Add server/cache support to gaeconfig.

appengine/gaeconfig/settings.go

Index: appengine/gaeconfig/settings.go
diff --git a/appengine/gaeconfig/settings.go b/appengine/gaeconfig/settings.go
deleted file mode 100644
index 74de730087c32d8f781a12f15a72cc0e8460edc6..0000000000000000000000000000000000000000
--- a/appengine/gaeconfig/settings.go
+++ /dev/null
@@ -1,144 +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/url"
-	"strconv"
-	"time"
-
-	"golang.org/x/net/context"
-
-	"github.com/luci/luci-go/server/settings"
-)
-
-// DefaultExpire is a reasonable default expiration value.
-const DefaultExpire = 10 * time.Minute
-
-// Settings are stored in the datastore via appengine/gaesettings package.
-type Settings struct {
-	// ConfigServiceURL is URL of luci-config service to fetch configs from.
-	ConfigServiceURL string `json:"config_service_url"`
-
-	// CacheExpirationSec is how long to hold configs in local cache.
-	CacheExpirationSec int `json:"cache_expiration_sec"`
-}
-
-// FetchCachedSettings fetches Settings from the settings store.
-//
-// Uses in-process global cache to avoid hitting datastore often. The cache
-// expiration time is 1 min (see gaesettings.expirationTime), meaning
-// the instance will refetch settings once a minute (blocking only one unlucky
-// request to do so).
-//
-// Returns errors only if there's no cached value (i.e. it is the first call
-// to this function in this process ever) and datastore operation fails.
-func FetchCachedSettings(c context.Context) (Settings, error) {
-	s := Settings{}
-	switch err := settings.Get(c, settingsKey, &s); err {
-	case nil:
-		return s, nil
-	case settings.ErrNoSettings:
-		return DefaultSettings(), nil
-	default:
-		return Settings{}, err
-	}
-}
-
-// DefaultSettings returns Settings to use if setting store is empty.
-func DefaultSettings() Settings {
-	return Settings{
-		CacheExpirationSec: int(DefaultExpire.Seconds()),
-	}
-}
-
-////////////////////////////////////////////////////////////////////////////////
-// UI for settings.
-
-// settingsKey is used internally to identify gaeconfig settings in settings
-// store.
-const settingsKey = "gaeconfig"
-
-type settingsUIPage struct {
-	settings.BaseUIPage
-}
-
-func (settingsUIPage) Title(c context.Context) (string, error) {
-	return "Configuration service settings", nil
-}
-
-func (settingsUIPage) Fields(c context.Context) ([]settings.UIField, error) {
-	return []settings.UIField{
-		{
-			ID:    "ConfigServiceURL",
-			Title: "Config service URL",
-			Type:  settings.UIFieldText,
-			Validator: func(v string) error {
-				if v != "" {
-					parsed, err := url.Parse(v)
-					if err != nil {
-						return fmt.Errorf("bad URL %q - %s", v, err)
-					}
-					if !parsed.IsAbs() || parsed.Path != "" {
-						return fmt.Errorf("bad URL %q - must be host root URL", v)
-					}
-					if parsed.Scheme != "https" {
-						return fmt.Errorf("bad URL %q - expecting https:// scheme", v)
-					}
-				}
-				return nil
-			},
-			Help: `<p>The application may fetch configuration files stored centrally
-in an instance of <a href="https://github.com/luci/luci-py/tree/master/appengine/config_service">luci-config</a>
-service. This is an URL of such service. If you don't know what this is, you
-probably don't use it and can keep this setting blank.</p>`,
-		},
-		{
-			ID:    "CacheExpirationSec",
-			Title: "Cache expiration, sec",
-			Type:  settings.UIFieldText,
-			Validator: func(v string) error {
-				if i, err := strconv.Atoi(v); err != nil || i < 0 {
-					return errors.New("expecting a non-negative integer")
-				}
-				return nil
-			},
-			Help: `<p>For better performance configuration files fetched from remote
-service are cached in memcache for specified amount of time. Set it to 0 to
-disable local cache.</p>`,
-		},
-	}, nil
-}
-
-func (settingsUIPage) ReadSettings(c context.Context) (map[string]string, error) {
-	s := DefaultSettings()
-	err := settings.GetUncached(c, settingsKey, &s)
-	if err != nil && err != settings.ErrNoSettings {
-		return nil, err
-	}
-	return map[string]string{
-		"ConfigServiceURL":   s.ConfigServiceURL,
-		"CacheExpirationSec": strconv.Itoa(s.CacheExpirationSec),
-	}, nil
-}
-
-func (settingsUIPage) WriteSettings(c context.Context, values map[string]string, who, why string) error {
-	modified := Settings{}
-	modified.ConfigServiceURL = values["ConfigServiceURL"]
-
-	var err error
-	modified.CacheExpirationSec, err = strconv.Atoi(values["CacheExpirationSec"])
-	if err != nil {
-		return err
-	}
-
-	return settings.SetIfChanged(c, settingsKey, &modified, who, why)
-}
-
-func init() {
-	settings.RegisterUIPage(settingsKey, settingsUIPage{})
-}