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versioning of CRI API

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Sergey Kanzhelev 2022-12-09 22:00:47 +00:00
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@ -9,6 +9,189 @@ The repository [kubernetes/cri-api](https://github.com/kubernetes/cri-api) is a
Please do NOT file issues or submit PRs against the [kubernetes/cri-api](https://github.com/kubernetes/cri-api)
repository as it is readonly, all development is done in [kubernetes/kubernetes](https://github.com/kubernetes/kubernetes).
CRI API is defined in [kubernetes/kubernetes](https://github.com/kubernetes/kubernetes)
repository and is ONLY intended to be used for kubelet to container runtime interactions.
It is NOT a common purpose container runtime API for general use and intended
to be Kubernetes-centric. We try to avoid it, but there may be logic in container
runtime optimized for the order or specific parameters of call kubelet makes.
## Version skew policy
On a single Node there may be installed multiple components implementing
different versions of CRI API.
For example, on a single node there might be:
- _Kubelet_ may call into _Container Runtime_ (e.g. [containerd](https://containerd.io))
and _Image Service Proxy_ (e.g. [stargz-snapshotter](https://github.com/containerd/stargz-snapshotter)).
_Container Runtime_ may be versioned with the OS Image, _Kubelet_ is installed
by system administrator and _Image Service proxy_ is versioned by the third party vendor.
- _Image Service Proxy_ calls into _Container Runtime_.
- _CRI tools_ (e.g. [crictl](https://kubernetes.io/docs/tasks/debug/debug-cluster/crictl/))
may be installed by end user to troubleshoot, same as a third party daemonsets.
All of them are used to call into the _Container Runtime_ to collect container information.
So on a single node it may happen that _Container Runtime_ is serving a newer
version'd kubelet and older versioned crictl. This is a supported scenario within
the version skew policy.
### Version Skew Policy for CRI API
CRI API has two versions:
- Major semantic version (known versions are `v1alpha2` ([removed in 1.26](https://kubernetes.io/blog/2022/12/09/kubernetes-v1-26-release/#cri-v1alpha2-removed)), `v1`).
- Kubernetes version (`@1.23`). Note, the library cri-api is versioned as `0.23` as it doesn't guarantee Go types backward compatibility.
Major semantic version (e.g. `v1`) is used to introduce breaking changes
and major new features that are incompatible with the current API.
Kubernetes version is used to indicate a specific feature set implemented
on top of the major semantic version. All changes made without the change
of a major semantic version API must be backward and forward compatible.
- _Kubelet_ must work with the older _Container Runtime_ if it implements
the same semantic version of CRI API (e.g. `v1`) of up to three Kubernetes minor
versions back. New features implemented in CRI API must be gracefully degraded.
For example, _Kubelet_ of version 1.26 must work with _Container Runtime_
implementing `k8s.io/cri-api@v0.23.0`+.
- _Kubelet_ must work with _Container Runtime_ if it implements
the same semantic version of CRI API (e.g. `v1`) of up to
three minor versions up. New features implemented in CRI API must not change
behavior of old method calls and response values. For example, _Kubelet_ of
version 1.22 must work with _Container Runtime_ implementing `k8s.io/cri-api@v0.25.5`.
## Versioning
This library contains go classes generated from the CRI API protocol buffers and gRPC API.
The library versioned as `0.XX` as Kubernetes doesn't provide any guarantees
on backward compatibility of Go wrappers between versions. However CRI API itself
(protocol buffers and gRPC API) is marked as stable `v1` version and it is
backward compatible between versions.
Versions like `v0.<minor>.<patch>` (e.g. `v0.25.5`) are considered stable.
It is discouraged to introduce CRI API changes in patch releases and recommended
to use versions like `v0.<minor>.0`.
All alpha and beta versions (e.g. `k8s.io/cri-api@v0.26.0-beta.0`) should be
backward and forward compatible.
## Feature development
Some features development requires changes in CRI API and corresponding changes
in _Container Runtime_. Coordinating between Kubernetes branches and release
versions and _Container Runtime_ versions is not always trivial.
The recommended feature development flow is following:
- Review proposed CRI API changes during the KEP review stage.
Some field names and types may not be spelled out exactly at this stage.
- Locally implement a prototype that implement changes in both - Kubernetes and Container Runtime.
- Submit a Pull Request for Kubernetes implementing CRI API changes alongside the feature code.
Feature must be developed to degrade gracefully when used with older Container Runtime
according to the Version Skew policy.
- Once PR is merged, wait for the next Kubernetes release tag being produced.
Find the corresponding CRI API tag (e.g. `k8s.io/cri-api@v0.26.0-beta.0`).
- This tag can be used to implement the feature in Container Runtime. It is recommended
to switch to the stable tag like (`k8s.io/cri-api@v0.26.0`) once available.
## Change history
Here is the change history of CRI API.
### v1.20
`git diff v1.19.0 v1.20.0 -- staging/src/k8s.io/cri-api/pkg/apis/runtime/v1/api.proto`
- CRI [v1 introduced](https://github.com/kubernetes/kubernetes/pull/96387)
### v1.21
`git diff v1.20.0 v1.21.0 -- staging/src/k8s.io/cri-api/pkg/apis/runtime/v1/api.proto`
No changes
### v1.22
`git diff v1.21.0 v1.22.0 -- staging/src/k8s.io/cri-api/pkg/apis/runtime/v1/api.proto`
- [Windows host process support](https://github.com/kubernetes/kubernetes/pull/99576)
- `PodSandboxConfig` has `windows` field of type `WindowsPodSandboxConfig`
- New type `WindowsPodSandboxConfig` introduced
- New type `WindowsSandboxSecurityContext` introduced
- The type `WindowsContainerSecurityContext` has a new `host_process` boolean field
- [Feature: add unified on CRI to support cgroup v2](https://github.com/kubernetes/kubernetes/pull/102578)
- The type `LinuxContainerResources` has a new field `unified` which is a map of strings
- [Alpha node swap support](https://github.com/kubernetes/kubernetes/pull/102823)
- The type `LinuxContainerResources` has a new `memory_swap_limit_in_bytes` int64 field
### v1.23
`git diff v1.22.0 v1.23.0 -- staging/src/k8s.io/cri-api/pkg/apis/runtime/v1/api.proto`
- [CRI: add fields for pod level stats to satisfy the /stats/summary API](https://github.com/kubernetes/kubernetes/pull/102789)
- New functions `PodSandboxStats`, `ListPodSandboxStats` with the corresponding types of request and response objects are introduced
- [pass sandbox resource requirements over CRI](https://github.com/kubernetes/kubernetes/pull/104886)
- New fields on `LinuxPodSandboxConfig`: `overhead` and `resources` of type `LinuxContainerResources`.
- [prevents garbage collection from removing pinned images](https://github.com/kubernetes/kubernetes/pull/103299)
- The type `Image` has a new boolean field `pinned`
### v1.24
`git diff v1.23.0 v1.24.0 -- staging/src/k8s.io/cri-api/pkg/apis/runtime/v1/api.proto`
- [Update CRI-API Capabilities to include a field that allows us to set ambient capabilities](https://github.com/kubernetes/kubernetes/pull/104620)
- The type `Capability` has a new string field `add_ambient_capabilities`
- [CRI-API - Add rootfs size to WindowsContainerResources](https://github.com/kubernetes/kubernetes/pull/108894)
- The type `WindowsContainerResources` has a new int64 field `rootfs_size_in_bytes`
### v1.25
`git diff v1.24.0 v1.25.0 -- staging/src/k8s.io/cri-api/pkg/apis/runtime/v1/api.proto`
- [kubelet: add CRI definitions for user namespaces](https://github.com/kubernetes/kubernetes/pull/110535)
- The new type `UserNamespace` introduced to represent user namespaces id mapping
- The type `NamespaceOption` has a new field `userns_options` of type `UserNamespace`
- [Minimal checkpointing support](https://github.com/kubernetes/kubernetes/pull/104907)
- The new method `CheckpointContainer` introduced with the corresponding request and response types
- [Update CRI API to support Evented PLEG](https://github.com/kubernetes/kubernetes/pull/111642)
- The new streaming method `GetContainerEvents` is introduced with the corresponding request and response types
- [CRI changes to support in-place pod resize](https://github.com/kubernetes/kubernetes/pull/111645)
- The new type `ContainerResources` is introduced
- The type `ContainerStatus` has a new field `resources` of type `ContainerResources`
- The semantic of `UpdateContainerResources` updated. The method must be implemented as synchronous and return error on failure
### v1.26
`git diff v1.25.0 v1.26.0 -- staging/src/k8s.io/cri-api/pkg/apis/runtime/v1/api.proto`
- [CRI: Add Windows Podsandbox Stats](https://github.com/kubernetes/kubernetes/pull/110754)
- Added fields to the type `WindowsPodSandboxStats` expressing stats required to be collected from windows pods.
- [Windows hostnetwork alpha](https://github.com/kubernetes/kubernetes/pull/112961)
- New type `WindowsNamespaceOption` introduced
- The type `WindowsSandboxSecurityContext` has a new field `namespace_options` of type `WindowsNamespaceOption`
- [Improve the API description of `PodSecurityContext.SupplementalGroups` to clarify its unfamiliar behavior](https://github.com/kubernetes/kubernetes/pull/113047)
- Clarified the expected behavior of `SupplementalGroups` field of `PodSecurityContext`
- [Add Support for Evented PLEG](https://github.com/kubernetes/kubernetes/pull/111384)
- The type `ContainerEventResponse` updated: the field `pod_sandbox_metadata` removed and fields `pod_sandbox_status` and `containers_statuses` added.
- The type `PodSandboxStatusResponse` has a new fields `containers_statuses` and `timestamp`
## Community, discussion, contribution, and support
Learn how to engage with the Kubernetes community on the [community