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server.go
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server.go
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package feature
import (
"context"
"fmt"
"sync"
"github.com/golang/protobuf/proto"
"google.golang.org/grpc"
featurepb "github.com/ajm188/go-ff/proto/feature"
)
var (
// Global singleton.
inst = &server{
features: map[string]*Feature{},
}
_ featurepb.FeaturesServer = (*server)(nil)
)
type server struct {
m sync.RWMutex
features map[string]*Feature
}
// DeleteFeature is part of the featurepb.FeaturesServer interface.
func (s *server) DeleteFeature(ctx context.Context, req *featurepb.DeleteFeatureRequest) (*featurepb.DeleteFeatureResponse, error) {
s.m.Lock()
defer s.m.Unlock()
if feat, ok := s.features[req.Name]; ok {
delete(s.features, req.Name)
return &featurepb.DeleteFeatureResponse{
Feature: feat.Feature,
}, nil
}
return &featurepb.DeleteFeatureResponse{}, nil
}
// GetFeature is part of the featurepb.FeaturesServer interface.
func (s *server) GetFeature(ctx context.Context, req *featurepb.GetFeatureRequest) (*featurepb.GetFeatureResponse, error) {
feat, err := s.getFeature(req.Name)
if err != nil {
return nil, err
}
return &featurepb.GetFeatureResponse{
Feature: feat.Feature,
}, nil
}
// getFeature separates the concurrent-safe Feature lookup from the gRPC service
// implementation so this can be reused by the package-level Get function.
func (s *server) getFeature(name string) (*Feature, error) {
s.m.RLock()
defer s.m.RUnlock()
if feat, ok := s.features[name]; ok {
return feat, nil
}
return nil, fmt.Errorf("%w with name %s", ErrNoFeature, name)
}
// GetFeatures is part of the featurepb.FeaturesServer interface.
func (s *server) GetFeatures(ctx context.Context, req *featurepb.GetFeaturesRequest) (*featurepb.GetFeaturesResponse, error) {
s.m.RLock()
defer s.m.RUnlock()
var (
features []*featurepb.Feature
names = make([]string, 0, len(s.features))
)
if !req.NamesOnly {
features = make([]*featurepb.Feature, 0, len(s.features))
}
for name, feat := range s.features {
names = append(names, name)
if !req.NamesOnly {
features = append(features, feat.Feature)
}
}
return &featurepb.GetFeaturesResponse{
Features: features,
Names: names,
}, nil
}
// SetFeature is part of the featurepb.FeaturesServer interface.
func (s *server) SetFeature(ctx context.Context, req *featurepb.SetFeatureRequest) (*featurepb.SetFeatureResponse, error) {
s.m.Lock()
defer s.m.Unlock()
var (
before *featurepb.Feature
after = proto.Clone(req.Feature).(*featurepb.Feature)
)
if feat, ok := s.features[req.Feature.Name]; ok {
before = feat.Feature
}
f := &Feature{Feature: after}
switch f.Type {
case featurepb.Feature_PERCENTAGE_BASED:
if f.Percentage < 0 || f.Percentage > 100 {
return nil, fmt.Errorf("%w percentage must be in [0, 100]; have %d", ErrInvalidFeature, f.Percentage)
}
case featurepb.Feature_EXPRESSION:
if err := f.parseExpression(); err != nil {
return nil, fmt.Errorf("could not parse expression %s: %w", f.Expression, err)
}
}
s.features[req.Feature.Name] = f
return &featurepb.SetFeatureResponse{
Before: before,
After: after,
}, nil
}
// RegisterServer adds the global feature server instance to the given gRPC
// server.
func RegisterServer(s *grpc.Server) {
featurepb.RegisterFeaturesServer(s, inst)
}