I'm starting to set up a development environment that I can use for 1.0 and 0.90.x right now.

Update: we've merged https://gerrit.wikimedia.org/r/#/c/115215/ to support 1.0 and we're testing Elasticsearch 1.0.1 in beta.

1.0.1 is in production as of last night and stable.

Can we also use Elasticsearch 1.1.0 ?

I haven't tried 1.1.0 yet but I'm excited to. It has two features which'll be great for big wikis: multiple rescores and phrase suggester speed boost. I don't see a reason why it won't "just work" but I'm waiting to try it because I'm watching an issue that might cause them to release a 1.1.1 pretty quickly (https://github.com/elasticsearch/elasticsearch/issues/5573). It doesn't effect Cirrus but if they spin out a new release in the next few days I don't want to have to reverify everything. Or upgrade the production cluster twice. That is a pain.

Thank you for the fast reply. I will wait for 1.1.1 then ;-)

It looks like that didn't make a 1.1.1 so I verified 1.1.0 yesterday/this morning. I've upgraded beta.wmflabs.org and everything seems fine. When I next work on backporting changes to the release branch I'll verify it there as well but I imagine that branch will work without any trouble.

Thank you Nik. I updated to ES 1.1.0 today (I am on REL_1.22) and the searches still seem to work :-)