Align plugin/template usage and syntax with other plugins (#1360)

* Align plugin/template usage and syntax with other plugins

* Use new fallthrough logic in plugin/template

* Use zone name normalization for plugin/template

* Test fallthrough parsing in plugin/template

* Rework scoping of match checks

Most matches are not plugin global but per template. The plugin does only a
very rough check while detailed checks are done per-template.

Per template checks include:
- Zones
- Class/Type
- Regex
- Fallthrough

* Remove trailing `.` from fully qualified domain names

* Register template metrics with zone/class/type instead of regex

* Remove trailing fqdn dot from multiple testcases

plugin/template/metrics.go

@@ -3,7 +3,10 @@ package template
 import (
 	"sync"
 
+	"github.com/coredns/coredns/core/dnsserver"
 	"github.com/coredns/coredns/plugin"
+	"github.com/coredns/coredns/plugin/metrics"
+	"github.com/mholt/caddy"
 
 	"github.com/prometheus/client_golang/prometheus"
 )
@@ -15,28 +18,38 @@ var (
 		Subsystem: "template",
 		Name:      "matches_total",
 		Help:      "Counter of template regex matches.",
-	}, []string{"regex"})
+	}, []string{"zone", "class", "type"})
 	TemplateFailureCount = prometheus.NewCounterVec(prometheus.CounterOpts{
 		Namespace: plugin.Namespace,
 		Subsystem: "template",
 		Name:      "template_failures_total",
 		Help:      "Counter of go template failures.",
-	}, []string{"regex", "section", "template"})
+	}, []string{"zone", "class", "type", "section", "template"})
 	TemplateRRFailureCount = prometheus.NewCounterVec(prometheus.CounterOpts{
 		Namespace: plugin.Namespace,
 		Subsystem: "template",
 		Name:      "rr_failures_total",
 		Help:      "Counter of mis-templated RRs.",
-	}, []string{"regex", "section", "template"})
+	}, []string{"zone", "class", "type", "section", "template"})
 )
 
 // OnStartupMetrics sets up the metrics on startup.
-func OnStartupMetrics() error {
-	metricsOnce.Do(func() {
-		prometheus.MustRegister(TemplateMatchesCount)
-		prometheus.MustRegister(TemplateFailureCount)
-		prometheus.MustRegister(TemplateRRFailureCount)
+func setupMetrics(c *caddy.Controller) error {
+	c.OnStartup(func() error {
+		metricsOnce.Do(func() {
+			m := dnsserver.GetConfig(c).Handler("prometheus")
+			if m == nil {
+				return
+			}
+			if x, ok := m.(*metrics.Metrics); ok {
+				x.MustRegister(TemplateMatchesCount)
+				x.MustRegister(TemplateFailureCount)
+				x.MustRegister(TemplateRRFailureCount)
+			}
+		})
+		return nil
 	})
+
 	return nil
 }