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features.go
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features.go
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// Copyright 2020 Google LLC 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 runtime
import (
"net/url"
"strconv"
"sync"
"github.com/pkg/errors"
"github.com/spf13/pflag"
"github.com/spf13/viper"
)
const (
// FeatureGateFlag is a name of a command line flag, which turns on specific tests for FeatureGates
FeatureGateFlag = "feature-gates"
// FeatureExample is an example feature gate flag, used for testing and demonstrative purposes
FeatureExample Feature = "Example"
// FeaturePlayerTracking is a feature flag to enable/disable player tracking features.
FeaturePlayerTracking Feature = "PlayerTracking"
// NodeExternalDNS is a feature flag to enable/disable node ExternalDNS and InternalDNS use as GameServer address
NodeExternalDNS Feature = "NodeExternalDNS"
// FeatureStateAllocationFilter is a feature flag that enables state filtering on Allocation.
FeatureStateAllocationFilter Feature = "StateAllocationFilter"
// FeaturePlayerAllocationFilter is a feature flag that enables the ability for Allocations to filter based on
// player capacity.
FeaturePlayerAllocationFilter Feature = "PlayerAllocationFilter"
// FeatureCustomFasSyncInterval is a feature flag that enables custom the FleetAutoscaler rsync interval
FeatureCustomFasSyncInterval Feature = "CustomFasSyncInterval"
// FeatureSDKGracefulTermination is a feature flag that enables SDK to support gracefulTermination
FeatureSDKGracefulTermination Feature = "SDKGracefulTermination"
)
var (
// featureDefaults is a map of all Feature Gates that are
// operational in Agones, and what their default configuration is.
// alpha features are disabled.
featureDefaults = map[Feature]bool{
FeatureExample: true,
FeaturePlayerTracking: false,
NodeExternalDNS: true,
FeatureStateAllocationFilter: false,
FeaturePlayerAllocationFilter: false,
FeatureCustomFasSyncInterval: false,
FeatureSDKGracefulTermination: false,
}
// featureGates is the storage of what features are enabled
// or disabled.
featureGates map[Feature]bool
// featureMutex ensures that updates to featureGates don't happen at the same time as reads.
// this is mostly to protect tests which can change gates in parallel.
featureMutex = sync.RWMutex{}
// FeatureTestMutex is a mutex to be shared between tests to ensure that a test that involves changing featureGates
// cannot accidentally run at the same time as another test that also changing feature flags.
FeatureTestMutex sync.Mutex
)
// Feature is a type for defining feature gates.
type Feature string
// FeaturesBindFlags does the Viper arguments configuration. Call before running pflag.Parse()
func FeaturesBindFlags() {
viper.SetDefault(FeatureGateFlag, "")
pflag.String(FeatureGateFlag, viper.GetString(FeatureGateFlag), "Flag to pass in the url query list of feature flags to enable or disable")
}
// FeaturesBindEnv binds the environment variables, based on the flags provided.
// call after viper.SetEnvKeyReplacer(...) if it is being set.
func FeaturesBindEnv() error {
return viper.BindEnv(FeatureGateFlag)
}
// ParseFeaturesFromEnv will parse the feature flags from the Viper args
// configured by FeaturesBindFlags() and FeaturesBindEnv()
func ParseFeaturesFromEnv() error {
return ParseFeatures(viper.GetString(FeatureGateFlag))
}
// ParseFeatures parses the url encoded query string of features and stores the value
// for later retrieval
func ParseFeatures(queryString string) error {
featureMutex.Lock()
defer featureMutex.Unlock()
features := map[Feature]bool{}
// copy the defaults into this map
for k, v := range featureDefaults {
features[k] = v
}
values, err := url.ParseQuery(queryString)
if err != nil {
return errors.Wrap(err, "error parsing query string for feature gates")
}
for k := range values {
f := Feature(k)
if _, ok := featureDefaults[f]; !ok {
return errors.Errorf("Feature Gate %q is not a valid Feature Gate", f)
}
b, err := strconv.ParseBool(values.Get(k))
if err != nil {
return errors.Wrapf(err, "error parsing bool value from flag %s ", k)
}
features[f] = b
}
featureGates = features
return nil
}
// EnableAllFeatures turns on all feature flags.
// This is useful for libraries/processes/tests that want to
// enable all Alpha/Beta features without having to track all
// the current feature flags.
func EnableAllFeatures() {
featureMutex.Lock()
defer featureMutex.Unlock()
features := map[Feature]bool{}
// copy the defaults into this map
for k := range featureDefaults {
features[k] = true
}
featureGates = features
}
// FeatureEnabled returns if a Feature is enabled or not
func FeatureEnabled(feature Feature) bool {
featureMutex.RLock()
defer featureMutex.RUnlock()
return featureGates[feature]
}
// EncodeFeatures returns the feature set as a URL encoded query string
func EncodeFeatures() string {
values := url.Values{}
featureMutex.RLock()
defer featureMutex.RUnlock()
for k, v := range featureGates {
values.Add(string(k), strconv.FormatBool(v))
}
return values.Encode()
}