+1 for Chandan; no doubt; he's always available on IRC to help when things go wrong in gate or promotion, and very often he's proposing the fix.
Providing thoroughful reviews, and multi-project contributors, I've seen Chandan involved not only in TripleO CI but also in other projects like RDO and TripleO itself. I've seen him contributing to the tripleo-common and tripleoclient projects; which make him someone capable to understand not only how CI works but also how the project in general works. Having him core is to me natural.
Number of commits/reviews shows his interests in the CI repos:
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I hate playing devil's advocate here but I'll give my honest (and hopefully constructive) opinion.
I would like to see more involvement from Arx in the TripleO community. He did a tremendous work on openstack-ansible-os_tempest; however this repo isn't governed by TripleO CI group. I would like to see more reviews; where he can bring his expertise; and not only in Gerrit but also on IRC when things aren't going well (gate issues, promotion blockers, etc).
Number of commits/reviews aren't low but IMHO can be better for a core reviewer.
I don't think it'll take time until Arx gets there but to me it's a -1 for now, for what it's worth.
Emilien