You are viewing documentation for Kubernetes version: v1.21
Kubernetes v1.21 documentation is no longer actively maintained. The version you are currently viewing is a static snapshot. For up-to-date documentation, see the latest version.
Service Internal Traffic Policy
Kubernetes v1.21 [alpha]
Service Internal Traffic Policy enables internal traffic restrictions to only route internal traffic to endpoints within the node the traffic originated from. The "internal" traffic here refers to traffic originated from Pods in the current cluster. This can help to reduce costs and improve performance.
Using Service Internal Traffic Policy
Once you have enabled the ServiceInternalTrafficPolicy
feature gate,
you can enable an internal-only traffic policy for a
Services, by setting its
.spec.internalTrafficPolicy
to Local
.
This tells kube-proxy to only use node local endpoints for cluster internal traffic.
Note: For pods on nodes with no endpoints for a given Service, the Service behaves as if it has zero endpoints (for Pods on this node) even if the service does have endpoints on other nodes.
The following example shows what a Service looks like when you set
.spec.internalTrafficPolicy
to Local
:
apiVersion: v1
kind: Service
metadata:
name: my-service
spec:
selector:
app: MyApp
ports:
- protocol: TCP
port: 80
targetPort: 9376
internalTrafficPolicy: Local
How it works
The kube-proxy filters the endpoints it routes to based on the
spec.internalTrafficPolicy
setting. When it's set to Local
, only node local
endpoints are considered. When it's Cluster
or missing, all endpoints are
considered.
When the feature gate
ServiceInternalTrafficPolicy
is enabled, spec.internalTrafficPolicy
defaults to "Cluster".
Constraints
- Service Internal Traffic Policy is not used when
externalTrafficPolicy
is set toLocal
on a Service. It is possible to use both features in the same cluster on different Services, just not on the same Service.
What's next
- Read about enabling Topology Aware Hints
- Read about Service External Traffic Policy
- Read Connecting Applications with Services