kubernetes
/
website
mirror of https://github.com/kubernetes/website.git
1
0
Fork 0
Code Issues Projects Releases Wiki Activity

Merge pull request #48044 from windsonsea/schesp 

Clean up a new blog: 2024-09-17-sig-scheduling-spotlight
pull/46230/head
Kubernetes Prow Robot 2024-10-07 18:14:22 +01:00 committed by GitHub
parent 9a27845924 79fcba47a6
commit 61cd60c85f
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
1 changed files with 47 additions and 51 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

98
content/en/blog/_posts/2024-09-17-sig-scheduling-spotlight.md
View File

@ -19,7 +19,7 @@ Kubernetes?**
**Kensei**: Hi, thanks for the opportunity! I’m Kensei Nakada
([@sanposhiho](https://github.com/sanposhiho/)), a software engineer at
[Tetrate.io](https://tetrate.io/). I have been contributing to Kubernetes in my free time for more
than 3 years, and now I’m an approver of SIG-Scheduling in Kubernetes. Also, I’m a founder/owner of
than 3 years, and now I’m an approver of SIG Scheduling in Kubernetes. Also, I’m a founder/owner of
two SIG subprojects,
[kube-scheduler-simulator](https://github.com/kubernetes-sigs/kube-scheduler-simulator) and
[kube-scheduler-wasm-extension](https://github.com/kubernetes-sigs/kube-scheduler-wasm-extension).
@ -32,14 +32,14 @@ brief overview of SIG Scheduling and explain its role within the Kubernetes ecos
**KN**: As the name implies, our responsibility is to enhance scheduling within
Kubernetes. Specifically, we develop the components that determine which Node is the best place for
each Pod. In Kubernetes, our main focus is on maintaining the
[kube-scheduler](https://kubernetes.io/docs/concepts/scheduling-eviction/kube-scheduler/), along
[kube-scheduler](/docs/concepts/scheduling-eviction/kube-scheduler/), along
with other scheduling-related components as part of our SIG subprojects.
**AP: I see, got it! That makes me curious--what recent innovations or developments has SIG
Scheduling introduced to Kubernetes scheduling?**
**KN**: From a feature perspective, there have been [several
enhancements](https://kubernetes.io/blog/2023/04/17/fine-grained-pod-topology-spread-features-beta/)
**KN**: From a feature perspective, there have been
[several enhancements](/blog/2023/04/17/fine-grained-pod-topology-spread-features-beta/)
to `PodTopologySpread` recently. `PodTopologySpread` is a relatively new feature in the scheduler,
and we are still in the process of gathering feedback and making improvements.
@ -53,59 +53,58 @@ reducing the likelihood of wasting scheduling cycles.
**A: That sounds interesting! Are there any other interesting topics or projects you are currently
working on within SIG Scheduling?**
**KN**: I’m leading the development of `QueueingHint` which I just shared. Given that it’s a big new
**KN**: I’m leading the development of `QueueingHint` which I just shared. Given that it’s a big new
challenge for us, we’ve been facing many unexpected challenges, especially around the scalability,
and we’re trying to solve each of them to eventually enable it by default.
And also, I believe
[kube-scheduler-wasm-extention](https://github.com/kubernetes-sigs/kube-scheduler-wasm-extension)
(SIG sub project) that I started last year would be interesting to many people. Kubernetes has
[kube-scheduler-wasm-extension](https://github.com/kubernetes-sigs/kube-scheduler-wasm-extension)
(a SIG subproject) that I started last year would be interesting to many people. Kubernetes has
various extensions from many components. Traditionally, extensions are provided via webhooks
([extender](https://github.com/kubernetes/design-proposals-archive/blob/main/scheduling/scheduler_extender.md)
in the scheduler) or Go SDK ([Scheduling
Framework](https://kubernetes.io/docs/concepts/scheduling-eviction/scheduling-framework/) in the
scheduler). However, these come with drawbacks - performance issues with webhooks and the need to
in the scheduler) or Go SDK ([Scheduling Framework](/docs/concepts/scheduling-eviction/scheduling-framework/)
in the scheduler). However, these come with drawbacks - performance issues with webhooks and the need to
rebuild and replace schedulers with Go SDK, posing difficulties for those seeking to extend the
scheduler but lacking familiarity with it. The project is trying to introduce a new solution to
scheduler but lacking familiarity with it. The project is trying to introduce a new solution to
this general challenge - a [WebAssembly](https://webassembly.org/) based extension. Wasm allows
users to build plugins easily, without worrying about recompiling or replacing their scheduler, and
sidestepping performance concerns.
Through this project, sig-scheduling has been learning valuable insights about WebAssembly's
Through this project, SIG Scheduling has been learning valuable insights about WebAssembly's
interaction with large Kubernetes objects. And I believe the experience that we’re gaining should be
useful broadly within the community, beyond sig-scheduling.
useful broadly within the community, beyond SIG Scheduling.
**A: Definitely! Now, there are currently 8 subprojects inside SIG Scheduling. Would you like to
**A: Definitely! Now, there are 8 subprojects inside SIG Scheduling. Would you like to
talk about them? Are there some interesting contributions by those teams you want to highlight?**
**KN**: Let me pick up three sub projects; Kueue, KWOK and descheduler.
**KN**: Let me pick up three subprojects: Kueue, KWOK and descheduler.
[Kueue](https://github.com/kubernetes-sigs/kueue):
[Kueue](https://github.com/kubernetes-sigs/kueue)
: Recently, many people have been trying to manage batch workloads with Kubernetes, and in 2022,
Kubernetes community founded
[WG-Batch](https://github.com/kubernetes/community/blob/master/wg-batch/README.md) for better
support for such batch workloads in Kubernetes. [Kueue](https://github.com/kubernetes-sigs/kueue)
is a project that takes a crucial role for it. It’s a job queueing controller, deciding when a job
should wait, when a job should be admitted to start, and when a job should be preempted. Kueue aims
to be installed on a vanilla Kubernetes cluster while cooperating with existing matured controllers
(scheduler, cluster-autoscaler, kube-controller-manager, etc).
Kubernetes community founded
[WG-Batch](https://github.com/kubernetes/community/blob/master/wg-batch/README.md) for better
support for such batch workloads in Kubernetes. [Kueue](https://github.com/kubernetes-sigs/kueue)
is a project that takes a crucial role for it. It’s a job queueing controller, deciding when a job
should wait, when a job should be admitted to start, and when a job should be preempted. Kueue aims
to be installed on a vanilla Kubernetes cluster while cooperating with existing matured controllers
(scheduler, cluster-autoscaler, kube-controller-manager, etc).
[KWOK](https://github.com/kubernetes-sigs/kwok):
[KWOK](https://github.com/kubernetes-sigs/kwok)
: KWOK is a component in which you can create a cluster of thousands of Nodes in seconds. It’s
mostly useful for simulation/testing as a lightweight cluster, and actually another SIG sub
project [kube-scheduler-simulator](https://github.com/kubernetes-sigs/kube-scheduler-simulator)
uses KWOK background.
[descheduler](https://github.com/kubernetes-sigs/descheduler):
: Descheduler is a component recreating pods that are running on undesired Nodes. In Kubernetes,
scheduling constraints (`PodAffinity`, `NodeAffinity`, `PodTopologySpread`, etc) are honored only at
Pod schedule, but it’s not guaranteed that the contrtaints are kept being satisfied afterwards.
Descheduler evicts Pods violating their scheduling constraints (or other undesired conditions) so
that they’re recreated and rescheduled.
[descheduler](https://github.com/kubernetes-sigs/descheduler)
: Descheduler is a component recreating pods that are running on undesired Nodes. In Kubernetes,
scheduling constraints (`PodAffinity`, `NodeAffinity`, `PodTopologySpread`, etc) are honored only at
Pod schedule, but it’s not guaranteed that the contrtaints are kept being satisfied afterwards.
Descheduler evicts Pods violating their scheduling constraints (or other undesired conditions) so
that they’re recreated and rescheduled.
[Descheduling Framework](https://github.com/kubernetes-sigs/descheduler/blob/master/keps/753-descheduling-framework/README.md).
: One very interesting on-going project, similar to [Scheduling
Framework](https://kubernetes.io/docs/concepts/scheduling-eviction/scheduling-framework/) in the
[Descheduling Framework](https://github.com/kubernetes-sigs/descheduler/blob/master/keps/753-descheduling-framework/README.md)
: One very interesting on-going project, similar to
[Scheduling Framework](/docs/concepts/scheduling-eviction/scheduling-framework/) in the
scheduler, aiming to make descheduling logic extensible and allow maintainers to focus on building
a core engine of descheduler.
@ -125,27 +124,26 @@ improving our components over the years.
**AP: Kubernetes is a community-driven project. Any recommendations for new contributors or
beginners looking to get involved and contribute to SIG scheduling? Where should they start?**
**KN**: Let me start with a general recommendation for contributing to any SIG: a common approach is
to look for
**KN**: Let me start with a general recommendation for contributing to any SIG: a common approach is to look for
[good-first-issue](https://github.com/kubernetes/kubernetes/issues?q=is%3Aopen+is%3Aissue+label%3A%22good+first+issue%22).
However, you'll soon realize that many people worldwide are trying to contribute to the Kubernetes
repository.
I suggest starting by examining the implementation of a component that interests you. If you have
any questions about it, ask in the corresponding Slack channel (e.g., #sig-scheduling for the
scheduler, #sig-node for kubelet, etc). Once you have a rough understanding of the implementation,
scheduler, #sig-node for kubelet, etc). Once you have a rough understanding of the implementation,
look at issues within the SIG (e.g.,
[sig-scheduling](https://github.com/kubernetes/kubernetes/issues?q=is%3Aopen+is%3Aissue+label%3Asig%2Fscheduling)),
where you'll find more unassigned issues compared to good-first-issue ones. You may also want to
where you'll find more unassigned issues compared to good-first-issue ones. You may also want to
filter issues with the
[kind/cleanup](https://github.com/kubernetes/kubernetes/issues?q=is%3Aopen+is%3Aissue++label%3Akind%2Fcleanup+)
label, which often indicates lower-priority tasks and can be starting points.
Specifically for SIG Scheduling, you should first understand the [Scheduling
Framework](https://kubernetes.io/docs/concepts/scheduling-eviction/scheduling-framework/), which is
the fundamental architecture of kube-scheduler. Most of the implementation is found in
[pkg/scheduler](https://github.com/kubernetes/kubernetes/tree/master/pkg/scheduler). I suggest
starting with
Specifically for SIG Scheduling, you should first understand the
[Scheduling Framework](/docs/concepts/scheduling-eviction/scheduling-framework/), which is
the fundamental architecture of kube-scheduler. Most of the implementation is found in
[pkg/scheduler](https://github.com/kubernetes/kubernetes/tree/master/pkg/scheduler).
I suggest starting with
[ScheduleOne](https://github.com/kubernetes/kubernetes/blob/0590bb1ac495ae8af2a573f879408e48800da2c5/pkg/scheduler/schedule_one.go#L66)
function and then exploring deeper from there.
@ -154,15 +152,14 @@ sub-projects. These typically have fewer maintainers and offer more opportunitie
significant impact. Despite being called "sub" projects, many have a large number of users and a
considerable impact on the community.
And last but not least, remember contributing to the community isn’t just about code. While I
And last but not least, remember contributing to the community isn’t just about code. While I
talked a lot about the implementation contribution, there are many ways to contribute, and each one
is valuable. One comment to an issue, one feedback to an existing feature, one review comment in PR,
one clarification on the documentation; every small contribution helps drive the Kubernetes
ecosystem forward.
**AP: Those are some pretty useful tips! And if I may ask, how do you assist new contributors in
getting started, and what skills are contributors likely to learn by participating in SIG
Scheduling?**
getting started, and what skills are contributors likely to learn by participating in SIG Scheduling?**
**KN**: Our maintainers are available to answer your questions in the #sig-scheduling Slack
channel. By participating, you'll gain a deeper understanding of Kubernetes scheduling and have the
@ -178,9 +175,8 @@ pain points?**
**KN**: Scheduling in Kubernetes can be quite challenging because of the diverse needs of different
organizations with different business requirements. Supporting all possible use cases in
kube-scheduler is impossible. Therefore, extensibility is a key focus for us. A few years ago, we
rearchitected kube-scheduler with [Scheduling
Framework](https://kubernetes.io/docs/concepts/scheduling-eviction/scheduling-framework/), which
offers flexible extensibility for users to implement various scheduling needs through plugins. This
rearchitected kube-scheduler with [Scheduling Framework](/docs/concepts/scheduling-eviction/scheduling-framework/),
which offers flexible extensibility for users to implement various scheduling needs through plugins. This
allows maintainers to focus on the core scheduling features and the framework runtime.
Another major issue is maintaining sufficient scheduling throughput. Typically, a Kubernetes cluster
@ -190,7 +186,7 @@ and, consequently, the cluster's scalability. Although we have an internal perfo
unfortunately, we sometimes overlook performance degradation in less common scenarios. It’s
difficult as even small changes, which look irrelevant to performance, can lead to degradation.
**AP: What are some upcoming goals or initiatives for SIG Scheduling? How do you envision the SIG evolving in the future?**
**AP: What are some upcoming goals or initiatives for SIG Scheduling? How do you envision the SIG evolving in the future?**
**KN**: Our primary goal is always to build and maintain _extensible_ and _stable_ scheduling
runtime, and I bet this goal will remain unchanged forever.
@ -198,7 +194,7 @@ runtime, and I bet this goal will remain unchanged forever.
As already mentioned, extensibility is key to solving the challenge of the diverse needs of
scheduling. Rather than trying to support every different use case directly in kube-scheduler, we
will continue to focus on enhancing extensibility so that it can accommodate various use
cases. [kube-scheduler-wasm-extention](https://github.com/kubernetes-sigs/kube-scheduler-wasm-extension)
cases. [kube-scheduler-wasm-extension](https://github.com/kubernetes-sigs/kube-scheduler-wasm-extension)
that I mentioned is also part of this initiative.
Regarding stability, introducing new optimizations like QueueHint is one of our
@ -217,7 +213,7 @@ about SIG Scheduling?**
**KN**: Scheduling is one of the most complicated areas in Kubernetes, and you may find it difficult
at first. But, as I shared earlier, you can find many opportunities for contributions, and many
maintainers are willing to help you understand things. We know your unique perspective and skills
are what makes our open source so powerful :)
are what makes our open source so powerful 😊
Feel free to reach out to us in Slack
([#sig-scheduling](https://kubernetes.slack.com/archives/C09TP78DV)) or