From 8c06b36013a7276fc55ac9c00fe73cf7c7c54e9e Mon Sep 17 00:00:00 2001
From: Florian Forster <ff@octo.it>
Date: Mon, 29 Jan 2018 10:53:30 +0100
Subject: [PATCH] Don't use context.Background().

AppEngine panics when you use a non-AppEngine context. Instead, we need
to load the config at request time.
---
 app/config.go | 10 ++++++++++
 kraftakt.go   | 18 ++++++++++++++----
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/app/config.go b/app/config.go
index f05a9e6..5b2d867 100644
--- a/app/config.go
+++ b/app/config.go
@@ -2,6 +2,7 @@ package app
 
 import (
 	"context"
+	"sync"
 
 	"google.golang.org/appengine/datastore"
 	"google.golang.org/appengine/log"
@@ -18,7 +19,16 @@ var Config struct {
 	GoogleClientSecret string
 }
 
+var mu sync.Mutex
+
 func LoadConfig(ctx context.Context) error {
+	mu.Lock()
+	defer mu.Unlock()
+
+	if Config.ProjectNumber != "" {
+		return nil
+	}
+
 	key := datastore.NewKey(ctx, "Config", "Production", 0, nil)
 	if err := datastore.Get(ctx, key, &Config); err != nil {
 		log.Errorf(ctx, `datastore.Get("Config", "Production") = %v`, err)
diff --git a/kraftakt.go b/kraftakt.go
index 69815c2..66668a6 100644
--- a/kraftakt.go
+++ b/kraftakt.go
@@ -28,10 +28,6 @@ func init() {
 	http.HandleFunc("/google/setup", googleSetupHandler)
 	http.Handle("/google/grant", AuthenticatedHandler(googleGrantHandler))
 	http.Handle("/", AuthenticatedHandler(indexHandler))
-
-	if err := app.LoadConfig(context.Background()); err != nil {
-		panic(err)
-	}
 }
 
 // ContextHandler implements http.Handler
@@ -40,6 +36,11 @@ type ContextHandler func(context.Context, http.ResponseWriter, *http.Request) er
 func (hndl ContextHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	ctx := appengine.NewContext(r)
 
+	if err := app.LoadConfig(ctx); err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
 	if err := hndl(ctx, w, r); err != nil {
 		http.Error(w, err.Error(), http.StatusInternalServerError)
 		return
@@ -51,6 +52,11 @@ type AuthenticatedHandler func(context.Context, http.ResponseWriter, *http.Reque
 func (hndl AuthenticatedHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	ctx := appengine.NewContext(r)
 
+	if err := app.LoadConfig(ctx); err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
 	gaeUser := user.Current(ctx)
 	if gaeUser == nil {
 		url, err := user.LoginURL(ctx, r.URL.String())
@@ -206,6 +212,10 @@ func fitbitNotifyHandler(ctx context.Context, w http.ResponseWriter, r *http.Req
 // handleNotifications parses fitbit notifications and requests the individual
 // activities from Fitbit. It is executed asynchronously via the delay package.
 func handleNotifications(ctx context.Context, payload []byte) error {
+	if err := app.LoadConfig(ctx); err != nil {
+		return err
+	}
+
 	var subscriptions []fitbit.Subscription
 	if err := json.Unmarshal(payload, &subscriptions); err != nil {
 		return err
-- 
2.11.0