LogDog: Handle archive failures.

appengine/logdog/coordinator/logStream.go

Index: appengine/logdog/coordinator/logStream.go
diff --git a/appengine/logdog/coordinator/logStream.go b/appengine/logdog/coordinator/logStream.go
index 4285bd3e4f25dd4708d0e45025d41964cb9ca775..212bb3b55db5dd7de6cf94da54b763fd287330e6 100644
--- a/appengine/logdog/coordinator/logStream.go
+++ b/appengine/logdog/coordinator/logStream.go
@@ -32,6 +32,27 @@ const (
 	LSArchived
 )
 
+// ArchiveState is the state of archival. It is valid on log streams whose
+// log stream state is LSArchived.
+type ArchiveState int
+
+const (
+	// NotArchived is the default archive state, indicating that the log stream is
+	// not archived.
+	NotArchived ArchiveState = iota
+	// Archived indicates that the log stream was archived completely and
+	// successfully.
+	Archived
+	// ArchivedPartially indicates that the log stream has been archived, but that
+	// there are missing log stream entries. This will happen when the stream has
+	// exceeded an archival threshold without all of its log entries available
+	// in intermediate storage.
+	ArchivedPartially
+	// ArchivedWithErrors indicates that the log stream is in an archived state,
+	// but that there were errors. Archive files may be present in any state.
+	ArchivedWithErrors
+)
+
 // LogStream is the primary datastore model containing information and state of
 // an individual log stream.
 //
@@ -65,6 +86,10 @@ const (
 // changed through service endpoint methods.
 //
 // LogStream's QueryBase is authortative.
+//
+// TODO(dnj): Migration schema checklist. Next migration, we will want to...
+//	- Add schema version.
+//	- Remove State, ArchiveWhole in favor of "_Terminated" and "ArchiveState".
 type LogStream struct {
 	// Prefix is this log stream's prefix value. Log streams with the same prefix
 	// are logically grouped.
@@ -114,7 +139,12 @@ type LogStream struct {
 	Source []string
 
 	// TerminalIndex is the log stream index of the last log entry in the stream.
-	// If the value is -1, the log is still streaming.
+	//
+	// When the value is <0:
+	//	- If the log is not archived, this means that the stream is still
+	//	  streaming without a known terminal index.
+	//	- If the log is archived, it means that the stream's archival has
+	//	  completed, but had no log entries.
 	TerminalIndex int64 `gae:",noindex"`
 
 	// ArchiveIndexURL is the Google Storage URL where the log stream's index is
@@ -139,7 +169,17 @@ type LogStream struct {
 	ArchiveDataSize int64 `gae:",noindex"`
 	// ArchiveWhole is true if archival is complete and the archived log stream
 	// was not missing any entries.
+	//
+	// TODO(dnj): Next migration, deprecate this in favor of ArchiveState. For
+	// now, we will parallel it.
 	ArchiveWhole bool
+	// ArchiveState is the state of log stream archival.
+	ArchiveState ArchiveState
+	// ArchiveErrors is the number of errors encountered during archival. This
+	// will be incremented when incomplete archival is permitted, but the archival
+	// still failed due to an error (e.g., data corruption). If this exceeds a
+	// threshold, the stream may be marked archived even if the archival failed.
+	ArchiveErrors int
 
 	// _ causes datastore to ignore unrecognized fields and strip them in future
 	// writes.
@@ -353,10 +393,15 @@ func (s *LogStream) Terminated() bool {
 	return s.State >= LSTerminated
 }
 
-// Archived returns true if this stream has been archived. A stream is archived
-// if it has any of its archival properties set.
+// Streaming returns true if this log stream is still streaming without a known
+// terminal index.
+func (s *LogStream) Streaming() bool {
+	return (s.State == LSPending && s.TerminalIndex < 0)
+}
+
+// Archived returns true if this stream has been archived.
 func (s *LogStream) Archived() bool {
-	return s.State >= LSArchived
+	return (s.ArchiveState != NotArchived) || (s.State >= LSArchived)
 }
 
 // ArchiveMatches tests if the supplied Stream, Index, and Data archival URLs