added support backward compatibility

Signed-off-by: Darya Melentsova <ifireice@gmail.com>

prometheus/graphite/bridge.go

@@ -38,11 +38,22 @@ const (
 	millisecondsPerSecond = 1000
 )
 
-// ErrorHandler is a function that handles errors
-type ErrorHandler func(err error)
+// HandlerErrorHandling defines how a Handler serving metrics will handle
+// errors.
+type HandlerErrorHandling int
 
-// DefaultErrorHandler skips received errors
-var DefaultErrorHandler = func(err error) {}
+// These constants cause handlers serving metrics to behave as described if
+// errors are encountered.
+const (
+	// Ignore errors and try to push as many metrics to Graphite as possible.
+	ContinueOnError HandlerErrorHandling = iota
+
+	// Abort the push to Graphite upon the first error encountered.
+	AbortOnError
+
+	// Execute callback function on error.
+	CallbackOnError
+)
 
 // Config defines the Graphite bridge config.
 type Config struct {
@@ -64,8 +75,16 @@ type Config struct {
 	// The Gatherer to use for metrics. Defaults to prometheus.DefaultGatherer.
 	Gatherer prometheus.Gatherer
 
-	// ErrorHandler defines how errors are handled.
-	ErrorHandler ErrorHandler
+	// The logger that messages are written to. Defaults to no logging.
+	Logger Logger
+
+	// ErrorHandling defines how errors are handled. Note that errors are
+	// logged regardless of the configured ErrorHandling provided Logger
+	// is not nil.
+	ErrorHandling HandlerErrorHandling
+
+	// ErrorCallbackFunc is a callback function that can be executed when error is occurred
+	ErrorCallbackFunc CallbackFunc
 }
 
 // Bridge pushes metrics to the configured Graphite server.
@@ -76,11 +95,23 @@ type Bridge struct {
 	interval time.Duration
 	timeout  time.Duration
 
-	errorHandler ErrorHandler
+	errorHandling     HandlerErrorHandling
+	errorCallbackFunc CallbackFunc
+	logger            Logger
 
 	g prometheus.Gatherer
 }
 
+// Logger is the minimal interface Bridge needs for logging. Note that
+// log.Logger from the standard library implements this interface, and it is
+// easy to implement by custom loggers, if they don't do so already anyway.
+type Logger interface {
+	Println(v ...interface{})
+}
+
+// CallbackFunc is a special type for callback functions
+type CallbackFunc func(error)
+
 // NewBridge returns a pointer to a new Bridge struct.
 func NewBridge(c *Config) (*Bridge, error) {
 	b := &Bridge{}
@@ -98,6 +129,10 @@ func NewBridge(c *Config) (*Bridge, error) {
 		b.g = c.Gatherer
 	}
 
+	if c.Logger != nil {
+		b.logger = c.Logger
+	}
+
 	if c.Prefix != "" {
 		b.prefix = c.Prefix
 	}
@@ -115,7 +150,11 @@ func NewBridge(c *Config) (*Bridge, error) {
 		b.timeout = c.Timeout
 	}
 
-	b.errorHandler = c.ErrorHandler
+	b.errorHandling = c.ErrorHandling
+
+	if c.ErrorCallbackFunc != nil {
+		b.errorCallbackFunc = c.ErrorCallbackFunc
+	}
 
 	return b, nil
 }
@@ -128,7 +167,9 @@ func (b *Bridge) Run(ctx context.Context) {
 	for {
 		select {
 		case <-ticker.C:
-			b.errorHandler(b.Push())
+			if err := b.Push(); err != nil && b.logger != nil {
+				b.logger.Println("error pushing to Graphite:", err)
+			}
 		case <-ctx.Done():
 			return
 		}
@@ -137,11 +178,27 @@ func (b *Bridge) Run(ctx context.Context) {
 
 // Push pushes Prometheus metrics to the configured Graphite server.
 func (b *Bridge) Push() error {
+	err := b.push()
+	switch b.errorHandling {
+	case AbortOnError:
+		return err
+	case ContinueOnError:
+		if b.logger != nil {
+			b.logger.Println("continue on error:", err)
+		}
+	case CallbackOnError:
+		if b.errorCallbackFunc != nil {
+			b.errorCallbackFunc(err)
+		}
+	}
+	return nil
+}
+
+func (b *Bridge) push() error {
 	mfs, err := b.g.Gather()
 	if err != nil {
 		return err
 	}
-
 	if len(mfs) == 0 {
 		return nil
 	}

prometheus/graphite/bridge_test.go

@@ -19,7 +19,9 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"log"
 	"net"
+	"os"
 	"reflect"
 	"regexp"
 	"sort"
@@ -436,12 +438,13 @@ type mockGraphite struct {
 
 func ExampleBridge() {
 	b, err := NewBridge(&Config{
-		URL:          "graphite.example.org:3099",
-		Gatherer:     prometheus.DefaultGatherer,
-		Prefix:       "prefix",
-		Interval:     15 * time.Second,
-		Timeout:      10 * time.Second,
-		ErrorHandler: func(err error) {},
+		URL:           "graphite.example.org:3099",
+		Gatherer:      prometheus.DefaultGatherer,
+		Prefix:        "prefix",
+		Interval:      15 * time.Second,
+		Timeout:       10 * time.Second,
+		ErrorHandling: AbortOnError,
+		Logger:        log.New(os.Stdout, "graphite bridge: ", log.Lshortfile),
 	})
 	if err != nil {
 		panic(err)
@@ -465,32 +468,47 @@ func ExampleBridge() {
 	b.Run(ctx)
 }
 
-func TestErrorHandler(t *testing.T) {
-	var internalError error
-	c := &Config{
-		URL:          "localhost",
-		Gatherer:     prometheus.DefaultGatherer,
-		Prefix:       "prefix",
-		Interval:     5 * time.Second,
-		Timeout:      2 * time.Second,
-		ErrorHandler: func(err error) { internalError = err },
-	}
-	b, err := NewBridge(c)
-	if err != nil {
-		panic(err)
+func TestErrorHandling(t *testing.T) {
+	var testCases = []struct {
+		errorHandling    HandlerErrorHandling
+		receivedError    error
+		interceptedError error
+	}{
+		{
+			errorHandling:    ContinueOnError,
+			receivedError:    nil,
+			interceptedError: nil,
+		},
+		{
+			errorHandling:    AbortOnError,
+			receivedError:    &net.OpError{},
+			interceptedError: nil,
+		},
+		{
+			errorHandling:    CallbackOnError,
+			receivedError:    nil,
+			interceptedError: &net.OpError{},
+		},
 	}
 
-	// Create a Context to control stopping the Run() loop that pushes
-	// metrics to Graphite. Multiplied by 2, because we need Run to be executed at least one time.
-	ctx, cancel := context.WithTimeout(context.Background(), c.Interval*2)
-	defer cancel()
+	for _, testCase := range testCases {
+		var interceptedError error
+		c := &Config{
+			URL:               "localhost",
+			ErrorHandling:     testCase.errorHandling,
+			ErrorCallbackFunc: func(err error) { interceptedError = err },
+		}
+		b, err := NewBridge(c)
+		if err != nil {
+			t.Fatal(err)
+		}
 
-	// Start pushing metrics to Graphite in the Run() loop.
-	b.Run(ctx)
-
-	// We haven't specified port
-	expError := fmt.Errorf("dial tcp: address localhost: missing port in address")
-	if internalError.Error() != expError.Error() {
-		t.Fatalf("Expected: '%s', actual: '%s'", expError, internalError)
+		receivedError := b.Push()
+		if reflect.TypeOf(receivedError) != reflect.TypeOf(testCase.receivedError) {
+			t.Errorf("expected to receive: %T, received: %T", testCase.receivedError, receivedError)
+		}
+		if reflect.TypeOf(interceptedError) != reflect.TypeOf(testCase.interceptedError) {
+			t.Errorf("expected to intercept: %T, intercepted: %T", testCase.interceptedError, interceptedError)
+		}
 	}
 }