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。

Shell代码


wget http://cloud.github.com/downloads/libevent/libevent/libevent-2.0.17-stable.tar.gz
2.Memcached

今天的主角

Shell代码


wget http://memcached.googlecode.com/files/memcached-1.4.13.tar.gz
二、安装

1.Libevent

解压缩

Shell代码


tar zxvf libevent-2.0.17-stable.tar.gz

编译、安装

Shell代码


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

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

Shell代码


tar zxvf memcached-1.4.13.tar.gz

编译、安装

Shell代码


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

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

Shell代码


memcached -d -m 512 -p 11211 -u root -c 256 -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

Shell代码


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

是否正常？Telnet上去看看

Shell代码


telnet xxx.xxx.xxx.xxx 11211

然后输入

Shell代码


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

Shell代码


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：

Shell代码


touch /etc/init.d/memcached

chmod +x /etc/init.d/memcached

memcached脚本如下：

Shell代码


#!/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：

Shell代码


chkconfig --add memcached

chkconfig memcached on

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

Shell代码


whereis libevent-2.0.so.5

引用

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

Shell代码


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代码


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

Shell代码


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

再试试：

Shell代码


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。

Php代码


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

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：

Shell代码


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



先到这里，后续做压力测试，Java客户端开发，Spring系统集成等。