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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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@ -44,7 +44,7 @@ for any Kubernetes Service that has a {{< glossary_tooltip text="selector"
term_id="selector" >}} specified. These EndpointSlices include
references to all the Pods that match the Service selector. EndpointSlices group
network endpoints together by unique combinations of protocol, port number, and
Service name.
Service name.
The name of a EndpointSlice object must be a valid
[DNS subdomain name](/docs/concepts/overview/working-with-objects/names#dns-subdomain-names).
@ -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" >}}