Add RocksDB to the project skeleton

[joelreymont]

No description provided.

[lucafavatella]

From #2 (comment) :

We should use RocksDB instead via the Erlang bindings.

I see there are two RocksDB bindings on hex:

• https://hex.pm/packages/erocksdb i.e. https://github.com/leo-project/erocksdb
• https://hex.pm/packages/rocksdb i.e. https://gitlab.com/barrel-db/erlang-rocksdb

[lucafavatella]

I am writing here my state on this so far. Next steps are:

• Summarize differences in the two forks. Draft notes:
  • One seems more stable, the other one more feature rich for the sake of operations (e.g. backup, snapshot);
  • To be checked whether Erlang API is the same;
  • Identify kind of integration i.e. NF, dirty.
• Select one;
• Attempt inclusion in project. The two bindings have different build system (rebar vs. rebar3) so the other could be taken for easing integration.

---

I see there are two RocksDB bindings on hex:

• https://hex.pm/packages/erocksdb i.e. https://github.com/leo-project/erocksdb
• https://hex.pm/packages/rocksdb i.e. https://gitlab.com/barrel-db/erlang-rocksdb

They diverged a year ago - see 1 that is the same as 2.

In the following is a summary of the differences:

	leo-project/erocksdb	barrel-db/erlang-rocksdb
Build system	rebar	rebar3
RocksDB version	4.13.5	5.7.2
Retrieval of C deps	Downloaded by script called by rebar hook	Committed in the git repository itself

[joelreymont]

What do you recommend?

[lucafavatella]

The work-in-progress branch for this ticket:
https://github.com/aeternity/epoch/tree/gh-42-add-rocksdb-wip (a8247f3).

[lucafavatella]

What do you recommend?

I expressed my recommendation, and motivations, in PR 57.