I have a couple Heroku CakePHP apps running on the cedar stack. My app is erroring out on every request when the cache engine tries to write out to a file.
[Sat Feb 09 05:56:51 2013] [error] [client x.x.x.x] PHP Fatal error: Uncaught exception 'CacheException' with message 'Cache engine _cake_core_ is not properly configured.' in /app/www/lib/Cake/Cache/Cache.php:165
Stack trace:
#0 /app/www/lib/Cake/Cache/Cache.php(135): Cache::_buildEngine('_cake_core_')
#1 /app/www/app/Config/core.php(277): Cache::config('_cake_core_', Array)
#2 /app/www/lib/Cake/Core/Configure.php(76): include('/app/www/app/Co...')
#3 /app/www/lib/Cake/bootstrap.php(163): Configure::bootstrap(true)
#4 /app/www/app/webroot/index.php(82): include('/app/www/lib/Ca...')
#5 {main}
thrown in /app/www/lib/Cake/Cache/Cache.php on line 1652013-02-09T05:56:51+00:00 app[web.1]: [Sat Feb 09 05:56:51 2013] [error] [client x.x.x.x] PHP Warning: /app/www/app/tmp/cache/persistent/ is not writable in /app/www/lib/Cake/Cache/Engine/FileEngine.php on line 336
2013-02-09T05:56:51+00:00 app[web.1]: [Sat Feb 09 05:56:51 2013] [error] [client x.x.x.x] PHP Warning: _cake_core_ cache was unable to write 'cake_dev_en-us' to File cache in /app/www/lib/Cake/Cache/Cache.php on line 309
I thought dynos on the cedar stack have writable ephemeral filesystems. Why am I getting not writable errors, and what can I do to fix them?