Currently there is no consensus on the order of includes. I'm currently working on MESOS-2275 and would suggest, that we follow the rules from the Google C++ Style Guide ( https://google.github.io/styleguide/cppguide.html#Names_and_Order_of_Includes) as much as possible but also follow the current grouping of includes by their level of indirection.
One important question that came up on RR ( https://reviews.apache.org/r/39449/) is, if we should include the "related header" of a source file first. Currently this header is included like any other header. How about we should change that practice and include this header first to avoid hidden dependencies? -- *Jan Schlicht* Distributed Systems Engineer, Mesosphere
