LogDog: enable services to fetch project configs

server/internal/logdog/service/service.go

Index: server/internal/logdog/service/service.go
diff --git a/server/internal/logdog/service/service.go b/server/internal/logdog/service/service.go
index b3d5874eec9d1c9c4f5fca65424e8f65e8c0953e..0850cf501e52bc3f0a5197fe08c1412e9fc1d903 100644
--- a/server/internal/logdog/service/service.go
+++ b/server/internal/logdog/service/service.go
@@ -14,10 +14,12 @@ import (
 	"path/filepath"
 	"runtime/pprof"
 	"sync/atomic"
+	"time"
 
 	"github.com/luci/luci-go/client/authcli"
 	"github.com/luci/luci-go/common/api/logdog_coordinator/services/v1"
 	"github.com/luci/luci-go/common/auth"
+	luciConfig "github.com/luci/luci-go/common/config"
 	"github.com/luci/luci-go/common/gcloud/gs"
 	log "github.com/luci/luci-go/common/logging"
 	"github.com/luci/luci-go/common/logging/gologger"
@@ -32,6 +34,7 @@ import (
 	"github.com/luci/luci-go/server/logdog/storage/bigtable"
 	"golang.org/x/net/context"
 	"google.golang.org/cloud"
+	"google.golang.org/cloud/compute/metadata"
 )
 
 var (
@@ -49,6 +52,10 @@ var (
 		"Set to one when service is present and ready. Alert on missing values.")
 )
 
+// projectConfigCacheDuration is the amount of time to cache a project's
+// configuration before reloading.
+const projectConfigCacheDuration = 30 * time.Minute
+
 // Service is a base class full of common LogDog service application parameters.
 type Service struct {
 	// Name is the name of this service. It is used for logging, metrics, and
@@ -68,12 +75,15 @@ type Service struct {
 
 	coordinatorHost           string
 	coordinatorInsecure       bool
+	projectID                 string
 	storageCredentialJSONPath string
 	cpuProfilePath            string
 	heapProfilePath           string
 
 	coord  logdog.ServicesClient
 	config *config.Manager
+
+	onGCE bool
 }
 
 // Run performs service-wide initialization and invokes the specified run
@@ -141,6 +151,17 @@ func (s *Service) runImpl(c context.Context, f func(context.Context) error) erro
 		}()
 	}
 
+	// Are we running on a GCE intance?
+	if err := s.probeGCEEnvironment(c); err != nil {
+		log.WithError(err).Errorf(c, "Failed to probe GCE environment.")
+		return err
+	}
+
+	// Validate the runtime environment.
+	if s.projectID == "" {
+		return errors.New("no project ID was configured")
+	}
+
 	// Configure our signal handler. It will listen for terminating signals and
 	// issue a shutdown signal if one is received.
 	signalC := make(chan os.Signal)
@@ -221,6 +242,10 @@ func (s *Service) addFlags(c context.Context, fs *flag.FlagSet) {
 	s.authFlags.Register(fs, auth.Options{})
 	s.configFlags.AddToFlagSet(fs)
 
+	fs.StringVar(&s.projectID, "project-id", "",
+		"Specify the cloud project ID that this instance is supporting. If empty, the project ID "+

[nodir, 2016/05/18 16:25:51]

Please rename to "app-id". Gcp SDK calls it "app" too 

[dnj (Google), 2016/05/18 16:50:31]

I'm using the luci-config concept here, not the GAE one.

[nodir, 2016/05/18 17:02:19]

Then why it says cloud project and why this flag is mapped to a field which is
populated with GCE metadata. I think it is so confusing even you confuse it

+			"will attempt to be resolved by probing the local environment. This probably will match the "+
+			"App ID of the Coordinator.")
 	fs.StringVar(&s.coordinatorHost, "coordinator", "",
 		"The Coordinator service's [host][:port].")
 	fs.BoolVar(&s.coordinatorInsecure, "coordinator-insecure", false,
@@ -233,6 +258,28 @@ func (s *Service) addFlags(c context.Context, fs *flag.FlagSet) {
 		"If supplied, enable CPU profiling and write the profile here.")
 }
 
+// probeGCEEnvironment fills in any parameters that can be probed from Google
+// Compute Engine metadata.
+//
+// If we're not running on GCE, this will return nil. An error will only be
+// returned if an operation that is expected to work fails.
+func (s *Service) probeGCEEnvironment(c context.Context) error {
+	s.onGCE = metadata.OnGCE()
+	if !s.onGCE {
+		return nil
+	}
+
+	// Determine our project ID.
+	if s.projectID == "" {
+		var err error
+		if s.projectID, err = metadata.ProjectID(); err != nil {
+			log.WithError(err).Errorf(c, "Failed to probe GCE project ID.")
+			return err
+		}
+	}
+	return nil
+}
+
 func (s *Service) initCoordinatorClient(c context.Context) (logdog.ServicesClient, error) {
 	if s.coordinatorHost == "" {
 		log.Errorf(c, "Missing Coordinator URL (-coordinator).")
@@ -275,6 +322,8 @@ func (s *Service) initConfig(c context.Context) (*config.Manager, error) {
 		log.WithError(err).Errorf(c, "Failed to load configuration parameters.")
 		return nil, err
 	}
+	o.ProjectID = s.projectID
+	o.ProjectConfigCacheDuration = projectConfigCacheDuration
 	o.KillFunc = s.shutdown
 
 	return config.NewManager(c, *o)
@@ -303,11 +352,25 @@ func (s *Service) Config() *svcconfig.Config {
 	return s.config.Config()
 }
 
+// ProjectConfig returns the cached project configuration.
+//
+// If the project configuration is not available, nil will be returned.
+func (s *Service) ProjectConfig(c context.Context, proj luciConfig.ProjectName) (*svcconfig.ProjectConfig, error) {
+	return s.config.ProjectConfig(c, proj)
+}
+
 // Coordinator returns the cached Coordinator client.
 func (s *Service) Coordinator() logdog.ServicesClient {
 	return s.coord
 }
 
+// ProjectID returns the project ID.
+//
+// This is synonymous with the AppEngine "app ID".
+func (s *Service) ProjectID() string {
+	return s.projectID
+}
+
 // IntermediateStorage instantiates the configured intermediate Storage
 // instance.
 func (s *Service) IntermediateStorage(c context.Context) (storage.Storage, error) {