Add server/cache support to gaeconfig.

appengine/gaeconfig/default.go

Index: appengine/gaeconfig/default.go
diff --git a/appengine/gaeconfig/default.go b/appengine/gaeconfig/default.go
deleted file mode 100644
index 18cd7db2fd97559735b62e9b06c743cae9f10e8a..0000000000000000000000000000000000000000
--- a/appengine/gaeconfig/default.go
+++ /dev/null
@@ -1,146 +0,0 @@
-// Copyright 2016 The LUCI Authors. All rights reserved.
-// Use of this source code is governed under the Apache License, Version 2.0
-// that can be found in the LICENSE file.
-
-package gaeconfig
-
-import (
-	"errors"
-	"fmt"
-	"net/http"
-	"os"
-	"path/filepath"
-	"sync"
-	"time"
-
-	"golang.org/x/net/context"
-
-	"github.com/luci/gae/service/info"
-	"github.com/luci/luci-go/common/config"
-	"github.com/luci/luci-go/common/config/impl/erroring"
-	"github.com/luci/luci-go/common/config/impl/filesystem"
-	"github.com/luci/luci-go/common/config/impl/remote"
-	"github.com/luci/luci-go/server/auth"
-)
-
-// ErrNotConfigured is returned by methods of config.Interface object returned
-// by New if config service URL is not set. Usually happens for new apps.
-var ErrNotConfigured = errors.New("config service URL is not set in settings")
-
-// devCfgDir is a name of the directory with config files when running in
-// local dev appserver model. See New for details.
-const devCfgDir = "devcfg"
-
-// implCache is used to avoid reallocating config.Interface implementation
-// during each request.
-//
-// config.Interface instances don't actually depend on the context and thus we
-// can share them between requests.
-//
-// Cache key is the current value of Settings struct. We don't bother to clean
-// up old entries, since in most cases there'll be none (the settings are mostly
-// static).
-var implCache struct {
-	lock  sync.RWMutex
-	cache map[Settings]config.Interface
-}
-
-// New constructs default luci-config client.
-//
-// The client is configured to use luci-config URL specified in the settings,
-// using GAE app service account for authentication.
-//
-// If running in prod, and the settings don't specify luci-config URL, produces
-// an implementation of config.Interface that returns ErrNotConfigured from all
-// methods.
-//
-// If running on devserver, and the settings don't specify luci-config URL,
-// returns a filesystem-based implementation that reads configs from a directory
-// (or a symlink) named 'devcfg' located in the GAE module directory (where
-// app.yaml is) or its immediate parent directory.
-//
-// If such directory can not be located, produces an implementation of
-// config.Interface that returns errors from all methods.
-//
-// Panics if it can't load the settings (should not happen since they are in
-// the local memory cache usually).
-func New(c context.Context) config.Interface {
-	settings, err := FetchCachedSettings(c)
-	if err != nil {
-		panic(err)
-	}
-
-	if settings.ConfigServiceURL == "" {
-		if info.IsDevAppServer(c) {
-			return devServerConfig()
-		}
-		return erroring.New(ErrNotConfigured)
-	}
-
-	return configImplForSettings(settings)
-}
-
-// configImplForSettings returns config.Interface based on given settings.
-//
-// Split out from New to enforce that returned config.Interface doesn't depend
-// on the context (since this function doesn't accept a context).
-func configImplForSettings(settings Settings) config.Interface {
-	implCache.lock.RLock()
-	impl, ok := implCache.cache[settings]
-	implCache.lock.RUnlock()
-	if ok {
-		return impl
-	}
-
-	implCache.lock.Lock()
-	defer implCache.lock.Unlock()
-
-	if impl, ok := implCache.cache[settings]; ok {
-		return impl
-	}
-
-	impl = remote.New(settings.ConfigServiceURL+"/_ah/api/config/v1/", authenticatedClient)
-	if settings.CacheExpirationSec != 0 {
-		impl = WrapWithCache(impl, time.Duration(settings.CacheExpirationSec)*time.Second)
-	}
-
-	if implCache.cache == nil {
-		implCache.cache = make(map[Settings]config.Interface, 1)
-	}
-	implCache.cache[settings] = impl
-
-	return impl
-}
-
-// devServerConfig returns config.Interface to use on a devserver.
-//
-// See New for details.
-func devServerConfig() config.Interface {
-	pwd := os.Getenv("PWD") // os.Getwd works funny with symlinks, use PWD
-	candidates := []string{
-		filepath.Join(pwd, devCfgDir),
-		filepath.Join(filepath.Dir(pwd), devCfgDir),
-	}
-	for _, dir := range candidates {
-		if _, err := os.Stat(dir); err == nil {
-			fs, err := filesystem.New(dir)
-			if err != nil {
-				return erroring.New(err)
-			}
-			return fs
-		}
-	}
-	return erroring.New(fmt.Errorf("luci-config: could not find local configs in any of %s", candidates))
-}
-
-// authenticatedClient returns http.Client to use for making authenticated
-// request to the config service.
-//
-// The returned client uses GAE app's service account for authentication.
-func authenticatedClient(ctx context.Context) (*http.Client, error) {
-	t, err := auth.GetRPCTransport(ctx, auth.AsSelf)
-	if err != nil {
-		return nil, err
-	}
-	return &http.Client{Transport: t}, nil
-}