Hi Yangze, Thanks for your feedback!
> 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. Could you elaborate on that? I didn't understand what's the benefit and smoother. > 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? The example assigned result is the final allocation result when flink user enables the cluster.evenly-spread-out-slots. We think the assigned result is expected, so I think your understanding is right. Best, Rui On Thu, Sep 28, 2023 at 1:10 PM Shammon FY <zjur...@gmail.com> wrote: > Thanks Yuepeng for initiating this discussion. > > +1 in general too, in fact we have implemented a similar mechanism > internally to ensure a balanced allocation of tasks to slots, it works > well. > > Some comments about the mechanism > > 1. This mechanism will be only supported in `SlotPool` or both `SlotPool` > and `DeclarativeSlotPool`? Currently the two slot pools are used in > different schedulers. I think this will also bring value to > `DeclarativeSlotPool`, but currently FLIP content seems to be based on > `SlotPool`, right? > > 2. In fine-grained resource management, we can set different resource > requirements for different nodes, which means that the resources of each > slot are different. What should be done when the slot selected by the > round-robin strategy cannot meet the resource requirements? Will this lead > to the failure of the balance strategy? > > 3. Is the assignment of tasks to slots balanced based on region or job > level? When multiple TMs fail over, will it cause the balancing strategy to > fail or even worse? What is the current processing strategy? > > For Zhuzhu and Rui: > > IIUC, the overall balance is divided into two parts: slot to TM and task to > slot. > 1. Slot to TM is guaranteed by SlotManager in ResourceManager > 2. Task to slot is guaranteed by the slot pool in JM > > These two are completely independent, what are the benefits of unifying > these two into one option? Also, do we want to share the same > option between SlotPool in JM and SlotManager in RM? This sounds a bit > strange. > > Best, > Shammon FY > > > > On Thu, Sep 28, 2023 at 12:08 PM Rui Fan <1996fan...@gmail.com> wrote: > > > Hi Zhu Zhu, > > > > Thanks for your feedback here! > > > > You are right, user needs to set 2 options: > > - cluster.evenly-spread-out-slots=true > > - slot.sharing-strategy=TASK_BALANCED_PREFERRED > > > > Update it to one option is useful at user side, so > > `taskmanager.load-balance.mode` sounds good to me. > > I want to check some points and behaviors about this option: > > > > 1. The default value is None, right? > > 2. When it's set to Tasks, how to assign slots to TM? > > - Option1: It's just check task number > > - Option2: It''s check the slot number first, then check the > > task number when the slot number is the same. > > > > Giving an example to explain what's the difference between them: > > > > - A session cluster has 2 flink jobs, they are jobA and jobB > > - Each TM has 4 slots. > > - The task number of one slot of jobA is 3 > > - The task number of one slot of jobB is 1 > > - We have 2 TaskManagers: > > - tm1 runs 3 slots of jobB, so tm1 runs 3 tasks > > - tm2 runs 1 slot of jobA, and 1 slot of jobB, so tm2 runs 4 tasks. > > > > Now, we need to run a new slot, which tm should offer it? > > - Option1: If we just check the task number, the tm1 is better. > > - Option2: If we check the slot number first, and then check task, the > tm2 > > is better > > > > The original FLIP selected option2, that's why we didn't add the > > third option. The option2 didn't break the semantics when > > `cluster.evenly-spread-out-slots` is true, and it just improve the > > behavior without the semantics is changed. > > > > In the other hands, if we choose option2, when user set > > `taskmanager.load-balance.mode` is Tasks. It also can achieve > > the goal when it's Slots. > > > > So I think the `Slots` enum isn't needed if we choose option2. > > Of course, If we choose the option1, the enum is needed. > > > > Looking forward to your feedback, thanks~ > > > > Best, > > Rui > > > > On Wed, Sep 27, 2023 at 9:11 PM Zhu Zhu <reed...@gmail.com> 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 <panyuep...@apache.org> 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 > > >> > > > > > >
