influxdb input: Use non-panicking type assertion

closes #1268

Author: sparrc

CHANGELOG.md

@@ -27,6 +27,7 @@ time before a new metric is included by the plugin.
 - [#1252](https://github.com/influxdata/telegraf/pull/1252): Fix systemd service. Thanks @zbindenren!
 - [#1221](https://github.com/influxdata/telegraf/pull/1221): Fix influxdb n_shards counter.
 - [#1258](https://github.com/influxdata/telegraf/pull/1258): Fix potential kernel plugin integer parse error.
+- [#1268](https://github.com/influxdata/telegraf/pull/1268): Fix potential influxdb input type assertion panic.
 
 ## v0.13.1 [2016-05-24]
 

plugins/inputs/influxdb/influxdb.go

@@ -157,43 +157,45 @@ func (i *InfluxDB) gatherURL(
 			return err
 		}
 
-		if key.(string) == "memstats" {
-			var m memstats
-			if err := dec.Decode(&m); err != nil {
-				continue
+		if keyStr, ok := key.(string); ok {
+			if keyStr == "memstats" {
+				var m memstats
+				if err := dec.Decode(&m); err != nil {
+					continue
+				}
+				acc.AddFields("influxdb_memstats",
+					map[string]interface{}{
+						"alloc":           m.Alloc,
+						"total_alloc":     m.TotalAlloc,
+						"sys":             m.Sys,
+						"lookups":         m.Lookups,
+						"mallocs":         m.Mallocs,
+						"frees":           m.Frees,
+						"heap_alloc":      m.HeapAlloc,
+						"heap_sys":        m.HeapSys,
+						"heap_idle":       m.HeapIdle,
+						"heap_inuse":      m.HeapInuse,
+						"heap_released":   m.HeapReleased,
+						"heap_objects":    m.HeapObjects,
+						"stack_inuse":     m.StackInuse,
+						"stack_sys":       m.StackSys,
+						"mspan_inuse":     m.MSpanInuse,
+						"mspan_sys":       m.MSpanSys,
+						"mcache_inuse":    m.MCacheInuse,
+						"mcache_sys":      m.MCacheSys,
+						"buck_hash_sys":   m.BuckHashSys,
+						"gc_sys":          m.GCSys,
+						"other_sys":       m.OtherSys,
+						"next_gc":         m.NextGC,
+						"last_gc":         m.LastGC,
+						"pause_total_ns":  m.PauseTotalNs,
+						"num_gc":          m.NumGC,
+						"gcc_pu_fraction": m.GCCPUFraction,
+					},
+					map[string]string{
+						"url": url,
+					})
 			}
-			acc.AddFields("influxdb_memstats",
-				map[string]interface{}{
-					"alloc":           m.Alloc,
-					"total_alloc":     m.TotalAlloc,
-					"sys":             m.Sys,
-					"lookups":         m.Lookups,
-					"mallocs":         m.Mallocs,
-					"frees":           m.Frees,
-					"heap_alloc":      m.HeapAlloc,
-					"heap_sys":        m.HeapSys,
-					"heap_idle":       m.HeapIdle,
-					"heap_inuse":      m.HeapInuse,
-					"heap_released":   m.HeapReleased,
-					"heap_objects":    m.HeapObjects,
-					"stack_inuse":     m.StackInuse,
-					"stack_sys":       m.StackSys,
-					"mspan_inuse":     m.MSpanInuse,
-					"mspan_sys":       m.MSpanSys,
-					"mcache_inuse":    m.MCacheInuse,
-					"mcache_sys":      m.MCacheSys,
-					"buck_hash_sys":   m.BuckHashSys,
-					"gc_sys":          m.GCSys,
-					"other_sys":       m.OtherSys,
-					"next_gc":         m.NextGC,
-					"last_gc":         m.LastGC,
-					"pause_total_ns":  m.PauseTotalNs,
-					"num_gc":          m.NumGC,
-					"gcc_pu_fraction": m.GCCPUFraction,
-				},
-				map[string]string{
-					"url": url,
-				})
 		}
 
 		// Attempt to parse a whole object into a point.