plugin/errors: 'consolidate' option (#2192)

- see more details at https://github.com/infobloxopen/coredns-plugin-errors/pull/3

plugin/errors/errors.go

@@ -1,8 +1,12 @@
-// Package errors implements an HTTP error handling plugin.
+// Package errors implements an error handling plugin.
 package errors
 
 import (
 	"context"
+	"regexp"
+	"sync/atomic"
+	"time"
+	"unsafe"
 
 	"github.com/coredns/coredns/plugin"
 	clog "github.com/coredns/coredns/plugin/pkg/log"
@@ -11,19 +15,98 @@ import (
 	"github.com/miekg/dns"
 )
 
+var log = clog.NewWithPlugin("errors")
+
+type pattern struct {
+	ptimer  unsafe.Pointer
+	count   uint32
+	period  time.Duration
+	pattern *regexp.Regexp
+}
+
+func (p *pattern) timer() *time.Timer {
+	return (*time.Timer)(atomic.LoadPointer(&p.ptimer))
+}
+
+func (p *pattern) setTimer(t *time.Timer) {
+	atomic.StorePointer(&p.ptimer, unsafe.Pointer(t))
+}
+
 // errorHandler handles DNS errors (and errors from other plugin).
-type errorHandler struct{ Next plugin.Handler }
+type errorHandler struct {
+	patterns []*pattern
+	eLogger  func(int, string, string, string)
+	cLogger  func(uint32, string, time.Duration)
+	stopFlag uint32
+	Next     plugin.Handler
+}
+
+func newErrorHandler() *errorHandler {
+	return &errorHandler{eLogger: errorLogger, cLogger: consLogger}
+}
+
+func errorLogger(code int, qName, qType, err string) {
+	log.Errorf("%d %s %s: %s", code, qName, qType, err)
+}
+
+func consLogger(cnt uint32, pattern string, p time.Duration) {
+	log.Errorf("%d errors like '%s' occured in last %s", cnt, pattern, p)
+}
+
+func (h *errorHandler) logPattern(i int) {
+	cnt := atomic.SwapUint32(&h.patterns[i].count, 0)
+	if cnt > 0 {
+		h.cLogger(cnt, h.patterns[i].pattern.String(), h.patterns[i].period)
+	}
+}
+
+func (h *errorHandler) inc(i int) bool {
+	if atomic.LoadUint32(&h.stopFlag) > 0 {
+		return false
+	}
+	if atomic.AddUint32(&h.patterns[i].count, 1) == 1 {
+		ind := i
+		t := time.AfterFunc(h.patterns[ind].period, func() {
+			h.logPattern(ind)
+		})
+		h.patterns[ind].setTimer(t)
+		if atomic.LoadUint32(&h.stopFlag) > 0 && t.Stop() {
+			h.logPattern(ind)
+		}
+	}
+	return true
+}
+
+func (h *errorHandler) stop() {
+	atomic.StoreUint32(&h.stopFlag, 1)
+	for i := range h.patterns {
+		t := h.patterns[i].timer()
+		if t != nil && t.Stop() {
+			h.logPattern(i)
+		}
+	}
+}
 
 // ServeDNS implements the plugin.Handler interface.
-func (h errorHandler) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
+func (h *errorHandler) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
 	rcode, err := plugin.NextOrFailure(h.Name(), h.Next, ctx, w, r)
 
 	if err != nil {
+		strErr := err.Error()
+		for i := range h.patterns {
+			if h.patterns[i].pattern.MatchString(strErr) {
+				if h.inc(i) {
+					return rcode, err
+				}
+				break
+			}
+		}
 		state := request.Request{W: w, Req: r}
-		clog.Errorf("%d %s %s: %v", rcode, state.Name(), state.Type(), err)
+		h.eLogger(rcode, state.Name(), state.Type(), strErr)
 	}
 
 	return rcode, err
 }
 
-func (h errorHandler) Name() string { return "errors" }
+// Name implements the plugin.Handler interface.
+func (h *errorHandler) Name() string { return "errors" }