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quota.go
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quota.go
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// Copyright 2017 Google Inc. 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 server
import (
"flag"
"fmt"
"sync"
"github.com/golang/glog"
"github.com/google/trillian/quota"
)
const (
// QuotaNoop represents the noop quota implementation.
QuotaNoop = "noop"
)
// NewQuotaManagerFunc is the signature of a function which can be registered
// to provide instances of a quota manager.
type NewQuotaManagerFunc func() (quota.Manager, error)
var (
// QuotaSystem is a flag specifying which quota system is in use.
QuotaSystem = flag.String("quota_system", "mysql", fmt.Sprintf("Quota system to use. One of: %v", quotaSystems()))
qpMu sync.RWMutex
qpByName map[string]NewQuotaManagerFunc
)
func init() {
if err := RegisterQuotaManager(QuotaNoop, func() (quota.Manager, error) {
return quota.Noop(), nil
}); err != nil {
glog.Fatalf("Failed to register %v: %v", QuotaNoop, err)
}
}
// RegisterQuotaManager registers the provided QuotaManager.
func RegisterQuotaManager(name string, qp NewQuotaManagerFunc) error {
qpMu.Lock()
defer qpMu.Unlock()
if qpByName == nil {
qpByName = make(map[string]NewQuotaManagerFunc)
}
_, exists := qpByName[name]
if exists {
return fmt.Errorf("quota provider %v already registered", name)
}
qpByName[name] = qp
return nil
}
// quotaSystems returns a slice of registered quota system names.
func quotaSystems() []string {
qpMu.RLock()
defer qpMu.RUnlock()
r := []string{}
for k := range qpByName {
r = append(r, k)
}
return r
}
// NewQuotaManagerFromFlags returns a quota.Manager implementation as speficied by flag.
func NewQuotaManagerFromFlags() (quota.Manager, error) {
return NewQuotaManager(*QuotaSystem)
}
// NewQuotaManager returns a quota.Manager implementation.
func NewQuotaManager(name string) (quota.Manager, error) {
qpMu.RLock()
defer qpMu.RUnlock()
f, exists := qpByName[name]
if !exists {
return nil, fmt.Errorf("unknown quota system: %v", name)
}
return f()
}