recover from panic log including stacktrace to help finding the origin (#5392)

plugin/errors/README.md

@@ -22,10 +22,13 @@ Extra knobs are available with an expanded syntax:
 
 ~~~
 errors {
+	stacktrace
 	consolidate DURATION REGEXP [LEVEL]
 }
 ~~~
 
+Option `stacktrace` will log a stacktrace during panic recovery.
+
 Option `consolidate` allows collecting several error messages matching the regular expression **REGEXP** during **DURATION**. After the **DURATION** since receiving the first such message, the consolidated message will be printed to standard output with
 log level, which is configurable by optional option **LEVEL**. Supported options for **LEVEL** option are `warning`,`error`,`info` and `debug`.
 ~~~

plugin/errors/setup.go

@@ -52,38 +52,41 @@ func errorsParse(c *caddy.Controller) (*errorHandler, error) {
 		}
 
 		for c.NextBlock() {
-			if err := parseBlock(c, handler); err != nil {
-				return nil, err
+			switch c.Val() {
+			case "stacktrace":
+				dnsserver.GetConfig(c).Stacktrace = true
+			case "consolidate":
+				pattern, err := parseConsolidate(c)
+				if err != nil {
+					return nil, err
+				}
+				handler.patterns = append(handler.patterns, pattern)
+			default:
+				return handler, c.SyntaxErr("Unknown field " + c.Val())
 			}
 		}
 	}
 	return handler, nil
 }
 
-func parseBlock(c *caddy.Controller, h *errorHandler) error {
-	if c.Val() != "consolidate" {
-		return c.SyntaxErr("consolidate")
-	}
-
+func parseConsolidate(c *caddy.Controller) (*pattern, error) {
 	args := c.RemainingArgs()
 	if len(args) < 2 || len(args) > 3 {
-		return c.ArgErr()
+		return nil, c.ArgErr()
 	}
 	p, err := time.ParseDuration(args[0])
 	if err != nil {
-		return c.Err(err.Error())
+		return nil, c.Err(err.Error())
 	}
 	re, err := regexp.Compile(args[1])
 	if err != nil {
-		return c.Err(err.Error())
+		return nil, c.Err(err.Error())
 	}
 	lc, err := parseLogLevel(c, args)
 	if err != nil {
-		return err
+		return nil, err
 	}
-	h.patterns = append(h.patterns, &pattern{period: p, pattern: re, logCallback: lc})
-
-	return nil
+	return &pattern{period: p, pattern: re, logCallback: lc}, nil
 }
 
 func parseLogLevel(c *caddy.Controller, args []string) (func(format string, v ...interface{}), error) {

plugin/errors/setup_test.go

@@ -7,55 +7,64 @@ import (
 	"testing"
 
 	"github.com/coredns/caddy"
+	"github.com/coredns/coredns/core/dnsserver"
 	clog "github.com/coredns/coredns/plugin/pkg/log"
 )
 
 func TestErrorsParse(t *testing.T) {
 	tests := []struct {
-		inputErrorsRules string
-		shouldErr        bool
-		optCount         int
+		inputErrorsRules        string
+		shouldErr               bool
+		optCount                int
+		stacktrace bool
 	}{
-		{`errors`, false, 0},
-		{`errors stdout`, false, 0},
-		{`errors errors.txt`, true, 0},
-		{`errors visible`, true, 0},
-		{`errors { log visible }`, true, 0},
+		{`errors`, false, 0, false},
+		{`errors stdout`, false, 0, false},
+		{`errors errors.txt`, true, 0, false},
+		{`errors visible`, true, 0, false},
+		{`errors { log visible }`, true, 0, false},
 		{`errors
-		  errors `, true, 0},
-		{`errors a b`, true, 0},
+		  errors `, true, 0, false},
+		{`errors a b`, true, 0, false},
 
 		{`errors {
 		    consolidate
-		  }`, true, 0},
+		  }`, true, 0, false},
 		{`errors {
 		    consolidate 1m
-		  }`, true, 0},
+		  }`, true, 0, false},
 		{`errors {
 		    consolidate 1m .* extra
-		  }`, true, 0},
+		  }`, true, 0, false},
 		{`errors {
 		    consolidate abc .*
-		  }`, true, 0},
+		  }`, true, 0, false},
 		{`errors {
 		    consolidate 1 .*
-		  }`, true, 0},
+		  }`, true, 0, false},
 		{`errors {
 		    consolidate 1m ())
-		  }`, true, 0},
+		  }`, true, 0, false},
+		{`errors {
+            stacktrace
+		  }`, false, 0, true},
+		{`errors {
+            stacktrace
+		    consolidate 1m ^exact$
+		  }`, false, 1, true},
 		{`errors {
 		    consolidate 1m ^exact$
-		  }`, false, 1},
+		  }`, false, 1, false},
 		{`errors {
 		    consolidate 1m error
-		  }`, false, 1},
+		  }`, false, 1, false},
 		{`errors {
 		    consolidate 1m "format error"
-		  }`, false, 1},
+		  }`, false, 1, false},
 		{`errors {
 		    consolidate 1m error1
 		    consolidate 5s error2
-		  }`, false, 2},
+		  }`, false, 2, false},
 	}
 	for i, test := range tests {
 		c := caddy.NewTestController("dns", test.inputErrorsRules)
@@ -69,6 +78,10 @@ func TestErrorsParse(t *testing.T) {
 			t.Errorf("Test %d: pattern count mismatch, expected %d, got %d",
 				i, test.optCount, len(h.patterns))
 		}
+		if dnsserver.GetConfig(c).Stacktrace != test.stacktrace {
+			t.Errorf("Test %d: stacktrace, expected %t, got %t",
+				i, test.stacktrace, dnsserver.GetConfig(c).Stacktrace)
+		}
 	}
 }