Memcache::addServer
Add a memcached server to connection pool
Description
bool Memcache::addServer(
string $host,
int $port = 11211,
bool $persistent = ?,
int $weight = ?,
int $timeout = ?,
int $retry_interval = ?,
bool $status = ?,
callable $failure_callback = ?,
int $timeoutms = ?
)
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
Returns true on success or false on failure.
Examples
Example #1 Memcache::addServer example
<?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.
See Also
- Memcache::connect
- Memcache::pconnect
- Memcache::close
- Memcache::setServerParams
- Memcache::getServerStatus