Add container health metrics to docker input (#3666)

plugins/inputs/docker/README.md

@@ -199,6 +199,9 @@ based on the availability of per-cpu stats on your system.
     - network
 - docker_container_blkio specific:
     - device
+- docker_container_health specific:
+    - health_status
+    - failing_streak
 - docker_swarm specific:
     - service_id
     - service_name
@@ -257,4 +260,4 @@ io_serviced_recursive_total=6599i,io_serviced_recursive_write=107i 1453409536840
 >docker_swarm,
 service_id=xaup2o9krw36j2dy1mjx1arjw,service_mode=replicated,service_name=test,\
 tasks_desired=3,tasks_running=3 1508968160000000000
-```
+```

plugins/inputs/docker/docker.go

@@ -391,12 +391,13 @@ func (d *Docker) gatherContainer(
 		}
 	}
 
+	info, err := d.client.ContainerInspect(ctx, container.ID)
+	if err != nil {
+		return fmt.Errorf("Error inspecting docker container: %s", err.Error())
+	}
+
 	// Add whitelisted environment variables to tags
 	if len(d.TagEnvironment) > 0 {
-		info, err := d.client.ContainerInspect(ctx, container.ID)
-		if err != nil {
-			return fmt.Errorf("Error inspecting docker container: %s", err.Error())
-		}
 		for _, envvar := range info.Config.Env {
 			for _, configvar := range d.TagEnvironment {
 				dock_env := strings.SplitN(envvar, "=", 2)
@@ -408,6 +409,14 @@ func (d *Docker) gatherContainer(
 		}
 	}
 
+	if info.State.Health != nil {
+		healthfields := map[string]interface{}{
+			"health_status":  info.State.Health.Status,
+			"failing_streak": info.ContainerJSONBase.State.Health.FailingStreak,
+		}
+		acc.AddFields("docker_container_health", healthfields, tags, time.Now())
+	}
+
 	gatherContainerStats(v, acc, tags, container.ID, d.PerDevice, d.Total, daemonOSType)
 
 	return nil

plugins/inputs/docker/docker_testdata.go

@@ -477,4 +477,12 @@ var containerInspect = types.ContainerJSON{
 			"PATH=/bin:/sbin",
 		},
 	},
+	ContainerJSONBase: &types.ContainerJSONBase{
+		State: &types.ContainerState{
+			Health: &types.Health{
+				FailingStreak: 1,
+				Status:        "Unhealthy",
+			},
+		},
+	},
 }