Memcached Telnet Interface

leonheart

　　http://lzone.de/articles/memcached.htm
　　
1、启动Memcache 常用参数
memcached 1.4.3
-p <num> 设置端口号(默认不设置为: 11211)
-U <num> UDP监听端口 (默认: 11211, 0 时关闭)
-l <ip_addr> 绑定地址 (默认:所有都允许,无论内外网或者本机更换IP，有安全隐患，若设置为127.0.0.1就只能本机访问)
-d 独立进程运行
-u <username> 绑定使用指定用于运行进程 <username>
-m <num> 允许最大内存用量，单位M (默认: 64 MB)
-P <file> 将PID写入文件<file>，这样可以使得后边进行快速进程终止, 需要与 -d 一起使用
如：
在linux下：./usr/local/bin/memcached -d -u jb-mc -l 192.168.1.197 -m 2048 -p 12121
在window下：d:\App_Serv\memcached\memcached.exe -d RunService -l 127.0.0.1 -p 11211 -m 500
在windows下注册为服务后运行：
sc.exe create jb-Memcached binpath= “d:\App_Serv\memcached\memcached.exe -d RunService -p 11211 -m 500&Prime; start= auto
net start jb-Memcached
　　
　　2、telnet连接
　　telnet 127.0.0.1 11211
　　
Supported Commands
　　The supported commands (the official ones and some unofficial) are documented in the doc/protocol.txt document.
　　Sadly the syntax description isn't really clear and a simple help command listing the existing commands would be much better. Here is an overview of the commands you can find in the source (as of 16.12.2008):

CommandDescriptionExample

get
Reads a value
get mykey


set
Set a key unconditionally
set mykey 0 60 5


add
Add a new key
add newkey 0 60 5


replace
Overwrite existing key
replace key 0 60 5


append
Append data to existing key
append key 0 60 15


prepend
Prepend data to existing key
prepend key 0 60 15


incr
Increments numerical key value by given number
incr mykey 2


decr
Decrements numerical key value by given number
decr mykey 5


delete
Deletes an existing key
delete mykey


flush_all
Invalidate specific items immediately
flush_all


Invalidate all items in n seconds
flush_all 900


stats
Prints general statistics
stats


Prints memory statistics
stats slabs


Prints memory statistics
stats malloc


Print higher level allocation statistics
stats items



stats detail



stats sizes


Resets statistics
stats reset


version
Prints server version.
version


verbosity
Increases log level
verbosity


quit
Terminate telnet session
quit

Traffic Statistics
　　You can query the current traffic statistics using the command

stats
　　You will get a listing which serves the number of connections, bytes in/out and much more.
　　
　　Example Output:

STAT pid 14868
STAT uptime 175931
STAT time 1220540125
STAT version 1.2.2
STAT pointer_size 32
STAT rusage_user 620.299700
STAT rusage_system 1545.703017
STAT curr_items 228
STAT total_items 779
STAT bytes 15525
STAT curr_connections 92
STAT total_connections 1740
STAT connection_structures 165
STAT cmd_get 7411
STAT cmd_set 28445156
STAT get_hits 5183
STAT get_misses 2228
STAT evictions 0
STAT bytes_read 2112768087
STAT bytes_written 1000038245
STAT limit_maxbytes 52428800
STAT threads 1
END

　　
Memory Statistics
　　You can query the current memory statistics using

stats slabs
　　
　　Example Output:

STAT 1:chunk_size 80
STAT 1:chunks_per_page 13107
STAT 1:total_pages 1
STAT 1:total_chunks 13107
STAT 1:used_chunks 13106
STAT 1:free_chunks 1
STAT 1:free_chunks_end 12886
STAT 2:chunk_size 100
STAT 2:chunks_per_page 10485
STAT 2:total_pages 1
STAT 2:total_chunks 10485
STAT 2:used_chunks 10484
STAT 2:free_chunks 1
STAT 2:free_chunks_end 10477
[...]
STAT active_slabs 3
STAT total_malloced 3145436
END

　　
Which Keys Are Used?
　　There seems to be no builtin function to determine the currently set keys. However you can use the

stats items
　　command to determine how many keys do exist.

stats items
STAT items:1:number 220
STAT items:1:age 83095
STAT items:2:number 7
STAT items:2:age 1405
[...]
END

　　This at least helps to see if any keys are used. To dump the key names from a PHP script that already does the memcache access you can use the PHP code from 100days.de.
　　
Never Set a Timeout > 30 Days!
　　While this has nothing to do with the telnet access this is a problem you might run into. If you try to "set" or "add" a key with a timeout bigger than the allowed maximum you might not get what you expect because memcached then treats the value as a Unix timestamp. Also if the timestamp is in the past it will do nothing at all. Your command will silently fail.
　　So if you want to use the maximum lifetime specify 2592000. Example:

set my_key 0 2592000 1
1

Disappearing Keys on Overflow
　　Despite the documentation saying something about wrapping around 64bit overflowing a value using "incr" causes the value to disappear. It needs to be created using "add"/"set" again.