Memcached的管理

1、数据存储（假设key为dbasky.net，value为88888）

printf "set dbasky.net 0 0 5\\r\\n88888\\r\\n" | nc 127.0.0.1 11211

STORED

2、数据取回（假设key为dbasky.net）

printf "get dbasky.net\\r\\n" | nc 127.0.0.1 11211

VALUE dbasky.net 0 5

88888

END

3、数值增加1（假设key为dbasky.net，并且value为正整数）

printf "incr dbasky.net 1\\r\\n" | nc 127.0.0.1 11211

88889

4、数值减少3（假设key为dbasky.net，并且value为正整数）

printf "decr dbasky.net 3\\r\\n" | nc 127.0.0.1 11211

88886

5、数据删除（假设key为dbasky.net）

printf "delete dbasky.net\\r\\n" | nc 127.0.0.1 11211

DELETED

6、查看Memcached状态

[root@app3 ~]# printf "stats\\r\\n" | nc 127.0.0.1 11211

STAT pid 20272

STAT uptime 927901

STAT time 1256541017

STAT version 1.2.8

STAT pointer_size 64

STAT rusage_user 72323.142211

STAT rusage_system 270758.303481

STAT curr_items 2255461

STAT total_items 2237096141

STAT bytes 3865876133

STAT curr_connections 156

STAT total_connections 2662892830

STAT connection_structures 2975

STAT cmd_flush 0

STAT cmd_get 7155551459

STAT cmd_set 2237096141

STAT get_hits 6275571127

STAT get_misses 879980332

STAT evictions 21174550

STAT bytes_read 5936788593022

STAT bytes_written 12278494693042

STAT limit_maxbytes 4294967296

STAT threads 9

STAT accepting_conns 1

STAT listen_disabled_num 0

END

7、模拟top命令，查看Memcached状态：

watch "printf \'stats\\r\\n\' | nc 127.0.0.1 11211"

或者

watch "echo stats | nc 127.0.0.1 11211"

[root@app3 ~]# watch "printf \'stats\\r\\n\' | nc 127.0.0.1 11211"

Every 2.0s: printf \'stats\\r\\n\' | nc 127.0.0.1 11211 Mon Oct 26 16:11:26 2009

STAT pid 20272

STAT uptime 927970

STAT time 1256541086

STAT version 1.2.8

STAT pointer_size 64

STAT rusage_user 72327.750510

STAT rusage_system 270774.932953

STAT curr_items 2255435

STAT total_items 2237240981

STAT bytes 3865771193

STAT curr_connections 269

STAT total_connections 2663066932

STAT connection_structures 2975

STAT cmd_flush 0

STAT cmd_get 7156031867

STAT cmd_set 2237240981

STAT get_hits 6275980308

STAT get_misses 880051559

STAT evictions 21177694

STAT bytes_read 5937174840056

STAT bytes_written 12279303680177

STAT limit_maxbytes 4294967296

STAT threads 9

STAT accepting_conns 1

STAT listen_disabled_num 0

END

下面解释下各项的含意：

uptime 是memcached运行的秒数，cmd_get是查询缓存的次数。这两个数据相除一下就能得到平均每秒请求缓存的次数，cmd_set 就是设置key=>value的次数。整个memcached是个大hash，用cmd_get没有找到的内容，就会调用一下cmd_set写进缓存里。紧跟着是get_hits，就是缓存命中的次数。缓存命中率 = get_hits/cmd_get *100%。get_misses的数字加上get_hits应该等于cmd_get。而total_itemscurr_items表示现在在缓存中的键值对个数，在图上total_items == cmd_set == get_misses，不过当可用最大内存用光时，memcached就会删掉一些内容，上面的等式就不成立了。