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Memcached::addServers

(PECL memcached >= 0.1.1)

Memcached::addServers向服务器池中增加多台服务器

说明

public Memcached::addServers(array $servers): bool

Memcached::addServers() 向服务器池中增加 serversservers 中的每个条目都应该是包含主机名、端口以及可选权重的数组。此时并不会与这些服务端建立连接。

同一台服务器可能会在服务器池中多次出现,因为这里没有做重复检测。但这并不可取;相反,应该使用 weight 选项增加此服务器的选择权重。

参数

array

增加到池中的服务器数组。

返回值

成功时返回 true, 或者在失败时返回 false

范例

示例 #1 Memcached::addServers() 示例

<?php
$m
= new Memcached();

$servers = array(
array(
'mem1.domain.com', 11211, 33),
array(
'mem2.domain.com', 11211, 67)
);
$m->addServers($servers);
?>

参见

add a note

User Contributed Notes 2 notes

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2
Michael Brenden
11 years ago
See the note for __construct()

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.
up
2
Aliaser
6 years ago
For a proper FailOver mechanism:

$memcached = new Memcached();
$memcached->setOption(Memcached::OPT_CONNECT_TIMEOUT, 10);
$memcached->setOption(Memcached::OPT_DISTRIBUTION, Memcached::DISTRIBUTION_CONSISTENT);
$memcached->setOption(Memcached::OPT_SERVER_FAILURE_LIMIT, 2);
$memcached->setOption(Memcached::OPT_REMOVE_FAILED_SERVERS, true);
$memcached->setOption(Memcached::OPT_RETRY_TIMEOUT, 1);
$memcached->addServers($servers);

Memcached::OPT_DISTRIBUTION: set it to consistent hashing. If one memcached node is dead, its keys (and only its keys) will be evenly distributed to other nodes. This is where the magic is done. This is really different from removing one server in your ->addServers() call.

Memcached::OPT_SERVER_FAILURE_LIMIT: number of connection issues before a server is marked as DEAD, and removed from the list of servers (default: 5).

Memcached::OPT_REMOVE_FAILED_SERVERS: set it to «true», to enable the removal of dead servers.

Memcached::OPT_RETRY_TIMEOUT: after a node is declared DEAD, libmemcached will try it again after that many seconds. Here I've set it to 1 second, but I'm working on PHP scripts that run for less than 100ms most of the time. That would only be useful for cron/daemonize scripts.

Memcached::OPT_CONNECT_TIMEOUT: the timeout after which a server is considered DEAD. As my servers are on the same LAN, ping is ~0.5ms, so 10ms is large enough to consider the server is DEAD. Note that you have to wait twice that time before a node is marked DEAD, so if it's 1000ms, your script will lock for 2 seconds before ignoring the DEAD server. That may affect your response times a lot, and that's why I've set it very low

Author of this is Yvan from Dugwood
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