pprof middleware (#138)

Add pprof middleware, enabled by pprof directive.

core/setup/pprof.go

@@ -0,0 +1,36 @@
+package setup
+
+import (
+	"sync"
+
+	"github.com/miekg/coredns/middleware"
+	"github.com/miekg/coredns/middleware/pprof"
+)
+
+var pprofOnce sync.Once
+
+// PProf returns a new instance of a pprof handler. It accepts no arguments or options.
+func PProf(c *Controller) (middleware.Middleware, error) {
+	found := false
+	for c.Next() {
+		if found {
+			return nil, c.Err("pprof can only be specified once")
+		}
+		if len(c.RemainingArgs()) != 0 {
+			return nil, c.ArgErr()
+		}
+		if c.NextBlock() {
+			return nil, c.ArgErr()
+		}
+		found = true
+	}
+	handler := &pprof.Handler{}
+	pprofOnce.Do(func() {
+		c.Startup = append(c.Startup, handler.Start)
+	})
+
+	return func(next middleware.Handler) middleware.Handler {
+		handler.Next = next
+		return handler
+	}, nil
+}