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Memcache::addServer

PHP function Edit on GitHub ✎

(PECL memcache >= 2.0.0)

Add a memcached server to connection pool

Description

Memcache::addServer(string $host, int $port = 11211, [bool $persistent], [int $weight], [int $timeout], [int $retry_interval], [bool $status], [callable $failure_callback], [int $timeoutms]): bool

memcache_add_server(Memcache $memcache, string $host, int $port = 11211, [bool $persistent], [int $weight], [int $timeout], [int $retry_interval], [bool $status], [callable $failure_callback], [int $timeoutms]): bool

Memcache::addServer() adds a server to the connection pool.

When using this method (as opposed to Memcache::connect() and Memcache::pconnect()) the network connection is not established until actually needed. Thus there is no overhead in adding a large number of servers to the pool, even though they might not all be used.

Failover may occur at any stage in any of the methods, as long as other servers are available the request the user won't notice. Any kind of socket or Memcached server level errors (except out-of-memory) may trigger the failover. Normal client errors such as adding an existing key will not trigger a failover.

Note

This function has been added to Memcache version 2.0.0.

Parameters

host

Point to the host where memcached is listening for connections. This parameter may also specify other transports like unix:///path/to/memcached.sock to use UNIX domain sockets, in this case port must also be set to 0.

port

Point to the port where memcached is listening for connections. Set this parameter to 0 when using UNIX domain sockets.

Please note: port defaults to memcache.default_port if not specified. For this reason it is wise to specify the port explicitly in this method call.

persistent

Controls the use of a persistent connection. Default to true.

weight

Number of buckets to create for this server which in turn control its probability of it being selected. The probability is relative to the total weight of all servers.

timeout

Value in seconds which will be used for connecting to the daemon. Think twice before changing the default value of 1 second - you can lose all the advantages of caching if your connection is too slow.

retry_interval

Controls how often a failed server will be retried, the default value is 15 seconds. Setting this parameter to -1 disables automatic retry. Neither this nor the persistent parameter has any effect when the extension is loaded dynamically via dl().

Each failed connection struct has its own timeout and before it has expired the struct will be skipped when selecting backends to serve a request. Once expired the connection will be successfully reconnected or marked as failed for another retry_interval seconds. The typical effect is that each web server child will retry the connection about every retry_interval seconds when serving a page.

status

Controls if the server should be flagged as online. Setting this parameter to false and retry_interval to -1 allows a failed server to be kept in the pool so as not to affect the key distribution algorithm. Requests for this server will then failover or fail immediately depending on the memcache.allow_failover setting. Default to true, meaning the server should be considered online.

failure_callback

Allows the user to specify a callback function to run upon encountering an error. The callback is run before failover is attempted. The function takes two parameters, the hostname and port of the failed server.

timeoutms

Return Values

Success

Examples

Memcache::addServer() example

php

<?php

/* OO API */

$memcache = new Memcache;
$memcache->addServer('memcache_host', 11211);
$memcache->addServer('memcache_host2', 11211);

/* procedural API */

$memcache_obj = memcache_connect('memcache_host', 11211);
memcache_add_server($memcache_obj, 'memcache_host2', 11211);

?>

Notes

Warning

When the port is unspecified, this method defaults to the value set of the PHP ini directive memcache.default_port If this value was changed elsewhere in your application it might lead to unexpected results: for this reason it is wise to always specify the port explicitly in this method call.