A short 15min deep dive into the handler chain of Kubernetes' API server.

1. Kubernetes API
DEEP DIVE INTO THE APISERVER
Dr. Stefan Schimanski, sttts@redhat.com

2. Restful
http API
/
/version
/api
/api/v1/pods
/api/v1/pods/status
/apis
/apis/batch
/apis/batch/v1alpha1
/apis/batch/v1alpha1/jobs
/apis/batch/v1alpha1/cronjobs
/apis/batch/v1beta1
/apis/batch/v1beta1/jobs
kube-apiserver $ kubectl create -f foo.yaml

3. Restful
http API
/
/version
/api
/api/v1/pods
/api/v1/pods/status
/apis
/apis/batch
/apis/batch/v2alpha1
/apis/batch/v2alpha1/jobs
/apis/batch/v2alpha1/cronjobs
/apis/batch/v1beta1
/apis/batch/v1beta1/jobs

4. Restful
http API
/
/version
/api
/api/v1/pods
/api/v1/pods/status
/apis
/apis/batch
/apis/batch/v2alpha1
/apis/batch/v2alpha1/jobs
/apis/batch/v2alpha1/cronjo
/apis/batch/v1beta1
/apis/batch/v1beta1/jobs

5. Restful
http API
/
/version
/api
/api/v1/pods
/api/v1/pods/status
/apis
/apis/batch
/apis/batch/v2alpha1
/apis/batch/v2alpha1/jobs
/apis/batch/v2alpha1/cronjo
/apis/batch/v1beta1
/apis/batch/v1beta1/jobs
/apis/batch/v2alpha1/jobs
Group Version ResourceHTTP paths:
In Go: gvk := schema.GroupVersionKind{Group: “batch“, Version: “v2alpha1“, Kind: “Job“}
obj := api.Schema.New(gvk)
codec := api.Codecs.LegacyCodec(gvk.GroupVersion())
codec.Decode(reqBody, gvk, obj)
type Job struct {
metav1.TypeMeta
metav1.ObjectMeta
Spec JobSpec
Status JobStatus
}
pkg/apis/batch/v2alpha1/types.go
type TypeMeta struct {
Kind string
APIVersion string
}
type ObjectMeta struct {
Name string
...
}

6. Restful
http API
/
/version
/api
/api/v1/pods
/api/v1/pods/status
/apis
/apis/batch
/apis/batch/v2alpha1
/apis/batch/v2alpha1/jobs
/apis/batch/v2alpha1/cronjo
/apis/batch/v1beta1
/apis/batch/v1beta1/jobs
MaxInFlightLimit
TimeoutForNonLongRunningRequests
Panic Recovery
CORS
Authentication
Audit
Impersonation
Authorization
k8s.io/apiserver/pkg/server.
DefaultBuildHandlerChain
„Filters“
k8s.io/apiserver/pkg/server/routes/index.go – /
k8s.io/apiserver/pkg/server/routes/version.go – /version
k8s.io/apiserver/pkg/server/routes/swagger.go – /swaggerapi
k8s.io/apiserver/pkg/server/routes/openapi.go – /swagger.json
„Routes“
mux
k8s.io/apiserver/pkg/endpoints.APIGroupVersion.InstallREST
AddSupportedResourcesWebService – /apis/batch/v2alpha1
k8s.io/apiserver/pkg/endpoints.APIInstaller.Install
/apis/batch/v2alpha1/jobs
/apis/batch/v2alpha1/cronjobs
...
WithRequestInfo
ctx.RequestInfo

7. Restful
http API
mux
k8s.io/apiserver/pkg/endpoints.APIGroupVersion.InstallREST
AddSupportedResourcesWebService – /apis/batch/v2alpha1
k8s.io/apiserver/pkg/endpoints.APIInstaller.Install
/apis/batch/v2alpha1/jobs
/apis/batch/v2alpha1/cronjobs
...
pkg/apis/batch
type Jobs struct
pkg/apis/batch/v2alpha1
type Jobs struct
api.Scheme
k8s.io/apiserver
pkg/api
api.Scheme.Convert(&internalJob, &v2alohaJob)
/apis/batch/v2alpha1/jobs
GET
PUT
POST
DELETE
...
/status
/scale
/proxy
...
subresources

8. Restful
http API
mux
pkg/apis/batch
type Jobs struct
pkg/apis/batch/v2alp
ha1
type Jobs struct
api.Sche
me api.Scheme.Convert(&job, &v1job)
POST
/apis/batch/v2alpha1/jobs
k8s.io/apiserver
pkg/endpoints/handlers.CreateNamedResource
binary
JSON
payload
Go struct
v2alpha1.Job
HTTP
Request
Go struct
internal.Job
Store
k8s.io/apiserver
pkg/registry/generic
Storage
k8s.io/apiserver
pkg/storage/etcd3
ProtoBuf
Job
Go struct
v2alpha1.Job
etcd

9. type Scheme struct
• AddKnownTypes(gv, obj Object)
• Default(src Object)
• Copy(src Object) Object
• Convert(in, out interface{})
• New(gvk) Object
ApiGroup
pkg/apis/batch
pkg/apis/batch/v1
pkg/apis/batch/v2alpha1
pkg/apis/batch/register.go
pgk/apis/batch/install
Group
Version
Kind
Resource
type Object interface
• GetObjectKind() string
client-go/pkg/api.Scheme
client-go/pkg/api.Codecs
Discovery
type APIGroupList struct
type APIVersions struct
type APIResourceList struct
GroupVersionKind „gvk“
GroupVersionResource
Unversioned types
Unstructured
List
Registry / Storage
type Storage interface
type Lister interface
type Updater interface
type Getter interface
type Deleter interface
....
deepcopy-gen
conversion-gen
defaulting-gen
Code Generation
type OwnerReference struct
type ObjectReference struct
type TypeMeta struct
type ObjectMeta struct
Meta
api.Scheme
api.Codecs
api.Registry
api.GroupFactoryRegistry
Globals