Scheduled cache priming: unbounded znode version?

[soxofaan]

Follow up of #74:
there is now a X-minutely cron background task that primes the caches (regardless of existing values). Consequently the Zookeeper znode version is bumped roughly 100 times a day (even though the actual data does not change that often).
Is there a risk of letting this grow unboundedly?

Some examples of current state after running this for just a couple of days (prod cache):

• version 1193 /openeo/aggregator/cache/CollectionCatalog/all
• version 1023 /openeo/aggregator/cache/Processing/all/1.0.0
• version 944 /openeo/aggregator/cache/general/file_formats

[soxofaan]

possible solutions:

• just prune the whole /openeo/aggregator/cache tree every X months. If I understand correctly, version start over from 0 again
• switch to a different caching solution (zookeeper is not really a caching solution anyway)
• make "cache priming" implementation smarter to not bump version if it is not necessary (new value equals cached version and mtime is not too old yet)