Problem/Motivation
For now, creating batches, using storage service, looks like \Drupal::service('batch.storage')->create($batch);. For instance, if batch defined as progressive, then it'll be created via the same construction inside of batch_process() function. Afterwards, when batch is finished and _batch_finished() executed, an entry will be deleted from storage by \Drupal::service('batch.storage')->delete($batch['id']);. Everything fine at the moment. My proposal is: take care about the storage and trigger the cleanup() method of the service inside of system_cron().
In addition to above, there could be a case when _batch_queue() function will try to construct wrong class. To resolve this, I propose to add an interface which will identify batch-related queues.
Proposed resolution
Add execution of \Drupal::service('batch.storage')->cleanup() to system_cron().
Remaining tasks
None.
User interface changes
None.
API changes
Add \Drupal\Core\Queue\BatchQueueInterface which must be implemented by every custom batch queue.
Data model changes
None.