go.chromium.org/luci@v0.0.0-20240309015107-7cdc2e660f33/config/appengine/gaeconfig/lazy.go (about)

     1  // Copyright 2023 The LUCI Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //      http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package gaeconfig
    16  
    17  import (
    18  	"context"
    19  	"sync"
    20  
    21  	"go.chromium.org/luci/config"
    22  )
    23  
    24  // lazyConfigClient is a lazily-constructed configClient that implements
    25  // config.Interface. The client will be initialized by the provided
    26  // clientFactory function.
    27  type lazyConfigClient struct {
    28  	clientFactory func(ctx context.Context) config.Interface
    29  
    30  	inner     config.Interface
    31  	innerOnce sync.Once
    32  }
    33  
    34  var _ config.Interface = (*lazyConfigClient)(nil)
    35  
    36  func newLazyConfigClient(factory func(ctx context.Context) config.Interface) *lazyConfigClient {
    37  	return &lazyConfigClient{
    38  		clientFactory: factory,
    39  	}
    40  }
    41  
    42  func (client *lazyConfigClient) lazyInit(ctx context.Context) {
    43  	client.innerOnce.Do(func() {
    44  		client.inner = client.clientFactory(ctx)
    45  	})
    46  }
    47  
    48  // GetConfig implements config.Interface.
    49  func (client *lazyConfigClient) GetConfig(ctx context.Context, configSet config.Set, path string, metaOnly bool) (*config.Config, error) {
    50  	client.lazyInit(ctx)
    51  	return client.inner.GetConfig(ctx, configSet, path, metaOnly)
    52  }
    53  
    54  // GetConfigs implements config.Interface.
    55  func (client *lazyConfigClient) GetConfigs(ctx context.Context, configSet config.Set, filter func(path string) bool, metaOnly bool) (map[string]config.Config, error) {
    56  	client.lazyInit(ctx)
    57  	return client.inner.GetConfigs(ctx, configSet, filter, metaOnly)
    58  }
    59  
    60  // GetProjectConfigs implements config.Interface.
    61  func (client *lazyConfigClient) GetProjectConfigs(ctx context.Context, path string, metaOnly bool) ([]config.Config, error) {
    62  	client.lazyInit(ctx)
    63  	return client.inner.GetProjectConfigs(ctx, path, metaOnly)
    64  }
    65  
    66  // GetProjects implements config.Interface.
    67  func (client *lazyConfigClient) GetProjects(ctx context.Context) ([]config.Project, error) {
    68  	client.lazyInit(ctx)
    69  	return client.inner.GetProjects(ctx)
    70  }
    71  
    72  // ListFiles implements config.Interface.
    73  func (client *lazyConfigClient) ListFiles(ctx context.Context, configSet config.Set) ([]string, error) {
    74  	client.lazyInit(ctx)
    75  	return client.inner.ListFiles(ctx, configSet)
    76  }
    77  
    78  // Close implements config.Interface.
    79  func (client *lazyConfigClient) Close() error {
    80  	// This is potentially racy if client is initialized and closed at the same
    81  	// time. But in this case, Close is never called so it's not a big deal.
    82  	if client.inner != nil {
    83  		return client.inner.Close()
    84  	}
    85  	return nil
    86  }