171 lines
8.7 KiB
Markdown
171 lines
8.7 KiB
Markdown
---
|
||
title: Kubernetes 调度器
|
||
content_type: concept
|
||
weight: 50
|
||
---
|
||
|
||
<!--
|
||
---
|
||
title: Kubernetes Scheduler
|
||
content_type: concept
|
||
weight: 50
|
||
---
|
||
-->
|
||
<!-- overview -->
|
||
|
||
<!--
|
||
In Kubernetes, _scheduling_ refers to making sure that {{< glossary_tooltip text="Pods" term_id="pod" >}}
|
||
are matched to {{< glossary_tooltip text="Nodes" term_id="node" >}} so that
|
||
{{< glossary_tooltip term_id="kubelet" >}} can run them.
|
||
-->
|
||
在 Kubernetes 中，_调度_ 是指将 {{< glossary_tooltip text="Pod" term_id="pod" >}} 放置到合适的
|
||
{{< glossary_tooltip text="Node" term_id="node" >}} 上，然后对应 Node 上的 {{< glossary_tooltip term_id="kubelet" >}} 才能够运行这些 pod。
|
||
|
||
|
||
|
||
<!-- body -->
|
||
<!--
|
||
## Scheduling overview {#scheduling}
|
||
-->
|
||
## 调度概览 {#scheduling}
|
||
|
||
<!--
|
||
A scheduler watches for newly created Pods that have no Node assigned. For
|
||
every Pod that the scheduler discovers, the scheduler becomes responsible
|
||
for finding the best Node for that Pod to run on. The scheduler reaches
|
||
this placement decision taking into account the scheduling principles
|
||
described below.
|
||
-->
|
||
调度器通过 kubernetes 的 watch 机制来发现集群中新创建且尚未被调度到 Node 上的 Pod。调度器会将发现的每一个未调度的 Pod 调度到一个合适的 Node 上来运行。调度器会依据下文的调度原则来做出调度选择。
|
||
|
||
<!--
|
||
If you want to understand why Pods are placed onto a particular Node,
|
||
or if you're planning to implement a custom scheduler yourself, this
|
||
page will help you learn about scheduling.
|
||
-->
|
||
如果你想要理解 Pod 为什么会被调度到特定的 Node 上，或者你想要尝试实现一个自定义的调度器，这篇文章将帮助你了解调度。
|
||
|
||
<!--
|
||
## kube-scheduler
|
||
-->
|
||
## kube-scheduler
|
||
|
||
<!--
|
||
[kube-scheduler](https://kubernetes.io/docs/reference/command-line-tools-reference/kube-scheduler/)
|
||
is the default scheduler for Kubernetes and runs as part of the
|
||
{{< glossary_tooltip text="control plane" term_id="control-plane" >}}.
|
||
kube-scheduler is designed so that, if you want and need to, you can
|
||
write your own scheduling component and use that instead.
|
||
-->
|
||
[kube-scheduler](/zh/docs/reference/command-line-tools-reference/kube-scheduler/) 是 Kubernetes 集群的默认调度器，并且是集群 {{< glossary_tooltip text="控制面" term_id="control-plane" >}} 的一部分。如果你真的希望或者有这方面的需求，kube-scheduler 在设计上是允许你自己写一个调度组件并替换原有的 kube-scheduler。
|
||
|
||
<!--
|
||
For every newly created pods or other unscheduled pods, kube-scheduler
|
||
selects a optimal node for them to run on. However, every container in
|
||
pods has different requirements for resources and every pod also has
|
||
different requirements. Therefore, existing nodes need to be filtered
|
||
according to the specific scheduling requirements.
|
||
-->
|
||
对每一个新创建的 Pod 或者是未被调度的 Pod，kube-scheduler 会选择一个最优的 Node 去运行这个 Pod。然而，Pod 内的每一个容器对资源都有不同的需求，而且 Pod 本身也有不同的资源需求。因此，Pod 在被调度到 Node 上之前，根据这些特定的资源调度需求，需要对集群中的 Node 进行一次过滤。
|
||
|
||
<!--
|
||
In a cluster, Nodes that meet the scheduling requirements for a Pod
|
||
are called _feasible_ nodes. If none of the nodes are suitable, the pod
|
||
remains unscheduled until the scheduler is able to place it.
|
||
-->
|
||
在一个集群中，满足一个 Pod 调度请求的所有 Node 称之为 _可调度节点_。如果没有任何一个 Node 能满足 Pod 的资源请求，那么这个 Pod 将一直停留在未调度状态直到调度器能够找到合适的 Node。
|
||
|
||
<!--
|
||
The scheduler finds feasible Nodes for a Pod and then runs a set of
|
||
functions to score the feasible Nodes and picks a Node with the highest
|
||
score among the feasible ones to run the Pod. The scheduler then notifies
|
||
the API server about this decision in a process called _binding_.
|
||
-->
|
||
调度器先在集群中找到一个 Pod 的所有可调度节点，然后根据一系列函数对这些可调度节点打分，然后选出其中得分最高的 Node 来运行 Pod。之后，调度器将这个调度决定通知给 kube-apiserver，这个过程叫做 _绑定_。
|
||
|
||
<!--
|
||
Factors that need taken into account for scheduling decisions include
|
||
individual and collective resource requirements, hardware / software /
|
||
policy constraints, affinity and anti-affinity specifications, data
|
||
locality, inter-workload interference, and so on.
|
||
-->
|
||
在做调度决定时需要考虑的因素包括：单独和整体的资源请求、硬件/软件/策略限制、亲和以及反亲和要求、数据局域性、负载间的干扰等等。
|
||
|
||
<!--
|
||
## Scheduling with kube-scheduler {#kube-scheduler-implementation}
|
||
-->
|
||
## kube-scheduler 调度流程 {#kube-scheduler-implementation}
|
||
|
||
<!--
|
||
kube-scheduler selects a node for the pod in a 2-step operation:
|
||
|
||
1. Filtering
|
||
2. Scoring
|
||
-->
|
||
kube-scheduler 给一个 pod 做调度选择包含两个步骤：
|
||
|
||
1. 过滤
|
||
2. 打分
|
||
|
||
<!--
|
||
The _filtering_ step finds the set of Nodes where it's feasible to
|
||
schedule the Pod. For example, the PodFitsResources filter checks whether a
|
||
candidate Node has enough available resource to meet a Pod's specific
|
||
resource requests. After this step, the node list contains any suitable
|
||
Nodes; often, there will be more than one. If the list is empty, that
|
||
Pod isn't (yet) schedulable.
|
||
-->
|
||
过滤阶段会将所有满足 Pod 调度需求的 Node 选出来。例如，PodFitsResources 过滤函数会检查候选 Node 的可用资源能否满足 Pod 的资源请求。在过滤之后，得出一个 Node 列表，里面包含了所有可调度节点；通常情况下，这个 Node 列表包含不止一个 Node。如果这个列表是空的，代表这个 Pod 不可调度。
|
||
|
||
<!--
|
||
In the _scoring_ step, the scheduler ranks the remaining nodes to choose
|
||
the most suitable Pod placement. The scheduler assigns a score to each Node
|
||
that survived filtering, basing this score on the active scoring rules.
|
||
-->
|
||
在打分阶段，调度器会为 Pod 从所有可调度节点中选取一个最合适的 Node。根据当前启用的打分规则，调度器会给每一个可调度节点进行打分。
|
||
|
||
<!--
|
||
Finally, kube-scheduler assigns the Pod to the Node with the highest ranking.
|
||
If there is more than one node with equal scores, kube-scheduler selects
|
||
one of these at random.
|
||
-->
|
||
最后，kube-scheduler 会将 Pod 调度到得分最高的 Node 上。如果存在多个得分最高的 Node，kube-scheduler 会从中随机选取一个。
|
||
|
||
<!--
|
||
There are two supported ways to configure the filtering and scoring behavior
|
||
of the scheduler:
|
||
-->
|
||
支持以下两种方式配置调度器的过滤和打分行为：
|
||
|
||
<!--
|
||
1. [Scheduling Policies](/docs/reference/scheduling/policies) allow you to
|
||
configure _Predicates_ for filtering and _Priorities_ for scoring.
|
||
1. [Scheduling Profiles](/docs/reference/scheduling/profiles) allow you to
|
||
configure Plugins that implement different scheduling stages, including:
|
||
`QueueSort`, `Filter`, `Score`, `Bind`, `Reserve`, `Permit`, and others. You
|
||
can also configure the kube-scheduler to run different profiles.
|
||
-->
|
||
1. [调度策略](/docs/reference/scheduling/policies) 允许你配置过滤的 _谓词(Predicates)_ 和打分的 _优先级(Priorities)_ 。
|
||
2. [调度配置](/docs/reference/scheduling/profiles) 允许你配置实现不同调度阶段的插件，包括：`QueueSort`, `Filter`, `Score`, `Bind`, `Reserve`, `Permit` 等等。你也可以配置 kube-scheduler 运行不同的配置文件。
|
||
|
||
|
||
## {{% heading "whatsnext" %}}
|
||
|
||
|
||
<!--
|
||
* Read about [scheduler performance tuning](/docs/concepts/scheduling-eviction/scheduler-perf-tuning/)
|
||
* Read about [Pod topology spread constraints](/docs/concepts/workloads/pods/pod-topology-spread-constraints/)
|
||
* Read the [reference documentation](/docs/reference/command-line-tools-reference/kube-scheduler/) for kube-scheduler
|
||
* Learn about [configuring multiple schedulers](/docs/tasks/administer-cluster/configure-multiple-schedulers/)
|
||
* Learn about [topology management policies](/docs/tasks/administer-cluster/topology-manager/)
|
||
* Learn about [Pod Overhead](/docs/concepts/configuration/pod-overhead/)
|
||
-->
|
||
|
||
* 阅读关于 [调度器性能调优](/zh/docs/concepts/scheduling-eviction/scheduler-perf-tuning/)
|
||
* 阅读关于 [Pod 拓扑分布约束](/zh/docs/concepts/workloads/pods/pod-topology-spread-constraints/)
|
||
* 阅读关于 kube-scheduler 的 [参考文档](/zh/docs/reference/command-line-tools-reference/kube-scheduler/)
|
||
* 了解关于 [配置多个调度器](/zh/docs/tasks/administer-cluster/configure-multiple-schedulers/) 的方式
|
||
* 了解关于 [拓扑结构管理策略](/zh/docs/tasks/administer-cluster/topology-manager/)
|
||
* 了解关于 [Pod 额外开销](/zh/docs/concepts/configuration/pod-overhead/)
|
||
|