memcache and memcached

The best solution i've found is to extend the Libmemcached class:

<?php

use Phalcon\Cache\Backend\Libmemcached;

class LibmemcachedPlugin extends Libmemcached
{
    public function isStarted()
    {
        $memcache = $this->_memcache;

        if (!is_object($memcache)) {
            $this->_connect();
            $memcache = $this->_memcache;
        }

        $stats = $memcache->getStats();
        foreach ($stats as $key => $value) {
            if ($stats[$key]['pid'] === -1) {
                return false;
            }
        }
        return true;
    }

    public function getStats()
    {
        $memcache = $this->_memcache;

        if (!is_object($memcache)) {
            $this->_connect();
            $memcache = $this->_memcache;
        }

        return $memcache->getStats();
    }
}

As I see, library does check whenever the connection is alive before trying to contact the daemon.

https://github.com/phalcon/cphalcon/blob/master/phalcon/cache/backend/libmemcached.zep#L136

But I guess you're talking about HA here, what happens if the daemon goes down. Since this is only a wrapper, there's no implementation for handling system level (daemon) processes, or even remote servers in case your memcacheD is hosted elsewhere.

That's why I implemented this in services container:

  // NOTE: exiting to command line puts too much overhead
     $libmemCheck = <<<DAEMON
ps -e | grep memcached | awk '{print $1}'
DAEMON;
    exec($libmemCheck, $rv, $status);
    !$status ? $pidMem = $rv[0] : $pidMem = 0x00;

    //you can also fetch the PID from file system and compare it with your ps command return value
    $pid = file_exists('/var/run/memcached.pid') ? file_get_contents('/var/run/memcached.pid') : false;

    //check process ID
    $pid = file_exists('/var/run/memcached.pid') ? true : false;
    //check socket
    $socketExists = file_exists($config->_daemon->socket) ? true : false; // socket defined as: /var/run/memcached.sock
    //throw exception if the daemon is N/A
    if (!$socketExists || !$pid) throw new \Phalcon\Exception('DAEMON is NaN!');

So, since I'm running on a same box, I do only this check which is the fastest and should at least catch daemon downtime.

 //check process ID
    $pid = file_exists('/var/run/memcached.pid') ? true : false;
    //check socket
    $socketExists = file_exists($config->_daemon->socket) ? true : false;
    //throw exception if the daemon is N/A
    if (!$socketExists || !$pid) throw new \Phalcon\Exception('DAEMON is NaN!');
    //now here we can try to start daemon again with either defining it in a php or to exec() system start.