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+---
+title: Kubernetes 调度器
+content_template: templates/concept
+weight: 60
+---
+
+<!--
+---
+title: Kubernetes Scheduler
+content_template: templates/concept
+weight: 60
+---
+-->
+{{% capture 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。
+
+{{% /capture %}}
+
+{{% capture 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](https://kubernetes.io/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。
+
+<!--
+### Default policies
+-->
+### 默认策略
+
+<!--
+kube-scheduler has a default set of scheduling policies.
+-->
+kube-scheduler 有一系列的默认调度策略。
+
+<!--
+### Filtering
+
+- `PodFitsHostPorts`: Checks if a Node has free ports (the network protocol kind)
+  for the Pod ports the the Pod is requesting.
+
+- `PodFitsHost`: Checks if a Pod specifies a specific Node by it hostname.
+
+- `PodFitsResources`: Checks if the Node has free resources (eg, CPU and Memory)
+  to meet the requirement of the Pod.
+
+- `PodMatchNodeSelector`: Checks if a Pod's Node {{< glossary_tooltip term_id="selector" >}}
+   matches the Node's {{< glossary_tooltip text="label(s)" term_id="label" >}}.
+
+- `NoVolumeZoneConflict`: Evaluate if the {{< glossary_tooltip text="Volumes" term_id="volume" >}}
+  that a Pod requests are available on the Node, given the failure zone restrictions for
+  that storage.
+
+- `NoDiskConflict`: Evaluates if a Pod can fit on a Node due to the volumes it requests,
+   and those that are already mounted.
+
+- `MaxCSIVolumeCount`: Decides how many {{< glossary_tooltip text="CSI" term_id="csi" >}}
+  volumes should be attached, and whether that's over a configured limit.
+
+- `CheckNodeMemoryPressure`: If a Node is reporting memory pressure, and there's no
+  configured exception, the Pod won't be scheduled there.
+
+- `CheckNodePIDPressure`: If a Node is reporting that process IDs are scarce, and
+  there's no configured exception, the Pod won't be scheduled there.
+
+- `CheckNodeDiskPressure`: If a Node is reporting storage pressure (a filesystem that
+   is full or nearly full), and there's no configured exception, the Pod won't be
+   scheduled there.
+
+- `CheckNodeCondition`: Nodes can report that they have a completely full filesystem,
+  that networking isn't available or that kubelet is otherwise not ready to run Pods.
+  If such a condition is set for a Node, and there's no configured exception, the Pod
+  won't be scheduled there.
+
+- `PodToleratesNodeTaints`: checks if a Pod's {{< glossary_tooltip text="tolerations" term_id="toleration" >}}
+  can tolerate the Node's {{< glossary_tooltip text="taints" term_id="taint" >}}.
+
+- `CheckVolumeBinding`: Evaluates if a Pod can fit due to the volumes it requests.
+  This applies for both bound and unbound
+  {{< glossary_tooltip text="PVCs" term_id="persistent-volume-claim" >}}
+-->
+### 过滤策略
+
+- `PodFitsHostPorts`：如果 Pod 中定义了 hostPort 属性，那么需要先检查这个指定端口是否
+  已经被 Node 上其他服务占用了。
+
+- `PodFitsHost`：若 pod 对象拥有 hostname 属性，则检查 Node 名称字符串与此属性是否匹配。
+
+- `PodFitsResources`：检查 Node 上是否有足够的资源（如，cpu 和内存）来满足 pod 的资源请求。
+
+- `PodMatchNodeSelector`：检查 Node 的 {{< glossary_tooltip text="label(s)" term_id="label" >}} 是否能匹配
+  Pod 属性上 Node 的 {{< glossary_tooltip text="label(s)" term_id="label" >}} 值。
+
+- `NoVolumeZoneConflict`：检测 pod 请求的 {{< glossary_tooltip text="Volumes" term_id="volume" >}} 在
+  Node 上是否可用，因为某些存储卷存在区域调度约束。
+
+- `NoDiskConflict`：检查 Pod 对象请求的存储卷在 Node 上是否可用，若不存在冲突则通过检查。
+
+- `MaxCSIVolumeCount`：检查 Node 上已经挂载的 {{< glossary_tooltip text="CSI" term_id="csi" >}}
+  存储卷数量是否超过了指定的最大值。
+
+- `CheckNodeMemoryPressure`：如果 Node 上报了内存资源压力过大，而且没有配置异常，那么 Pod 将不会被调度到这个 Node 上。
+
+- `CheckNodePIDPressure`：如果 Node 上报了 PID 资源压力过大，而且没有配置异常，那么 Pod 将不会被调度到这个 Node 上。
+
+- `CheckNodeDiskPressure`：如果 Node 上报了磁盘资源压力过大（文件系统满了或者将近满了），
+  而且配置异常，那么 Pod 将不会被调度到这个 Node 上。
+
+- `CheckNodeCondition`：Node 可以上报其自身的状态，如磁盘、网络不可用，表明 kubelet 未准备好运行 pod。
+  如果 Node 被设置成这种状态，那么 pod 将不会被调度到这个 Node 上。
+
+- `PodToleratesNodeTaints`：检查 pod 属性上的 {{< glossary_tooltip text="tolerations" term_id="toleration" >}} 能否容忍
+  Node 的 {{< glossary_tooltip text="taints" term_id="taint" >}}。
+
+- `CheckVolumeBinding`：检查 Node 上已经绑定的和未绑定的 {{< glossary_tooltip text="PVCs" term_id="persistent-volume-claim" >}}
+  能否满足 Pod 对象的存储卷需求。
+
+<!--
+### Scoring
+
+- `SelectorSpreadPriority`: Spreads Pods across hosts, considering Pods that
+   belonging to the same {{< glossary_tooltip text="Service" term_id="service" >}},
+   {{< glossary_tooltip term_id="statefulset" >}} or
+   {{< glossary_tooltip term_id="replica-set" >}}.
+
+- `InterPodAffinityPriority`: Computes a sum by iterating through the elements
+  of weightedPodAffinityTerm and adding “weight” to the sum if the corresponding
+  PodAffinityTerm is satisfied for that node; the node(s) with the highest sum
+  are the most preferred.
+
+- `LeastRequestedPriority`: Favors nodes with fewer requested resources. In other
+  words, the more Pods that are placed on a Node, and the more resources those
+  Pods use, the lower the ranking this policy will give.
+
+- `MostRequestedPriority`: Favors nodes with most requested resources. This policy
+  will fit the scheduled Pods onto the smallest number of Nodes needed to run your
+  overall set of workloads.
+
+- `RequestedToCapacityRatioPriority`: Creates a requestedToCapacity based ResourceAllocationPriority using default resource scoring function shape.
+
+- `BalancedResourceAllocation`: Favors nodes with balanced resource usage.
+
+- `NodePreferAvoidPodsPriority`: Priorities nodes according to the node annotation
+  `scheduler.alpha.kubernetes.io/preferAvoidPods`. You can use this to hint that
+  two different Pods shouldn't run on the same Node.
+
+- `NodeAffinityPriority`: Prioritizes nodes according to node affinity scheduling
+   preferences indicated in PreferredDuringSchedulingIgnoredDuringExecution.
+   You can read more about this in [Assigning Pods to Nodes](https://kubernetes.io/docs/concepts/configuration/assign-pod-node/)
+
+- `TaintTolerationPriority`: Prepares the priority list for all the nodes, based on
+  the number of intolerable taints on the node. This policy adjusts a node's rank
+  taking that list into account.
+
+- `ImageLocalityPriority`: Favors nodes that already have the
+  {{< glossary_tooltip text="container images" term_id="image" >}} for that
+  Pod cached locally.
+
+- `ServiceSpreadingPriority`: For a given Service, this policy aims to make sure that
+  the Pods for the Service run on different nodes. It favouring scheduling onto nodes
+  that don't have Pods for the service already assigned there. The overall outcome is
+  that the Service becomes more resilient to a single Node failure.
+
+- `CalculateAntiAffinityPriorityMap`: This policy helps implement
+  [pod anti-affinity](https://kubernetes.io/docs/concepts/configuration/assign-pod-node/#affinity-and-anti-affinity).
+
+- `EqualPriorityMap`: Gives an equal weight of one to all nodes.
+-->
+### 打分策略
+
+- `SelectorSpreadPriority`：尽量将归属于同一个 {{< glossary_tooltip text="Service" term_id="service" >}}、{{< glossary_tooltip term_id="statefulset" >}} 或 {{< glossary_tooltip term_id="replica-set" >}} 的 Pod 资源分散到不同的 Node 上。
+
+- `InterPodAffinityPriority`：遍历 Pod 对象的亲和性条目，并将那些能够匹配到给定 Node 的条目的权重相加，结果值越大的 Node 得分越高。
+
+- `LeastRequestedPriority`：空闲资源比例越高的 Node 得分越高。换句话说，Node 上的 Pod 越多，并且资源被占用的越多，那么这个 Node 的得分就会越少。
+
+- `MostRequestedPriority`：空闲资源比例越低的 Node 得分越高。这个调度策略将会把你所有的工作负载（Pod）调度到尽量少的 Node 上。
+
+- `RequestedToCapacityRatioPriority`：为 Node 上每个资源占用比例设定得分值，给资源打分函数在打分时使用。
+
+- `BalancedResourceAllocation`：Node 上与调度有关的多种资源的占用比例越接近，得分越高。
+
+- `NodePreferAvoidPodsPriority`：这个策略将根据 Node 的注解信息中是否含有 `scheduler.alpha.kubernetes.io/preferAvoidPods` 来
+  计算其优先级。使用这个策略可以将两个不同 Pod 运行在不同的 Node 上。
+
+- `NodeAffinityPriority`：基于 Pod 属性中 PreferredDuringSchedulingIgnoredDuringExecution 来进行 Node 亲和性调度。你可以通过这篇文章
+  [Assigning Pods to Nodes](https://kubernetes.io/docs/concepts/configuration/assign-pod-node/) 来了解到更详细的内容。
+
+- `TaintTolerationPriority`：基于 Pod 中对每个 Node 上污点容忍程度进行优先级评估，这个策略能够调整待选 Node 的排名。
+
+- `ImageLocalityPriority`：Node 上已经拥有 Pod 需要的 {{< glossary_tooltip text="容器镜像" term_id="image" >}} 的 Node 会有较高的优先级。
+
+- `ServiceSpreadingPriority`：这个调度策略的主要目的是确保将归属于同一个 Service 的 Pod 调度到不同的 Node 上。如果 Node 上
+  没有归属于同一个 Service 的 Pod，这个策略更倾向于将 Pod 调度到这类 Node 上。最终的目的：即使在一个 Node 宕机之后 Service 也具有很强容灾能力。
+
+- `CalculateAntiAffinityPriorityMap`：这个策略主要是用来实现[pod反亲和]
+  (https://kubernetes.io/docs/concepts/configuration/assign-pod-node/#affinity-and-anti-affinity)。
+
+- `EqualPriorityMap`：将所有的 Node 设置成相同的权重为 1。
+
+{{% /capture %}}
+{{% capture whatsnext %}}
+* 阅读关于 [调度器性能调优](/docs/concepts/scheduling/scheduler-perf-tuning/)
+* 阅读关于 [Pod topology spread constraints](/docs/concepts/workloads/pods/pod-topology-spread-constraints/)
+* 阅读关于 kube-scheduler 的 [参考文档](/docs/reference/command-line-tools-reference/kube-scheduler/)
+* 了解关于 [配置多个调度器](/docs/tasks/administer-cluster/configure-multiple-schedulers/) 的方式
+* 了解关于 [topology management policies](/docs/tasks/administer-cluster/topology-manager/)
+* 了解关于 [Pod Overhead](/docs/concepts/configuration/pod-overhead/)
+{{% /capture %}}