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Lightweight library for implementing APIServer extensions
The other API extension libraries were too opinionated, or not flexible enough to provide exactly what we need -- register a single verb in the API, not have storage, give full control over the http lifecycle. This provides just enough functionality for what we need, while also providing extension points in case we need to expand the API surface area in the future - such as a more explict OpenAPI spec. This is the foundational work that is required for converting GameServerAllocations into an API Extension - next step will be to use this library to implement that functionality.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,219 @@ | ||
| // Copyright 2019 Google Inc. All Rights Reserved. | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
|
|
||
| // Package apiserver manages kubernetes api extension apis | ||
| package apiserver | ||
|
|
||
| import ( | ||
| "encoding/json" | ||
| "fmt" | ||
| "net/http" | ||
| "strings" | ||
|
|
||
| "agones.dev/agones/pkg/util/https" | ||
| "agones.dev/agones/pkg/util/runtime" | ||
| "github.com/go-openapi/spec" | ||
| "github.com/munnerz/goautoneg" | ||
| "github.com/pkg/errors" | ||
| "github.com/sirupsen/logrus" | ||
| metav1 "k8s.io/apimachinery/pkg/apis/meta/v1" | ||
| k8sruntime "k8s.io/apimachinery/pkg/runtime" | ||
| "k8s.io/apimachinery/pkg/runtime/schema" | ||
| "k8s.io/apimachinery/pkg/runtime/serializer" | ||
| ) | ||
|
|
||
| var ( | ||
| // Reference: | ||
| // https://github.com/GoogleCloudPlatform/agones/blob/master/vendor/k8s.io/apiextensions-apiserver/pkg/apiserver/apiserver.go | ||
| // These are public as they may be needed by CRDHandler implementations (usually for returning Status values) | ||
|
|
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| // Scheme scheme for unversioned types - such as APIResourceList, and Status | ||
| Scheme = k8sruntime.NewScheme() | ||
| // Codecs for unversioned types - such as APIResourceList, and Status | ||
| Codecs = serializer.NewCodecFactory(Scheme) | ||
|
|
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| unversionedVersion = schema.GroupVersion{Version: "v1"} | ||
| unversionedTypes = []k8sruntime.Object{ | ||
| &metav1.Status{}, | ||
| &metav1.APIResourceList{}, | ||
| } | ||
| ) | ||
|
|
||
| const ( | ||
| // ContentTypeHeader = "Content-Type" | ||
| ContentTypeHeader = "Content-Type" | ||
| // AcceptHeader = "Accept" | ||
| AcceptHeader = "Accept" | ||
| ) | ||
|
|
||
| func init() { | ||
| Scheme.AddUnversionedTypes(unversionedVersion, unversionedTypes...) | ||
| } | ||
|
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| // CRDHandler is a http handler, that gets passed the Namespace it's working | ||
| // on, and returns an error if a server error occurs | ||
| type CRDHandler func(http.ResponseWriter, *http.Request, string) error | ||
|
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| // APIServer is a lightweight library for registering, and providing handlers | ||
| // for Kubernetes APIServer extensions. | ||
| type APIServer struct { | ||
| logger *logrus.Entry | ||
| mux *http.ServeMux | ||
| resourceList map[string]*metav1.APIResourceList | ||
| swagger *spec.Swagger | ||
| delegates map[string]CRDHandler | ||
| } | ||
|
|
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| // NewAPIServer returns a new API Server from the given Mux. | ||
| // creates a empty Swagger definition and sets up the endpoint. | ||
| func NewAPIServer(mux *http.ServeMux) *APIServer { | ||
| s := &APIServer{ | ||
| mux: mux, | ||
| resourceList: map[string]*metav1.APIResourceList{}, | ||
| swagger: &spec.Swagger{SwaggerProps: spec.SwaggerProps{}}, | ||
| delegates: map[string]CRDHandler{}, | ||
| } | ||
| s.logger = runtime.NewLoggerWithType(s) | ||
|
|
||
| // we don't *have* to have a swagger api, so just do an empty one for now, and we can expand as needed. | ||
| // kube-openapi could be a potential library to look at for future if we want to be more specific. | ||
| // This at least stops the K8s api pinging us for every iteration of a api descriptor that may exist | ||
| s.swagger.SwaggerProps.Info = &spec.Info{InfoProps: spec.InfoProps{Title: "allocation.agones.dev"}} | ||
|
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| mux.HandleFunc("/openapi/v2", func(w http.ResponseWriter, r *http.Request) { | ||
| w.Header().Set(ContentTypeHeader, k8sruntime.ContentTypeJSON) | ||
| err := json.NewEncoder(w).Encode(s.swagger) | ||
| if err != nil { | ||
| s.logger.WithError(errors.WithStack(err)).Error("error return openapi") | ||
| http.Error(w, err.Error(), http.StatusInternalServerError) | ||
| } | ||
| }) | ||
|
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| return s | ||
| } | ||
|
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| // AddAPIResource stores the APIResource under the given groupVersion string, and returns it | ||
| // in the appropriate place for the K8s discovery service | ||
| // e.g. http://localhost:8001/apis/scheduling.k8s.io/v1beta1 | ||
| // as well as registering a CRDHandler that all http requests for the given APIResource are routed to | ||
| func (as *APIServer) AddAPIResource(groupVersion string, resource metav1.APIResource, handler CRDHandler) { | ||
| list, ok := as.resourceList[groupVersion] | ||
| if !ok { | ||
| // discovery handler | ||
| list = &metav1.APIResourceList{GroupVersion: groupVersion, APIResources: []metav1.APIResource{}} | ||
| as.resourceList[groupVersion] = list | ||
| pattern := fmt.Sprintf("/apis/%s", groupVersion) | ||
| as.addSerializedHandler(pattern, list) | ||
| as.logger.WithField("groupversion", groupVersion).WithField("pattern", pattern).Info("Adding Discovery Handler") | ||
|
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||
| // e.g. /apis/stable.agones.dev/v1alpha1/namespaces/default/gameservers | ||
| // CRD handler | ||
| pattern = fmt.Sprintf("/apis/%s/namespaces/", groupVersion) | ||
| as.mux.HandleFunc(pattern, https.ErrorHTTPHandler(as.logger, as.resourceHandler(groupVersion))) | ||
| as.logger.WithField("groupversion", groupVersion).WithField("pattern", pattern).Info("Adding Resource Handler") | ||
| } | ||
|
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| // discovery resource | ||
| list.APIResources = append(as.resourceList[groupVersion].APIResources, resource) | ||
|
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| // add specific crd resource handler | ||
| key := fmt.Sprintf("%s/%s", groupVersion, resource.Name) | ||
| as.delegates[key] = handler | ||
|
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| as.logger.WithField("groupversion", groupVersion).WithField("apiresource", resource).Info("Adding APIResource") | ||
| } | ||
|
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| // resourceHandler handles namespaced resource calls, and sends them to the appropriate CRDHandler delegate | ||
| func (as *APIServer) resourceHandler(gv string) https.ErrorHandlerFunc { | ||
| return func(w http.ResponseWriter, r *http.Request) error { | ||
| namespace, resource, err := splitNameSpaceResource(r.URL.Path) | ||
| if err != nil { | ||
| https.FourZeroFour(as.logger.WithError(err), w, r) | ||
| return nil | ||
| } | ||
|
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| delegate, ok := as.delegates[fmt.Sprintf("%s/%s", gv, resource)] | ||
| if !ok { | ||
| https.FourZeroFour(as.logger, w, r) | ||
| return nil | ||
| } | ||
|
|
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| if err = delegate(w, r, namespace); err != nil { | ||
| return err | ||
| } | ||
|
|
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| return nil | ||
| } | ||
| } | ||
|
|
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| // addSerializedHandler sets up a handler than will send the serialised content | ||
| // to the specified path. | ||
| func (as *APIServer) addSerializedHandler(pattern string, m k8sruntime.Object) { | ||
| as.mux.HandleFunc(pattern, https.ErrorHTTPHandler(as.logger, func(w http.ResponseWriter, r *http.Request) error { | ||
| if r.Method == http.MethodGet { | ||
| info, err := AcceptedSerializer(r, Codecs) | ||
| if err != nil { | ||
| return err | ||
| } | ||
|
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| w.Header().Set(ContentTypeHeader, info.MediaType) | ||
| err = Codecs.EncoderForVersion(info.Serializer, unversionedVersion).Encode(m, w) | ||
| if err != nil { | ||
| return errors.New("error marshalling") | ||
| } | ||
| } else { | ||
| https.FourZeroFour(as.logger, w, r) | ||
| } | ||
|
|
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| return nil | ||
| })) | ||
| } | ||
|
|
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| // AcceptedSerializer takes the request, and returns a serialiser (if it exists) | ||
| // for the given codec factory and | ||
| // for the Accepted media types. If not found, returns error | ||
| func AcceptedSerializer(r *http.Request, codecs serializer.CodecFactory) (k8sruntime.SerializerInfo, error) { | ||
| // this is so we know what we can accept | ||
| mediaTypes := codecs.SupportedMediaTypes() | ||
| alternatives := make([]string, len(mediaTypes)) | ||
| for i, media := range mediaTypes { | ||
| alternatives[i] = media.MediaType | ||
| } | ||
| header := r.Header.Get(AcceptHeader) | ||
| accept := goautoneg.Negotiate(header, alternatives) | ||
| if len(accept) == 0 { | ||
| accept = k8sruntime.ContentTypeJSON | ||
| } | ||
| info, ok := k8sruntime.SerializerInfoForMediaType(mediaTypes, accept) | ||
| if !ok { | ||
| return info, errors.Errorf("Could not find serializer for Accept: %s", header) | ||
| } | ||
|
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| return info, nil | ||
| } | ||
|
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| // splitNameSpaceResource returns the namespace and the type of resource | ||
| func splitNameSpaceResource(path string) (namespace, resource string, err error) { | ||
| list := strings.Split(strings.Trim(path, "/"), "/") | ||
| if len(list) < 3 { | ||
| return namespace, resource, errors.Errorf("could not find namespace and resource in path: %s", path) | ||
| } | ||
| last := list[len(list)-3:] | ||
|
|
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| if last[0] != "namespaces" { | ||
| return namespace, resource, errors.Errorf("wrong format in path: %s", path) | ||
| } | ||
|
|
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| return last[1], last[2], err | ||
| } |
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