mirror of
https://github.com/ceph/ceph-csi.git
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365 lines
11 KiB
Go
365 lines
11 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 featuregate
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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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"sync/atomic"
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"github.com/spf13/pflag"
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"k8s.io/apimachinery/pkg/util/naming"
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"k8s.io/klog"
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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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// allBetaGate is a global toggle for beta features. Per-feature key
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// values override the default set by allBetaGate. Examples:
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// AllBeta=false,NewFeature=true will result in NewFeature=true
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// AllBeta=true,NewFeature=false will result in NewFeature=false
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allBetaGate Feature = "AllBeta"
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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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allBetaGate: {Default: false, PreRelease: Beta},
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}
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// Special handling for a few gates.
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specialFeatures = map[Feature]func(known map[Feature]FeatureSpec, enabled map[Feature]bool, val bool){
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allAlphaGate: setUnsetAlphaGates,
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allBetaGate: setUnsetBetaGates,
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}
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)
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type FeatureSpec struct {
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// Default is the default enablement state for the feature
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Default bool
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// LockToDefault indicates that the feature is locked to its default and cannot be changed
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LockToDefault bool
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// PreRelease indicates the maturity level of the feature
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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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// Deprecated
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Deprecated = prerelease("DEPRECATED")
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)
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// FeatureGate indicates whether a given feature is enabled or not
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type FeatureGate interface {
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// Enabled returns true if the key is enabled.
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Enabled(key Feature) bool
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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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// DeepCopy returns a deep copy of the FeatureGate object, such that gates can be
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// set on the copy without mutating the original. This is useful for validating
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// config against potential feature gate changes before committing those changes.
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DeepCopy() MutableFeatureGate
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}
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// MutableFeatureGate 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 MutableFeatureGate interface {
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FeatureGate
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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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// SetFromMap stores flag gates for known features from a map[string]bool or returns an error
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SetFromMap(m map[string]bool) error
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// Add adds features to the featureGate.
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Add(features map[Feature]FeatureSpec) error
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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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featureGateName string
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special map[Feature]func(map[Feature]FeatureSpec, map[Feature]bool, bool)
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// lock guards writes to known, enabled, and reads/writes of closed
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lock sync.Mutex
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// known holds a map[Feature]FeatureSpec
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known *atomic.Value
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// enabled holds a map[Feature]bool
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enabled *atomic.Value
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// closed is set to true when AddFlag is called, and prevents subsequent calls to Add
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closed bool
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}
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func setUnsetAlphaGates(known map[Feature]FeatureSpec, enabled map[Feature]bool, val bool) {
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for k, v := range known {
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if v.PreRelease == Alpha {
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if _, found := enabled[k]; !found {
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enabled[k] = val
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}
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}
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}
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}
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func setUnsetBetaGates(known map[Feature]FeatureSpec, enabled map[Feature]bool, val bool) {
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for k, v := range known {
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if v.PreRelease == Beta {
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if _, found := enabled[k]; !found {
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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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// internalPackages are packages that ignored when creating a name for featureGates. These packages are in the common
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// call chains, so they'd be unhelpful as names.
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var internalPackages = []string{"k8s.io/component-base/featuregate/feature_gate.go"}
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func NewFeatureGate() *featureGate {
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known := map[Feature]FeatureSpec{}
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for k, v := range defaultFeatures {
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known[k] = v
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}
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knownValue := &atomic.Value{}
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knownValue.Store(known)
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enabled := map[Feature]bool{}
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enabledValue := &atomic.Value{}
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enabledValue.Store(enabled)
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f := &featureGate{
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featureGateName: naming.GetNameFromCallsite(internalPackages...),
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known: knownValue,
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special: specialFeatures,
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enabled: enabledValue,
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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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m := make(map[string]bool)
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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 := strings.TrimSpace(arr[0])
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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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m[k] = boolValue
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}
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return f.SetFromMap(m)
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}
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// SetFromMap stores flag gates for known features from a map[string]bool or returns an error
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func (f *featureGate) SetFromMap(m map[string]bool) error {
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f.lock.Lock()
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defer f.lock.Unlock()
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// Copy existing state
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known := map[Feature]FeatureSpec{}
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for k, v := range f.known.Load().(map[Feature]FeatureSpec) {
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known[k] = v
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}
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enabled := map[Feature]bool{}
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for k, v := range f.enabled.Load().(map[Feature]bool) {
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enabled[k] = v
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}
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for k, v := range m {
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k := Feature(k)
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featureSpec, ok := known[k]
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if !ok {
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return fmt.Errorf("unrecognized feature gate: %s", k)
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}
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if featureSpec.LockToDefault && featureSpec.Default != v {
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return fmt.Errorf("cannot set feature gate %v to %v, feature is locked to %v", k, v, featureSpec.Default)
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}
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enabled[k] = v
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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(known, enabled, v)
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}
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if featureSpec.PreRelease == Deprecated {
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klog.Warningf("Setting deprecated feature gate %s=%t. It will be removed in a future release.", k, v)
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} else if featureSpec.PreRelease == GA {
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klog.Warningf("Setting GA feature gate %s=%t. It will be removed in a future release.", k, v)
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}
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}
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// Persist changes
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f.known.Store(known)
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f.enabled.Store(enabled)
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klog.V(1).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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pairs := []string{}
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for k, v := range f.enabled.Load().(map[Feature]bool) {
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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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// Copy existing state
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known := map[Feature]FeatureSpec{}
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for k, v := range f.known.Load().(map[Feature]FeatureSpec) {
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known[k] = v
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}
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for name, spec := range features {
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if existingSpec, found := 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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known[name] = spec
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}
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// Persist updated state
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f.known.Store(known)
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return nil
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}
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// Enabled returns true if the key is enabled. If the key is not known, this call will panic.
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func (f *featureGate) Enabled(key Feature) bool {
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if v, ok := f.enabled.Load().(map[Feature]bool)[key]; ok {
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return v
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}
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if v, ok := f.known.Load().(map[Feature]FeatureSpec)[key]; ok {
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return v.Default
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}
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panic(fmt.Errorf("feature %q is not registered in FeatureGate %q", key, f.featureGateName))
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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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// TODO(mtaufen): Shouldn't we just close it on the first Set/SetFromMap instead?
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// Not all components expose a feature gates flag using this AddFlag method, and
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// in the future, all components will completely stop exposing a feature gates flag,
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// in favor of componentconfig.
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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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// Deprecated and GA features are hidden from the list.
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func (f *featureGate) KnownFeatures() []string {
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var known []string
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for k, v := range f.known.Load().(map[Feature]FeatureSpec) {
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if v.PreRelease == GA || v.PreRelease == Deprecated {
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continue
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}
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known = append(known, fmt.Sprintf("%s=true|false (%s - default=%t)", k, v.PreRelease, 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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// DeepCopy returns a deep copy of the FeatureGate object, such that gates can be
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// set on the copy without mutating the original. This is useful for validating
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// config against potential feature gate changes before committing those changes.
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func (f *featureGate) DeepCopy() MutableFeatureGate {
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// Copy existing state.
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known := map[Feature]FeatureSpec{}
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for k, v := range f.known.Load().(map[Feature]FeatureSpec) {
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known[k] = v
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}
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enabled := map[Feature]bool{}
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for k, v := range f.enabled.Load().(map[Feature]bool) {
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enabled[k] = v
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}
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// Store copied state in new atomics.
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knownValue := &atomic.Value{}
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knownValue.Store(known)
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enabledValue := &atomic.Value{}
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enabledValue.Store(enabled)
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// Construct a new featureGate around the copied state.
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// Note that specialFeatures is treated as immutable by convention,
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// and we maintain the value of f.closed across the copy.
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return &featureGate{
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special: specialFeatures,
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known: knownValue,
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enabled: enabledValue,
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closed: f.closed,
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}
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}
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