memcached 入门介绍

文献引用---memcached 入门：
http://blog.sina.com.cn/s/blog_62c5a4810100ndl5.html

在linux上安装memcached

由于memcached安装时，需要使用libevent类库，所以先安装libevent
libevent下载网址:http://www.monkey.org/~provos/libevent/

本手册中下载的是 libevent-1.4.8-stable.tar.gz版本安装步骤如下:
1. 解压缩
tar xzfv libevent-1.4.8-stable.tar.gz

2. 进入到 libevent-1.4.8-stable目录
    cd libevent-1.4.8-stable
  
3. 编译，安装
    ./configure
    make
    make install
注：默认安装到/usr/local/lib/目录

接下来，安装memcached
memcached下载网址:http://www.danga.com/memcached/download.bml
本手册中下载的是 memcached-1.2.6.tar.gz版本

安装步骤如下:
1. 解压缩
tar xzfv memcached-1.2.6.tar.gz

2. 进入到 memcached-1.2.6目录
cd memcached-1.2.6
  
3. 编译，安装
    ./configure --prefix=/local/memcached
    make
    make install

安装完成后，会在 /local/memcached 出现 bin和share目录

进行 bin目录，启动 memcache
方法如下:
./memcached -d -u nobody -m 512 127.0.0.1 -p 11211
此时，会报一个异常
error while loading shared libraries: libevent-1.4.so.2: cannot open shared object file: No such file or directory

原因是找不到libevent-1.4.so.2类库，解决办法如下：

使用LD_DEBUG=help ./memcached -v来确定 加载的类库路径,方法如下:
LD_DEBUG=libs ./memcached -v 2>&1 > /dev/null | less

则系统会显示:
linux:/local/memcached/bin # LD_DEBUG=libs ./memcached -v 2>&1 > /dev/null | less
     20421:     find library=libevent-1.4.so.2; searching
     20421:      search cache=/etc/ld.so.cache
     20421:      search path=/lib/tls/i686/sse2:/lib/tls/i686:/lib/tls/sse2:/lib/tls:/lib/i686/sse2:/lib/i686:/lib/sse2:/lib:/usr/lib/tls/i686
/sse2:/usr/lib/tls/i686:/usr/lib/tls/sse2:/usr/lib/tls:/usr/lib/i686/sse2:/usr/lib/i686:/usr/lib/sse2:/usr/lib          (system search path)
     20421:       trying file=/lib/tls/i686/sse2/libevent-1.4.so.2
     20421:       trying file=/lib/tls/i686/libevent-1.4.so.2
     20421:       trying file=/lib/tls/sse2/libevent-1.4.so.2
     20421:       trying file=/lib/tls/libevent-1.4.so.2
     20421:       trying file=/lib/i686/sse2/libevent-1.4.so.2
     20421:       trying file=/lib/i686/libevent-1.4.so.2
     20421:       trying file=/lib/sse2/libevent-1.4.so.2
     20421:       trying file=/lib/libevent-1.4.so.2
     20421:       trying file=/usr/lib/tls/i686/sse2/libevent-1.4.so.2
     20421:       trying file=/usr/lib/tls/i686/libevent-1.4.so.2
     20421:       trying file=/usr/lib/tls/sse2/libevent-1.4.so.2
     20421:       trying file=/usr/lib/tls/libevent-1.4.so.2
     20421:       trying file=/usr/lib/i686/sse2/libevent-1.4.so.2
     20421:       trying file=/usr/lib/i686/libevent-1.4.so.2
     20421:       trying file=/usr/lib/sse2/libevent-1.4.so.2
     20421:       trying file=/usr/lib/libevent-1.4.so.2
     20421:   
./memcached: error while loading shared libraries: libevent-1.4.so.2: cannot open shared object file: No such file or directory


我们看到，memcached会到很多地方去找，所以根据其它求，我们只需建一个软链接，指定到我们安装的类库上即可
方法如下：
ln -s /usr/local/lib/libevent-1.4.so.2 /lib/libevent-1.4.so.2

现在可以正常启动memcached了
./memcached -d -u nobody -m 512 127.0.0.1 -p 11211

到这里，看到memcached已经启动，说明安装成功。

memcache启动参数说明:
The options for memcached are:

    -l <ip_addr> 
    Listen on <ip_addr>; default to INDRR_ANY. This is an important option to consider as there is no other way to secure the installation. Binding to an internal or firewalled network interface is suggested.
    -d
    Run memcached as a daemon.
    -u <username>
    Assume the identity of <username> (only when run as root).
    -m <num>
    Use <num> MB memory max to use for object storage; the default is 64 megabytes.
    -M
    Instead of throwing items from the cache when max memory is reached, throw an error
    -c <num>
    Use <num> max simultaneous connections; the default is 1024.
    -k
    Lock down all paged memory. This is a somewhat dangerous option with large caches, so consult the README and memcached homepage for configuration suggestions.
    -p <num>
    Listen on port <num>, the default is port 11211.
    -r
    Maximize core file limit
    -M
    Disable automatic removal of items from the cache when out of memory. Additions will not be possible until adequate space is freed up.
    -r
    Raise the core file size limit to the maximum allowable.
    -h
    Show the version of memcached and a summary of options.
    -v
    Be verbose during the event loop; print out errors and warnings.
    -vv
    Be even more verbose; same as -v but also print client commands and responses.
    -i
    Print memcached and libevent licenses.
    -P <filename>
    Print pidfile to <filename>, only used under -d option.