I am noob to using both Varnish and Memcached. I have been following some copy and paste install guides.

I have both servers installed and running. Memcached seems to be working fine. Varnish is serving pages but there are a lot of cache misses. I am trying to enable the Drupal module to make Varnish aware to cache the pages, the css etc.

However, when I copy the settings.php snippet from the README.txt file in the Varnish module to my own settings.php I get a white page and this message in the Apache error log:

PHP Fatal error:  Class 'MemCacheDrupal' not found in /var/www/myhost/includes/cache.inc on line 31

Here is the cache section added to my settings.php. The Varnish part is commented out because it causes the above error with MemCached.

# Memcache
$conf['cache_backends'][] = 'sites/all/modules/contrib/memcache/memcache.inc';
// The 'cache_form' bin must be assigned no non-volatile storage.
$conf['cache_class_cache_form'] = 'DrupalDatabaseCache';
$conf['cache_default_class'] = 'MemCacheDrupal';
$conf['memcache_key_prefix'] = 'myhost';
# Varnish
// Add Varnish as the page cache handler.
#$conf['cache_backends'][] = array('sites/all/modules/contrib/varnish/varnish.cache.inc');
#$conf['cache_class_cache_page'] = 'VarnishCache';
// Drupal 7 does not cache pages when we invoke hooks during bootstrap.
// This needs to be disabled.
#$conf['page_cache_invoke_hooks'] = FALSE;

What is wrong with the Varnish snippet or with my setup in general?

I tried re-ordering to put the Varnish lines before the Memcached lines and I got this error:

PHP Fatal error:  require_once(): Failed opening required '/var/www/myhost/Array' (include_path='.:/usr/share/php:/usr/share/pear') in /var/www/myhost/includes/bootstrap.inc on line 2308

2 Answers 2


I got it a little bit later. It was just the array format being different in the two sources I copies and pasted from. The problem line was:

#$conf['cache_backends'][] = array('sites/all/modules/contrib/varnish/varnish.cache.inc');

It should be:

#$conf['cache_backends'][] = 'sites/all/modules/contrib/varnish/varnish.cache.inc';

I was in the same issue and my "solution" was to change the order settings without changing the line that was your solution as:

  1. Varnish
  2. Memcache

My settings (Drupal 7.34, Varnish 3, Memcache 3.8.0):

// Varnish
// Add Varnish as a cache bin.
$conf['cache_backends'] = array('sites/all/modules/contrib/varnish/varnish.cache.inc');

//If you plan to use the expire module to be selective with your cache clearing you should add as a new cache bin.

//$conf['cache_class_external_varnish_page'] = 'VarnishCache';

// If you are not going to use the expire module you should replace the default pagecache with varnish.

$conf['cache_class_cache_page'] = 'VarnishCache';

// Memcache
$conf['cache_backends'][] = 'sites/all/modules/contrib/memcache/memcache.inc';
$conf['lock_inc'] = 'sites/all/modules/contrib/memcache/memcache-lock.inc';
$conf['memcache_stampede_protection'] = TRUE;
$conf['cache_default_class'] = 'MemCacheDrupal';

// The 'cache_form' bin must be assigned to non-volatile storage.
$conf['cache_class_cache_form'] = 'DrupalDatabaseCache';

// Don't bootstrap the database when serving pages from the cache.
$conf['page_cache_without_database'] = TRUE;
$conf['page_cache_invoke_hooks'] = FALSE;

//Note that no servers or bins are defined.  The default server and bin
//configuration which is used in this case is equivalant to setting:

$conf['memcache_servers'] = array('localhost:11211' => 'default');

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