83-high performance, distributed cache Memcache analysis

I. Memcached INTRODUCTION

Memcached is a high-performance, distributed memory object caching system, generic in nature, but intended Speeding up Dynamic Web applications by alleviating database load.

(developed by LiveJournal's Danga Interactive)

#高性能, distributed Cache system

Cache server:

Caching: Cache, no persistent storage function;

Bypass cache # side-Hanging cache

K/V cache, only supports storage streaming data;

Characteristics:

K/V cache: Serializable data only; Storage: k/v (Key:value)

The intelligence half relies on the client (call memcached API Development program), half relies on the service side;

Distributed cache: Distributed cluster with non-communication;

Distributed System Request Routing method: Modulus method (the number of machines to determine which machine to send to),

consistent hashing algorithm (clockwise Hashi);

Algorithm complexity: O (1)

Purge Expired Cache Entries:

Cache exhaustion: LRU

Cache entry Expiration: Lazy cleanup mechanism

#即会定期检查缓存, when the cache fails, it does not clean up, but it has new cache write-ins

Overwrite the old cached content directly

Two. Installation configuration:

Available directly from the CentOS 7 base warehouse:

Port to listen on:

11211/TCP, 11211/UDP

Main program:/usr/bin/memcached

Configuration file:/etc/sysconfig/memcached

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Unit File:memcached.service

Management tools: Memcached-tool

Protocol format: memcached protocol

Text Format

binary format

Three. Memcache Command detailed

Detailed protocol Help:/usr/share/doc/memcached-1.4.15/protocol.txt

Command:

Statistics class: Stats, stats items, stats slabs, stats sizes

Storage class: Set, Add, replace, append, prepend

Command format: <command name> <key> <flags> <exptime> <bytes>

Extra Information Expiration Time size

<cas unique> #回车后才能输入值

Key key to find cached values

Flags can include integer parameters for key-value pairs, which the client uses to store additional information about key-value pairs

# 1 is the default

Expiration the length of time (in seconds, 0) that a key-value pair is saved in the cache

Far

Bytes The byte points stored in the cache

Value stored values (always on the second row)

Retrieving classes: Get, delete, INCR/DECR

Empty: Flush_all

Example:

telnet> add KEY <flags> <expiretime> <bytes> \ r

Telnet> Value parameter Usage

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Common options for memcached programs:

-M <num>:use <num> MB memory Max to use for object storage; The

Default is megabytes.

-C <num>:use <num> Max simultaneous connections; The default is 1024.

-U <username>: Runs the process as a specified user;

-L <IP_ADDR>: Listening IP address, default to native all address;

-P <num>: Listening TCP port, the default is Port 11211.

-U <num>:listen on UDP Port <num>, and the default is Port 11211, 0 is off.

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-M: When memory is exhausted, the LRU cleanup cache is not executed, but the new cache entry is rejected until there are extra empty

is available;

-F <factor>: growth factor (the size of the memory chunk increases in multiples); default is 1.25;

-T <threads>: The number of threads initiated to respond to user requests;

memcached default No authentication mechanism, can be used for SASL certification;

Sasl:simple Authentication Secure Layer

three. API:

Php-pecl-memcache

Php-pecl-memcached

Python-memcached

Libmemcached

#此工具包中包含多个memcache的命令行管理工具

Libmemcached-devel

Command-line tools:

Memcached-tool Server:port COMMAND

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[Email protected] ~]# RPM-QL libmemcached

/usr/bin/memaslap

/usr/bin/memcapable

/usr/bin/memcat

/usr/bin/memcp

/usr/bin/memdump

/usr/bin/memerror

/usr/bin/memexist

/usr/bin/memflush

/usr/bin/memparse

/usr/bin/memping

/usr/bin/memrm

/usr/bin/memslap

/usr/bin/memstat

/usr/bin/memtouch

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Four. Using Telnet to manage the memcache example

1. Yum Install Telnet

--telnet localhost 11211

Stats

 

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Five. Nginx support for Memcache

Required modules: Ngx_http_memcached_module

Syntax:memcached_bind address [transparent] | Off

default:-

Context:http, Server, location

#用于绑定 memcache Server

Syntax:memcached_pass address;

default:-

Context:location, if in location

#绑定memcache Cluster

eg

server {

Location/{

Set $memcached _key "$uri? $args";

#将指定的key into Memcache to generate the cache;

Memcached_pass host:11211;

Error_page 404 502 504 = @fallback;

}

Location @fallback {

Proxy_pass Http://backend;

}

}

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83-high performance, distributed cache Memcache analysis