Add config for exporting container metrics to prom

This adds an option for the cgroups monitor to include container metrics
in the prometheus output.  We will have to use the plugin to emit oom
events via the events service but when the `no_prom` setting is set for
the plugin container metrics will not be included in the prom output.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

metrics/cgroups/blkio.go

@@ -3,6 +3,8 @@
 package cgroups
 
 import (
+	"strconv"
+
 	"github.com/containerd/cgroups"
 	metrics "github.com/docker/go-metrics"
 	"github.com/prometheus/client_golang/prometheus"
@@ -101,3 +103,14 @@ var blkioMetrics = []*metric{
 		},
 	},
 }
+
+func blkioValues(l []*cgroups.BlkIOEntry) []value {
+	var out []value
+	for _, e := range l {
+		out = append(out, value{
+			v: float64(e.Value),
+			l: []string{e.Op, e.Device, strconv.FormatUint(e.Major, 10), strconv.FormatUint(e.Minor, 10)},
+		})
+	}
+	return out
+}

metrics/cgroups/cgroups.go

@@ -15,24 +15,33 @@ import (
 	"golang.org/x/net/context"
 )
 
+type Config struct {
+	NoPrometheus bool `toml:"no_prometheus"`
+}
+
 func init() {
 	plugin.Register(&plugin.Registration{
-		Type: plugin.TaskMonitorPlugin,
-		ID:   "cgroups",
-		Init: New,
+		Type:   plugin.TaskMonitorPlugin,
+		ID:     "cgroups",
+		Init:   New,
+		Config: &Config{},
 	})
 }
 
 func New(ic *plugin.InitContext) (interface{}, error) {
-	var (
-		ns        = metrics.NewNamespace("container", "", nil)
-		collector = NewCollector(ns)
-	)
+	var ns *metrics.Namespace
+	config := ic.Config.(*Config)
+	if !config.NoPrometheus {
+		ns = metrics.NewNamespace("container", "", nil)
+	}
+	collector := NewCollector(ns)
 	oom, err := NewOOMCollector(ns)
 	if err != nil {
 		return nil, err
 	}
-	metrics.Register(ns)
+	if ns != nil {
+		metrics.Register(ns)
+	}
 	return &cgroupsMonitor{
 		collector: collector,
 		oom:       oom,

metrics/cgroups/metrics.go

@@ -5,7 +5,6 @@ package cgroups
 import (
 	"errors"
 	"fmt"
-	"strconv"
 	"sync"
 
 	"github.com/containerd/cgroups"
@@ -26,6 +25,9 @@ type Trigger func(string, string, cgroups.Cgroup)
 // New registers the Collector with the provided namespace and returns it so
 // that cgroups can be added for collection
 func NewCollector(ns *metrics.Namespace) *Collector {
+	if ns == nil {
+		return &Collector{}
+	}
 	// add machine cpus and memory info
 	c := &Collector{
 		ns:      ns,
@@ -91,6 +93,9 @@ func (c *Collector) collect(id, namespace string, cg cgroups.Cgroup, ch chan<- p
 
 // Add adds the provided cgroup and id so that metrics are collected and exported
 func (c *Collector) Add(id, namespace string, cg cgroups.Cgroup) error {
+	if c.ns == nil {
+		return nil
+	}
 	c.mu.Lock()
 	defer c.mu.Unlock()
 	if _, ok := c.cgroups[taskID(id, namespace)]; ok {
@@ -104,32 +109,12 @@ func (c *Collector) Add(id, namespace string, cg cgroups.Cgroup) error {
 	return nil
 }
 
-// Get returns the cgroup that is being collected under the provided id
-// returns ErrCgroupNotExists if the id is not being collected
-func (c *Collector) Get(id, namespace string) (cgroups.Cgroup, error) {
-	c.mu.Lock()
-	defer c.mu.Unlock()
-	t, ok := c.cgroups[taskID(id, namespace)]
-	if !ok {
-		return nil, ErrCgroupNotExists
-	}
-	return t.cgroup, nil
-}
-
 // Remove removes the provided cgroup by id from the collector
 func (c *Collector) Remove(id, namespace string) {
+	if c.ns == nil {
+		return
+	}
 	c.mu.Lock()
 	defer c.mu.Unlock()
 	delete(c.cgroups, taskID(id, namespace))
 }
-
-func blkioValues(l []*cgroups.BlkIOEntry) []value {
-	var out []value
-	for _, e := range l {
-		out = append(out, value{
-			v: float64(e.Value),
-			l: []string{e.Op, e.Device, strconv.FormatUint(e.Major, 10), strconv.FormatUint(e.Minor, 10)},
-		})
-	}
-	return out
-}

metrics/cgroups/oom.go

@@ -19,12 +19,18 @@ func NewOOMCollector(ns *metrics.Namespace) (*OOMCollector, error) {
 	if err != nil {
 		return nil, err
 	}
+	var desc *prometheus.Desc
+	if ns != nil {
+		desc = ns.NewDesc("memory_oom", "The number of times a container has received an oom event", metrics.Total, "container_id", "namespace")
+	}
 	c := &OOMCollector{
 		fd:   fd,
-		desc: ns.NewDesc("memory_oom", "The number of times a container has received an oom event", metrics.Total, "container_id", "namespace"),
+		desc: desc,
 		set:  make(map[uintptr]*oom),
 	}
-	ns.Add(c)
+	if ns != nil {
+		ns.Add(c)
+	}
 	go c.start()
 	return c, nil
 }