Fix panic when droppping measurement while writing to it concurrently

Fixes #2608

CHANGELOG.md

@@ -42,6 +42,7 @@
 - [#3155](https://github.com/influxdb/influxdb/pull/3155): Instantiate UDP batcher before listening for UDP traffic, otherwise a panic may result.
 - [#2678](https://github.com/influxdb/influxdb/issues/2678): Server allows tags with an empty string for the key and/or value
 - [#3061](https://github.com/influxdb/influxdb/issues/3061): syntactically incorrect line protocol insert panics the database
+- [#2608](https://github.com/influxdb/influxdb/issues/2608): drop measurement while writing points to that measurement has race condition that can panic
 
 ## v0.9.0 [2015-06-11]
 

tsdb/shard.go

@@ -243,6 +243,12 @@ func (s *Shard) WritePoints(points []Point) error {
 			s.mu.RLock()
 			mf := s.measurementFields[p.Name()]
 			s.mu.RUnlock()
+
+			// If a measurement is dropped while writes for it are in progress, this could be nil
+			if mf == nil {
+				return ErrFieldNotFound
+			}
+
 			data, err := mf.codec.EncodeFields(p.Fields())
 			if err != nil {
 				return err