed VIP

Address to main Memcached database , Even if the back-end database is switched from master to slave , There is no need to change the address . Because being the Lord

Memcached Database Memcached When the service stops ,keepalived From Memcached Server reacquires

The original VIP Address , So as to realize master-slave switching , This process is called VIP Address drift .