Replaced erlang:now with erlang:timestamp

[TBK145]

Replaced erlang:now with erlang:timestamp as erlang:now is deprecated in Erlang 18.

[TBK145]

Here is the issue I created about it: #86.

[nickelization]

Hi Thijs, thanks for the contribution! However, we currently need to maintain backwards compatibility with Erlang R16, which does not have the erlang:timestamp function. Once we're at a point where we can drop support for previous Erlang versions, then we may be ready to migrate to erlang:timestamp, but for the time being I think we will unfortunately need to stick with erlang:now.

[nickelization]

I'm also concerned about potential race conditions that might occur, since unlike erlang:now, erlang:timestamp does not guarantee that consecutive calls on the same node return monotonically increasing values. I'm not sure if this would actually be an issue, but I'd need to look over the code some more and experiment....

[nickelization]

On the other hand, if your issue is just that warnings_as_errors is enabled and you can't get riak_ensemble to compile under R18, I would be happy to consider a pull request that adds the nowarn_deprecated_function compile flag :)

[cmeiklejohn]

The recommended approach here is to use time_compat to ensure that you have backwards compatibility. We just addressed this in Lasp, our support libraries, and our fork of Helium's Plumtree.

[cmeiklejohn]

👎 to the approach that adds the nowarn_deprecated_function flag.

[TBK145]

So I guess both these occurrences can be replaced by erlang:unique_integer() using the time_compat library?

[nickelization]

@cmeiklejohn Thanks for the info on time_compat, I didn't know about that module/approach (though I guess I should've figured someone had written something like that). Anyway, I agree, that would definitely be nicer than resorting to nowarn_deprecated_function.

[cmeiklejohn]

We've put it in a standalone library so we can include it in the Lasp libraries, given you run into problems if you just copy time_compat in if two (or more) packages both include it.

https://github.com/lasp-lang/time_compat

[jadeallenx]

Thanks @cmeiklejohn! Sometimes Erlang's flat module namespace can be a real PITA.

[jadeallenx]

Sorry hit the wrong button 😝

[TBK145]

This time I used the time_compat library, which also removed the use of timestamp/1 in synctree_leveldb.erl. Just like in riak_core I used time_compat:timestamp/0 once, because the original format was a timestamp as well. Let me know if this should be changed.

[mdaiter]

Bump.

I'd also recommend os:timestamp(), as it's backwards compatible on Erlang R16