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Switching consistent hashing (Libketama) off by default

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as for just 2 Memcached servers it creates an extrem unbalanced 
distribution favoring the 2. server and has no benefits,
as requests to the failed node can only go to the other one anyway.
This commit is contained in:
Ralf Becker 2018-02-28 10:44:00 +01:00
parent f2ad6e630b
commit c1e8ac6324
1 changed files with 19 additions and 4 deletions
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23
api/src/Cache/Memcached.php
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@ -42,6 +42,17 @@ class Memcached extends Base implements ProviderMultiple
*/ */
private $timeout = 20; private $timeout = 20;
/**
* Use Libketama consistent hashing
*
* Off by default as for just 2 Memcached servers it creates an extrem
* unbalanced distribution favoring the 2. server and has no benefits
* as requests to the failed node can only go to the other one anyway.
*
* @var boolean
*/
private $consistent = false;
/** /**
* Retry on node failure: 0: no retry, 1: retry on set/add/delete, 2: allways retry * Retry on node failure: 0: no retry, 1: retry on set/add/delete, 2: allways retry
* *
@ -55,7 +66,7 @@ class Memcached extends Base implements ProviderMultiple
* @throws Exception if connection to backend could not be established * @throws Exception if connection to backend could not be established
* @param array $params eg. array('localhost'[,'localhost:11211',...]) * @param array $params eg. array('localhost'[,'localhost:11211',...])
* "timeout" in ms, "retry" on node failure 0: no retry (default), 1: retry on set/add/delete, 2: allways retry * "timeout" in ms, "retry" on node failure 0: no retry (default), 1: retry on set/add/delete, 2: allways retry
* "prefix" prefix for keys * "prefix" prefix for keys and "consistent=1" to enable (by default disabled) consistent caching
*/ */
function __construct(array $params=null) function __construct(array $params=null)
{ {
@ -76,6 +87,10 @@ class Memcached extends Base implements ProviderMultiple
$prefix = $params['prefix']; $prefix = $params['prefix'];
unset($params['prefix']); unset($params['prefix']);
} }
if (isset($params['consistent']))
{
$this->consistent = !empty($params['consistent']);
}
check_load_extension('memcached',true); check_load_extension('memcached',true);
// using a persitent connection for identical $params // using a persitent connection for identical $params
@ -86,10 +101,10 @@ class Memcached extends Base implements ProviderMultiple
\Memcached::OPT_CONNECT_TIMEOUT => $this->timeout, \Memcached::OPT_CONNECT_TIMEOUT => $this->timeout,
\Memcached::OPT_SEND_TIMEOUT => $this->timeout, \Memcached::OPT_SEND_TIMEOUT => $this->timeout,
\Memcached::OPT_RECV_TIMEOUT => $this->timeout, \Memcached::OPT_RECV_TIMEOUT => $this->timeout,
// use more effician binary protocol (also required for consistent hashing // use more efficient binary protocol (also required for consistent hashing)
\Memcached::OPT_BINARY_PROTOCOL => true, \Memcached::OPT_BINARY_PROTOCOL => true,
// enable Libketama compatible consistent hashing // Libketama compatible consistent hashing
\Memcached::OPT_LIBKETAMA_COMPATIBLE => true, \Memcached::OPT_LIBKETAMA_COMPATIBLE => $this->consistent,
// automatic failover and disabling of failed nodes // automatic failover and disabling of failed nodes
\Memcached::OPT_SERVER_FAILURE_LIMIT => 2, \Memcached::OPT_SERVER_FAILURE_LIMIT => 2,
// setting a prefix for all keys // setting a prefix for all keys