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cacher.go
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cacher.go
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// Copyright 2020 Google LLC
//
// 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 secrets
import (
"context"
"fmt"
"time"
"github.com/google/exposure-notifications-server/pkg/cache"
)
// Compile-time check to verify implements interface.
var _ SecretManager = (*Cacher)(nil)
// Cacher is a secret manager implementation that wraps another secret manager
// and caches secret values.
type Cacher struct {
sm SecretManager
cache *cache.Cache
}
// NewCacher creates a new secret manager that caches results for the given ttl.
func NewCacher(ctx context.Context, f SecretManagerFunc, ttl time.Duration) (SecretManager, error) {
sm, err := f(ctx)
if err != nil {
return nil, fmt.Errorf("cacher: %w", err)
}
return WrapCacher(ctx, sm, ttl)
}
// WrapCacher wraps an existing SecretManager with caching.
func WrapCacher(ctx context.Context, sm SecretManager, ttl time.Duration) (SecretManager, error) {
cache, err := cache.New(ttl)
if err != nil {
return nil, err
}
return &Cacher{
sm: sm,
cache: cache,
}, nil
}
// GetSecretValue implements the SecretManager interface, but caches values and
// retrieves them from the cache.
func (sm *Cacher) GetSecretValue(ctx context.Context, name string) (string, error) {
lookup := func() (interface{}, error) {
// Delegate lookup to parent sm.
plaintext, err := sm.sm.GetSecretValue(ctx, name)
if err != nil {
return "", err
}
return plaintext, nil
}
cacheVal, err := sm.cache.WriteThruLookup(name, lookup)
if err != nil {
return "", err
}
plaintext := cacheVal.(string)
return plaintext, nil
}