Memcached笔记——（一）安装&常规错误&监控

一、下载
1.Libevent
简单的说就是一个事件触发的网络库，Memcached离不开它。

wgethttp://cloud.github.com/downloads/libevent/libevent/libevent-2.0.17-stable.tar.gz

2.Memcached
今天的主角

wgethttp://memcached.googlecode.com/files/memcached-1.4.13.tar.gz

二、安装
1.Libevent
解压缩

tarzxvflibevent-2.0.17-stable.tar.gz

编译、安装

./configure--prefix=/usr&&make&&makeinstall

这里一定要注意指定--prefix，后面配置memcached的时候就有必要用到。
2.Memcached
解压

tarzxvfmemcached-1.4.13.tar.gz

编译、安装

./configure--with-libevent=/usr/lib&&make&&makeinstall

这里一定要指定libevent的路径，否则启动的时候就有找不到libevent的so文件的错误！
启动

memcached-d-m512-p11211-uroot-c256-P/var/run/memcached.pid

参数

引用

-p <num> TCP port number to listen on (default: 11211)
-U <num> UDP port number to listen on (default: 11211, 0 is off)
-l <addr> interface to listen on (default: INADDR_ANY, all addresses)
<addr> may be specified as host:port. If you don't specify
a port number, the value you specified with -p or -U is
used. You may specify multiple addresses separated by comma
or by using -l multiple times
-d run as a daemon
-u <username> assume identity of <username> (only when run as root)
-m <num> max memory to use for items in megabytes (default: 64 MB)
-M return error on memory exhausted (rather than removing items)
-c <num> max simultaneous connections (default: 1024)
-v verbose (print errors/warnings while in event loop)
-P <file> save PID in <file>, only used with -d option

要关掉memcached

kill-9`cat/var/run/memcached.pid`

是否正常？Telnet上去看看

telnetxxx.xxx.xxx.xxx11211

然后输入

stats

接着就能看到：

引用

STAT pid 3021
STAT uptime 3621
STAT time 1331261509
STAT version 1.4.13
STAT libevent 2.0.17-stable
STAT pointer_size 64
STAT rusage_user 0.000000
STAT rusage_system 0.000999
STAT curr_connections 6
STAT total_connections 7
STAT connection_structures 7
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 72
STAT bytes_written 1038
STAT limit_maxbytes 52428800
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

上面状况说明Memcached服务正常。
还可以试试get、set、delete、replace

引用

set foo 0 0 3 （保存命令）
bar （数据）
STORED （结果）
get foo （取得命令）
VALUE foo 0 3 （数据）
bar （数据）

输入

quit

退出。

三、系统服务
参照Nginx的系统服务，自己写了一个Memcached的系统服务脚本。
先构建/etc/init.d/memcahed这个文件，然后赋予其可执行权限：

touch/etc/init.d/memcached
chmod+x/etc/init.d/memcached

memcached脚本如下：

#!/bin/bash
#v.0.0.1
#createbysnowolfat2012.5.25
#
#memcached-Thisshellscripttakescareofstartingandstoppingmemcached.
#
#chkconfig:-9010
#description:Memcacheprovidesfastmemorybasedstorage.
#processname:memcached

memcached_path="/usr/local/bin/memcached"
memcached_pid="/var/run/memcached.pid"
memcached_memory="1024"

#Sourcefunctionlibrary.
./etc/rc.d/init.d/functions

[-x$memcached_path]||exit0

RETVAL=0
prog="memcached"

#Startdaemons.
start(){
if[-e$memcached_pid-a!-z$memcached_pid];then
echo$prog"alreadyrunning...."
exit1
fi

echo-n$"Starting$prog"
#Singleinstanceforallcaches
$memcached_path-m$memcached_memory-l0.0.0.0-p11211-uroot-d-P$memcached_pid
RETVAL=$?
[$RETVAL-eq0]&&{
touch/var/lock/subsys/$prog
success$"$prog"
}
echo
return$RETVAL
}


#Stopdaemons.
stop(){
echo-n$"Stopping$prog"
killproc-d10$memcached_path
echo
[$RETVAL=0]&&rm-f$memcached_pid/var/lock/subsys/$prog

RETVAL=$?
return$RETVAL
}

#Seehowwewerecalled.
case"$1"in
start)
start
;;
stop)
stop
;;
status)
status$prog
RETVAL=$?
;;
restart)
stop
start
;;
*)
echo$"Usage:$0{start|stop|status|restart}"
exit1
esac
exit$RETVAL

注意这几行配置，请根据实际情况配置memcached执行文件路径，以及Memcached使用内存大小：

引用

memcached_path="/usr/local/bin/memcached"
memcached_memory="1024"

追加为系统服务：

chkconfig--addmemcached
chkconfigmemcachedon

然后就可以通过service memcached start|stop|status|restart控制memcached了！

四、常规错误
一开始没有指定libevent路径安装memcached的时候，启动memcached就报这个错误：

引用

memcached: error while loading shared libraries: libevent-2.0.so.5: cannot open shared object file: No such file or directory

其实这个文件就在/usr/lib下。错就错在Linux是64bit系统，如果没有指定libevent路径，memcached就会去/usr/lib64下去找。
找到这个文件

whereislibevent-2.0.so.5

引用

libevent-2.0.so: /usr/lib/libevent-2.0.so.5

ldd/usr/local/bin/memcached

提示找不到libevent-2.0.so.5

引用

linux-vdso.so.1 => (0x00007fff41dfd000)
libevent-2.0.so.5 => not found
librt.so.1 => /lib64/librt.so.1 (0x0000003c94a00000)
libpthread.so.0 => /lib64/libpthread.so.0 (0x0000003c93a00000)
libc.so.6 => /lib64/libc.so.6 (0x0000003c92e00000)
/lib64/ld-linux-x86-64.so.2 (0x0000003c92a00000)

定位

LD_DEBUG=libs/usr/local/bin/memcached-v

引用

19905: find library=libevent-2.0.so.5 [0]; searching
19905: search path=/usr/lib/lib/tls/x86_64:/usr/lib/lib/tls:/usr/lib/lib/x86_64:/usr/lib/lib (RPATH from file /usr/local/bin/memcached)
19905: trying file=/usr/lib/lib/tls/x86_64/libevent-2.0.so.5
19905: trying file=/usr/lib/lib/tls/libevent-2.0.so.5
19905: trying file=/usr/lib/lib/x86_64/libevent-2.0.so.5
19905: trying file=/usr/lib/lib/libevent-2.0.so.5
19905: search cache=/etc/ld.so.cache
19905: search path=/lib64/tls/x86_64:/lib64/tls:/lib64/x86_64:/lib64:/usr/lib64/tls/x86_64:/usr/lib64/tls:/usr/lib64/x86_64:/usr/lib64 (system search path)
19905: trying file=/lib64/tls/x86_64/libevent-2.0.so.5
19905: trying file=/lib64/tls/libevent-2.0.so.5
19905: trying file=/lib64/x86_64/libevent-2.0.so.5
19905: trying file=/lib64/libevent-2.0.so.5
19905: trying file=/usr/lib64/tls/x86_64/libevent-2.0.so.5
19905: trying file=/usr/lib64/tls/libevent-2.0.so.5
19905: trying file=/usr/lib64/x86_64/libevent-2.0.so.5
19905: trying file=/usr/lib64/libevent-2.0.so.5
19905:
/usr/local/bin/memcached: error while loading shared libraries: libevent-2.0.so.5: cannot open shared object file: No such file or directory

注意这句：

引用

19905: trying file=/usr/lib64/libevent-2.0.so.5

做个软连接

ln-s/usr/lib/libevent-2.0.so.5/usr/lib64/libevent-2.0.so.5

再试试：

ldd/usr/local/bin/memcached

这回找到了！

引用

linux-vdso.so.1 => (0x00007fffffef6000)
libevent-2.0.so.5 => /usr/lib64/libevent-2.0.so.5 (0x00002b5608a26000)
librt.so.1 => /lib64/librt.so.1 (0x0000003c94a00000)
libpthread.so.0 => /lib64/libpthread.so.0 (0x0000003c93a00000)
libc.so.6 => /lib64/libc.so.6 (0x0000003c92e00000)
/lib64/ld-linux-x86-64.so.2 (0x0000003c92a00000)

五、监控
可以在服务器上配置一个PHP页面来监测Memcached的情况，
下载MemcachePHP



配置也比较简单，主要包括账户配置，以及Memcached Server地址配置。

define('ADMIN_USERNAME','memcache');//AdminUsername
define('ADMIN_PASSWORD','password');//AdminPassword
define('DATE_FORMAT','Y/m/dH:i:s');
define('GRAPH_SIZE',200);
define('MAX_ITEM_DUMP',50);

$MEMCACHE_SERVERS[]='mymemcache-server1:11211';//addmoreasanarray
$MEMCACHE_SERVERS[]='mymemcache-server2:11211';//addmoreasanarray

如果不方便搭建PHP服务，可以使用Perl脚本memcache-top
修改@default_instances或使用--instances参数：

perlmemcache-top-v0.6--instances10.11.155.2610.11.155.41

先到这里，后续做压力测试，Java客户端开发，Spring系统集成等。