Thanks for driving this FLIP, Yuepeng Pan. +1 for the overall proposal to support balanced scheduling.
Some questions on the Waiting mechanism and Allocation strategy for slot to TM: 1. Is it possible for the SlotPool to get the slot allocation results from the SlotManager in advance instead of waiting for the actual physical slots to be registered, and perform pre-allocation? The benefit of doing this is to make the task deployment process smoother, especially when there are a large number of tasks in the job. 2. If user enable the cluster.evenly-spread-out-slots, the issue in example 2 of section 2.2.3 can be resolved. Do I understand it correctly? Best, Yangze Guo On Wed, Sep 27, 2023 at 9:12 PM Zhu Zhu <[email protected]> wrote: > > Thanks Yuepeng and Rui for creating this FLIP. > > +1 in general > The idea is straight forward: best-effort gather all the slot requests > and offered slots to form an overview before assigning slots, trying to > balance the loads of task managers when assigning slots. > > I have one comment regarding the configuration for ease of use: > > IIUC, this FLIP uses an existing config 'cluster.evenly-spread-out-slots' > as the main switch of the new feature. That is, from user perspective, > with this improvement, the 'cluster.evenly-spread-out-slots' feature not > only balances the number of slots on task managers, but also balances the > number of tasks. This is a behavior change anyway. Besides that, it also > requires users to set 'slot.sharing-strategy' to 'TASK_BALANCED_PREFERRED' > to balance the tasks in each slot. > > I think we can introduce a new config option > `taskmanager.load-balance.mode`, > which accepts "None"/"Slots"/"Tasks". `cluster.evenly-spread-out-slots` > can be superseded by the "Slots" mode and get deprecated. In the future > it can support more mode, e.g. "CpuCores", to work better for jobs with > fine-grained resources. The proposed config option > `slot.request.max-interval` > then can be renamed to `taskmanager.load-balance.request-stablizing-timeout` > to show its relation with the feature. The proposed `slot.sharing-strategy` > is not needed, because the configured "Tasks" mode will do the work. > > WDYT? > > Thanks, > Zhu Zhu > > Yuepeng Pan <[email protected]> 于2023年9月25日周一 16:26写道： > > > Hi all, > > > > > > I and Fan Rui(CC’ed) created the FLIP-370[1] to support balanced tasks > > scheduling. > > > > > > The current strategy of Flink to deploy tasks sometimes leads some > > TMs(TaskManagers) to have more tasks while others have fewer tasks, > > resulting in excessive resource utilization at some TMs that contain more > > tasks and becoming a bottleneck for the entire job processing. Developing > > strategies to achieve task load balancing for TMs and reducing job > > bottlenecks becomes very meaningful. > > > > > > The raw design and discussions could be found in the Flink JIRA[2] and > > Google doc[3]. We really appreciate Zhu Zhu(CC’ed) for providing some > > valuable help and suggestions in advance. > > > > > > Please refer to the FLIP[1] document for more details about the proposed > > design and implementation. We welcome any feedback and opinions on this > > proposal. > > > > > > [1] > > https://cwiki.apache.org/confluence/display/FLINK/FLIP-370%3A+Support+Balanced+Tasks+Scheduling > > > > [2] https://issues.apache.org/jira/browse/FLINK-31757 > > > > [3] > > https://docs.google.com/document/d/14WhrSNGBdcsRl3IK7CZO-RaZ5KXU2X1dWqxPEFr3iS8 > > > > > > Best, > > > > Yuepeng Pan > >
