Service有userspace、iptables、ipvs三种工作模式，可在配置文件/etc/sysconfig/kubelet中添加配置参数KUBE_PROXY_MODE=ipvs来改变kubernetes的工作模式(后续版本版本此配置路径可能发生更改，可以用rpm -ql kubelet来查看配置文件路径)；ExternalName, ClusterIP, NodePort, and LoadBalancer五种service类型type，默认为ClusterIP；port、targetPort、nodePort三种端口选项，若使用NodePort类型，使用nodePort才生效。

实例：

apiVersion: v1

kind: Service

metadata:

name: redis

namespace: default

spec:

selector:

app: redis

role: logstor

clusterIP: 10.97.97.97

type: ClusterIP

ports:

- port: 6379

targetPort: 6379

默认clusterIP系统会自动分配，为了不造成IP冲突可以不指定，让系统自动分配；如果clusterIP设置为None，即没有service IP地址，直接调用pod的IP地址。

service配置清单spec主要包含如下选项：

[root@master1 yaml]# kubectl explain service.spec

KIND: Service

VERSION: v1

RESOURCE: spec

DESCRIPTION:

Spec defines the behavior of a service.

https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#spec-and-status

ServiceSpec describes the attributes that a user creates on a service.

FIELDS:

clusterIP

clusterIP is the IP address of the service and is usually assigned randomly

by the master. If an address is specified manually and is not in use by

others, it will be allocated to the service; otherwise, creation of the

service will fail. This field can not be changed through updates. Valid

values are "None", empty string (""), or a valid IP address. "None" can be

specified for headless services when proxying is not required. Only applies

to types ClusterIP, NodePort, and LoadBalancer. Ignored if type is

ExternalName. More info:

https://kubernetes.io/docs/concepts/services-networking/service/#virtual-ips-and-service-proxies

externalIPs

externalIPs is a list of IP addresses for which nodes in the cluster will

also accept traffic for this service. These IPs are not managed by

Kubernetes. The user is responsible for ensuring that traffic arrives at a

node with this IP. A common example is external load-balancers that are not

part of the Kubernetes system.

externalName

externalName is the external reference that kubedns or equivalent will

return as a CNAME record for this service. No proxying will be involved.

Must be a valid RFC-1123 hostname (https://tools.ietf.org/html/rfc1123) and

requires Type to be ExternalName.

externalTrafficPolicy

externalTrafficPolicy denotes if this Service desires to route external

traffic to node-local or cluster-wide endpoints. "Local" preserves the

client source IP and avoids a second hop for LoadBalancer and Nodeport type

services, but risks potentially imbalanced traffic spreading. "Cluster"

obscures the client source IP and may cause a second hop to another node,

but should have good overall load-spreading.

healthCheckNodePort

healthCheckNodePort specifies the healthcheck nodePort for the service. If

not specified, HealthCheckNodePort is created by the service api backend

with the allocated nodePort. Will use user-specified nodePort value if

specified by the client. Only effects when Type is set to LoadBalancer and

ExternalTrafficPolicy is set to Local.

ipFamily

ipFamily specifies whether this Service has a preference for a particular

IP family (e.g. IPv4 vs. IPv6). If a specific IP family is requested, the

clusterIP field will be allocated from that family, if it is available in

the cluster. If no IP family is requested, the cluster's primary IP family

will be used. Other IP fields (loadBalancerIP, loadBalancerSourceRanges,

externalIPs) and controllers which allocate external load-balancers should

use the same IP family. Endpoints for this Service will be of this family.

This field is immutable after creation. Assigning a ServiceIPFamily not

available in the cluster (e.g. IPv6 in IPv4 only cluster) is an error

condition and will fail during clusterIP assignment.

loadBalancerIP

Only applies to Service Type: LoadBalancer LoadBalancer will get created

with the IP specified in this field. This feature depends on whether the

underlying cloud-provider supports specifying the loadBalancerIP when a

load balancer is created. This field will be ignored if the cloud-provider

does not support the feature.

loadBalancerSourceRanges

If specified and supported by the platform, this will restrict traffic

through the cloud-provider load-balancer will be restricted to the

specified client IPs. This field will be ignored if the cloud-provider does

not support the feature." More info:

https://kubernetes.io/docs/tasks/access-application-cluster/configure-cloud-provider-firewall/

ports

The list of ports that are exposed by this service. More info:

https://kubernetes.io/docs/concepts/services-networking/service/#virtual-ips-and-service-proxies

publishNotReadyAddresses

publishNotReadyAddresses, when set to true, indicates that DNS

implementations must publish the notReadyAddresses of subsets for the

Endpoints associated with the Service. The default value is false. The

primary use case for setting this field is to use a StatefulSet's Headless

Service to propagate SRV records for its Pods without respect to their

readiness for purpose of peer discovery.

selector

Route service traffic to pods with label keys and values matching this

selector. If empty or not present, the service is assumed to have an

external process managing its endpoints, which Kubernetes will not modify.

Only applies to types ClusterIP, NodePort, and LoadBalancer. Ignored if

type is ExternalName. More info:

https://kubernetes.io/docs/concepts/services-networking/service/

sessionAffinity

Supports "ClientIP" and "None". Used to maintain session affinity. Enable

client IP based session affinity. Must be ClientIP or None. Defaults to

None. More info:

https://kubernetes.io/docs/concepts/services-networking/service/#virtual-ips-and-service-proxies

sessionAffinityConfig

sessionAffinityConfig contains the configurations of session affinity.

topologyKeys

topologyKeys is a preference-order list of topology keys which

implementations of services should use to preferentially sort endpoints

when accessing this Service, it can not be used at the same time as

externalTrafficPolicy=Local. Topology keys must be valid label keys and at

most 16 keys may be specified. Endpoints are chosen based on the first

topology key with available backends. If this field is specified and all

entries have no backends that match the topology of the client, the service

has no backends for that client and connections should fail. The special

value "*" may be used to mean "any topology". This catch-all value, if

used, only makes sense as the last value in the list. If this is not

specified or empty, no topology constraints will be applied.

type

type determines how the Service is exposed. Defaults to ClusterIP. Valid

options are ExternalName, ClusterIP, NodePort, and LoadBalancer.

"ExternalName" maps to the specified externalName. "ClusterIP" allocates a

cluster-internal IP address for load-balancing to endpoints. Endpoints are

determined by the selector or if that is not specified, by manual

construction of an Endpoints object. If clusterIP is "None", no virtual IP

is allocated and the endpoints are published as a set of endpoints rather

than a stable IP. "NodePort" builds on ClusterIP and allocates a port on

every node which routes to the clusterIP. "LoadBalancer" builds on NodePort

and creates an external load-balancer (if supported in the current cloud)

which routes to the clusterIP. More info:

https://kubernetes.io/docs/concepts/services-networking/service/#publishing-services-service-types

kubectl patch svc myapp -p ‘{“spec”:{“sessionAffinity”:”ClientIP”}}’: 打补丁设置sessionAffinity为ClientIP后 ，是pod资源仅运行在某个node上面