fix panics in manager

internals/overlord/logstate/fake.go

@@ -37,5 +37,7 @@ func (c *bufferingClient) Flush() error {
 	for _, entry := range c.entries {
 		fmt.Printf("%v [%s] %s", entry.Time, entry.Service, entry.Message)
 	}
+	fmt.Println()
+	c.entries = c.entries[:0]
 	return nil
 }

internals/overlord/logstate/manager.go

@@ -35,6 +35,7 @@ func NewLogManager() *LogManager {
 	return &LogManager{
 		gatherers:   map[string]*logGatherer{},
 		newGatherer: newLogGatherer,
+		buffers:     map[string]*servicelog.RingBuffer{},
 	}
 }
 
@@ -78,8 +79,10 @@ func (m *LogManager) PlanChanged(pl *plan.Plan) {
 					buffer, ok := m.buffers[service.Name]
 					if ok {
 						iterator = buffer.TailIterator()
-						parser := servicelog.NewParser(iterator, parserSize)
+						iterator.Notify(gatherer.notifyChan)
 						newIterators[service.Name] = iterator
+
+						parser := servicelog.NewParser(iterator, parserSize)
 						newParsers[service.Name] = parser
 					}
 				} else {
@@ -110,11 +113,18 @@ func (m *LogManager) ServiceStarted(service *plan.Service, buffer *servicelog.Ri
 	m.buffers[service.Name] = buffer
 	for _, target := range m.plan.LogTargets {
 		if service.LogsTo(target) {
-			gatherer := m.gatherers[service.Name]
+			gatherer := m.gatherers[target.Name]
+			if gatherer == nil {
+				logger.Noticef("Internal error: couldn't find gatherer for target %q", target.Name)
+				continue
+			}
+
 			gatherer.itLock.Lock()
 			iterator := buffer.TailIterator()
-			parser := servicelog.NewParser(iterator, parserSize)
+			iterator.Notify(gatherer.notifyChan)
 			gatherer.iterators[service.Name] = iterator
+
+			parser := servicelog.NewParser(iterator, parserSize)
 			gatherer.parsers[service.Name] = parser
 			gatherer.itLock.Unlock()
 		}