Warning: Memcache::get() [memcache.get]: Node no longer exists - memcached

Question

I am new to memcached but I do need to fix this error quick on the website
I don't know where to cut in?
Anything that I can do to find out which node or key memcached failed to get?
Any log files can I look into?

Answer 1

This occurs when you store an object which has references to recources such as file descriptors or database connections. It can also occur if the object you get is of a class which isn't loaded when you get it from memcached.
To find out which memcached key fails, you could set a custom error handler, which can access the memcached key, just before the call to Memcached::get and restore it afterwards. Then you can log the warning together with the key.
[Edit] Here's an example:
<?
class MyMemcachedWrapper {
private $key;
public function get($key) {
// Save the key in an instance variable so it will be available in
// the error handler
$this->key = $key;
set_error_handler(array($this, 'handleError'));
$value = Memcached::get($key);
restore_error_handler();
return $value;
}
public function handleError($errno, $errstr) {
// Here we have both the key and the error message from memcached
$message = "Memcached error '$errstr' while fetching key '{this->key}'";
// ... and we can log it to a file or db or something
file_put_contents("memcached-errors.log", $message, FILE_APPEND);
}
}
// Then use it like this
$memcached_wrapper = new MyMemcachedWrapper();
$value = $memcached_wrapper->get('xyz');