plugin/autopath: Add metrics and remove log line (#1143)

* plugin/autopath: Add namespace selector and metrics

Add a namespace, so autopathing only is performed in this namespace.
This will make caching work for the cluster again.

Also export metrics that we've done a successful autopath

* dont shadow

* Fix

* Back the namespacing changes

plugin/autopath/README.md

@@ -24,6 +24,12 @@ Currently the following set of plugin has implemented *autopath*:
 * *kubernetes*
 * *erratic*
 
+## Metrics
+ 
+If monitoring is enabled (via the *prometheus* directive) then the following metric is exported:
+ 
+* `coredns_autopath_success_count_total{}` - counter of successfully autopath-ed queries.
+
 ## Examples
 
 ~~~
@@ -41,5 +47,5 @@ Use the search path dynamically retrieved from the kubernetes plugin.
 
 ## Bugs
 
-When the *cache* plugin is enabled it is possible for pods in different namespaces to get the
-same answer.
+Replies from this plugin are not cached, as the *cache* plugin is configured after this one (see
+plugin.cfg).

plugin/autopath/autopath.go

@@ -32,8 +32,6 @@ func (m Plugins ) AutoPath(state request.Request) []string {
 package autopath
 
 import (
-	"log"
-
 	"github.com/coredns/coredns/plugin"
 	"github.com/coredns/coredns/plugin/pkg/dnsutil"
 	"github.com/coredns/coredns/plugin/pkg/nonwriter"
@@ -76,7 +74,6 @@ func (a *AutoPath) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Ms
 	}
 
 	if len(searchpath) == 0 {
-		log.Printf("[WARNING] No search path available for autopath")
 		return plugin.NextOrFailure(a.Name(), a.Next, ctx, w, r)
 	}
 
@@ -87,7 +84,7 @@ func (a *AutoPath) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Ms
 	origQName := state.QName()
 
 	// Establish base name of the query. I.e what was originally asked.
-	base, err := dnsutil.TrimZone(state.QName(), searchpath[0]) // TODO(miek): we loose the original case of the query here.
+	base, err := dnsutil.TrimZone(state.QName(), searchpath[0])
 	if err != nil {
 		return dns.RcodeServerFailure, err
 	}
@@ -128,6 +125,7 @@ func (a *AutoPath) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Ms
 
 		// Write whatever non-nxdomain answer we've found.
 		w.WriteMsg(msg)
+		AutoPathCount.WithLabelValues().Add(1)
 		return rcode, err
 
 	}

plugin/autopath/metrics.go

+package autopath
+
+import (
+	"sync"
+
+	"github.com/coredns/coredns/plugin"
+
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+// Metrics for autopath.
+var (
+	AutoPathCount = prometheus.NewCounterVec(prometheus.CounterOpts{
+		Namespace: plugin.Namespace,
+		Subsystem: "autopath",
+		Name:      "success_count_total",
+		Help:      "Counter of requests that did autopath.",
+	}, []string{})
+)
+
+// OnStartupMetrics sets up the metrics on startup.
+func OnStartupMetrics() error {
+	metricsOnce.Do(func() {
+		prometheus.MustRegister(AutoPathCount)
+	})
+	return nil
+}
+
+var metricsOnce sync.Once

plugin/autopath/setup.go

@@ -26,6 +26,8 @@ func setup(c *caddy.Controller) error {
 		return plugin.Error("autopath", err)
 	}
 
+	c.OnStartup(OnStartupMetrics)
+
 	// Do this in OnStartup, so all plugin has been initialized.
 	c.OnStartup(func() error {
 		m := dnsserver.GetConfig(c).Handler(mw)