add mesos role feature

[zhanglong2015]

Problems

We are from eBay platform team. Previously, we used marathon to generate Jenkins master instance in dedicated vms and recieve resource offer from same dedicated vms. For the details, please refer to
http://www.ebaytechblog.com/2014/04/04/delivering-ebays-ci-solution-with-apache-mesos-part-i/#.VNQUuC6_SPU

Now, we found Aurora is more stable and powerful. We are moving from Marathon to Aurora. During the move, we found there is no mesos role in Aurora now. But we need use mesos role way to solve the problem in section "Frameworks stopped receiving offers after a while" of the given url.

Here is a snippet of the problem description:

We noticed occurred after we used Marathon to create the initial set of CI masters. As those CI masters started registering themselves as frameworks, Marathon stopped receiving any offers from Mesos; essentially, no new CI masters could be launched. Let’s start with Marathon. In the DRF model, it was unfair to treat Marathon in the same bucket/role alongside hundreds of connected Jenkins frameworks. After launching all these Jenkins frameworks, Marathon had a large resource share and Mesos would aggressively offer resources to frameworks that were using little or no resources. Marathon was placed last in priority and got starved out.

We decided to define a dedicated Mesos role for Marathon and to have all of the Mesos slaves that were reserved for Jenkins master instances support that Mesos role. Jenkins frameworks were left with the default role “”.* This solved the problem – Mesos offered resources per role and hence Marathon never got starved out. A framework with a special role will get resource offers from both slaves supporting that special role and also from the default role “”.* However, since we were using placement constraints, Marathon accepted resource offers only from slaves that supported both the role and the placement constraints.

Solution

So we add role feature is the source code to solve the problem in same way: When accept a resource offer, Aurora will send back the needed resources to Mesos with the mesos role in resource offer.

How to configure the Mesos role:
1.Add cmd option --mesos_role=${Mesos role name} when start Aurora scheduler.

We change the test cases according code change. Each changed test case is green.

[davelester]

Thanks for this patch! Would you mind moving this patch to ReviewBoard? You'll find contributions guidelines in the Aurora documentation: http://aurora.incubator.apache.org/documentation/latest/contributing/

[wfarner]

Cool! Others have mentioned wanting this feature, really glad to see the patch! As @davelester mentioned, our development takes place on Apache's ReviewBoard. Please add me as a reviewer once you post it and i'll take a look ASAP!

[zhanglong2015]

Thanks for the comments. Have publish review request https://reviews.apache.org/r/30710/