Do we need a process for ETS tables?

[sasajuric]

@LostKobrakai

I’d think less about “if ETS fails” or “which approach is better”, but rather in terms of data locality and data consistency. A ETS table being e.g. a read-through cache for some external resource should be co-located to the process accessing the external resource. Maybe they should even restart together in certain scenarios to prevent stale data in the cache

This is the key insight here. By having a GenServer owner of an ETS table, and placing that owner in a proper place in the supervision tree, we can ensure the desired stop and restart behaviour on a case-by-case basis. In other words, it’s equally straightforward to ensure that the cache is purged on termination, as well as to ensure that the cached data lives on after the restart.

Occasionally, I find myself using a supervisor as the owner of a table, but more often I tend to have a dedicated GenServer for that purpose. I used to start tables during app start too, but I never do this anymore. The small convenience gain is not worth the confusion which comes this approach (e.g. the data lives on until the app is stopped, and it’s not clear from the code where the table is created and who owns it).