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Nathan Roberts updated YARN-4287: --------------------------------- Attachment: YARN-4287-v3.patch V3 of patch. Thanks again for the comments. bq. RACK_LOCALITY_EXTRA_DELAY -> RACK_LOCALITY_DELAY, same as configuration property name (rack-locality-delay) Done - changed to absolute instead of relative to nodeLocality bq. Do you think if is it a good idea to separate old rack-locality-delay computation (using getLocalityWaitFactor) and new rack-locality-delay config? Now rack-locality-delay = min(old-computed-delay, new-specified-delay), since the getLocalityWaitFactor has some flaws, I think we can make this configurable so user can choose to use specified or computed. I simplified the code a little in this area to make it easier to see where the computed-locality-delay is used. I didn't separate them in this version of the patch because I still want to be able to specify rack-locality-delay BUT have the computed delay take effect when an application is not asking for locality OR is really small. This is a very important capability for at least our use cases. My opinion is that we shouldn't make it configurable to get the old behavior. I can be convinced otherwise, if that's what folks want. Here's my reasoning: - This is a behavior change, but I can't think of any good cases where someone would prefer the old behavior to the new. Let me know if you can think of some. - Node locality might go down a little bit but I think it's quite unlikely this will happen in practice. As soon as it sees a node-local assignment, it immediately goes back to waiting for node-locality - so it's quite hard to only get rack locality when there is node locality to be had. - Rack locality will go up because previously the computedDelay used for OFFSWITCH would actually kick-in prior to a rack-local opportunity, which wasn't ideal. I would think this would offset any node locality we lost. > Capacity Scheduler: Rack Locality improvement > --------------------------------------------- > > Key: YARN-4287 > URL: https://issues.apache.org/jira/browse/YARN-4287 > Project: Hadoop YARN > Issue Type: Improvement > Components: capacityscheduler > Affects Versions: 2.7.1 > Reporter: Nathan Roberts > Assignee: Nathan Roberts > Attachments: YARN-4287-v2.patch, YARN-4287-v3.patch, YARN-4287.patch > > > YARN-4189 does an excellent job describing the issues with the current delay > scheduling algorithms within the capacity scheduler. The design proposal also > seems like a good direction. > This jira proposes a simple interim solution to the key issue we've been > experiencing on a regular basis: > - rackLocal assignments trickle out due to nodeLocalityDelay. This can have > significant impact on things like CombineFileInputFormat which targets very > specific nodes in its split calculations. > I'm not sure when YARN-4189 will become reality so I thought a simple interim > patch might make sense. The basic idea is simple: > 1) Separate delays for rackLocal, and OffSwitch (today there is only 1) > 2) When we're getting rackLocal assignments, subsequent rackLocal assignments > should not be delayed > Patch will be uploaded shortly. No big deal if the consensus is to go > straight to YARN-4189. -- This message was sent by Atlassian JIRA (v6.3.4#6332)