08年的時候接觸過 Memcached，當時還對它的用戶端產品嗤之以鼻，畢竟手工代碼沒有各種ORM原生XML配置方便。儘管如此，Memcached現在已經成了伺服器架構裡不可或缺的一部分。
相關連結：
Memcached筆記——（一）安裝&常規錯誤&監控
Memcached筆記——（二）XMemcached&Spring整合
Memcached筆記——（三）Memcached使用總結
Memcached筆記——（四）應對高並發攻擊
一、下載
1. Libevent
簡單的說就是一個事件觸發的網路程式庫，Memcached離不開它。
Shell代碼 wget http://cloud.github.com/downloads/libevent/libevent/libevent-2.0.17-stable.tar.gz
wget http://cloud.github.com/downloads/libevent/libevent/libevent-2.0.17-stable.tar.gz
2. Memcached
今天的主角
Shell代碼 wget http://memcached.googlecode.com/files/memcached-1.4.13.tar.gz
wget http://memcached.googlecode.com/files/memcached-1.4.13.tar.gz
二、安裝
1. Libevent
解壓縮
Shell代碼 tar zxvf libevent-2.0.17-stable.tar.gz
tar zxvf libevent-2.0.17-stable.tar.gz
編譯、安裝
Shell代碼 ./configure --prefix=/usr && make && make install
./configure --prefix=/usr && make && make install
這裡一定要注意指定
--prefix，後面配置memcached的時候就有必要用到。
2. Memcached
解壓
Shell代碼 tar zxvf memcached-1.4.13.tar.gz
tar zxvf memcached-1.4.13.tar.gz
編譯、安裝
Shell代碼 ./configure --with-libevent=/usr/lib && make && make install
./configure --with-libevent=/usr/lib && make && make install
這裡一定要指定
libevent的路徑，否則啟動的時候就有找不到libevent的so檔案的錯誤。
啟動
Shell代碼 memcached -d -m 512 -p 11211 -u root -c 256 -P /var/run/memcached.pid
memcached -d -m 512 -p 11211 -u root -c 256 -P /var/run/memcached.pid
參數
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
要關掉memcached
Shell代碼 kill -9 `cat /var/run/memcached.pid`
kill -9 `cat /var/run/memcached.pid`
是否正常。Telnet上去看看
Shell代碼 telnet xxx.xxx.xxx.xxx 11211
telnet xxx.xxx.xxx.xxx 11211
然後輸入 Shell代碼 stats
stats
接著就能看到：
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
上面狀況說明Memcached服務正常。
還可以試試get、set、delete、replace
引用 set foo 0 0 3 （儲存命令）
bar （資料）
STORED （結果）
get foo （取得命令）
VALUE foo 0 3 （資料）
bar （資料）
輸入 Shell代碼 quit
quit
退出。
三、系統服務
參照Nginx的系統服務，自己寫了一個Memcached的系統服務指令碼。
先構建
/etc/init.d/memcahed這個檔案，然後賦予其可執行許可權：
Shell代碼 touch /etc/init.d/memcached chmod +x /etc/init.d/memcached
touch /etc/init.d/memcachedchmod +x /etc/init.d/memcached
memcached指令碼如下：
Shell代碼 #!/bin/bash # v.0.0.1 # create by snowolf at 2012.5.25 # # memcached - This shell script takes care of starting and stopping memcached. # # chkconfig: - 90 10 # description: Memcache provides fast memory based storage. # processname: memcached memcached_path="/usr/local/bin/memcached" memcached_pid="/var/run/memcached.pid" memcached_memory="1024" # Source function library. . /etc/rc.d/init.d/functions [ -x $memcached_path ] || exit 0 RETVAL=0 prog="memcached" # Start daemons. start() { if [ -e $memcached_pid -a ! -z $memcached_pid ];then echo $prog" already running...." exit 1 fi echo -n $"Starting $prog " # Single instance for all caches $memcached_path -m $memcached_memory -l 0.0.0.0 -p 11211 -u root -d -P $memcached_pid RETVAL=$? [ $RETVAL -eq 0 ] && { touch /var/lock/subsys/$prog success $"$prog" } echo return $RETVAL } # Stop daemons. stop() { echo -n $"Stopping $prog " killproc -d 10 $memcached_path echo [ $RETVAL = 0 ] && rm -f $memcached_pid /var/lock/subsys/$prog RETVAL=$? return $RETVAL } # See how we were called. case "$1" in start) start ;; stop) stop ;; status) status $prog RETVAL=$? ;; restart) stop start ;; *) echo $"Usage: $0 {start|stop|status|restart}" exit 1 esac exit $RETVAL
#!/bin/bash# v.0.0.1# create by snowolf at 2012.5.25## memcached - This shell script takes care of starting and stopping memcached.## chkconfig: - 90 10# description: Memcache provides fast memory based storage.# processname: memcachedmemcached_path="/usr/local/bin/memcached"memcached_pid="/var/run/memcached.pid"memcached_memory="1024"# Source function library.. /etc/rc.d/init.d/functions[ -x $memcached_path ] || exit 0RETVAL=0prog="memcached"# Start daemons.start() { if [ -e $memcached_pid -a ! -z $memcached_pid ];then echo $prog" already running...." exit 1 fi echo -n $"Starting $prog " # Single instance for all caches $memcached_path -m $memcached_memory -l 0.0.0.0 -p 11211 -u root -d -P $memcached_pid RETVAL=$? [ $RETVAL -eq 0 ] && { touch /var/lock/subsys/$prog success $"$prog" } echo return $RETVAL}# Stop daemons.stop() { echo -n $"Stopping $prog " killproc -d 10 $memcached_path echo [ $RETVAL = 0 ] && rm -f $memcached_pid /var/lock/subsys/$prog RETVAL=$? return $RETVAL}# See how we were called.case "$1" in start) start ;; stop) stop ;; status) status $prog RETVAL=$? ;; restart) stop start ;; *) echo $"Usage: $0 {start|stop|status|restart}" exit 1esacexit $RETVAL
注意這幾行配置，請根據實際情況配置memcached執行檔案路徑，以及Memcached使用記憶體大小：
引用 memcached_path="/usr/local/bin/memcached"
memcached_memory="1024"
追加為系統服務：
Shell代碼 chkconfig --add memcached chkconfig memcached on
chkconfig --add memcachedchkconfig memcached on
然後就可以通過
service memcached start|stop|status|restart控制memcached了。
四、常規錯誤
一開始沒有指定libevent路徑安裝memcached的時候，啟動memcached就報這個錯誤：
引用 memcached: error while loading shared libraries: libevent-2.0.so.5: cannot open shared object file: No such file or directory
其實這個檔案就在
/usr/lib下。錯就錯在Linux是64bit系統，如果沒有指定libevent路徑，memcached就會去
/usr/lib64下去找。
找到這個檔案
Shell代碼 whereis libevent-2.0.so.5
whereis libevent-2.0.so.5
引用 libevent-2.0.so: /usr/lib/libevent-2.0.so.5
Shell代碼
