plugins/traffic-control: add status information in metadata

This patch sends the delay and packet loss values along with
the container metadata. In this way the user has a direct feedback
about the traffic control plugin status.

examples/plugins/traffic-control/report.go

@@ -13,12 +13,23 @@ type report struct {
 }
 
 type topology struct {
-	Nodes    map[string]node    `json:"nodes"`
-	Controls map[string]control `json:"controls"`
+	Nodes             map[string]node             `json:"nodes"`
+	Controls          map[string]control          `json:"controls"`
+	MetadataTemplates map[string]metadataTemplate `json:"metadata_templates,omitempty"`
+}
+
+type metadataTemplate struct {
+	ID       string  `json:"id"`
+	Label    string  `json:"label,omitempty"`    // Human-readable descriptor for this row
+	Truncate int     `json:"truncate,omitempty"` // If > 0, truncate the value to this length.
+	Datatype string  `json:"dataType,omitempty"`
+	Priority float64 `json:"priority,omitempty"`
+	From     string  `json:"from,omitempty"` // Defines how to get the value from a report node
 }
 
 type node struct {
 	LatestControls map[string]controlEntry `json:"latestControls,omitempty"`
+	Latest         map[string]stringEntry  `json:"latest,omitempty"`
 }
 
 type controlEntry struct {
@@ -37,6 +48,11 @@ type control struct {
 	Rank  int    `json:"rank"`
 }
 
+type stringEntry struct {
+	Timestamp time.Time `json:"timestamp"`
+	Value     string    `json:"value"`
+}
+
 type pluginSpec struct {
 	ID          string   `json:"id"`
 	Label       string   `json:"label"`
@@ -58,8 +74,9 @@ func NewReporter(store *Store) *Reporter {
 func (r *Reporter) RawReport() ([]byte, error) {
 	rpt := &report{
 		Container: topology{
-			Nodes:    r.getContainerNodes(),
-			Controls: getTrafficControls(),
+			Nodes:             r.getContainerNodes(),
+			Controls:          getTrafficControls(),
+			MetadataTemplates: getMetadataTemplate(),
 		},
 		Plugins: []pluginSpec{
 			{
@@ -120,14 +137,34 @@ func (r *Reporter) getContainerNodes() map[string]node {
 			fallthrough
 		case Running:
 			nodeID := containerIDToNodeID(containerID)
+			latency, _ := getLatency(container.PID)
 			nodes[nodeID] = node{
 				LatestControls: getTrafficNodeControls(timestamp, dead),
+				Latest: map[string]stringEntry{
+					"traffic-control-latency": {
+						Timestamp: timestamp,
+						Value:     latency,
+					},
+				},
 			}
 		}
 	})
 	return nodes
 }
 
+func getMetadataTemplate() map[string]metadataTemplate {
+	return map[string]metadataTemplate{
+		"traffic-control-latency": metadataTemplate{
+			ID:       "traffic-control-latency",
+			Label:    "Latency",
+			Truncate: 0,
+			Datatype: "",
+			Priority: 13.5,
+			From:     "latest",
+		},
+	}
+}
+
 func getTrafficNodeControls(timestamp time.Time, dead bool) map[string]controlEntry {
 	controls := map[string]controlEntry{}
 	entry := controlEntry{

examples/plugins/traffic-control/tc.go

@@ -46,6 +46,67 @@ func DoTrafficControl(pid int, delay uint32) error {
 	return nil
 }
 
+func getLatency(pid int) (string, error) {
+	output := "-"
+	var err error
+	if output, err = getStatus(pid); err != nil {
+		return "-", err
+	} else if output == "" {
+		return "-", fmt.Errorf("Error: output is empty")
+	}
+	outputSplited := split(output)
+	for i, s := range outputSplited {
+		if s == "delay" {
+			if i < len(outputSplited)-1 {
+				output = outputSplited[i+1]
+			} else {
+				output = "-"
+			}
+			return output, nil
+		}
+	}
+	return output, fmt.Errorf("delay not found")
+}
+
+func getPktLoss(pid int) (string, error) {
+	output := "-"
+	var err error
+	if output, err = getStatus(pid); err != nil {
+		return "-", err
+	} else if output == "" {
+		return "-", fmt.Errorf("Error: output is empty")
+	}
+	outputSplited := split(output)
+	for i, s := range outputSplited {
+		if s == "loss" {
+			if i < len(outputSplited)-1 {
+				output = outputSplited[i+1]
+			} else {
+				output = "-"
+			}
+			return output, nil
+		}
+	}
+	return output, fmt.Errorf("delay not found")
+}
+
+func getStatus(pid int) (string, error) {
+	cmd := split("tc qdisc show dev eth0")
+	netNS := fmt.Sprintf("/proc/%d/ns/net", pid)
+	var output string
+	err := ns.WithNetNSPath(netNS, func(hostNS ns.NetNS) error {
+		if cmdOut, err := exec.Command(cmd[0], cmd[1:]...).CombinedOutput(); err != nil {
+			log.Error(string(cmdOut))
+			output = "-"
+			return fmt.Errorf("failed to execute command: tc qdisc show dev eth0: %v", err)
+		} else {
+			output = string(cmdOut)
+		}
+		return nil
+	})
+	return output, err
+}
+
 func split(cmd string) []string {
 	return strings.Split(cmd, " ")
 }