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Memcached
LibreNMS can store SQL results in memcached to achieve performance advantages of in-memory value storage and removing work load for frequent queries off the MySQL backend.
To enable memcached in your install you need to have memcached installed and the PHP extension php5-memcached or php-memcached and add the following lines to your config.php:
$config['memcached']['enable'] = true;
$config['memcached']['host'] = "localhost";
$config['memcached']['port'] = 11211;
By default values are kept for 4 Minutes inside the memcached, you can adjust this retention time by modifying the $config['memcached']['ttl'] value to any desired amount of seconds.
It's strongly discouraged to set this above 300 (5 Minutes) to avoid interferences with the polling, discovery and alerting processes.
If you use the Distributed Poller, you can point this to the same memcached instance. However a local memcached will perform better in any case.