Strip container_version from container_image tag

closes #1413

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ### Features
 
+- [#1413](https://github.com/influxdata/telegraf/issues/1413): Separate container_version from container_image tag.
+
 ### Bugfixes
 
 - [#1519](https://github.com/influxdata/telegraf/pull/1519): Fix error race conditions and partial failures.

plugins/inputs/docker/docker.go

@@ -207,9 +207,18 @@ func (d *Docker) gatherContainer(
 		cname = strings.TrimPrefix(container.Names[0], "/")
 	}
 
+	// the image name sometimes has a version part.
+	//   ie, rabbitmq:3-management
+	imageParts := strings.Split(container.Image, ":")
+	imageName := imageParts[0]
+	imageVersion := "unknown"
+	if len(imageParts) > 1 {
+		imageVersion = imageParts[1]
+	}
 	tags := map[string]string{
-		"container_name":  cname,
-		"container_image": container.Image,
+		"container_name":    cname,
+		"container_image":   imageName,
+		"container_version": imageVersion,
 	}
 	if len(d.ContainerNames) > 0 {
 		if !sliceContains(cname, d.ContainerNames) {

plugins/inputs/docker/docker_test.go

@@ -378,9 +378,10 @@ func TestDockerGatherInfo(t *testing.T) {
 			"container_id": "b7dfbb9478a6ae55e237d4d74f8bbb753f0817192b5081334dc78476296e2173",
 		},
 		map[string]string{
-			"container_name":  "etcd2",
-			"container_image": "quay.io/coreos/etcd:v2.2.2",
-			"cpu":             "cpu3",
+			"container_name":    "etcd2",
+			"container_image":   "quay.io/coreos/etcd",
+			"cpu":               "cpu3",
+			"container_version": "v2.2.2",
 		},
 	)
 	acc.AssertContainsTaggedFields(t,
@@ -423,8 +424,9 @@ func TestDockerGatherInfo(t *testing.T) {
 			"container_id":              "b7dfbb9478a6ae55e237d4d74f8bbb753f0817192b5081334dc78476296e2173",
 		},
 		map[string]string{
-			"container_name":  "etcd2",
-			"container_image": "quay.io/coreos/etcd:v2.2.2",
+			"container_name":    "etcd2",
+			"container_image":   "quay.io/coreos/etcd",
+			"container_version": "v2.2.2",
 		},
 	)