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Merge pull request #15339 from erictune/exp-api

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10
docs/admin/daemons.md
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@@ -209,9 +209,13 @@ all or certain hosts, and when it needs to start before other pods.
## Caveats
DaemonSet is part of the experimental API group, so it is not subject to the same compatibility
guarantees as objects in the main API. It may not be enabled. Enable by setting
`--runtime-config=experimental/v1alpha1` on the apiserver.
DaemonSet objects are in the [`extensions` API Group](../api.md#api-groups). This API group may or
may not be enabled on your cluster.
DaemonSet objects effectively have [API version `v1alpha1`](../api.md#api-versioning).
Alpha objects may change or even be discontinued in future software releases.
However, due to to a known issue, they may appear as API version `v1beta1` if enabled.
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docs/api.md
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@@ -55,11 +55,63 @@ What constitutes a compatible change and how to change the API are detailed by t
## API versioning
To make it easier to eliminate fields or restructure resource representations, Kubernetes supports multiple API versions, each at a different API path prefix, such as `/api/v1beta3`. These are simply different interfaces to read and/or modify the same underlying resources. In general, all API resources are accessible via all API versions, though there may be some cases in the future where that is not true.
To make it easier to eliminate fields or restructure resource representations, Kubernetes supports
multiple API versions, each at a different API path, such as `/api/v1` or
`/apis/extensions/v1beta1`.
We chose to version at the API level rather than at the resource or field level to ensure that the API presents a clear, consistent view of system resources and behavior, and to enable controlling access to end-of-lifed and/or experimental APIs.
The [API and release versioning proposal](design/versioning.md) describes the current thinking on the API version evolution process.
Note that API versioning and Software versioning are only indirectly related. The [API and release
versioning proposal](design/versioning.md) describes the relationship between API versioning and
software versioning.
Different API versions imply different levels of stability and support. The criteria for each level are described
in more detail in the [API Changes documentation](devel/api_changes.md#alpha-beta-and-stable-versions). They are summarized here:
- Alpha level:
- The version names contain `alpha` (e.g. `v1alpha1`).
- May be buggy. Enabling the feature may expose bugs. Disabled by default.
- Support for feature may be dropped at any time without notice.
- The API may change in incompatible ways in a later software release without notice.
- Recommended for use only in short-lived testing clusters, due to increased risk of bugs and lack of long-term support.
- Beta level:
- The version names contain `beta` (e.g. `v2beta3`).
- Code is well tested. Enabling the feature is considered safe. Enabled by default.
- Support for the overall feature will not be dropped, though details may change.
- The schema and/or semantics of objects may change in incompatible ways in a subsequent beta or stable release. When this happens,
we will provide instructions for migrating to the next version. This may require deleting, editing, and re-creating
API objects. The editing process may require some thought. This may require downtime for appplications that rely on the feature.
- Recommended for only non-business-critical uses because of potential for incompatible changes in subsequent releases. If you have
multiple clusters which can be upgraded independently, you may be able to relax this restriction.
- **Please do try our beta features and give feedback on them! Once they exit beta, it may not be practical for us to make more changes.**
- Stable level:
- The version name is `vX` where `X` is an integer.
- Stable versions of features will appear in released software for many subsequent versions.
## API groups
To make it easier to extend the Kubernetes API, we are in the process of implementing [*API
groups*](proposals/api-groups.md). These are simply different interfaces to read and/or modify the
same underlying resources. The API group is specified in a REST path and in the `apiVersion` field
of a serialized object.
Currently there are two API groups in use:
1. the "core" group, which is at REST path `/api/v1` and is not specified as part of the `apiVersion` field, e.g.
`apiVersion: v1`.
1. the "extensions" group, which is at REST path `/apis/extensions/$VERSION`, and which uses
`apiVersion: extensions/$VERSION` (e.g. currently `apiVersion: extensions/v1beta1`).
In the future we expect that there will be more API groups, all at REST path `/apis/$API_GROUP` and
using `apiVersion: $API_GROUP/$VERSION`. We expect that there will be a way for (third parties to
create their own API groups](design/extending-api.md), and to avoid naming collisions.
## Enabling the extensions group
Enable `extensions/v1beta1` objects by adding the following flags to your API server:
- `--runtime-config=extensions/v1beta1=true`
## v1beta1, v1beta2, and v1beta3 are deprecated; please move to v1 ASAP

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docs/devel/api_changes.md
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@@ -535,6 +535,69 @@ The API spec changes should be in a commit separate from your other changes.
TODO(smarterclayton): write this.
## Alpha, Beta, and Stable Versions
New feature development proceeds through a series of stages of increasing maturity:
- Development level
- Object Versioning: no convention
- Availability: not commited to main kubernetes repo, and thus not available in offical releases
- Audience: other developers closely collaborating on a feature or proof-of-concept
- Upgradeability, Reliability, Completeness, and Support: no requirements or guarantees
- Alpha level
- Object Versioning: API version name contains `alpha` (e.g. `v1alpha1`)
- Availability: committed to main kubernetes repo; appears in an official release; feature is
disabled by default, but may be enabled by flag
- Audience: developers and expert users interested in giving early feedback on features
- Completeness: some API operations, CLI commands, or UI support may not be implemented; the API
need not have had an *API review* (an intensive and targeted review of the API, on top of a normal
code review)
- Upgradeability: the object schema and semantics may change in a later software release, without
any provision for preserving objects in an existing cluster;
removing the upgradability concern allows developers to make rapid progress; in particular,
API versions can increment faster than the minor release cadence and the developer need not
maintain multiple versions; developers should still increment the API version when object schema
or semantics change in an [incompatible way](#on-compatibility)
- Cluster Reliability: because the feature is relatively new, and may lack complete end-to-end
tests, enabling the feature via a flag might expose bugs with destabilize the cluster (e.g. a
bug in a control loop might rapidly create excessive numbers of object, exhausting API storage).
- Support: there is *no commitment* from the project to complete the feature; the feature may be
dropped entirely in a later software release
- Recommended Use Cases: only in short-lived testing clusters, due to complexity of upgradeability
and lack of long-term support and lack of upgradability.
- Beta level:
- Object Versioning: API version name contains `beta` (e.g. `v2beta3`)
- Availability: in official Kubernetes releases, and enabled by default
- Audience: users interested in providing feedback on features
- Completeness: all API operations, CLI commands, and UI support should be implemented; end-to-end
tests complete; the API has had a thorough API review and is thought to be complete, though use
during beta may frequently turn up API issues not thought of during review
- Upgradeability: the object schema and semantics may change in a later software release; when
this happens, an upgrade path will be documentedr; in some cases, objects will be automatically
converted to the new version; in other cases, a manual upgrade may be necessary; a manual
upgrade may require downtime for anything relying on the new feature, and may require
manual conversion of objects to the new version; when manual conversion is necessary, the
project will provide documentation on the process (for an example, see [v1 conversion
tips](../api.md))
- Cluster Reliability: since the feature has e2e tests, enabling the feature via a flag should not
create new bugs in unrelated features; because the feature is new, it may have minor bugs
- Support: the project commits to complete the feature, in some form, in a subsequent Stable
version; typically this will happen within 3 months, but sometimes longer; releases should
simultaneously support two consecutive versions (e.g. `v1beta1` and `v1beta2`; or `v1beta2` and
`v1`) for at least one minor release cycle (typically 3 months) so that users have enough time
to upgrade and migrate objects
- Recommended Use Cases: in short-lived testing clusters; in production clusters as part of a
short-lived evaluation of the feature in order to provide feedback
- Stable level:
- Object Versioning: API version `vX` where `X` is an integer (e.g. `v1`)
- Availability: in official Kubernetes releases, and enabled by default
- Audience: all users
- Completeness: same as beta
- Upgradeability: only [strictly compatible](#on-compatibility) changes allowed in subsequent
software releases
- Cluster Reliability: high
- Support: API version will continue to be present for many subsequent software releases;
- Recommended Use Cases: any
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docs/user-guide/jobs.md
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@@ -241,9 +241,12 @@ value is `Always`.)
## Caveats
Job is part of the experimental API group, so it is not subject to the same compatibility
guarantees as objects in the main API. It may not be enabled. Enable by setting
`--runtime-config=experimental/v1alpha1` on the apiserver.
Job objects are in the [`extensions` API Group](../api.md#api-groups). This API group may or
may not be enabled on your cluster.
Job objects have [API version `v1beta1`](../api.md#api-versioning). Beta objects may
undergo changes to their schema and/or semantics in future software releases, but
similar functionality will be supported.
## Future work