Pod 亲和性（podAffinity）主要解决 Pod 可以和哪些 Pod 部署在同一个拓扑域中的问题（其中拓扑域用主机标签实现，可以是单个主机，也可以是多个主机组成的 cluster、zone 等等），而 Pod 反亲和性主要是解决 Pod 不能和哪些 Pod 部署在同一个拓扑域中的问题，它们都是处理的 Pod 与 Pod 之间的关。
[root@k8s-01 ~]# kubectl explain deploy.spec.template.spec.affinity.podAffinity.requiredDuringSchedulingIgnoredDuringExecution
KIND: Deployment
VERSION: apps/v1
RESOURCE: requiredDuringSchedulingIgnoredDuringExecution <[]Object>
DESCRIPTION:
If the affinity requirements specified by this field are not met at
scheduling time, the pod will not be scheduled onto the node. If the
affinity requirements specified by this field cease to be met at some point
during pod execution (e.g. due to a pod label update), the system may or
may not try to eventually evict the pod from its node. When there are
multiple elements, the lists of nodes corresponding to each podAffinityTerm
are intersected, i.e. all terms must be satisfied.
Defines a set of pods (namely those matching the labelSelector relative to
the given namespace(s)) that this pod should be co-located (affinity) or
not co-located (anti-affinity) with, where co-located is defined as running
on a node whose value of the label with key <topologyKey> matches that of
any node on which a pod of the set of pods is running
FIELDS:
labelSelector <Object>
A label query over a set of resources, in this case pods.
namespaceSelector <Object>
A label query over the set of namespaces that the term applies to. The term
is applied to the union of the namespaces selected by this field and the
ones listed in the namespaces field. null selector and null or empty
namespaces list means "this pod's namespace". An empty selector ({})
matches all namespaces. This field is beta-level and is only honored when
PodAffinityNamespaceSelector feature is enabled.
namespaces <[]string>
namespaces specifies a static list of namespace names that the term applies
to. The term is applied to the union of the namespaces listed in this field
and the ones selected by namespaceSelector. null or empty namespaces list
and null namespaceSelector means "this pod's namespace"
topologyKey <string> -required-
This pod should be co-located (affinity) or not co-located (anti-affinity)
with the pods matching the labelSelector in the specified namespaces, where
co-located is defined as running on a node whose value of the label with
key topologyKey matches that of any node on which any of the selected pods
is running. Empty topologyKey is not allowed.
[root@k8s-01 ~]#
