notice - Contribute
#1596980032 InvalidArgumentException A cache identifier was not set.
When debugged the corresponding cache.definition might look like this:
'' => array('groups' => array('pages', 'all'))
This error is able to drive the complete frontend and backend unusable.
Before TYPO3 version 10 it was common that the variable $_EXTKEY was replaced automatically by the extension-key of the corresponding extension.
This has changed and the variable either has to be defined or any cases directly replaced with the extension-key.
As the variable was undefined in the case where this error was remarked, the array-key for the cache-definition just was empty.
So in this case it was an incomplete extension-update.
How to fix
Search in all extensions for usage of $_EXTKEY in the file ext_localconf.php.
If the variable is used but not defined in that file, define it in the beginning or replace it by the extension-key.