LogDog: Update to archival V2.

appengine/logdog/coordinator/logStream_migrate.go

Index: appengine/logdog/coordinator/logStream_migrate.go
diff --git a/appengine/logdog/coordinator/logStream_migrate.go b/appengine/logdog/coordinator/logStream_migrate.go
new file mode 100644
index 0000000000000000000000000000000000000000..d1d7c26b87e093ec142bff7079ee640294014426
--- /dev/null
+++ b/appengine/logdog/coordinator/logStream_migrate.go
@@ -0,0 +1,81 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package coordinator
+
+import (
+	"fmt"
+	"time"
+
+	ds "github.com/luci/gae/service/datastore"
+)
+
+func (s *LogStream) migrateSchema() error {
+	switch s.Schema {
+	case "":
+		// Pre-schema versioned schema. Migrate to "1".
+		//
+		// To do this, we:
+		// - See if the ArchiveWhole property is available. If it is, we set the
+		//   ArchiveLogEntryCount to equal TerminalIndex+1. Otherwise, we leave
+		//   ArchiveLogEntryCount at zero, as there is no (easy) way to determine
+		//   its value.
+
+		// Determine archival state.
+		if s.Archived() {
+			switch props := s.extra["ArchiveWhole"]; len(props) {
+			case 0:
+				break
+
+			case 1:
+				if v, ok := props[0].Value().(bool); ok && v {
+					s.ArchiveLogEntryCount = s.TerminalIndex + 1
+				}
+
+			default:
+				return fmt.Errorf("pre-schema ArchiveWhole has %d values", len(props))
+			}
+		}
+
+		// Backfill time based on state.
+		switch {
+		case s.Archived():
+			if dt := dateTimeProp(s.extra["ArchivedTime"]); dt.IsZero() {
+				s.ArchivedTime = s.Created
+			}
+			fallthrough
+
+		case s.Terminated():
+			if dt := dateTimeProp(s.extra["TerminatedTime"]); dt.IsZero() {
+				s.TerminatedTime = s.Created
+			}
+			fallthrough
+
+		default:
+			break
+		}
+
+		// Migration complete!
+		s.Schema = currentLogStreamSchema
+		fallthrough
+
+	case currentLogStreamSchema:
+		return nil
+
+	default:
+		return fmt.Errorf("unrecognized log stream schema %q", s.Schema)
+	}
+}
+
+// dateTimeProp returns the time.Time value of a single-property slice, or
+// a zero time.Time if the slice wasn't single-value or didn't contain a
+// time.Time.
+func dateTimeProp(props []ds.Property) time.Time {
+	if len(props) == 1 {
+		if t, ok := props[0].Value().(time.Time); ok {
+			return t
+		}
+	}
+	return time.Time{}
+}