Laravel multiple memcached: failover does not work - php

Question

I have two memcached servers. I set up the following config and my expectation was that my PHP app can use alive memcached even if one of the two servers is down. But it did not work. I got "No Memcached servers added" error when I execute memcached's get() method.
'memcached' => [
'driver' => 'memcached',
'options' => [
Memcached::OPT_CONNECT_TIMEOUT => 10,
Memcached::OPT_DISTRIBUTION => Memcached::DISTRIBUTION_CONSISTENT,
Memcached::OPT_SERVER_FAILURE_LIMIT => 2,
Memcached::OPT_REMOVE_FAILED_SERVERS => true,
Memcached::OPT_RETRY_TIMEOUT => 1,
],
'servers' => [
[
'host' => 'xxx.0.0.1', 'port' => 11211, 'weight' => 100,
],
[
'host' => 'xxx.0.0.2', 'port' => 11211, 'weight' => 100,
],
],
],
I'm using the latest version of memcached servers and client.
memcached 1.4.25-2ubuntu1
php-memcached version 3.0.0b1
libmemcached version 1.0.18
Do you have any ideas?
Edit 1
"No Memcached servers added" error is came from here.
https://github.com/illuminate/cache/blob/master/MemcachedConnector.php
Edit 2
I found Memcached::XXX options are integer values. So options values are not passed to the server. I fixed this but the result was not changed.
'options' => array('10', '1', '2', true, '1')
Edit 3
Laravel's cache example setting is memtioned here
https://github.com/laravel/laravel/blob/master/config/cache.php#L60
Edit 4
I tried it by using PHP without Laravel then I figured out that getVersion() returned null when one of the two server is dead.
<?php
$m = new Memcached();
$m->addServer('127.0.0.1', 11211);
$m->addServer('127.0.0.1', 11212);
$status = $m->getVersion();
if ($status == null){
echo "null";
} else {
echo "not null";
}
* when both the two servers are alive
// not null
// $status = array('127.0.0.1:11211' => '1.4.25', '127.0.0.1:11212' => '1.4.14')
* when one of the two server is dead
// null
// $status = null

Answer 1

I was struggling with this for a couple of days now and I finally found a solution for it https://packagist.org/packages/fingo/laravel-cache-fallback
It is quite easy to install:
composer require fingo/laravel-cache-fallback
Add the provider Fingo\LaravelCacheFallback\CacheFallbackServiceProvider::class into 'config/app.php`
Default fallback order is: redis, memcached, database, cookie, file, array.If needed to change fallback order, publish vendors: php artisan vendor:publish --provider="Fingo\LaravelCacheFallback\CacheFallbackServiceProvider"
I'm using Laravel 5.2 with PhP7, the requirements for the library are:php: ~5.6|~7.0, illuminate/cache: ~5.1
LE: I've implemented a different way to failover from one Memcached server to the other one and if both of them are down then it will failover to the 'file' driver.
config/cache.php:
'memcached' => [
'driver' => 'memcached',
// To use the options we need to install the PHP driver: sudo yum install php-memcached
'options' => [
Memcached::OPT_CONNECT_TIMEOUT => 3,
Memcached::OPT_DISTRIBUTION => Memcached::DISTRIBUTION_CONSISTENT,
Memcached::OPT_SERVER_FAILURE_LIMIT => 2,
Memcached::OPT_REMOVE_FAILED_SERVERS => true,
Memcached::OPT_RETRY_TIMEOUT => 1,
],
'servers' => [
[
'host' => 'xxx.xxx.xxx.xxx',
'port' => 11211,
'weight' => 90,
],
]
],
'memcached249' => [
'driver' => 'memcached',
// To use the options we need to install the PHP driver: sudo yum install php-memcached
'options' => [
Memcached::OPT_CONNECT_TIMEOUT => 3,
Memcached::OPT_DISTRIBUTION => Memcached::DISTRIBUTION_CONSISTENT,
Memcached::OPT_SERVER_FAILURE_LIMIT => 2,
Memcached::OPT_REMOVE_FAILED_SERVERS => true,
Memcached::OPT_RETRY_TIMEOUT => 1,
],
'servers' => [
[
'host' => 'xxx.xxx.xxx.xxx',
'port' => 11211,
'weight' => 100,
],
]
],
config/cache_fallback.php
return [
'fallback_order' => [
'memcached',
'memcached249',
'file',
]
];
The only problem is that if the first memcached server is down, it slows down the entire system (but at least it's not breaking the main server). Hope this helps :)