239 lines
6 KiB
Go
239 lines
6 KiB
Go
/*
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Copyright 2016 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package feature
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import (
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"fmt"
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"sort"
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"strconv"
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"strings"
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"sync"
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"github.com/golang/glog"
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"github.com/spf13/pflag"
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)
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type Feature string
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const (
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flagName = "feature-gates"
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// allAlphaGate is a global toggle for alpha features. Per-feature key
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// values override the default set by allAlphaGate. Examples:
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// AllAlpha=false,NewFeature=true will result in newFeature=true
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// AllAlpha=true,NewFeature=false will result in newFeature=false
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allAlphaGate Feature = "AllAlpha"
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)
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var (
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// The generic features.
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defaultFeatures = map[Feature]FeatureSpec{
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allAlphaGate: {Default: false, PreRelease: Alpha},
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}
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// Special handling for a few gates.
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specialFeatures = map[Feature]func(f *featureGate, val bool){
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allAlphaGate: setUnsetAlphaGates,
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}
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// DefaultFeatureGate is a shared global FeatureGate.
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DefaultFeatureGate FeatureGate = NewFeatureGate()
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)
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type FeatureSpec struct {
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Default bool
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PreRelease prerelease
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}
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type prerelease string
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const (
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// Values for PreRelease.
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Alpha = prerelease("ALPHA")
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Beta = prerelease("BETA")
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GA = prerelease("")
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)
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// FeatureGate parses and stores flag gates for known features from
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// a string like feature1=true,feature2=false,...
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type FeatureGate interface {
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// AddFlag adds a flag for setting global feature gates to the specified FlagSet.
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AddFlag(fs *pflag.FlagSet)
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// Set parses and stores flag gates for known features
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// from a string like feature1=true,feature2=false,...
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Set(value string) error
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// Enabled returns true if the key is enabled.
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Enabled(key Feature) bool
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// Add adds features to the featureGate.
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Add(features map[Feature]FeatureSpec) error
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// KnownFeatures returns a slice of strings describing the FeatureGate's known features.
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KnownFeatures() []string
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}
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// featureGate implements FeatureGate as well as pflag.Value for flag parsing.
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type featureGate struct {
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lock sync.RWMutex
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known map[Feature]FeatureSpec
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special map[Feature]func(*featureGate, bool)
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enabled map[Feature]bool
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// is set to true when AddFlag is called. Note: initialization is not go-routine safe, lookup is
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closed bool
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}
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func setUnsetAlphaGates(f *featureGate, val bool) {
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for k, v := range f.known {
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if v.PreRelease == Alpha {
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if _, found := f.enabled[k]; !found {
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f.enabled[k] = val
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}
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}
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}
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}
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// Set, String, and Type implement pflag.Value
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var _ pflag.Value = &featureGate{}
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func NewFeatureGate() *featureGate {
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f := &featureGate{
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known: map[Feature]FeatureSpec{},
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special: specialFeatures,
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enabled: map[Feature]bool{},
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}
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for k, v := range defaultFeatures {
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f.known[k] = v
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}
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return f
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}
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// Set Parses a string of the form "key1=value1,key2=value2,..." into a
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// map[string]bool of known keys or returns an error.
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func (f *featureGate) Set(value string) error {
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f.lock.Lock()
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defer f.lock.Unlock()
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for _, s := range strings.Split(value, ",") {
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if len(s) == 0 {
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continue
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}
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arr := strings.SplitN(s, "=", 2)
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k := Feature(strings.TrimSpace(arr[0]))
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_, ok := f.known[Feature(k)]
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if !ok {
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return fmt.Errorf("unrecognized key: %s", k)
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}
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if len(arr) != 2 {
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return fmt.Errorf("missing bool value for %s", k)
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}
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v := strings.TrimSpace(arr[1])
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boolValue, err := strconv.ParseBool(v)
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if err != nil {
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return fmt.Errorf("invalid value of %s: %s, err: %v", k, v, err)
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}
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f.enabled[k] = boolValue
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// Handle "special" features like "all alpha gates"
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if fn, found := f.special[k]; found {
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fn(f, boolValue)
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}
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}
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glog.Infof("feature gates: %v", f.enabled)
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return nil
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}
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// String returns a string containing all enabled feature gates, formatted as "key1=value1,key2=value2,...".
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func (f *featureGate) String() string {
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f.lock.RLock()
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defer f.lock.RUnlock()
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pairs := []string{}
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for k, v := range f.enabled {
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pairs = append(pairs, fmt.Sprintf("%s=%t", k, v))
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}
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sort.Strings(pairs)
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return strings.Join(pairs, ",")
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}
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func (f *featureGate) Type() string {
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return "mapStringBool"
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}
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// Add adds features to the featureGate.
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func (f *featureGate) Add(features map[Feature]FeatureSpec) error {
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f.lock.Lock()
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defer f.lock.Unlock()
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if f.closed {
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return fmt.Errorf("cannot add a feature gate after adding it to the flag set")
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}
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for name, spec := range features {
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if existingSpec, found := f.known[name]; found {
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if existingSpec == spec {
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continue
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}
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return fmt.Errorf("feature gate %q with different spec already exists: %v", name, existingSpec)
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}
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f.known[name] = spec
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}
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return nil
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}
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// Enabled returns true if the key is enabled.
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func (f *featureGate) Enabled(key Feature) bool {
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f.lock.RLock()
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defer f.lock.RUnlock()
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defaultValue := f.known[key].Default
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if f.enabled != nil {
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if v, ok := f.enabled[key]; ok {
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return v
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}
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}
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return defaultValue
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}
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// AddFlag adds a flag for setting global feature gates to the specified FlagSet.
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func (f *featureGate) AddFlag(fs *pflag.FlagSet) {
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f.lock.Lock()
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f.closed = true
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f.lock.Unlock()
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known := f.KnownFeatures()
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fs.Var(f, flagName, ""+
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"A set of key=value pairs that describe feature gates for alpha/experimental features. "+
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"Options are:\n"+strings.Join(known, "\n"))
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}
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// KnownFeatures returns a slice of strings describing the FeatureGate's known features.
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func (f *featureGate) KnownFeatures() []string {
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f.lock.RLock()
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defer f.lock.RUnlock()
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var known []string
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for k, v := range f.known {
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pre := ""
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if v.PreRelease != GA {
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pre = fmt.Sprintf("%s - ", v.PreRelease)
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}
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known = append(known, fmt.Sprintf("%s=true|false (%sdefault=%t)", k, pre, v.Default))
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}
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sort.Strings(known)
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return known
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}
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