How do I set up a site to use Redis as cache handler?

Question

I'm trying to enable Redis on my Drupal site but when I check the status of the module I keep getting this warning message.

No Redis client connected, this module is useless thereof. Ensure that you enabled module using it or disable it.

The steps I followed to enable Redis are the following.

1. I edited the config.yml file to add the following lines

   installed_extras:
     - redis
     - php-redis
   

2. I enabled the Redis module

3. I edited the settings.php file to add the following lines

   $settings['cache']['default'] = 'cache.backend.redis';
   $settings['redis.connection']['interface'] = 'PhpRedis';
   $settings['container_yamls'][] = 'modules/redis/example.services.yml';
   $settings['container_yamls'][] = 'modules/redis/redis.services.yml';
   

I also tried to execute the following code in index.php and the cache appears to be working.

$redis = new Redis();
$redis->connect('127.0.0.1');
$cache = $redis->get('key');
if ($cache === false) {
  echo "miss";
  $cache = "test";
  $redis->set('key',$cache);
}
else {
  echo "didn't miss";
}
// At this point $cache is either the retrieved cache or a fresh copy, so echo it.
echo $cache;
exit();

It appears that Redis is working but for some reason it isn't used by Drupal.

How do I set up Drupal to use Redis as cache handler?

Answer 1

For Drupal 8, use this code in the settings.php file:

$settings['redis.connection']['host'] = 'localhost';
$settings['redis.connection']['port'] = NULL;
$settings['cache']['default'] = 'cache.backend.redis';
$settings['redis.connection']['base'] = 101;

You can check whether or not Redis is running by viewing the status report at: /admin/reports/status