Steps to replicate the issue:
pwb -simulate archivebot -lang:en -async
What happens?:
The memory usage increases a lot. Probably a MemoryError could occurr when running for the whole wiki.
The reason is the internal queue of ThreadPoolExecutor which is an unlimited SimpleQueue (or unlimited Queue for < Python 3.7). This queue holds all pending tasks references to the archive template retrieved from generator.
What should have happened instead?:
The memory usage should not be exhausing.
Software version:
Pywikibot 8.1.0dev3