memcached 运行状态监控

memcached服务器的运行状态监控一般可以用个专门的运营系统监控起来，不过一般开发者可以用memcached协议支持的统计命令(stats)在linux下直接得到。

1、使用telnet连接memcached服务器

telnet 10.10.10.10 11211

2、memcached统计命令

一些常用的统计信息或者配置信息可以通过stats命令来得到。完成步骤1连接到memcached服务器之后进入telnet命令行并输入stats，回车之后就可以得到这些统计信息了。这些统计信息包含的信息如下：

pid: Process id of this server process（memcached服务器的进程号）
uptime: Number of secs since the server started(memcache服务器运行时间，单位秒)
time:current UNIX time according to the server（memcached服务所在机器的时间，单位秒）
version:Version string of this server（当前memcached的版本号）
pointer_size:Default size of pointers on the host OS (generally 32 or 64)（默认指针地址长度，根据操作系统，该值可以为32或者64）
rusage_user: Accumulated user time for this process(seconds:microseconds)（累计用户使用时间，精确到毫秒）
rusage_system: Accumulated system time for this process  (seconds:microseconds)（累计系统使用时间，精确到毫秒）
curr_items :Current number of items stored（当前存储的数据项个数）
total_items :Total number of items stored since  the server started（自启动之后，此服务器存储过的数据项个数）
bytes:Current number of bytes used to store items（memcached服务器当前占用的内存，单位字节）
curr_connections:Number of open connections（当前打开的连接数）
total_connections :Total number of connections opened since the server started running（自启动之后，此服务器打开过的连接数）
connection_structures :Number of connection structures allocated  by the server（此服务器分配的连接结构）
cmd_get :Cumulative number of retrieval reqs（获取请求数）
cmd_set:Cumulative number of storage reqs（存储请求数）
get_hits:Number of keys that have been requested and found present（请求成功的key的个数，缓存命中率=get_hits / cmd_get * 100% ）
get_misses:Number of items that have been requested and not found（请求失败的key的个数）
delete_misses:Number of deletions reqs for missing keys（删除数据请求不命中key的个数）
delete_hits：Number of deletion reqs resulting in an item being removed.（删除数据请求命中key的个数）
incr_misses ：Number of incr reqs against missing keys.
incr_hits： Number of successful incr reqs.
decr_misses：Number of decr reqs against missing keys.
decr_hits ：Number of successful decr reqs.
cas_misses：Number of CAS reqs against missing keys.
cas_hits ：Number of successful CAS reqs.
cas_badval： Number of CAS reqs for which a key was found, but the CAS value did not match.
auth_cmds： Number of authentication commands handled, success or failure.
auth_errors：Number of failed authentications.
evictions：Number of valid items removed from cache  to free memory for new items（为了存储新数据，利用LRU算法剔除有效数据的个数）
reclaimed：Number of times an entry was stored using memory from an expired entry（在已过期的数据占用的空间中存储新数据数据的次数，  memcached优先使用过期数据占用的空间）
bytes_read ： Total number of bytes read by this server from network（总共存储的字节数）
bytes_written：Total number of bytes sent by this server to network（中共发送的字节数）
limit_maxbytes： Number of bytes this server is allowed to  use for storage.
threads ：Number of worker threads requested.  (see doc/threads.txt)
conn_yields： Number of times any connection yielded to another due to hitting the -R limit.

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3、参考信息
memcached文本协议：https://github.com/memcached/memcached/blob/master/doc/protocol.txt