Thanks Jian. In what sense is the "capacity" resources "guaranteed"?
Let's say there are two queues at the root level, A and B. Both have capacity of 50% and max capacity of 70%. If queue A is only currently using 40% and queue B is using 50% and needs more, then it will be able to borrow 10% from queue A, so now queue A is using 40% and queue B is using 60%. But what happens if queue A now needs 50%? Will the scheduler take away the 10% from queue B and give it back to queue A even if queue B needs it? If not, it would seem that the scheduler is reneging on its guarantee. On Wed, Feb 19, 2014 at 6:01 PM, Jian He <[email protected]> wrote: > Hi Alex > > You can find good explanation from here: > http://hortonworks.com/blog/understanding-apache-hadoops-capacity-scheduler/ > Short term: Capacity is the soft limit that queue is guaranteed for such > an amount of resource. For the purpose of necessary elasticity, queue can > go beyond capacity limit but can not go beyond Max-Capacity limit which is > the hard limit. > > Jian > > > On Wed, Feb 19, 2014 at 11:08 AM, Alex Nastetsky > <[email protected]>wrote: > >> Please help me understand how "capacity" and "maximum-capacity" on a >> queue work in the Capacity Scheduler. >> >> My understanding is that a queue is allocated "capacity" amount of >> resources, and if it needs more, it can "stretch" up to "maximum-capacity" >> resources. >> >> But if that's the case, why do we need "capacity" at all? It seems like >> "maximum-capacity" is the true limit and "capacity" is ignored? >> >> Thanks in advance, >> Alex. >> > > > CONFIDENTIALITY NOTICE > NOTICE: This message is intended for the use of the individual or entity > to which it is addressed and may contain information that is confidential, > privileged and exempt from disclosure under applicable law. If the reader > of this message is not the intended recipient, you are hereby notified that > any printing, copying, dissemination, distribution, disclosure or > forwarding of this communication is strictly prohibited. If you have > received this communication in error, please contact the sender immediately > and delete it from your system. Thank You.
