Add --follow to journald ctr logging

Signed-off-by: Peter Hunt <pehunt@redhat.com>

docs/podman-logs.1.md

@@ -23,8 +23,6 @@ Note: If you are following a container which is removed `podman container rm`
 or removed on exit `podman run --rm ...`, then there is a chance the the log
 file will be removed before `podman logs` reads the final content.
 
-Also note: **--follow** is not currently supported when the container's log driver is journald
-
 **--latest, -l**
 
 Instead of providing the container name or ID, use the last created container. If you use methods other than Podman

libpod/container_log.go

@@ -63,9 +63,6 @@ func (c *Container) ReadLog(options *LogOptions, logChannel chan *LogLine) error
 	// TODO Skip sending logs until journald logs can be read
 	// TODO make this not a magic string
 	if c.LogDriver() == JournaldLogging {
-		if options.Follow {
-			return errors.Errorf("The follow option with journald logging is not currently supported")
-		}
 		return c.readFromJournal(options, logChannel)
 	}
 	return c.readFromLogFile(options, logChannel)

libpod/container_log_linux.go

@@ -57,6 +57,20 @@ func (c *Container) readFromJournal(options *LogOptions, logChannel chan *LogLin
 		r.Rewind()
 	}
 
+	if options.Follow {
+		go func() {
+			follower := FollowBuffer{logChannel}
+			err := r.Follow(nil, follower)
+			if err != nil {
+				logrus.Debugf(err.Error())
+			}
+			r.Close()
+			options.WaitGroup.Done()
+			return
+		}()
+		return nil
+	}
+
 	go func() {
 		bytes := make([]byte, bufLen)
 		// /me complains about no do-while in go
@@ -84,8 +98,8 @@ func (c *Container) readFromJournal(options *LogOptions, logChannel chan *LogLin
 
 func journalFormatter(entry *journal.JournalEntry) (string, error) {
 	usec := entry.RealtimeTimestamp
-	timestamp := time.Unix(0, int64(usec)*int64(time.Microsecond))
-	output := timestamp.Format(logTimeFormat) + " "
+	tsString := time.Unix(0, int64(usec)*int64(time.Microsecond)).Format(logTimeFormat)
+	output := fmt.Sprintf("%s ", tsString)
 	priority, ok := entry.Fields["PRIORITY"]
 	if !ok {
 		return "", errors.Errorf("no PRIORITY field present in journal entry")
@@ -113,3 +127,17 @@ func journalFormatter(entry *journal.JournalEntry) (string, error) {
 	output += strings.TrimSpace(msg)
 	return output, nil
 }
+
+type FollowBuffer struct {
+	logChannel chan *LogLine
+}
+
+func (f FollowBuffer) Write(p []byte) (int, error) {
+	bytestr := string(p)
+	logLine, err := newLogLine(bytestr)
+	if err != nil {
+		return -1, err
+	}
+	f.logChannel <- logLine
+	return len(p), nil
+}