Add UseFlex(c) for the cloud implementation.

impl/cloud/context.go

 // 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 cloud
 
 import (
+        "fmt"
+
         "github.com/luci/gae/impl/dummy"
+        "github.com/luci/gae/impl/memory"
         ds "github.com/luci/gae/service/datastore"
         "github.com/luci/gae/service/mail"
         mc "github.com/luci/gae/service/memcache"
         "github.com/luci/gae/service/module"
         "github.com/luci/gae/service/taskqueue"
         "github.com/luci/gae/service/user"
 
+        "cloud.google.com/go/compute/metadata"
         "cloud.google.com/go/datastore"
         "github.com/bradfitz/gomemcache/memcache"
 
         "golang.org/x/net/context"
 )
 
 // Config is a full-stack cloud service configuration. A user can selectively
 // populate its fields, and services for the populated fields will be installed
 // in the Context and available.
 //
@@ skipping 18 matching lines @@
         // Dummy services that we don't support.
         c = mail.Set(c, dummy.Mail())
         c = module.Set(c, dummy.Module())
         c = taskqueue.SetRaw(c, dummy.TaskQueue())
         c = user.Set(c, dummy.User())
 
         c = useInfo(c)
 
         // datastore service
         if cfg.DS != nil {
-                c = UseDatastore(c, cfg.DS)
+                cds := cloudDatastore{
+                        client: cfg.DS,
+                }
+                c = cds.use(c)
         } else {
                 c = ds.SetRaw(c, dummy.Datastore())
         }
 
         // memcache service
         if cfg.MC != nil {
                 mc := memcacheClient{
                         client: cfg.MC,
                 }
                 c = mc.use(c)
         } else {
                 c = mc.SetRaw(c, dummy.Memcache())
         }
 
         return c
 }
 
-// UseDatastore installs a datastore implementation into the context.
-func UseDatastore(c context.Context, client *datastore.Client) context.Context {
+// UseFlex installs a set of cloud services into the context with services
+// supported by AppEngine Flex, including:
+// * Info
+// * Datastore
+func UseFlex(c context.Context) context.Context {
+        // Flex is on GCE, so we can get the project ID from the metadata server.
+        project, err := metadata.Get("project/project-id")
+        if err != nil {
+                panic(fmt.Errorf("could not get project ID, not on GCE? %s", err.Error()))
+        }
+        // Use the memory implementation of Info.
+        c = memory.UseInfo(c, project)
+        // Create a datastore client.
+        client, err := datastore.NewClient(c, project)
+        if err != nil {
+                panic(err)
+        }
         cds := cloudDatastore{
                 client: client,
         }
         return cds.use(c)
 }