Merge Redis support PR

[n5nk]

Hi,

Can the maintainer review Redis PR for Janusgraph #3018 this would be helpful for everyone running Atlas in distributed mode.

[li-boxuan]

I left a review last year but haven't heard back from the authors since then. If you are desperately in need of it, try forking their branch and build a custom version of JanusGraph.

[n5nk]

Thanks @li-boxuan will do

[n5nk]

@li-boxuan , Need small help to understand the PR. What is the purpose of redisIndexKeys here in the PR

[li-boxuan]

@n5nk I myself haven't got a chance to review that PR thoroughly. I suggest you ping the original authors.