Getting 'unable to write' errors in CakePHP site

Question

I've a CakePHP site which is throwing errors (it was fine at first, and has been online for several months - not sure when the problem started).

I'm getting:

Warning (512): _cake_core_ cache was unable to write 'cake_dev_en-us' to Apc cache [CORE/Cake/Cache/Cache.php, line 310] Warning (512): _cake_core_ cache was unable to write 'cake_en-us' to Apc cache [CORE/Cake/Cache/Cache.php, line 310] Warning (512): _cake_model_ cache was unable to write 'default_projects' to Apc cache

[CORE/Cake/Cache/Cache.php, line 310]
Warning (512): _cake_model_ cache was unable to write 'default_projects' to Apc cache [CORE/Cake/Cache/Cache.php, line 310]
Warning (512): _cake_model_ cache was unable to write 'default_clients' to Apc cache [CORE/Cake/Cache/Cache.php, line 310]
Warning (512): _cake_model_ cache was unable to write 'default_clients' to Apc cache [CORE/Cake/Cache/Cache.php, line 310]
Warning (512): _cake_model_ cache was unable to write 'default_projectpages' to Apc cache [CORE/Cake/Cache/Cache.php, line 310]
Warning (512): _cake_model_ cache was unable to write 'default_projectpages' to Apc cache [CORE/Cake/Cache/Cache.php, line 310]
Warning (512): _cake_model_ cache was unable to write 'default_settings' to Apc cache [CORE/Cake/Cache/Cache.php, line 310]
Warning (512): _cake_model_ cache was unable to write 'default_settings' to Apc cache [CORE/Cake/Cache/Cache.php, line 310]

I've made sure that the tmp directory is writeable (have set it and all contained folders and files to 0777; also checked that it did update properly, and it did); I've also switched off error reporting in core.php by setting the debug level to 0.

Most of the site is fine, but this particular page is pulled in by AJAX, and I don't know whether that's making any difference.

I've patched it by setting "display: none" on cake-error, but I need to understand why this is happening. Firstly, what's causing the error? And secondly, why is the core setting being ignored?

The warning says it can't write to Apc cache, which is different than File cache. Do you know what kind of cache you're using? If not try using File cache in core.php — ori
Possibly because APC is running out of its allocated memory. — tigrang
Thanks - I hadn't set any of the cache engine configurations, and when I enabled 'File', the errors vanished. Thanks for your help! — Sharon

Simon East Simon East · Accepted Answer · 2015-02-10T06:07:42

I was getting this APC caching error when running a CakePHP site on Zend Server 7. Unfortunately Zend Server appears to ship with a fake/substitute APC layer, and from my tests the variable data-store doesn't work (the functions always return false) which is what CakePHP is complaining about.

This screen in the ZendServer dashboard shows APC.

APC Compatibility Layer in Zend Server 7

The solution is to either:

Completely disable APC caching by editing app/Config/core.php to comment out the following lines...

/*if (extension_loaded('apc') && function_exists('apc_dec') && (php_sapi_name() !== 'cli' || ini_get('apc.enable_cli'))) {
    $engine = 'Apc';
}*/

OR, you can only load APC conditionally. In my case I just wanted to just disable it on my local development server but leave it active for production.

$isLocalDevelopment = strpos($_SERVER['SERVER_NAME'], '.dev');
if (!$isLocalDevelopment && extension_loaded('apc') && function_exists('apc_dec') && (php_sapi_name() !== 'cli' || ini_get('apc.enable_cli'))) {
    $engine = 'Apc';
}

Getting 'unable to write' errors in CakePHP site

4 Answers