I'm also facing the same issue. Please find below which is logged in log file.
[2015-12-07 11:56:48,346][DEBUG][action.bulk ] [Betty Ross Banner] observer: timeout notification from cluster service. timeout setting [1m], time since start [1m]
Can someone please help me how to solve this. I'm using Elasticsearch 1.6.0 version.
Thanks,
Vani Aravinda