fix(helm):Overload the ToDiscoveryClient method

Signed-off-by: Dong Gang <dong.gang@daocloud.io>

pkg/kube/config_flags.go

@@ -17,12 +17,24 @@ limitations under the License.
 package kube
 
 import (
+	"path/filepath"
+	"regexp"
+	"strings"
+	"time"
+
 	"k8s.io/cli-runtime/pkg/genericclioptions"
+	"k8s.io/client-go/discovery"
+	diskcached "k8s.io/client-go/discovery/cached/disk"
 	"k8s.io/client-go/rest"
+	"k8s.io/client-go/util/homedir"
 
 	"helm.sh/helm/v3/internal/version"
 )
 
+var defaultCacheDir = filepath.Join(homedir.HomeDir(), ".kube", "http-cache")
+
+// ConfigFlags composes the set of values necessary
+// for obtaining a REST client config
 type ConfigFlags struct {
 	genericclioptions.ConfigFlags
 }
@@ -39,3 +51,40 @@ func (f *ConfigFlags) ToRESTConfig() (*rest.Config, error) {
 	config.UserAgent = version.GetUserAgent()
 	return config, err
 }
+
+// ToDiscoveryClient implements RESTClientGetter.
+// Expects the AddFlags method to have been called.
+// Returns a CachedDiscoveryInterface using a computed RESTConfig.
+func (f *ConfigFlags) ToDiscoveryClient() (discovery.CachedDiscoveryInterface, error) {
+	config, err := f.ToRESTConfig()
+	if err != nil {
+		return nil, err
+	}
+
+	// The more groups you have, the more discovery requests you need to make.
+	// given 25 groups (our groups + a few custom resources) with one-ish version each, discovery needs to make 50 requests
+	// double it just so we don't end up here again for a while.  This config is only used for discovery.
+	config.Burst = 100
+
+	// retrieve a user-provided value for the "cache-dir"
+	// defaulting to ~/.kube/http-cache if no user-value is given.
+	httpCacheDir := defaultCacheDir
+	if f.CacheDir != nil {
+		httpCacheDir = *f.CacheDir
+	}
+
+	discoveryCacheDir := computeDiscoverCacheDir(filepath.Join(homedir.HomeDir(), ".kube", "cache", "discovery"), config.Host)
+	return diskcached.NewCachedDiscoveryClientForConfig(config, discoveryCacheDir, httpCacheDir, time.Duration(10*time.Minute))
+}
+
+// overlyCautiousIllegalFileCharacters matches characters that *might* not be supported.  Windows is really restrictive, so this is really restrictive
+var overlyCautiousIllegalFileCharacters = regexp.MustCompile(`[^(\w/\.)]`)
+
+// computeDiscoverCacheDir takes the parentDir and the host and comes up with a "usually non-colliding" name.
+func computeDiscoverCacheDir(parentDir, host string) string {
+	// strip the optional scheme from host if its there:
+	schemelessHost := strings.Replace(strings.Replace(host, "https://", "", 1), "http://", "", 1)
+	// now do a simple collapse of non-AZ09 characters.  Collisions are possible but unlikely.  Even if we do collide the problem is short lived
+	safeHost := overlyCautiousIllegalFileCharacters.ReplaceAllString(schemelessHost, "_")
+	return filepath.Join(parentDir, safeHost)
+}