c-go: Use http Etag cache

Add a new command-line cachedir flag to specify where to store the http
cache responses. This cache will only be used for OpenAPI Swagger spec
for now (as this is the only end-point that returns an ETag).

staging/src/k8s.io/client-go/rest/config.go

@@ -71,6 +71,10 @@ type Config struct {
 	// TODO: demonstrate an OAuth2 compatible client.
 	BearerToken string
 
+	// CacheDir is the directory where we'll store HTTP cached responses.
+	// If set to empty string, no caching mechanism will be used.
+	CacheDir string
+
 	// Impersonate is the configuration that RESTClient will use for impersonation.
 	Impersonate ImpersonationConfig
 

staging/src/k8s.io/client-go/rest/config_test.go

@@ -249,6 +249,7 @@ func TestAnonymousConfig(t *testing.T) {
 		expected.BearerToken = ""
 		expected.Username = ""
 		expected.Password = ""
+		expected.CacheDir = ""
 		expected.AuthProvider = nil
 		expected.AuthConfigPersister = nil
 		expected.TLSClientConfig.CertData = nil

staging/src/k8s.io/client-go/rest/transport.go

@@ -89,6 +89,7 @@ func (c *Config) TransportConfig() (*transport.Config, error) {
 		},
 		Username:    c.Username,
 		Password:    c.Password,
+		CacheDir:    c.CacheDir,
 		BearerToken: c.BearerToken,
 		Impersonate: transport.ImpersonationConfig{
 			UserName: c.Impersonate.UserName,

staging/src/k8s.io/client-go/tools/clientcmd/client_config.go

@@ -22,6 +22,7 @@ import (
 	"io/ioutil"
 	"net/url"
 	"os"
+	"path/filepath"
 	"strings"
 
 	"github.com/golang/glog"
@@ -31,16 +32,19 @@ import (
 	restclient "k8s.io/client-go/rest"
 	clientauth "k8s.io/client-go/tools/auth"
 	clientcmdapi "k8s.io/client-go/tools/clientcmd/api"
+	"k8s.io/client-go/util/homedir"
 )
 
 var (
 	// ClusterDefaults has the same behavior as the old EnvVar and DefaultCluster fields
 	// DEPRECATED will be replaced
 	ClusterDefaults = clientcmdapi.Cluster{Server: getDefaultServer()}
+	cacheDirDefault = filepath.Join(homedir.HomeDir(), ".kube", "http-cache")
 	// DefaultClientConfig represents the legacy behavior of this package for defaulting
 	// DEPRECATED will be replace
 	DefaultClientConfig = DirectClientConfig{*clientcmdapi.NewConfig(), "", &ConfigOverrides{
 		ClusterDefaults: ClusterDefaults,
+		CacheDir:        cacheDirDefault,
 	}, nil, NewDefaultClientConfigLoadingRules(), promptedCredentials{}}
 )
 
@@ -131,6 +135,7 @@ func (config *DirectClientConfig) ClientConfig() (*restclient.Config, error) {
 
 	clientConfig := &restclient.Config{}
 	clientConfig.Host = configClusterInfo.Server
+	clientConfig.CacheDir = config.overrides.CacheDir
 
 	if len(config.overrides.Timeout) > 0 {
 		timeout, err := ParseTimeout(config.overrides.Timeout)

staging/src/k8s.io/client-go/tools/clientcmd/overrides.go

@@ -17,11 +17,13 @@ limitations under the License.
 package clientcmd
 
 import (
+	"path/filepath"
 	"strconv"
 
 	"github.com/spf13/pflag"
 
 	clientcmdapi "k8s.io/client-go/tools/clientcmd/api"
+	"k8s.io/client-go/util/homedir"
 )
 
 // ConfigOverrides holds values that should override whatever information is pulled from the actual Config object.  You can't
@@ -34,6 +36,7 @@ type ConfigOverrides struct {
 	Context         clientcmdapi.Context
 	CurrentContext  string
 	Timeout         string
+	CacheDir        string
 }
 
 // ConfigOverrideFlags holds the flag names to be used for binding command line flags.  Notice that this structure tightly
@@ -44,6 +47,7 @@ type ConfigOverrideFlags struct {
 	ContextOverrideFlags ContextOverrideFlags
 	CurrentContext       FlagInfo
 	Timeout              FlagInfo
+	CacheDir             FlagInfo
 }
 
 // AuthOverrideFlags holds the flag names to be used for binding command line flags for AuthInfo objects
@@ -146,10 +150,12 @@ const (
 	FlagUsername         = "username"
 	FlagPassword         = "password"
 	FlagTimeout          = "request-timeout"
+	FlagCacheDir         = "cachedir"
 )
 
 // RecommendedConfigOverrideFlags is a convenience method to return recommended flag names prefixed with a string of your choosing
 func RecommendedConfigOverrideFlags(prefix string) ConfigOverrideFlags {
+	defaultCacheDir := filepath.Join(homedir.HomeDir(), ".kube", "http-cache")
 	return ConfigOverrideFlags{
 		AuthOverrideFlags:    RecommendedAuthOverrideFlags(prefix),
 		ClusterOverrideFlags: RecommendedClusterOverrideFlags(prefix),
@@ -157,6 +163,7 @@ func RecommendedConfigOverrideFlags(prefix string) ConfigOverrideFlags {
 
 		CurrentContext: FlagInfo{prefix + FlagContext, "", "", "The name of the kubeconfig context to use"},
 		Timeout:        FlagInfo{prefix + FlagTimeout, "", "0", "The length of time to wait before giving up on a single server request. Non-zero values should contain a corresponding time unit (e.g. 1s, 2m, 3h). A value of zero means don't timeout requests."},
+		CacheDir:       FlagInfo{prefix + FlagCacheDir, "", defaultCacheDir, "Path to http-cache directory"},
 	}
 }
 
@@ -198,6 +205,7 @@ func BindOverrideFlags(overrides *ConfigOverrides, flags *pflag.FlagSet, flagNam
 	BindContextFlags(&overrides.Context, flags, flagNames.ContextOverrideFlags)
 	flagNames.CurrentContext.BindStringFlag(flags, &overrides.CurrentContext)
 	flagNames.Timeout.BindStringFlag(flags, &overrides.Timeout)
+	flagNames.CacheDir.BindStringFlag(flags, &overrides.CacheDir)
 }
 
 // BindAuthInfoFlags is a convenience method to bind the specified flags to their associated variables

staging/src/k8s.io/client-go/transport/BUILD

@@ -30,6 +30,9 @@ go_library(
     tags = ["automanaged"],
     deps = [
         "//vendor/github.com/golang/glog:go_default_library",
+        "//vendor/github.com/gregjones/httpcache:go_default_library",
+        "//vendor/github.com/gregjones/httpcache/diskcache:go_default_library",
+        "//vendor/github.com/peterbourgon/diskv:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/util/net:go_default_library",
     ],
 )

staging/src/k8s.io/client-go/transport/config.go

@@ -34,6 +34,10 @@ type Config struct {
 	// Bearer token for authentication
 	BearerToken string
 
+	// CacheDir is the directory where we'll store HTTP cached responses.
+	// If set to empty string, no caching mechanism will be used.
+	CacheDir string
+
 	// Impersonate is the config that this Config will impersonate using
 	Impersonate ImpersonationConfig
 

staging/src/k8s.io/client-go/transport/round_trippers.go

@@ -23,6 +23,9 @@ import (
 	"time"
 
 	"github.com/golang/glog"
+	"github.com/gregjones/httpcache"
+	"github.com/gregjones/httpcache/diskcache"
+	"github.com/peterbourgon/diskv"
 
 	utilnet "k8s.io/apimachinery/pkg/util/net"
 )
@@ -56,6 +59,9 @@ func HTTPWrappersForConfig(config *Config, rt http.RoundTripper) (http.RoundTrip
 		len(config.Impersonate.Extra) > 0 {
 		rt = NewImpersonatingRoundTripper(config.Impersonate, rt)
 	}
+	if len(config.CacheDir) > 0 {
+		rt = NewCacheRoundTripper(config.CacheDir, rt)
+	}
 	return rt, nil
 }
 
@@ -87,6 +93,17 @@ type authProxyRoundTripper struct {
 	rt http.RoundTripper
 }
 
+// NewCacheRoundTripper creates a roundtripper that reads the ETag on
+// response headers and send the If-None-Match header on subsequent
+// corresponding requests.
+func NewCacheRoundTripper(cacheDir string, rt http.RoundTripper) http.RoundTripper {
+	d := diskv.New(diskv.Options{BasePath: cacheDir})
+	t := httpcache.NewTransport(diskcache.NewWithDiskv(d))
+	t.Transport = rt
+
+	return t
+}
+
 // NewAuthProxyRoundTripper provides a roundtripper which will add auth proxy fields to requests for
 // authentication terminating proxy cases
 // assuming you pull the user from the context: