PHP 7.1.0 Released

Memcached::addServers

(PECL memcached >= 0.1.1)

Memcached::addServersAdd multiple servers to the server pool

Description

public bool Memcached::addServers ( array $servers )

Memcached::addServers() adds servers to the server pool. Each entry in servers is supposed to be an array containing hostname, port, and, optionally, weight of the server. No connection is established to the servers at this time.

The same server may appear multiple times in the server pool, because no duplication checks are made. This is not advisable; instead, use the weight option to increase the selection weighting of this server.

Parameters

array

Array of the servers to add to the pool.

Return Values

Returns TRUE on success or FALSE on failure.

Examples

Example #1 Memcached::addServers() example

<?php
$m 
= new Memcached();

$servers = array(
    array(
'mem1.domain.com'1121133),
    array(
'mem2.domain.com'1121167)
);
$m->addServers($servers);
?>

See Also

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User Contributed Notes 2 notes

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4
Michael Brenden
5 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.
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2
Aliaser
8 months 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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