(PECL memcached >= 0.1.0)
Memcached::addServer — 向服务器池中增加一个服务器
$host
, int $port
[, int $weight = 0
] )
Memcached::addServer()增加指定服务器到服务器池中。此时不会建立与服务端的连接，
但是，如果你使用一致性key分布选项（Memcached::DISTRIBUTION_CONSISTENT或
Memcached::OPT_LIBKETAMA_COMPATIBLE），一些内部的数据结构将会被更新。
因此，如果你需要增加多台服务器，更好的方式是使用 Memcached::addServers()
以确保这种更新只发生一次。
同一台服务器可以在服务器池中多次出现，因为这里没有做重复检测。但这是不推荐的做法，对于期望提高某台服务器
权重的需求，请使用weight参数。
host
memcached服务端主机名。如果主机名无效，相关的数据操作的返回代码将被设置为Memcached::RES_HOST_LOOKUP_FAILURE。
port
memcached服务端端口号，通常是11211。
weight
此服务器相对于服务器池中所有服务器的权重。此参数用来控制服务器在操作时被选种的概率。这个仅用于一致性 分布选项，并且这个值通常是由服务端分配的内存来设置的。
成功时返回 TRUE， 或者在失败时返回 FALSE。
Example #1 Memcached::addServer() example
<?php
$m = new Memcached();
/* Add 2 servers, so that the second one
is twice as likely to be selected. */
$m->addServer('mem1.domain.com', 11211, 33);
$m->addServer('mem2.domain.com', 11211, 67);
?>
Dave (2012-11-20 10:42:27)
As of version 2.0.0b1 you can use Unix socket.
<?php
$m = new Memcached();
$m->addServer('/path/to/socket',0);
?>
Not to be confused with Memcache that use 'unix:///path/to/socket'
mbarriolinares at gmail dot com (2012-09-10 18:55:08)
Important to not call ->addServers() every run -- only call it if no servers exist (check getServerList() ); otherwise, since addServers() does not check for dups, it will let you add the same server again and again and again, resultings in hundreds if not thousands of connections to the MC daemon. Specially when using FastCGI.
Example:
<?php
class Cache {
private $id;
private $obj;
function __construct($id){
$this->id = $id;
$this->obj = new Memcached($id);
}
public function connect($host , $port){
$servers = $this->obj->getServerList();
if(is_array($servers)) {
foreach ($servers as $server)
if($server['host'] == $host and $server['port'] == $port)
return true;
}
return $this->obj->addServer($host , $port);
}
}
?>
Robbie De Lise (2011-08-22 22:08:44)
On my Debian Squeeze system I was getting WRITE FAILURE errors. After debugging and finally tcpdump it seems that the problem was me adding the server 'localhost', which resolved to '::1' (ipv6) while the default memcached server on debian only listens to '127.0.0.1' (ipv4). DNS automatically prefers ipv6 over ipv4.
I added the server '127.0.0.1' instead and everything worked. You could also disable ipv6 or have memcached listen on ::1
Bill Getas (2010-08-30 11:26:26)
Unix sockets are not yet supported by PECL/memcached