Evaluate adding a gokv.Store implementation for ElasticSearch

[philippgille]

As with some other implementations, ElasticSearch is not meant to be used as simple key-value store. It's for uploading and then indexing data, that can later be searched. But the data are (usually?) JSON documents and there's an API for PUT ("Index"), GET and DELETE via an ID, which serves as key. So 1) it's probably usable as key-value storage, and 2) as mentioned, like with other gokv.Store implementations, if users are already running an ElasticSearch cluster, why not use it, instead of having to set up and administrate another service like Redis?

So, check out if ElasticSearch's PUT, GET and DELETE APIs are actually usable for our purpose.

• API docs: https://www.elastic.co/guide/en/elasticsearch/reference/current/docs.html
• Go package: https://github.com/olivere/elastic