Memcached筆記——（一）安裝&常規錯誤&監控

Memcached現在已經成了服務器架構裏不可或缺的一部分！

一、下載
1.Libevent
簡單的說就是一個事件觸發的網絡庫，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

這裏一定要注意指定--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

這裏一定要指定libevent的路徑，否則啓動的時候就有找不到libevent的so文件的錯誤！
啓動

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     （保存命令）
bar               （數據）
STORED            （結果）
get foo           （取得命令）
VALUE foo 0 3     （數據）
bar               （數據）

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的系統服務腳本。

先構建/etc/init.d/memcahed這個文件，然後賦予其可執行權限：

Shell代碼

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

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

memcached腳本如下：

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: 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

注意這幾行配置，請根據實際情況配置memcached執行文件路徑，以及Memcached使用內存大小：

引用

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

追加爲系統服務：

Shell代碼

chkconfig --add memcached
chkconfig memcached on

chkconfig --add memcached
chkconfig 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，啓動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

其實這個文件就在/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。
找到這個文件

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

ldd /usr/local/bin/memcached

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

Shell代碼

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

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

注意這句：

引用

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

做個軟連接

Shell代碼

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

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

再試試：

Shell代碼

ldd /usr/local/bin/memcached

ldd /usr/local/bin/memcached

這回找到了！

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、監控
可以在服務器上配置一個PHP頁面來監測Memcached的情況，
下載MemcachePHP

配置也比較簡單，主要包括賬戶配置，以及Memcached Server地址配置。

Php代碼

define('ADMIN_USERNAME','memcache'); // Admin Username
define('ADMIN_PASSWORD','password'); // Admin Password
define('DATE_FORMAT','Y/m/d H:i:s');
define('GRAPH_SIZE',200);
define('MAX_ITEM_DUMP',50);
$MEMCACHE_SERVERS[] = 'mymemcache-server1:11211'; // add more as an array
$MEMCACHE_SERVERS[] = 'mymemcache-server2:11211'; // add more as an array

define('ADMIN_USERNAME','memcache'); 	// Admin Username
define('ADMIN_PASSWORD','password');  	// Admin Password
define('DATE_FORMAT','Y/m/d H:i:s');
define('GRAPH_SIZE',200);
define('MAX_ITEM_DUMP',50);

$MEMCACHE_SERVERS[] = 'mymemcache-server1:11211'; // add more as an array
$MEMCACHE_SERVERS[] = 'mymemcache-server2:11211'; // add more as an array

常見錯誤：

引用

Warning: date(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected the timezone 'UTC' for now, but please set date.timezone to select your timezone. in /home/usr/local/apache.../memcache.php on line 726

在memcache.php頂端加上“date_default_timezone_set('Asia/Hong_Kong');”即可，具體地域設置參考：http://www.php.net/manual/zh/datetime.configuration.php#ini.date.timezone

如果不方便搭建PHP服務，可以使用Perl腳本memcache-top
修改@default_instances或使用--instances參數：

Shell代碼

perl memcache-top-v0.6 --instances 10.11.155.26 10.11.155.41

perl memcache-top-v0.6 --instances 10.11.155.26 10.11.155.41

先到這裏，後續做壓力測試，Java客戶端開發，Spring系統集成等。

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