148422597X Kubernetes Management Design Patterns [Vohra 2017-01-29] {E559F6BB}

Chapter 9 ■ Scheduling Pods on Nodes
Overview
Kubernetes Scheduler is a Kubernetes component or process that runs alongside the other components
such as API Server. The purpose of the Scheduler is to monitor the API for pods that need to be scheduled,
find a suitable node to schedule a pod, and schedule the pod, one pod at a time. This chapter looks at the
following topics.
Defining a scheduling policy
Setting the environment
Using the default scheduler
Scheduling pods without a node selector
Setting node labels
Scheduling pods with node selector
Setting node affinity
Setting requiredDuringSchedulingIgnoredDuringExecution
Setting preferredDuringSchedulingIgnoredDuringExecution
Defining a Scheduling Policy
Scheduling is determined by a scheduling policy, involving predicates and priority functions. Scheduling
involves the following process, starting with all nodes being viable to schedule a pod:
1. Filter out nodes using filtering policy predicates. The objective of filtering out
nodes is to exclude those nodes that do not meet certain requirements of a pod.
2. Nodes are ranked using priority functions.
3. The pod is scheduled onto the node with the highest priority. If multiple nodes
have equal priority, one of the nodes is chosen at random.
Some of the salient predicates that implement filtering policy are discussed in Table 9-1.
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