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From John Omernik <j...@omernik.com>
Subject Dynamic Reservations and --roles
Date Fri, 11 Dec 2015 15:34:56 GMT
I am following http://mesos.apache.org/documentation/latest/reservation/ to
learn how to do dynamic reservations.  I don't want to statically assign
roles, therefore, I started my slaves only with the (*) resources.

I used the HTTP endpoints to reserve some resources.  And it returned
successful. In addition, I've checked the /slaves endpoint and indeed the
resources are allocated.

Now when I try to uses those roles, I get an error:

sched.cpp:1024] Got error 'Role 'dev' is not present in the master's
--roles'

Ok, so looking I indeed likely need to specify --roles at startup of
master.  This got me thinking, is this an oversight or by design?  If it's
an oversight, then I will file a JIRA, if by designed, I'd like to
understand more.

What I mean is this: The whole point of /reserver /unreserve is not have to
specify the resources at slave startup.  That's great.  Then when I
reserver or unreserve, from how I understand it one of two things should
happen (This is where I need feedback)

1. If the role specified in the reserve/unreserve operation doesn't exist
in --roles on the master, it should reject the reservation on the /reserve
endpoint.  Why allow the reservation of roles if you can't use them if they
are specified

2. If the role doesn't exist in --roles, and a reservation comes through,
it should be added dynamically. This seems to make more sense to me. I.e.
adding roles doesn't require a master restart.

If there is a 3rd option here, that I am not seeing, please let me know,
otherwise I will file a JIRA to this...

John

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