Why return NULL_ASSIGNMENT when one app can not assign to this leaf queue but not continue?

[杨逸帆Steven <me...@legato.ninja>]

HI,

I am learning Yarn source code, and have this confussion.

In the assignContainers@LeafQueue.java, yarn will iterate all active
applications and try to do the schedule work. however, I notive if one
application's require is over queue limit, the function will return but not
break.

Say I have app#2 needs 500mb, and next app# needs 300mb. The queue now has
only 400mb available left, so when app#2 canAssignToThisQueue fails,
function return and leaves app#3 without schedule. And in this case, app#3
is able to run.

So, what is the reason to Return here?


Thank you.

P.S can I disable reservation? and how to do that?

Sincerely,
Steven