LogDog: Add log rendering view.

appengine/logdog/coordinator/service.go

Index: appengine/logdog/coordinator/service.go
diff --git a/appengine/logdog/coordinator/service.go b/appengine/logdog/coordinator/service.go
index 660293f369eabeb116da508156d0ac1247a5319f..475c72af03298a08f5509cd80662a50c564a581f 100644
--- a/appengine/logdog/coordinator/service.go
+++ b/appengine/logdog/coordinator/service.go
@@ -9,6 +9,7 @@ import (
 	"github.com/luci/luci-go/common/gcloud/gs"
 	log "github.com/luci/luci-go/common/logging"
 	"github.com/luci/luci-go/server/logdog/storage"
+	"github.com/luci/luci-go/server/logdog/storage/archive"
 	"golang.org/x/net/context"
 )
 
@@ -59,3 +60,38 @@ func (s *Service) GSClient(c context.Context) (gs.Client, error) {
 	}
 	return gsc, nil
 }
+
+// GetLogStreamStorage returns the Storage instance to use for a given
+// LogStream. The caller is responsible for calling Close on the returned
+// Storage instance if successful.
+func (s *Service) GetLogStreamStorage(c context.Context, ls *LogStream) (storage.Storage, error) {
+	if !ls.Archived() {
+		log.Debugf(c, "Log is not archived. Fetching from intermediate storage.")
+
+		// Logs are not archived. Fetch from intermediate storage.
+		return s.Storage(c)
+	}
+
+	log.Debugf(c, "Log is archived. Fetching from archive storage.")
+	gs, err := s.GSClient(c)
+	if err != nil {
+		log.WithError(err).Errorf(c, "Failed to create Google Storage client.")
+		return nil, err
+	}
+	defer func() {
+		if err := gs.Close(); err != nil {
+			log.WithError(err).Warningf(c, "Failed to close Google Storage client.")
+		}
+	}()
+
+	st, err := archive.New(c, archive.Options{
+		IndexURL:  ls.ArchiveIndexURL,
+		StreamURL: ls.ArchiveStreamURL,
+		Client:    gs,
+	})
+	if err != nil {
+		log.WithError(err).Errorf(c, "Failed to create Google Storage storage instance.")
+		return nil, err
+	}
+	return st, nil
+}