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Merge pull request #25229 from andrewsykim/epslice-terminating-docs 

add docs for EndpointSlice conditions
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Kubernetes Prow Robot 2020-12-02 07:10:50 -08:00 committed by GitHub
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content/en/docs/concepts/services-networking/endpoint-slices.md
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@ -93,6 +93,46 @@ EndpointSlices support three address types:
* IPv6
* FQDN (Fully Qualified Domain Name)
### Conditions
The EndpointSlice API stores conditions about endpoints that may be useful for consumers.
The three conditions are `ready`, `serving`, and `terminating`.
#### Ready
`ready` is a condition that maps to a Pod's `Ready` condition. A running Pod with the `Ready`
condition set to `True` should have this EndpointSlice condition also set to `true`. For
compatibility reasons, `ready` is NEVER `true` when a Pod is terminating. Consumers should refer
to the `serving` condition to inspect the readiness of terminating Pods. The only exception to
this rule is for Services with `spec.publishNotReadyAddresses` set to `true`. Endpoints for these
Services will always have the `ready` condition set to `true`.
#### Serving
{{< feature-state for_k8s_version="v1.20" state="alpha" >}}
`serving` is identical to the `ready` condition, except it does not account for terminating states.
Consumers of the EndpointSlice API should check this condition if they care about pod readiness while
the pod is also terminating.
{{< note >}}
Although `serving` is almost identical to `ready`, it was added to prevent break the existing meaning
of `ready`. It may be unexpected for existing clients if `ready` could be `true` for terminating
endpoints, since historically terminating endpoints were never included in the Endpoints or
EndpointSlice API to begin with. For this reason, `ready` is _always_ `false` for terminating
endpoints, and a new condition `serving` was added in v1.20 so that clients can track readiness
for terminating pods independent of the existing semantics for `ready`.
{{< /note >}}
#### Terminating
{{< feature-state for_k8s_version="v1.20" state="alpha" >}}
`Terminating` is a condition that indicates whether an endpoint is terminating.
For pods, this is any pod that has a deletion timestamp set.
### Topology information {#topology}
{{< feature-state for_k8s_version="v1.20" state="deprecated" >}}