Memcached快速入门

What is Memcached

Memcached 是一个高性能的分布式内存对象缓存系统，用于动态Web应用以减轻数据库负载。它通过在内存中缓存数据和对象来减少读取数据库的次数，从而提高动态、数据库驱动网站的速度。

安装

Ubuntu

$ sudo apt-get install memcached

$ ps aux | grep memcached
memcache 26355  0.0  0.0 325400  1208 ?        Sl   16:30   0:00 /usr/bin/memcached -m 64 -p 11211 -u memcache -l 127.0.0.1

源码

sudo apt-get install g++ make libevent-dev

curl -O --location http://memcached.org/latest
mv latest memcached-latest.tar.gz
tar vxzf memcached-latest.tar.gz

cd memcached-*
./configure && make

sudo make install

配置

vim /etc/memcached.conf

• -l 127.0.0.1 监听ip
• -m 64 允许最大内存，这里默认时4 Megabytes(MB)

和memcached通信

安装telnet

sudo apt-get install telnet

试试

$ telnet localhost 11211
Trying 127.0.0.1...
Connected to localhost.
Escape character is ‘^]‘.

详细的ASCII（文本）协议

https://github.com/memcached/memcached/blob/master/doc/protocol.txt

查询基本信息

stats
STAT pid 26355
STAT uptime 457
STAT time 1404290303
STAT version 1.4.14
STAT libevent 2.0.21-stable
STAT pointer_size 64
STAT rusage_user 0.007959
STAT rusage_system 0.007959
STAT curr_connections 5
STAT total_connections 6
STAT connection_structures 6
STAT reserved_fds 20
STAT cmd_get 0
STAT cmd_set 0
STAT cmd_flush 0
STAT cmd_touch 0
STAT get_hits 0
STAT get_misses 0
STAT delete_misses 0
STAT delete_hits 0
STAT incr_misses 0
STAT incr_hits 0
STAT decr_misses 0
STAT decr_hits 0
STAT cas_misses 0
STAT cas_hits 0
STAT cas_badval 0
STAT touch_hits 0
STAT touch_misses 0
STAT auth_cmds 0
STAT auth_errors 0
STAT bytes_read 7
STAT bytes_written 0
STAT limit_maxbytes 67108864
STAT accepting_conns 1
STAT listen_disabled_num 0
STAT threads 4
STAT conn_yields 0
STAT hash_power_level 16
STAT hash_bytes 524288
STAT hash_is_expanding 0
STAT expired_unfetched 0
STAT evicted_unfetched 0
STAT bytes 0
STAT curr_items 0
STAT total_items 0
STAT evictions 0
STAT reclaimed 0
END

查看配置

stats settings
STAT maxbytes 67108864
STAT maxconns 1024
STAT tcpport 11211
STAT udpport 11211
STAT inter 127.0.0.1
STAT verbosity 0
STAT oldest 0
STAT evictions on
STAT domain_socket NULL
STAT umask 700
STAT growth_factor 1.25
STAT chunk_size 48
STAT num_threads 4
STAT num_threads_per_udp 4
STAT stat_key_prefix :
STAT detail_enabled no
STAT reqs_per_event 20
STAT cas_enabled yes
STAT tcp_backlog 1024
STAT binding_protocol auto-negotiate
STAT auth_enabled_sasl no
STAT item_size_max 1048576
STAT maxconns_fast no
STAT hashpower_init 0
STAT slab_reassign no
STAT slab_automove 0
END

保存值

set mykey 0 300 16
I Love Memcached

按回车将会得到STORED

set mykey 0 300 16
I Love Memcached
STORED

现在我们就可以通过get获取值了

get mykey
VALUE mykey 0 16
I Love Memcached
END

set格式：

<command name> <key> <flags> <exptime> <bytes>

设置Memcached开机启动

$ /etc/init.d/memcached status
 * memcached is running

disable

sudo update-rc.d memcached disable

enable

sudo update-rc.d memcached enable

确认运行默认级别:

sudo update-rc.d memcached defaults

分布式部署

memcached -p 3030
memcached -p 3031

import pylibmc
mc = pylibmc.Client(["127.0.0.1:3030", "127.0.0.1:3031"], binary=True,
behaviors={"tcp_nodelay": True, "ketama": True})
mc["ahmed"] = "Hello World"
mc["tek"] = "Hello World"

• binary = True: 二进制协议，非ASCII协议
• behaviors={"tcp_nodelay": True, "ketama": True} :"ketama" = True 意味使用md5的hash算法进行对key进行分布