Memcached Telnet Interface

​​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″ 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):

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.