Use go-events package

TBD: Queue not converted yet

Signed-off-by: Elliot Pahl <elliot.pahl@gmail.com>

go.mod

@@ -16,6 +16,7 @@ require (
 	github.com/denverdino/aliyungo v0.0.0-20190125010748-a747050bb1ba
 	github.com/dgrijalva/jwt-go v0.0.0-20170104182250-a601269ab70c // indirect
 	github.com/dnaeon/go-vcr v1.0.1 // indirect
+	github.com/docker/go-events v0.0.0-20190806004212-e31b211e4f1c
 	github.com/docker/go-metrics v0.0.1
 	github.com/docker/libtrust v0.0.0-20150114040149-fa567046d9b1
 	github.com/garyburd/redigo v0.0.0-20150301180006-535138d7bcd7

go.sum

@@ -35,6 +35,8 @@ github.com/dgrijalva/jwt-go v0.0.0-20170104182250-a601269ab70c h1:KJAnOBuY9cTKVq
 github.com/dgrijalva/jwt-go v0.0.0-20170104182250-a601269ab70c/go.mod h1:E3ru+11k8xSBh+hMPgOLZmtrrCbhqsmaPHjLKYnJCaQ=
 github.com/dnaeon/go-vcr v1.0.1 h1:r8L/HqC0Hje5AXMu1ooW8oyQyOFv4GxqpL0nRP7SLLY=
 github.com/dnaeon/go-vcr v1.0.1/go.mod h1:aBB1+wY4s93YsC3HHjMBMrwTj2R9FHDzUr9KyGc8n1E=
+github.com/docker/go-events v0.0.0-20190806004212-e31b211e4f1c h1:+pKlWGMw7gf6bQ+oDZB4KHQFypsfjYlq/C4rfL7D3g8=
+github.com/docker/go-events v0.0.0-20190806004212-e31b211e4f1c/go.mod h1:Uw6UezgYA44ePAFQYUehOuCzmy5zmg/+nl2ZfMWGkpA=
 github.com/docker/go-metrics v0.0.1 h1:AgB/0SvBxihN0X8OR4SjsblXkbMvalQ8cjmtKQ2rQV8=
 github.com/docker/go-metrics v0.0.1/go.mod h1:cG1hvH2utMXtqgqqYE9plW6lDxS3/5ayHzueweSI3Vw=
 github.com/docker/libtrust v0.0.0-20150114040149-fa567046d9b1 h1:ZClxb8laGDf5arXfYcAtECDFgAgHklGI8CxgjHnXKJ4=

notifications/bridge.go

@@ -8,6 +8,7 @@ import (
 	"github.com/docker/distribution/context"
 	"github.com/docker/distribution/reference"
 	"github.com/docker/distribution/uuid"
+	events "github.com/docker/go-events"
 	"github.com/opencontainers/go-digest"
 )
 
@@ -17,7 +18,7 @@ type bridge struct {
 	actor             ActorRecord
 	source            SourceRecord
 	request           RequestRecord
-	sink              Sink
+	sink              events.Sink
 }
 
 var _ Listener = &bridge{}
@@ -32,7 +33,7 @@ type URLBuilder interface {
 // using the actor and source. Any urls populated in the events created by
 // this bridge will be created using the URLBuilder.
 // TODO(stevvooe): Update this to simply take a context.Context object.
-func NewBridge(ub URLBuilder, source SourceRecord, actor ActorRecord, request RequestRecord, sink Sink, includeReferences bool) Listener {
+func NewBridge(ub URLBuilder, source SourceRecord, actor ActorRecord, request RequestRecord, sink events.Sink, includeReferences bool) Listener {
 	return &bridge{
 		ub:                ub,
 		includeReferences: includeReferences,

notifications/bridge_test.go

@@ -8,6 +8,7 @@ import (
 	"github.com/docker/distribution/reference"
 	v2 "github.com/docker/distribution/registry/api/v2"
 	"github.com/docker/distribution/uuid"
+	events "github.com/docker/go-events"
 	"github.com/docker/libtrust"
 	"github.com/opencontainers/go-digest"
 )
@@ -46,8 +47,8 @@ var (
 )
 
 func TestEventBridgeManifestPulled(t *testing.T) {
-	l := createTestEnv(t, testSinkFn(func(events ...Event) error {
+	l := createTestEnv(t, testSinkFn(func(event events.Event) error {
-		checkCommonManifest(t, EventActionPull, events...)
+		checkCommonManifest(t, EventActionPull, event)
 
 		return nil
 	}))
@@ -59,8 +60,8 @@ func TestEventBridgeManifestPulled(t *testing.T) {
 }
 
 func TestEventBridgeManifestPushed(t *testing.T) {
-	l := createTestEnv(t, testSinkFn(func(events ...Event) error {
+	l := createTestEnv(t, testSinkFn(func(event events.Event) error {
-		checkCommonManifest(t, EventActionPush, events...)
+		checkCommonManifest(t, EventActionPush, event)
 
 		return nil
 	}))
@@ -72,10 +73,10 @@ func TestEventBridgeManifestPushed(t *testing.T) {
 }
 
 func TestEventBridgeManifestPushedWithTag(t *testing.T) {
-	l := createTestEnv(t, testSinkFn(func(events ...Event) error {
+	l := createTestEnv(t, testSinkFn(func(event events.Event) error {
-		checkCommonManifest(t, EventActionPush, events...)
+		checkCommonManifest(t, EventActionPush, event)
-		if events[0].Target.Tag != "latest" {
+		if event.(Event).Target.Tag != "latest" {
-			t.Fatalf("missing or unexpected tag: %#v", events[0].Target)
+			t.Fatalf("missing or unexpected tag: %#v", event.(Event).Target)
 		}
 
 		return nil
@@ -88,10 +89,10 @@ func TestEventBridgeManifestPushedWithTag(t *testing.T) {
 }
 
 func TestEventBridgeManifestPulledWithTag(t *testing.T) {
-	l := createTestEnv(t, testSinkFn(func(events ...Event) error {
+	l := createTestEnv(t, testSinkFn(func(event events.Event) error {
-		checkCommonManifest(t, EventActionPull, events...)
+		checkCommonManifest(t, EventActionPull, event)
-		if events[0].Target.Tag != "latest" {
+		if event.(Event).Target.Tag != "latest" {
-			t.Fatalf("missing or unexpected tag: %#v", events[0].Target)
+			t.Fatalf("missing or unexpected tag: %#v", event.(Event).Target)
 		}
 
 		return nil
@@ -104,10 +105,10 @@ func TestEventBridgeManifestPulledWithTag(t *testing.T) {
 }
 
 func TestEventBridgeManifestDeleted(t *testing.T) {
-	l := createTestEnv(t, testSinkFn(func(events ...Event) error {
+	l := createTestEnv(t, testSinkFn(func(event events.Event) error {
-		checkDeleted(t, EventActionDelete, events...)
+		checkDeleted(t, EventActionDelete, event)
-		if events[0].Target.Digest != dgst {
+		if event.(Event).Target.Digest != dgst {
-			t.Fatalf("unexpected digest on event target: %q != %q", events[0].Target.Digest, dgst)
+			t.Fatalf("unexpected digest on event target: %q != %q", event.(Event).Target.Digest, dgst)
 		}
 		return nil
 	}))
@@ -119,10 +120,10 @@ func TestEventBridgeManifestDeleted(t *testing.T) {
 }
 
 func TestEventBridgeTagDeleted(t *testing.T) {
-	l := createTestEnv(t, testSinkFn(func(events ...Event) error {
+	l := createTestEnv(t, testSinkFn(func(event events.Event) error {
-		checkDeleted(t, EventActionDelete, events...)
+		checkDeleted(t, EventActionDelete, event)
-		if events[0].Target.Tag != m.Tag {
+		if event.(Event).Target.Tag != m.Tag {
-			t.Fatalf("unexpected tag on event target: %q != %q", events[0].Target.Tag, m.Tag)
+			t.Fatalf("unexpected tag on event target: %q != %q", event.(Event).Target.Tag, m.Tag)
 		}
 		return nil
 	}))
@@ -134,8 +135,8 @@ func TestEventBridgeTagDeleted(t *testing.T) {
 }
 
 func TestEventBridgeRepoDeleted(t *testing.T) {
-	l := createTestEnv(t, testSinkFn(func(events ...Event) error {
+	l := createTestEnv(t, testSinkFn(func(event events.Event) error {
-		checkDeleted(t, EventActionDelete, events...)
+		checkDeleted(t, EventActionDelete, event)
 		return nil
 	}))
 
@@ -162,36 +163,29 @@ func createTestEnv(t *testing.T, fn testSinkFn) Listener {
 	return NewBridge(ub, source, actor, request, fn, true)
 }
 
-func checkDeleted(t *testing.T, action string, events ...Event) {
+func checkDeleted(t *testing.T, action string, event events.Event) {
-	if len(events) != 1 {
+	if event.(Event).Source != source {
-		t.Fatalf("unexpected number of events: %v != 1", len(events))
+		t.Fatalf("source not equal: %#v != %#v", event.(Event).Source, source)
 	}
 
-	event := events[0]
+	if event.(Event).Request != request {
-
+		t.Fatalf("request not equal: %#v != %#v", event.(Event).Request, request)
-	if event.Source != source {
-		t.Fatalf("source not equal: %#v != %#v", event.Source, source)
 	}
 
-	if event.Request != request {
+	if event.(Event).Actor != actor {
-		t.Fatalf("request not equal: %#v != %#v", event.Request, request)
+		t.Fatalf("request not equal: %#v != %#v", event.(Event).Actor, actor)
 	}
 
-	if event.Actor != actor {
+	if event.(Event).Target.Repository != repo {
-		t.Fatalf("request not equal: %#v != %#v", event.Actor, actor)
+		t.Fatalf("unexpected repository: %q != %q", event.(Event).Target.Repository, repo)
-	}
-
-	if event.Target.Repository != repo {
-		t.Fatalf("unexpected repository: %q != %q", event.Target.Repository, repo)
 	}
 }
 
-func checkCommonManifest(t *testing.T, action string, events ...Event) {
+func checkCommonManifest(t *testing.T, action string, event events.Event) {
-	checkCommon(t, events...)
+	checkCommon(t, event)
 
-	event := events[0]
+	if event.(Event).Action != action {
-	if event.Action != action {
+		t.Fatalf("unexpected event action: %q != %q", event.(Event).Action, action)
-		t.Fatalf("unexpected event action: %q != %q", event.Action, action)
 	}
 
 	repoRef, _ := reference.WithName(repo)
@@ -201,57 +195,51 @@ func checkCommonManifest(t *testing.T, action string, events ...Event) {
 		t.Fatalf("error building expected url: %v", err)
 	}
 
-	if event.Target.URL != u {
+	if event.(Event).Target.URL != u {
-		t.Fatalf("incorrect url passed: \n%q != \n%q", event.Target.URL, u)
+		t.Fatalf("incorrect url passed: \n%q != \n%q", event.(Event).Target.URL, u)
 	}
 
-	if len(event.Target.References) != len(layers) {
+	if len(event.(Event).Target.References) != len(layers) {
-		t.Fatalf("unexpected number of references %v != %v", len(event.Target.References), len(layers))
+		t.Fatalf("unexpected number of references %v != %v", len(event.(Event).Target.References), len(layers))
 	}
-	for i, targetReference := range event.Target.References {
+	for i, targetReference := range event.(Event).Target.References {
 		if targetReference.Digest != layers[i].BlobSum {
 			t.Fatalf("unexpected reference: %q != %q", targetReference.Digest, layers[i].BlobSum)
 		}
 	}
 }
 
-func checkCommon(t *testing.T, events ...Event) {
+func checkCommon(t *testing.T, event events.Event) {
-	if len(events) != 1 {
+	if event.(Event).Source != source {
-		t.Fatalf("unexpected number of events: %v != 1", len(events))
+		t.Fatalf("source not equal: %#v != %#v", event.(Event).Source, source)
 	}
 
-	event := events[0]
+	if event.(Event).Request != request {
-
+		t.Fatalf("request not equal: %#v != %#v", event.(Event).Request, request)
-	if event.Source != source {
-		t.Fatalf("source not equal: %#v != %#v", event.Source, source)
 	}
 
-	if event.Request != request {
+	if event.(Event).Actor != actor {
-		t.Fatalf("request not equal: %#v != %#v", event.Request, request)
+		t.Fatalf("request not equal: %#v != %#v", event.(Event).Actor, actor)
 	}
 
-	if event.Actor != actor {
+	if event.(Event).Target.Digest != dgst {
-		t.Fatalf("request not equal: %#v != %#v", event.Actor, actor)
+		t.Fatalf("unexpected digest on event target: %q != %q", event.(Event).Target.Digest, dgst)
 	}
 
-	if event.Target.Digest != dgst {
+	if event.(Event).Target.Length != int64(len(payload)) {
-		t.Fatalf("unexpected digest on event target: %q != %q", event.Target.Digest, dgst)
+		t.Fatalf("unexpected target length: %v != %v", event.(Event).Target.Length, len(payload))
 	}
 
-	if event.Target.Length != int64(len(payload)) {
+	if event.(Event).Target.Repository != repo {
-		t.Fatalf("unexpected target length: %v != %v", event.Target.Length, len(payload))
+		t.Fatalf("unexpected repository: %q != %q", event.(Event).Target.Repository, repo)
-	}
-
-	if event.Target.Repository != repo {
-		t.Fatalf("unexpected repository: %q != %q", event.Target.Repository, repo)
 	}
 
 }
 
-type testSinkFn func(events ...Event) error
+type testSinkFn func(event events.Event) error
 
-func (tsf testSinkFn) Write(events ...Event) error {
+func (tsf testSinkFn) Write(event events.Event) error {
-	return tsf(events...)
+	return tsf(event)
 }
 
 func (tsf testSinkFn) Close() error { return nil }

notifications/endpoint.go

@@ -5,6 +5,7 @@ import (
 	"time"
 
 	"github.com/docker/distribution/configuration"
+	events "github.com/docker/go-events"
 )
 
 // EndpointConfig covers the optional configuration parameters for an active
@@ -42,7 +43,7 @@ func (ec *EndpointConfig) defaults() {
 // services when events are written. Writes are non-blocking and always
 // succeed for callers but events may be queued internally.
 type Endpoint struct {
-	Sink
+	events.Sink
 	url  string
 	name string
 
@@ -64,7 +65,7 @@ func NewEndpoint(name, url string, config EndpointConfig) *Endpoint {
 	endpoint.Sink = newHTTPSink(
 		endpoint.url, endpoint.Timeout, endpoint.Headers,
 		endpoint.Transport, endpoint.metrics.httpStatusListener())
-	endpoint.Sink = newRetryingSink(endpoint.Sink, endpoint.Threshold, endpoint.Backoff)
+	endpoint.Sink = events.NewRetryingSink(endpoint.Sink, events.NewBreaker(endpoint.Threshold, endpoint.Backoff))
 	endpoint.Sink = newEventQueue(endpoint.Sink, endpoint.metrics.eventQueueListener())
 	mediaTypes := append(config.Ignore.MediaTypes, config.IgnoredMediaTypes...)
 	endpoint.Sink = newIgnoredSink(endpoint.Sink, mediaTypes, config.Ignore.Actions)

notifications/event.go

@@ -5,6 +5,7 @@ import (
 	"time"
 
 	"github.com/docker/distribution"
+	events "github.com/docker/go-events"
 )
 
 // EventAction constants used in action field of Event.
@@ -30,7 +31,7 @@ const (
 type Envelope struct {
 	// Events make up the contents of the envelope. Events present in a single
 	// envelope are not necessarily related.
-	Events []Event `json:"events,omitempty"`
+	Events []events.Event `json:"events,omitempty"`
 }
 
 // TODO(stevvooe): The event type should be separate from the json format. It
@@ -148,16 +149,3 @@ var (
 	// retries will not be successful.
 	ErrSinkClosed = fmt.Errorf("sink: closed")
 )
-
-// Sink accepts and sends events.
-type Sink interface {
-	// Write writes one or more events to the sink. If no error is returned,
-	// the caller will assume that all events have been committed and will not
-	// try to send them again. If an error is received, the caller may retry
-	// sending the event. The caller should cede the slice of memory to the
-	// sink and not modify it after calling this method.
-	Write(events ...Event) error
-
-	// Close the sink, possibly waiting for pending events to flush.
-	Close() error
-}

notifications/http.go

@@ -7,6 +7,8 @@ import (
 	"net/http"
 	"sync"
 	"time"
+
+	events "github.com/docker/go-events"
 )
 
 // httpSink implements a single-flight, http notification endpoint. This is
@@ -45,15 +47,15 @@ func newHTTPSink(u string, timeout time.Duration, headers http.Header, transport
 
 // httpStatusListener is called on various outcomes of sending notifications.
 type httpStatusListener interface {
-	success(status int, events ...Event)
+	success(status int, event events.Event)
-	failure(status int, events ...Event)
+	failure(status int, events events.Event)
-	err(err error, events ...Event)
+	err(err error, events events.Event)
 }
 
 // Accept makes an attempt to notify the endpoint, returning an error if it
 // fails. It is the caller's responsibility to retry on error. The events are
 // accepted or rejected as a group.
-func (hs *httpSink) Write(events ...Event) error {
+func (hs *httpSink) Write(event events.Event) error {
 	hs.mu.Lock()
 	defer hs.mu.Unlock()
 	defer hs.client.Transport.(*headerRoundTripper).CloseIdleConnections()
@@ -63,7 +65,7 @@ func (hs *httpSink) Write(events ...Event) error {
 	}
 
 	envelope := Envelope{
-		Events: events,
+		Events: []events.Event{event},
 	}
 
 	// TODO(stevvooe): It is not ideal to keep re-encoding the request body on
@@ -73,7 +75,7 @@ func (hs *httpSink) Write(events ...Event) error {
 	p, err := json.MarshalIndent(envelope, "", "   ")
 	if err != nil {
 		for _, listener := range hs.listeners {
-			listener.err(err, events...)
+			listener.err(err, event)
 		}
 		return fmt.Errorf("%v: error marshaling event envelope: %v", hs, err)
 	}
@@ -82,7 +84,7 @@ func (hs *httpSink) Write(events ...Event) error {
 	resp, err := hs.client.Post(hs.url, EventsMediaType, body)
 	if err != nil {
 		for _, listener := range hs.listeners {
-			listener.err(err, events...)
+			listener.err(err, event)
 		}
 
 		return fmt.Errorf("%v: error posting: %v", hs, err)
@@ -94,7 +96,7 @@ func (hs *httpSink) Write(events ...Event) error {
 	switch {
 	case resp.StatusCode >= 200 && resp.StatusCode < 400:
 		for _, listener := range hs.listeners {
-			listener.success(resp.StatusCode, events...)
+			listener.success(resp.StatusCode, event)
 		}
 
 		// TODO(stevvooe): This is a little accepting: we may want to support
@@ -104,7 +106,7 @@ func (hs *httpSink) Write(events ...Event) error {
 		return nil
 	default:
 		for _, listener := range hs.listeners {
-			listener.failure(resp.StatusCode, events...)
+			listener.failure(resp.StatusCode, event)
 		}
 		return fmt.Errorf("%v: response status %v unaccepted", hs, resp.Status)
 	}

notifications/http_test.go

@@ -14,6 +14,7 @@ import (
 	"testing"
 
 	"github.com/docker/distribution/manifest/schema1"
+	events "github.com/docker/go-events"
 )
 
 // TestHTTPSink mocks out an http endpoint and notifies it under a couple of
@@ -68,8 +69,8 @@ func TestHTTPSink(t *testing.T) {
 		&endpointMetricsHTTPStatusListener{safeMetrics: metrics})
 
 	// first make sure that the default transport gives x509 untrusted cert error
-	events := []Event{}
+	event := Event{}
-	err := sink.Write(events...)
+	err := sink.Write(event)
 	if !strings.Contains(err.Error(), "x509") && !strings.Contains(err.Error(), "unknown ca") {
 		t.Fatal("TLS server with default transport should give unknown CA error")
 	}
@@ -83,12 +84,13 @@ func TestHTTPSink(t *testing.T) {
 	}
 	sink = newHTTPSink(server.URL, 0, nil, tr,
 		&endpointMetricsHTTPStatusListener{safeMetrics: metrics})
-	err = sink.Write(events...)
+	err = sink.Write(event)
 	if err != nil {
-		t.Fatalf("unexpected error writing events: %v", err)
+		t.Fatalf("unexpected error writing event: %v", err)
 	}
 
 	// reset server to standard http server and sink to a basic sink
+	metrics = newSafeMetrics("")
 	server = httptest.NewServer(serverHandler)
 	sink = newHTTPSink(server.URL, 0, nil, nil,
 		&endpointMetricsHTTPStatusListener{safeMetrics: metrics})
@@ -111,46 +113,52 @@ func TestHTTPSink(t *testing.T) {
 	}()
 
 	for _, tc := range []struct {
-		events     []Event // events to send
+		event      events.Event // events to send
 		url        string
-		failure    bool // true if there should be a failure.
+		isFailure  bool // true if there should be a failure.
+		isError    bool // true if the request returns an error
 		statusCode int  // if not set, no status code should be incremented.
 	}{
 		{
 			statusCode: http.StatusOK,
-			events: []Event{
+			event:      createTestEvent("push", "library/test", schema1.MediaTypeSignedManifest),
-				createTestEvent("push", "library/test", schema1.MediaTypeSignedManifest)},
 		},
 		{
 			statusCode: http.StatusOK,
-			events: []Event{
+			event:      createTestEvent("push", "library/test", schema1.MediaTypeSignedManifest),
-				createTestEvent("push", "library/test", schema1.MediaTypeSignedManifest),
-				createTestEvent("push", "library/test", layerMediaType),
-				createTestEvent("push", "library/test", layerMediaType),
 		},
+		{
+			statusCode: http.StatusOK,
+			event:      createTestEvent("push", "library/test", layerMediaType),
+		},
+		{
+			statusCode: http.StatusOK,
+			event:      createTestEvent("push", "library/test", layerMediaType),
 		},
 		{
 			statusCode: http.StatusTemporaryRedirect,
 		},
 		{
 			statusCode: http.StatusBadRequest,
-			failure:    true,
+			isFailure:  true,
 		},
 		{
 			// Case where connection is immediately closed
-			url:     closeL.Addr().String(),
+			url:     "http://" + closeL.Addr().String(),
-			failure: true,
+			isError: true,
 		},
 	} {
 
-		if tc.failure {
+		if tc.isFailure {
-			expectedMetrics.Failures += len(tc.events)
+			expectedMetrics.Failures++
+		} else if tc.isError {
+			expectedMetrics.Errors++
 		} else {
-			expectedMetrics.Successes += len(tc.events)
+			expectedMetrics.Successes++
 		}
 
 		if tc.statusCode > 0 {
-			expectedMetrics.Statuses[fmt.Sprintf("%d %s", tc.statusCode, http.StatusText(tc.statusCode))] += len(tc.events)
+			expectedMetrics.Statuses[fmt.Sprintf("%d %s", tc.statusCode, http.StatusText(tc.statusCode))]++
 		}
 
 		url := tc.url
@@ -161,11 +169,11 @@ func TestHTTPSink(t *testing.T) {
 		url += fmt.Sprintf("?status=%v", tc.statusCode)
 		sink.url = url
 
-		t.Logf("testcase: %v, fail=%v", url, tc.failure)
+		t.Logf("testcase: %v, fail=%v, error=%v", url, tc.isFailure, tc.isError)
 		// Try a simple event emission.
-		err := sink.Write(tc.events...)
+		err := sink.Write(tc.event)
 
-		if !tc.failure {
+		if !tc.isFailure && !tc.isError {
 			if err != nil {
 				t.Fatalf("unexpected error send event: %v", err)
 			}
@@ -173,6 +181,7 @@ func TestHTTPSink(t *testing.T) {
 			if err == nil {
 				t.Fatalf("the endpoint should have rejected the request")
 			}
+			t.Logf("write error: %v", err)
 		}
 
 		if !reflect.DeepEqual(metrics.EndpointMetrics, expectedMetrics) {

notifications/metrics.go

@@ -7,6 +7,7 @@ import (
 	"sync"
 
 	prometheus "github.com/docker/distribution/metrics"
+	events "github.com/docker/go-events"
 	"github.com/docker/go-metrics"
 )
 
@@ -70,32 +71,32 @@ type endpointMetricsHTTPStatusListener struct {
 
 var _ httpStatusListener = &endpointMetricsHTTPStatusListener{}
 
-func (emsl *endpointMetricsHTTPStatusListener) success(status int, events ...Event) {
+func (emsl *endpointMetricsHTTPStatusListener) success(status int, event events.Event) {
 	emsl.safeMetrics.Lock()
 	defer emsl.safeMetrics.Unlock()
-	emsl.Statuses[fmt.Sprintf("%d %s", status, http.StatusText(status))] += len(events)
+	emsl.Statuses[fmt.Sprintf("%d %s", status, http.StatusText(status))]++
-	emsl.Successes += len(events)
+	emsl.Successes++
 
 	statusCounter.WithValues(fmt.Sprintf("%d %s", status, http.StatusText(status)), emsl.EndpointName).Inc(1)
-	eventsCounter.WithValues("Successes", emsl.EndpointName).Inc(float64(len(events)))
+	eventsCounter.WithValues("Successes", emsl.EndpointName).Inc(1)
 }
 
-func (emsl *endpointMetricsHTTPStatusListener) failure(status int, events ...Event) {
+func (emsl *endpointMetricsHTTPStatusListener) failure(status int, event events.Event) {
 	emsl.safeMetrics.Lock()
 	defer emsl.safeMetrics.Unlock()
-	emsl.Statuses[fmt.Sprintf("%d %s", status, http.StatusText(status))] += len(events)
+	emsl.Statuses[fmt.Sprintf("%d %s", status, http.StatusText(status))]++
-	emsl.Failures += len(events)
+	emsl.Failures++
 
 	statusCounter.WithValues(fmt.Sprintf("%d %s", status, http.StatusText(status)), emsl.EndpointName).Inc(1)
-	eventsCounter.WithValues("Failures", emsl.EndpointName).Inc(float64(len(events)))
+	eventsCounter.WithValues("Failures", emsl.EndpointName).Inc(1)
 }
 
-func (emsl *endpointMetricsHTTPStatusListener) err(err error, events ...Event) {
+func (emsl *endpointMetricsHTTPStatusListener) err(err error, event events.Event) {
 	emsl.safeMetrics.Lock()
 	defer emsl.safeMetrics.Unlock()
-	emsl.Errors += len(events)
+	emsl.Errors++
 
-	eventsCounter.WithValues("Errors", emsl.EndpointName).Inc(float64(len(events)))
+	eventsCounter.WithValues("Errors", emsl.EndpointName).Inc(1)
 }
 
 // endpointMetricsEventQueueListener maintains the incoming events counter and
@@ -104,20 +105,20 @@ type endpointMetricsEventQueueListener struct {
 	*safeMetrics
 }
 
-func (eqc *endpointMetricsEventQueueListener) ingress(events ...Event) {
+func (eqc *endpointMetricsEventQueueListener) ingress(event events.Event) {
 	eqc.Lock()
 	defer eqc.Unlock()
-	eqc.Events += len(events)
+	eqc.Events++
-	eqc.Pending += len(events)
+	eqc.Pending++
 
 	eventsCounter.WithValues("Events", eqc.EndpointName).Inc()
-	pendingGauge.WithValues(eqc.EndpointName).Inc(float64(len(events)))
+	pendingGauge.WithValues(eqc.EndpointName).Inc(1)
 }
 
-func (eqc *endpointMetricsEventQueueListener) egress(events ...Event) {
+func (eqc *endpointMetricsEventQueueListener) egress(event events.Event) {
 	eqc.Lock()
 	defer eqc.Unlock()
-	eqc.Pending -= len(events)
+	eqc.Pending--
 
 	pendingGauge.WithValues(eqc.EndpointName).Dec(1)
 }

notifications/sinks.go

@@ -4,107 +4,16 @@ import (
 	"container/list"
 	"fmt"
 	"sync"
-	"time"
 
+	events "github.com/docker/go-events"
 	"github.com/sirupsen/logrus"
 )
 
-// NOTE(stevvooe): This file contains definitions for several utility sinks.
-// Typically, the broadcaster is the only sink that should be required
-// externally, but others are suitable for export if the need arises. Albeit,
-// the tight integration with endpoint metrics should be removed.
-
-// Broadcaster sends events to multiple, reliable Sinks. The goal of this
-// component is to dispatch events to configured endpoints. Reliability can be
-// provided by wrapping incoming sinks.
-type Broadcaster struct {
-	sinks  []Sink
-	events chan []Event
-	closed chan chan struct{}
-}
-
-// NewBroadcaster ...
-// Add appends one or more sinks to the list of sinks. The broadcaster
-// behavior will be affected by the properties of the sink. Generally, the
-// sink should accept all messages and deal with reliability on its own. Use
-// of EventQueue and RetryingSink should be used here.
-func NewBroadcaster(sinks ...Sink) *Broadcaster {
-	b := Broadcaster{
-		sinks:  sinks,
-		events: make(chan []Event),
-		closed: make(chan chan struct{}),
-	}
-
-	// Start the broadcaster
-	go b.run()
-
-	return &b
-}
-
-// Write accepts a block of events to be dispatched to all sinks. This method
-// will never fail and should never block (hopefully!). The caller cedes the
-// slice memory to the broadcaster and should not modify it after calling
-// write.
-func (b *Broadcaster) Write(events ...Event) error {
-	select {
-	case b.events <- events:
-	case <-b.closed:
-		return ErrSinkClosed
-	}
-	return nil
-}
-
-// Close the broadcaster, ensuring that all messages are flushed to the
-// underlying sink before returning.
-func (b *Broadcaster) Close() error {
-	logrus.Infof("broadcaster: closing")
-	select {
-	case <-b.closed:
-		// already closed
-		return fmt.Errorf("broadcaster: already closed")
-	default:
-		// do a little chan handoff dance to synchronize closing
-		closed := make(chan struct{})
-		b.closed <- closed
-		close(b.closed)
-		<-closed
-		return nil
-	}
-}
-
-// run is the main broadcast loop, started when the broadcaster is created.
-// Under normal conditions, it waits for events on the event channel. After
-// Close is called, this goroutine will exit.
-func (b *Broadcaster) run() {
-	for {
-		select {
-		case block := <-b.events:
-			for _, sink := range b.sinks {
-				if err := sink.Write(block...); err != nil {
-					logrus.Errorf("broadcaster: error writing events to %v, these events will be lost: %v", sink, err)
-				}
-			}
-		case closing := <-b.closed:
-
-			// close all the underlying sinks
-			for _, sink := range b.sinks {
-				if err := sink.Close(); err != nil {
-					logrus.Errorf("broadcaster: error closing sink %v: %v", sink, err)
-				}
-			}
-			closing <- struct{}{}
-
-			logrus.Debugf("broadcaster: closed")
-			return
-		}
-	}
-}
-
 // eventQueue accepts all messages into a queue for asynchronous consumption
 // by a sink. It is unbounded and thread safe but the sink must be reliable or
 // events will be dropped.
 type eventQueue struct {
-	sink      Sink
+	sink      events.Sink
 	events    *list.List
 	listeners []eventQueueListener
 	cond      *sync.Cond
@@ -114,13 +23,13 @@ type eventQueue struct {
 
 // eventQueueListener is called when various events happen on the queue.
 type eventQueueListener interface {
-	ingress(events ...Event)
+	ingress(event events.Event)
-	egress(events ...Event)
+	egress(event events.Event)
 }
 
 // newEventQueue returns a queue to the provided sink. If the updater is non-
 // nil, it will be called to update pending metrics on ingress and egress.
-func newEventQueue(sink Sink, listeners ...eventQueueListener) *eventQueue {
+func newEventQueue(sink events.Sink, listeners ...eventQueueListener) *eventQueue {
 	eq := eventQueue{
 		sink:      sink,
 		events:    list.New(),
@@ -134,7 +43,7 @@ func newEventQueue(sink Sink, listeners ...eventQueueListener) *eventQueue {
 
 // Write accepts the events into the queue, only failing if the queue has
 // beend closed.
-func (eq *eventQueue) Write(events ...Event) error {
+func (eq *eventQueue) Write(event events.Event) error {
 	eq.mu.Lock()
 	defer eq.mu.Unlock()
 
@@ -143,9 +52,9 @@ func (eq *eventQueue) Write(events ...Event) error {
 	}
 
 	for _, listener := range eq.listeners {
-		listener.ingress(events...)
+		listener.ingress(event)
 	}
-	eq.events.PushBack(events)
+	eq.events.PushBack(event)
 	eq.cond.Signal() // signal waiters
 
 	return nil
@@ -171,18 +80,18 @@ func (eq *eventQueue) Close() error {
 // run is the main goroutine to flush events to the target sink.
 func (eq *eventQueue) run() {
 	for {
-		block := eq.next()
+		event := eq.next()
 
-		if block == nil {
+		if event == nil {
 			return // nil block means event queue is closed.
 		}
 
-		if err := eq.sink.Write(block...); err != nil {
+		if err := eq.sink.Write(event); err != nil {
 			logrus.Warnf("eventqueue: error writing events to %v, these events will be lost: %v", eq.sink, err)
 		}
 
 		for _, listener := range eq.listeners {
-			listener.egress(block...)
+			listener.egress(event)
 		}
 	}
 }
@@ -190,7 +99,7 @@ func (eq *eventQueue) run() {
 // next encompasses the critical section of the run loop. When the queue is
 // empty, it will block on the condition. If new data arrives, it will wake
 // and return a block. When closed, a nil slice will be returned.
-func (eq *eventQueue) next() []Event {
+func (eq *eventQueue) next() events.Event {
 	eq.mu.Lock()
 	defer eq.mu.Unlock()
 
@@ -204,7 +113,7 @@ func (eq *eventQueue) next() []Event {
 	}
 
 	front := eq.events.Front()
-	block := front.Value.([]Event)
+	block := front.Value.(events.Event)
 	eq.events.Remove(front)
 
 	return block
@@ -213,12 +122,12 @@ func (eq *eventQueue) next() []Event {
 // ignoredSink discards events with ignored target media types and actions.
 // passes the rest along.
 type ignoredSink struct {
-	Sink
+	events.Sink
 	ignoreMediaTypes map[string]bool
 	ignoreActions    map[string]bool
 }
 
-func newIgnoredSink(sink Sink, ignored []string, ignoreActions []string) Sink {
+func newIgnoredSink(sink events.Sink, ignored []string, ignoreActions []string) events.Sink {
 	if len(ignored) == 0 {
 		return sink
 	}
@@ -242,146 +151,14 @@ func newIgnoredSink(sink Sink, ignored []string, ignoreActions []string) Sink {
 
 // Write discards events with ignored target media types and passes the rest
 // along.
-func (imts *ignoredSink) Write(events ...Event) error {
+func (imts *ignoredSink) Write(event events.Event) error {
-	var kept []Event
+	if imts.ignoreMediaTypes[event.(Event).Target.MediaType] || imts.ignoreActions[event.(Event).Action] {
-	for _, e := range events {
-		if !imts.ignoreMediaTypes[e.Target.MediaType] {
-			kept = append(kept, e)
-		}
-	}
-	if len(kept) == 0 {
 		return nil
 	}
 
-	var results []Event
+	return imts.Sink.Write(event)
-	for _, e := range kept {
-		if !imts.ignoreActions[e.Action] {
-			results = append(results, e)
-		}
-	}
-	if len(results) == 0 {
-		return nil
-	}
-	return imts.Sink.Write(results...)
 }
 
-// retryingSink retries the write until success or an ErrSinkClosed is
+func (imts *ignoredSink) Close() error {
-// returned. Underlying sink must have p > 0 of succeeding or the sink will
-// block. Internally, it is a circuit breaker retries to manage reset.
-// Concurrent calls to a retrying sink are serialized through the sink,
-// meaning that if one is in-flight, another will not proceed.
-type retryingSink struct {
-	mu     sync.Mutex
-	sink   Sink
-	closed bool
-
-	// circuit breaker heuristics
-	failures struct {
-		threshold int
-		recent    int
-		last      time.Time
-		backoff   time.Duration // time after which we retry after failure.
-	}
-}
-
-// TODO(stevvooe): We are using circuit break here, which actually doesn't
-// make a whole lot of sense for this use case, since we always retry. Move
-// this to use bounded exponential backoff.
-
-// newRetryingSink returns a sink that will retry writes to a sink, backing
-// off on failure. Parameters threshold and backoff adjust the behavior of the
-// circuit breaker.
-func newRetryingSink(sink Sink, threshold int, backoff time.Duration) *retryingSink {
-	rs := &retryingSink{
-		sink: sink,
-	}
-	rs.failures.threshold = threshold
-	rs.failures.backoff = backoff
-
-	return rs
-}
-
-// Write attempts to flush the events to the downstream sink until it succeeds
-// or the sink is closed.
-func (rs *retryingSink) Write(events ...Event) error {
-	rs.mu.Lock()
-	defer rs.mu.Unlock()
-
-retry:
-
-	if rs.closed {
-		return ErrSinkClosed
-	}
-
-	if !rs.proceed() {
-		logrus.Warnf("%v encountered too many errors, backing off", rs.sink)
-		rs.wait(rs.failures.backoff)
-		goto retry
-	}
-
-	if err := rs.write(events...); err != nil {
-		if err == ErrSinkClosed {
-			// terminal!
-			return err
-		}
-
-		logrus.Errorf("retryingsink: error writing events: %v, retrying", err)
-		goto retry
-	}
-
 	return nil
 }
-
-// Close closes the sink and the underlying sink.
-func (rs *retryingSink) Close() error {
-	rs.mu.Lock()
-	defer rs.mu.Unlock()
-
-	if rs.closed {
-		return fmt.Errorf("retryingsink: already closed")
-	}
-
-	rs.closed = true
-	return rs.sink.Close()
-}
-
-// write provides a helper that dispatches failure and success properly. Used
-// by write as the single-flight write call.
-func (rs *retryingSink) write(events ...Event) error {
-	if err := rs.sink.Write(events...); err != nil {
-		rs.failure()
-		return err
-	}
-
-	rs.reset()
-	return nil
-}
-
-// wait backoff time against the sink, unlocking so others can proceed. Should
-// only be called by methods that currently have the mutex.
-func (rs *retryingSink) wait(backoff time.Duration) {
-	rs.mu.Unlock()
-	defer rs.mu.Lock()
-
-	// backoff here
-	time.Sleep(backoff)
-}
-
-// reset marks a successful call.
-func (rs *retryingSink) reset() {
-	rs.failures.recent = 0
-	rs.failures.last = time.Time{}
-}
-
-// failure records a failure.
-func (rs *retryingSink) failure() {
-	rs.failures.recent++
-	rs.failures.last = time.Now().UTC()
-}
-
-// proceed returns true if the call should proceed based on circuit breaker
-// heuristics.
-func (rs *retryingSink) proceed() bool {
-	return rs.failures.recent < rs.failures.threshold ||
-		time.Now().UTC().After(rs.failures.last.Add(rs.failures.backoff))
-}

notifications/sinks_test.go

@@ -1,68 +1,17 @@
 package notifications
 
 import (
-	"fmt"
-	"math/rand"
 	"reflect"
 	"sync"
 	"time"
 
+	events "github.com/docker/go-events"
+
 	"github.com/sirupsen/logrus"
 
 	"testing"
 )
 
-func TestBroadcaster(t *testing.T) {
-	const nEvents = 1000
-	var sinks []Sink
-
-	for i := 0; i < 10; i++ {
-		sinks = append(sinks, &testSink{})
-	}
-
-	b := NewBroadcaster(sinks...)
-
-	var block []Event
-	var wg sync.WaitGroup
-	for i := 1; i <= nEvents; i++ {
-		block = append(block, createTestEvent("push", "library/test", "blob"))
-
-		if i%10 == 0 && i > 0 {
-			wg.Add(1)
-			go func(block ...Event) {
-				if err := b.Write(block...); err != nil {
-					t.Errorf("error writing block of length %d: %v", len(block), err)
-				}
-				wg.Done()
-			}(block...)
-
-			block = nil
-		}
-	}
-
-	wg.Wait() // Wait until writes complete
-	if t.Failed() {
-		t.FailNow()
-	}
-	checkClose(t, b)
-
-	// Iterate through the sinks and check that they all have the expected length.
-	for _, sink := range sinks {
-		ts := sink.(*testSink)
-		ts.mu.Lock()
-		defer ts.mu.Unlock()
-
-		if len(ts.events) != nEvents {
-			t.Fatalf("not all events ended up in testsink: len(testSink) == %d, not %d", len(ts.events), nEvents)
-		}
-
-		if !ts.closed {
-			t.Fatalf("sink should have been closed")
-		}
-	}
-
-}
-
 func TestEventQueue(t *testing.T) {
 	const nevents = 1000
 	var ts testSink
@@ -75,20 +24,16 @@ func TestEventQueue(t *testing.T) {
 		}, metrics.eventQueueListener())
 
 	var wg sync.WaitGroup
-	var block []Event
+	var event events.Event
 	for i := 1; i <= nevents; i++ {
-		block = append(block, createTestEvent("push", "library/test", "blob"))
+		event = createTestEvent("push", "library/test", "blob")
-		if i%10 == 0 && i > 0 {
 		wg.Add(1)
-			go func(block ...Event) {
+		go func(event events.Event) {
-				if err := eq.Write(block...); err != nil {
+			if err := eq.Write(event); err != nil {
 				t.Errorf("error writing event block: %v", err)
 			}
 			wg.Done()
-			}(block...)
+		}(event)
-
-			block = nil
-		}
 	}
 
 	wg.Wait()
@@ -102,8 +47,8 @@ func TestEventQueue(t *testing.T) {
 	metrics.Lock()
 	defer metrics.Unlock()
 
-	if len(ts.events) != nevents {
+	if ts.count != nevents {
-		t.Fatalf("events did not make it to the sink: %d != %d", len(ts.events), 1000)
+		t.Fatalf("events did not make it to the sink: %d != %d", ts.count, 1000)
 	}
 
 	if !ts.closed {
@@ -126,16 +71,14 @@ func TestIgnoredSink(t *testing.T) {
 	type testcase struct {
 		ignoreMediaTypes []string
 		ignoreActions    []string
-		expected         []Event
+		expected         events.Event
 	}
 
 	cases := []testcase{
-		{nil, nil, []Event{blob, manifest}},
+		{nil, nil, blob},
-		{[]string{"other"}, []string{"other"}, []Event{blob, manifest}},
+		{[]string{"other"}, []string{"other"}, blob},
-		{[]string{"blob"}, []string{"other"}, []Event{manifest}},
 		{[]string{"blob", "manifest"}, []string{"other"}, nil},
-		{[]string{"other"}, []string{"push"}, []Event{manifest}},
+		{[]string{"other"}, []string{"pull"}, blob},
-		{[]string{"other"}, []string{"pull"}, []Event{blob}},
 		{[]string{"other"}, []string{"pull", "push"}, nil},
 	}
 
@@ -143,78 +86,54 @@ func TestIgnoredSink(t *testing.T) {
 		ts := &testSink{}
 		s := newIgnoredSink(ts, c.ignoreMediaTypes, c.ignoreActions)
 
-		if err := s.Write(blob, manifest); err != nil {
+		if err := s.Write(blob); err != nil {
 			t.Fatalf("error writing event: %v", err)
 		}
 
 		ts.mu.Lock()
-		if !reflect.DeepEqual(ts.events, c.expected) {
+		if !reflect.DeepEqual(ts.event, c.expected) {
-			t.Fatalf("unexpected events: %#v != %#v", ts.events, c.expected)
+			t.Fatalf("unexpected event: %#v != %#v", ts.event, c.expected)
+		}
+		ts.mu.Unlock()
+	}
+
+	cases = []testcase{
+		{nil, nil, manifest},
+		{[]string{"other"}, []string{"other"}, manifest},
+		{[]string{"blob"}, []string{"other"}, manifest},
+		{[]string{"blob", "manifest"}, []string{"other"}, nil},
+		{[]string{"other"}, []string{"push"}, manifest},
+		{[]string{"other"}, []string{"pull", "push"}, nil},
+	}
+
+	for _, c := range cases {
+		ts := &testSink{}
+		s := newIgnoredSink(ts, c.ignoreMediaTypes, c.ignoreActions)
+
+		if err := s.Write(manifest); err != nil {
+			t.Fatalf("error writing event: %v", err)
+		}
+
+		ts.mu.Lock()
+		if !reflect.DeepEqual(ts.event, c.expected) {
+			t.Fatalf("unexpected event: %#v != %#v", ts.event, c.expected)
 		}
 		ts.mu.Unlock()
 	}
 }
 
-func TestRetryingSink(t *testing.T) {
-
-	// Make a sync that fails most of the time, ensuring that all the events
-	// make it through.
-	var ts testSink
-	flaky := &flakySink{
-		rate: 1.0, // start out always failing.
-		Sink: &ts,
-	}
-	s := newRetryingSink(flaky, 3, 10*time.Millisecond)
-
-	var wg sync.WaitGroup
-	var block []Event
-	for i := 1; i <= 100; i++ {
-		block = append(block, createTestEvent("push", "library/test", "blob"))
-
-		// Above 50, set the failure rate lower
-		if i > 50 {
-			s.mu.Lock()
-			flaky.rate = 0.90
-			s.mu.Unlock()
-		}
-
-		if i%10 == 0 && i > 0 {
-			wg.Add(1)
-			go func(block ...Event) {
-				defer wg.Done()
-				if err := s.Write(block...); err != nil {
-					t.Errorf("error writing event block: %v", err)
-				}
-			}(block...)
-
-			block = nil
-		}
-	}
-
-	wg.Wait()
-	if t.Failed() {
-		t.FailNow()
-	}
-	checkClose(t, s)
-
-	ts.mu.Lock()
-	defer ts.mu.Unlock()
-
-	if len(ts.events) != 100 {
-		t.Fatalf("events not propagated: %d != %d", len(ts.events), 100)
-	}
-}
-
 type testSink struct {
-	events []Event
+	event  events.Event
+	count  int
 	mu     sync.Mutex
 	closed bool
 }
 
-func (ts *testSink) Write(events ...Event) error {
+func (ts *testSink) Write(event events.Event) error {
 	ts.mu.Lock()
 	defer ts.mu.Unlock()
-	ts.events = append(ts.events, events...)
+	ts.event = event
+	ts.count++
 	return nil
 }
 
@@ -228,29 +147,16 @@ func (ts *testSink) Close() error {
 }
 
 type delayedSink struct {
-	Sink
+	events.Sink
 	delay time.Duration
 }
 
-func (ds *delayedSink) Write(events ...Event) error {
+func (ds *delayedSink) Write(event events.Event) error {
 	time.Sleep(ds.delay)
-	return ds.Sink.Write(events...)
+	return ds.Sink.Write(event)
 }
 
-type flakySink struct {
+func checkClose(t *testing.T, sink events.Sink) {
-	Sink
-	rate float64
-}
-
-func (fs *flakySink) Write(events ...Event) error {
-	if rand.Float64() < fs.rate {
-		return fmt.Errorf("error writing %d events", len(events))
-	}
-
-	return fs.Sink.Write(events...)
-}
-
-func checkClose(t *testing.T, sink Sink) {
 	if err := sink.Close(); err != nil {
 		t.Fatalf("unexpected error closing: %v", err)
 	}
@@ -261,7 +167,7 @@ func checkClose(t *testing.T, sink Sink) {
 	}
 
 	// Write after closed should be an error
-	if err := sink.Write([]Event{}...); err == nil {
+	if err := sink.Write(Event{}); err == nil {
 		t.Fatalf("write after closed did not have an error")
 	} else if err != ErrSinkClosed {
 		t.Fatalf("error should be ErrSinkClosed")

registry/handlers/app.go

@@ -36,6 +36,7 @@ import (
 	"github.com/docker/distribution/registry/storage/driver/factory"
 	storagemiddleware "github.com/docker/distribution/registry/storage/driver/middleware"
 	"github.com/docker/distribution/version"
+	events "github.com/docker/go-events"
 	"github.com/docker/go-metrics"
 	"github.com/docker/libtrust"
 	"github.com/garyburd/redigo/redis"
@@ -70,7 +71,7 @@ type App struct {
 
 	// events contains notification related configuration.
 	events struct {
-		sink   notifications.Sink
+		sink   events.Sink
 		source notifications.SourceRecord
 	}
 
@@ -446,7 +447,7 @@ func (app *App) register(routeName string, dispatch dispatchFunc) {
 // configureEvents prepares the event sink for action.
 func (app *App) configureEvents(configuration *configuration.Configuration) {
 	// Configure all of the endpoint sinks.
-	var sinks []notifications.Sink
+	var sinks []events.Sink
 	for _, endpoint := range configuration.Notifications.Endpoints {
 		if endpoint.Disabled {
 			dcontext.GetLogger(app).Infof("endpoint %s disabled, skipping", endpoint.Name)
@@ -470,7 +471,7 @@ func (app *App) configureEvents(configuration *configuration.Configuration) {
 	// replacing broadcaster with a rabbitmq implementation. It's recommended
 	// that the registry instances also act as the workers to keep deployment
 	// simple.
-	app.events.sink = notifications.NewBroadcaster(sinks...)
+	app.events.sink = events.NewBroadcaster(sinks...)
 
 	// Populate registry event source
 	hostname, err := os.Hostname()

vendor/github.com/docker/go-events/.gitignore

@@ -0,0 +1,24 @@
+# Compiled Object files, Static and Dynamic libs (Shared Objects)
+*.o
+*.a
+*.so
+
+# Folders
+_obj
+_test
+
+# Architecture specific extensions/prefixes
+*.[568vq]
+[568vq].out
+
+*.cgo1.go
+*.cgo2.c
+_cgo_defun.c
+_cgo_gotypes.go
+_cgo_export.*
+
+_testmain.go
+
+*.exe
+*.test
+*.prof

vendor/github.com/docker/go-events/CONTRIBUTING.md

@@ -0,0 +1,70 @@
+# Contributing to Docker open source projects
+
+Want to hack on go-events? Awesome! Here are instructions to get you started.
+
+go-events is part of the [Docker](https://www.docker.com) project, and
+follows the same rules and principles. If you're already familiar with the way
+Docker does things, you'll feel right at home.
+
+Otherwise, go read Docker's
+[contributions guidelines](https://github.com/docker/docker/blob/master/CONTRIBUTING.md),
+[issue triaging](https://github.com/docker/docker/blob/master/project/ISSUE-TRIAGE.md),
+[review process](https://github.com/docker/docker/blob/master/project/REVIEWING.md) and
+[branches and tags](https://github.com/docker/docker/blob/master/project/BRANCHES-AND-TAGS.md).
+
+For an in-depth description of our contribution process, visit the
+contributors guide: [Understand how to contribute](https://docs.docker.com/opensource/workflow/make-a-contribution/)
+
+### Sign your work
+
+The sign-off is a simple line at the end of the explanation for the patch. Your
+signature certifies that you wrote the patch or otherwise have the right to pass
+it on as an open-source patch. The rules are pretty simple: if you can certify
+the below (from [developercertificate.org](http://developercertificate.org/)):
+
+```
+Developer Certificate of Origin
+Version 1.1
+
+Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
+660 York Street, Suite 102,
+San Francisco, CA 94110 USA
+
+Everyone is permitted to copy and distribute verbatim copies of this
+license document, but changing it is not allowed.
+
+Developer's Certificate of Origin 1.1
+
+By making a contribution to this project, I certify that:
+
+(a) The contribution was created in whole or in part by me and I
+    have the right to submit it under the open source license
+    indicated in the file; or
+
+(b) The contribution is based upon previous work that, to the best
+    of my knowledge, is covered under an appropriate open source
+    license and I have the right under that license to submit that
+    work with modifications, whether created in whole or in part
+    by me, under the same open source license (unless I am
+    permitted to submit under a different license), as indicated
+    in the file; or
+
+(c) The contribution was provided directly to me by some other
+    person who certified (a), (b) or (c) and I have not modified
+    it.
+
+(d) I understand and agree that this project and the contribution
+    are public and that a record of the contribution (including all
+    personal information I submit with it, including my sign-off) is
+    maintained indefinitely and may be redistributed consistent with
+    this project or the open source license(s) involved.
+```
+
+Then you just add a line to every git commit message:
+
+    Signed-off-by: Joe Smith <joe.smith@email.com>
+
+Use your real name (sorry, no pseudonyms or anonymous contributions.)
+
+If you set your `user.name` and `user.email` git configs, you can sign your
+commit automatically with `git commit -s`.

vendor/github.com/docker/go-events/LICENSE

@@ -0,0 +1,201 @@
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
+
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
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+
+      "Work" shall mean the work of authorship, whether in Source or
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+      copyright notice that is included in or attached to the work
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+
+      "Derivative Works" shall mean any work, whether in Source or Object
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+      editorial revisions, annotations, elaborations, or other modifications
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+      of this License, Derivative Works shall not include works that remain
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+      "Contribution" shall mean any work of authorship, including
+      the original version of the Work and any modifications or additions
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+      communication on electronic mailing lists, source code control systems,
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+      "Contributor" shall mean Licensor and any individual or Legal Entity
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+      subsequently incorporated within the Work.
+
+   2. Grant of Copyright License. Subject to the terms and conditions of
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+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
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+   4. Redistribution. You may reproduce and distribute copies of the
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+      meet the following conditions:
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+      (a) You must give any other recipients of the Work or
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+      (b) You must cause any modified files to carry prominent notices
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+      (d) If the Work includes a "NOTICE" text file as part of its
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+          of the NOTICE file are for informational purposes only and
+          do not modify the License. You may add Your own attribution
+          notices within Derivative Works that You distribute, alongside
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+          that such additional attribution notices cannot be construed
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+
+      You may add Your own copyright statement to Your modifications and
+      may provide additional or different license terms and conditions
+      for use, reproduction, or distribution of Your modifications, or
+      for any such Derivative Works as a whole, provided Your use,
+      reproduction, and distribution of the Work otherwise complies with
+      the conditions stated in this License.
+
+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+
+   6. Trademarks. This License does not grant permission to use the trade
+      names, trademarks, service marks, or product names of the Licensor,
+      except as required for reasonable and customary use in describing the
+      origin of the Work and reproducing the content of the NOTICE file.
+
+   7. Disclaimer of Warranty. Unless required by applicable law or
+      agreed to in writing, Licensor provides the Work (and each
+      Contributor provides its Contributions) on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+      implied, including, without limitation, any warranties or conditions
+      of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+      PARTICULAR PURPOSE. You are solely responsible for determining the
+      appropriateness of using or redistributing the Work and assume any
+      risks associated with Your exercise of permissions under this License.
+
+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
+      incidental, or consequential damages of any character arising as a
+      result of this License or out of the use or inability to use the
+      Work (including but not limited to damages for loss of goodwill,
+      work stoppage, computer failure or malfunction, or any and all
+      other commercial damages or losses), even if such Contributor
+      has been advised of the possibility of such damages.
+
+   9. Accepting Warranty or Additional Liability. While redistributing
+      the Work or Derivative Works thereof, You may choose to offer,
+      and charge a fee for, acceptance of support, warranty, indemnity,
+      or other liability obligations and/or rights consistent with this
+      License. However, in accepting such obligations, You may act only
+      on Your own behalf and on Your sole responsibility, not on behalf
+      of any other Contributor, and only if You agree to indemnify,
+      defend, and hold each Contributor harmless for any liability
+      incurred by, or claims asserted against, such Contributor by reason
+      of your accepting any such warranty or additional liability.
+
+   END OF TERMS AND CONDITIONS
+
+   APPENDIX: How to apply the Apache License to your work.
+
+      To apply the Apache License to your work, attach the following
+      boilerplate notice, with the fields enclosed by brackets "{}"
+      replaced with your own identifying information. (Don't include
+      the brackets!)  The text should be enclosed in the appropriate
+      comment syntax for the file format. We also recommend that a
+      file or class name and description of purpose be included on the
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+
+   Copyright 2016 Docker, Inc.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.

vendor/github.com/docker/go-events/MAINTAINERS

@@ -0,0 +1,46 @@
+# go-events maintainers file
+#
+# This file describes who runs the docker/go-events project and how.
+# This is a living document - if you see something out of date or missing, speak up!
+#
+# It is structured to be consumable by both humans and programs.
+# To extract its contents programmatically, use any TOML-compliant parser.
+#
+# This file is compiled into the MAINTAINERS file in docker/opensource.
+#
+[Org]
+	[Org."Core maintainers"]
+		people = [
+			"aaronlehmann",
+			"aluzzardi",
+			"lk4d4",
+			"stevvooe",
+		]
+
+[people]
+
+# A reference list of all people associated with the project.
+# All other sections should refer to people by their canonical key
+# in the people section.
+
+	# ADD YOURSELF HERE IN ALPHABETICAL ORDER
+
+	[people.aaronlehmann]
+	Name = "Aaron Lehmann"
+	Email = "aaron.lehmann@docker.com"
+	GitHub = "aaronlehmann"
+
+	[people.aluzzardi]
+	Name = "Andrea Luzzardi"
+	Email = "al@docker.com"
+	GitHub = "aluzzardi"
+
+	[people.lk4d4]
+	Name = "Alexander Morozov"
+	Email = "lk4d4@docker.com"
+	GitHub = "lk4d4"
+
+	[people.stevvooe]
+	Name = "Stephen Day"
+	Email = "stephen.day@docker.com"
+	GitHub = "stevvooe"

vendor/github.com/docker/go-events/README.md

@@ -0,0 +1,117 @@
+# Docker Events Package
+
+[![GoDoc](https://godoc.org/github.com/docker/go-events?status.svg)](https://godoc.org/github.com/docker/go-events)
+[![Circle CI](https://circleci.com/gh/docker/go-events.svg?style=shield)](https://circleci.com/gh/docker/go-events)
+
+The Docker `events` package implements a composable event distribution package
+for Go.
+
+Originally created to implement the [notifications in Docker Registry
+2](https://github.com/docker/distribution/blob/master/docs/notifications.md),
+we've found the pattern to be useful in other applications. This package is
+most of the same code with slightly updated interfaces. Much of the internals
+have been made available.
+
+## Usage
+
+The `events` package centers around a `Sink` type.  Events are written with
+calls to `Sink.Write(event Event)`. Sinks can be wired up in various
+configurations to achieve interesting behavior.
+
+The canonical example is that employed by the
+[docker/distribution/notifications](https://godoc.org/github.com/docker/distribution/notifications)
+package. Let's say we have a type `httpSink` where we'd like to queue
+notifications. As a rule, it should send a single http request and return an
+error if it fails:
+
+```go
+func (h *httpSink) Write(event Event) error {
+	p, err := json.Marshal(event)
+	if err != nil {
+		return err
+	}
+	body := bytes.NewReader(p)
+	resp, err := h.client.Post(h.url, "application/json", body)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+	
+	if resp.Status != 200 {
+		return errors.New("unexpected status")
+	}
+
+	return nil
+}
+
+// implement (*httpSink).Close()
+```
+
+With just that, we can start using components from this package. One can call
+`(*httpSink).Write` to send events as the body of a post request to a
+configured URL.
+
+### Retries
+
+HTTP can be unreliable. The first feature we'd like is to have some retry:
+
+```go
+hs := newHTTPSink(/*...*/)
+retry := NewRetryingSink(hs, NewBreaker(5, time.Second))
+```
+
+We now have a sink that will retry events against the `httpSink` until they
+succeed. The retry will backoff for one second after 5 consecutive failures
+using the breaker strategy.
+
+### Queues
+
+This isn't quite enough. We we want a sink that doesn't block while we are
+waiting for events to be sent. Let's add a `Queue`:
+
+```go
+queue := NewQueue(retry)
+```
+
+Now, we have an unbounded queue that will work through all events sent with
+`(*Queue).Write`. Events can be added asynchronously to the queue without
+blocking the current execution path. This is ideal for use in an http request.
+
+### Broadcast
+
+It usually turns out that you want to send to more than one listener. We can
+use `Broadcaster` to support this:
+
+```go
+var broadcast = NewBroadcaster() // make it available somewhere in your application.
+broadcast.Add(queue) // add your queue!
+broadcast.Add(queue2) // and another!
+```
+
+With the above, we can now call `broadcast.Write` in our http handlers and have
+all the events distributed to each queue. Because the events are queued, not
+listener blocks another.
+
+### Extending
+
+For the most part, the above is sufficient for a lot of applications. However,
+extending the above functionality can be done implementing your own `Sink`. The
+behavior and semantics of the sink can be completely dependent on the
+application requirements. The interface is provided below for reference:
+
+```go
+type Sink {
+	Write(Event) error
+	Close() error
+}
+```
+
+Application behavior can be controlled by how `Write` behaves. The examples
+above are designed to queue the message and return as quickly as possible.
+Other implementations may block until the event is committed to durable
+storage.
+
+## Copyright and license
+
+Copyright © 2016 Docker, Inc. go-events is licensed under the Apache License,
+Version 2.0. See [LICENSE](LICENSE) for the full license text.

vendor/github.com/docker/go-events/broadcast.go

@@ -0,0 +1,178 @@
+package events
+
+import (
+	"fmt"
+	"sync"
+
+	"github.com/sirupsen/logrus"
+)
+
+// Broadcaster sends events to multiple, reliable Sinks. The goal of this
+// component is to dispatch events to configured endpoints. Reliability can be
+// provided by wrapping incoming sinks.
+type Broadcaster struct {
+	sinks   []Sink
+	events  chan Event
+	adds    chan configureRequest
+	removes chan configureRequest
+
+	shutdown chan struct{}
+	closed   chan struct{}
+	once     sync.Once
+}
+
+// NewBroadcaster appends one or more sinks to the list of sinks. The
+// broadcaster behavior will be affected by the properties of the sink.
+// Generally, the sink should accept all messages and deal with reliability on
+// its own. Use of EventQueue and RetryingSink should be used here.
+func NewBroadcaster(sinks ...Sink) *Broadcaster {
+	b := Broadcaster{
+		sinks:    sinks,
+		events:   make(chan Event),
+		adds:     make(chan configureRequest),
+		removes:  make(chan configureRequest),
+		shutdown: make(chan struct{}),
+		closed:   make(chan struct{}),
+	}
+
+	// Start the broadcaster
+	go b.run()
+
+	return &b
+}
+
+// Write accepts an event to be dispatched to all sinks. This method will never
+// fail and should never block (hopefully!). The caller cedes the memory to the
+// broadcaster and should not modify it after calling write.
+func (b *Broadcaster) Write(event Event) error {
+	select {
+	case b.events <- event:
+	case <-b.closed:
+		return ErrSinkClosed
+	}
+	return nil
+}
+
+// Add the sink to the broadcaster.
+//
+// The provided sink must be comparable with equality. Typically, this just
+// works with a regular pointer type.
+func (b *Broadcaster) Add(sink Sink) error {
+	return b.configure(b.adds, sink)
+}
+
+// Remove the provided sink.
+func (b *Broadcaster) Remove(sink Sink) error {
+	return b.configure(b.removes, sink)
+}
+
+type configureRequest struct {
+	sink     Sink
+	response chan error
+}
+
+func (b *Broadcaster) configure(ch chan configureRequest, sink Sink) error {
+	response := make(chan error, 1)
+
+	for {
+		select {
+		case ch <- configureRequest{
+			sink:     sink,
+			response: response}:
+			ch = nil
+		case err := <-response:
+			return err
+		case <-b.closed:
+			return ErrSinkClosed
+		}
+	}
+}
+
+// Close the broadcaster, ensuring that all messages are flushed to the
+// underlying sink before returning.
+func (b *Broadcaster) Close() error {
+	b.once.Do(func() {
+		close(b.shutdown)
+	})
+
+	<-b.closed
+	return nil
+}
+
+// run is the main broadcast loop, started when the broadcaster is created.
+// Under normal conditions, it waits for events on the event channel. After
+// Close is called, this goroutine will exit.
+func (b *Broadcaster) run() {
+	defer close(b.closed)
+	remove := func(target Sink) {
+		for i, sink := range b.sinks {
+			if sink == target {
+				b.sinks = append(b.sinks[:i], b.sinks[i+1:]...)
+				break
+			}
+		}
+	}
+
+	for {
+		select {
+		case event := <-b.events:
+			for _, sink := range b.sinks {
+				if err := sink.Write(event); err != nil {
+					if err == ErrSinkClosed {
+						// remove closed sinks
+						remove(sink)
+						continue
+					}
+					logrus.WithField("event", event).WithField("events.sink", sink).WithError(err).
+						Errorf("broadcaster: dropping event")
+				}
+			}
+		case request := <-b.adds:
+			// while we have to iterate for add/remove, common iteration for
+			// send is faster against slice.
+
+			var found bool
+			for _, sink := range b.sinks {
+				if request.sink == sink {
+					found = true
+					break
+				}
+			}
+
+			if !found {
+				b.sinks = append(b.sinks, request.sink)
+			}
+			// b.sinks[request.sink] = struct{}{}
+			request.response <- nil
+		case request := <-b.removes:
+			remove(request.sink)
+			request.response <- nil
+		case <-b.shutdown:
+			// close all the underlying sinks
+			for _, sink := range b.sinks {
+				if err := sink.Close(); err != nil && err != ErrSinkClosed {
+					logrus.WithField("events.sink", sink).WithError(err).
+						Errorf("broadcaster: closing sink failed")
+				}
+			}
+			return
+		}
+	}
+}
+
+func (b *Broadcaster) String() string {
+	// Serialize copy of this broadcaster without the sync.Once, to avoid
+	// a data race.
+
+	b2 := map[string]interface{}{
+		"sinks":   b.sinks,
+		"events":  b.events,
+		"adds":    b.adds,
+		"removes": b.removes,
+
+		"shutdown": b.shutdown,
+		"closed":   b.closed,
+	}
+
+	return fmt.Sprint(b2)
+}

vendor/github.com/docker/go-events/channel.go

@@ -0,0 +1,61 @@
+package events
+
+import (
+	"fmt"
+	"sync"
+)
+
+// Channel provides a sink that can be listened on. The writer and channel
+// listener must operate in separate goroutines.
+//
+// Consumers should listen on Channel.C until Closed is closed.
+type Channel struct {
+	C chan Event
+
+	closed chan struct{}
+	once   sync.Once
+}
+
+// NewChannel returns a channel. If buffer is zero, the channel is
+// unbuffered.
+func NewChannel(buffer int) *Channel {
+	return &Channel{
+		C:      make(chan Event, buffer),
+		closed: make(chan struct{}),
+	}
+}
+
+// Done returns a channel that will always proceed once the sink is closed.
+func (ch *Channel) Done() chan struct{} {
+	return ch.closed
+}
+
+// Write the event to the channel. Must be called in a separate goroutine from
+// the listener.
+func (ch *Channel) Write(event Event) error {
+	select {
+	case ch.C <- event:
+		return nil
+	case <-ch.closed:
+		return ErrSinkClosed
+	}
+}
+
+// Close the channel sink.
+func (ch *Channel) Close() error {
+	ch.once.Do(func() {
+		close(ch.closed)
+	})
+
+	return nil
+}
+
+func (ch *Channel) String() string {
+	// Serialize a copy of the Channel that doesn't contain the sync.Once,
+	// to avoid a data race.
+	ch2 := map[string]interface{}{
+		"C":      ch.C,
+		"closed": ch.closed,
+	}
+	return fmt.Sprint(ch2)
+}

vendor/github.com/docker/go-events/errors.go

@@ -0,0 +1,10 @@
+package events
+
+import "fmt"
+
+var (
+	// ErrSinkClosed is returned if a write is issued to a sink that has been
+	// closed. If encountered, the error should be considered terminal and
+	// retries will not be successful.
+	ErrSinkClosed = fmt.Errorf("events: sink closed")
+)

vendor/github.com/docker/go-events/event.go

@@ -0,0 +1,15 @@
+package events
+
+// Event marks items that can be sent as events.
+type Event interface{}
+
+// Sink accepts and sends events.
+type Sink interface {
+	// Write an event to the Sink. If no error is returned, the caller will
+	// assume that all events have been committed to the sink. If an error is
+	// received, the caller may retry sending the event.
+	Write(event Event) error
+
+	// Close the sink, possibly waiting for pending events to flush.
+	Close() error
+}

vendor/github.com/docker/go-events/filter.go

@@ -0,0 +1,52 @@
+package events
+
+// Matcher matches events.
+type Matcher interface {
+	Match(event Event) bool
+}
+
+// MatcherFunc implements matcher with just a function.
+type MatcherFunc func(event Event) bool
+
+// Match calls the wrapped function.
+func (fn MatcherFunc) Match(event Event) bool {
+	return fn(event)
+}
+
+// Filter provides an event sink that sends only events that are accepted by a
+// Matcher. No methods on filter are goroutine safe.
+type Filter struct {
+	dst     Sink
+	matcher Matcher
+	closed  bool
+}
+
+// NewFilter returns a new filter that will send to events to dst that return
+// true for Matcher.
+func NewFilter(dst Sink, matcher Matcher) Sink {
+	return &Filter{dst: dst, matcher: matcher}
+}
+
+// Write an event to the filter.
+func (f *Filter) Write(event Event) error {
+	if f.closed {
+		return ErrSinkClosed
+	}
+
+	if f.matcher.Match(event) {
+		return f.dst.Write(event)
+	}
+
+	return nil
+}
+
+// Close the filter and allow no more events to pass through.
+func (f *Filter) Close() error {
+	// TODO(stevvooe): Not all sinks should have Close.
+	if f.closed {
+		return nil
+	}
+
+	f.closed = true
+	return f.dst.Close()
+}

vendor/github.com/docker/go-events/queue.go

@@ -0,0 +1,111 @@
+package events
+
+import (
+	"container/list"
+	"sync"
+
+	"github.com/sirupsen/logrus"
+)
+
+// Queue accepts all messages into a queue for asynchronous consumption
+// by a sink. It is unbounded and thread safe but the sink must be reliable or
+// events will be dropped.
+type Queue struct {
+	dst    Sink
+	events *list.List
+	cond   *sync.Cond
+	mu     sync.Mutex
+	closed bool
+}
+
+// NewQueue returns a queue to the provided Sink dst.
+func NewQueue(dst Sink) *Queue {
+	eq := Queue{
+		dst:    dst,
+		events: list.New(),
+	}
+
+	eq.cond = sync.NewCond(&eq.mu)
+	go eq.run()
+	return &eq
+}
+
+// Write accepts the events into the queue, only failing if the queue has
+// been closed.
+func (eq *Queue) Write(event Event) error {
+	eq.mu.Lock()
+	defer eq.mu.Unlock()
+
+	if eq.closed {
+		return ErrSinkClosed
+	}
+
+	eq.events.PushBack(event)
+	eq.cond.Signal() // signal waiters
+
+	return nil
+}
+
+// Close shutsdown the event queue, flushing
+func (eq *Queue) Close() error {
+	eq.mu.Lock()
+	defer eq.mu.Unlock()
+
+	if eq.closed {
+		return nil
+	}
+
+	// set closed flag
+	eq.closed = true
+	eq.cond.Signal() // signal flushes queue
+	eq.cond.Wait()   // wait for signal from last flush
+	return eq.dst.Close()
+}
+
+// run is the main goroutine to flush events to the target sink.
+func (eq *Queue) run() {
+	for {
+		event := eq.next()
+
+		if event == nil {
+			return // nil block means event queue is closed.
+		}
+
+		if err := eq.dst.Write(event); err != nil {
+			// TODO(aaronl): Dropping events could be bad depending
+			// on the application. We should have a way of
+			// communicating this condition. However, logging
+			// at a log level above debug may not be appropriate.
+			// Eventually, go-events should not use logrus at all,
+			// and should bubble up conditions like this through
+			// error values.
+			logrus.WithFields(logrus.Fields{
+				"event": event,
+				"sink":  eq.dst,
+			}).WithError(err).Debug("eventqueue: dropped event")
+		}
+	}
+}
+
+// next encompasses the critical section of the run loop. When the queue is
+// empty, it will block on the condition. If new data arrives, it will wake
+// and return a block. When closed, a nil slice will be returned.
+func (eq *Queue) next() Event {
+	eq.mu.Lock()
+	defer eq.mu.Unlock()
+
+	for eq.events.Len() < 1 {
+		if eq.closed {
+			eq.cond.Broadcast()
+			return nil
+		}
+
+		eq.cond.Wait()
+	}
+
+	front := eq.events.Front()
+	block := front.Value.(Event)
+	eq.events.Remove(front)
+
+	return block
+}

vendor/github.com/docker/go-events/retry.go

@@ -0,0 +1,260 @@
+package events
+
+import (
+	"fmt"
+	"math/rand"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/sirupsen/logrus"
+)
+
+// RetryingSink retries the write until success or an ErrSinkClosed is
+// returned. Underlying sink must have p > 0 of succeeding or the sink will
+// block. Retry is configured with a RetryStrategy.  Concurrent calls to a
+// retrying sink are serialized through the sink, meaning that if one is
+// in-flight, another will not proceed.
+type RetryingSink struct {
+	sink     Sink
+	strategy RetryStrategy
+	closed   chan struct{}
+	once     sync.Once
+}
+
+// NewRetryingSink returns a sink that will retry writes to a sink, backing
+// off on failure. Parameters threshold and backoff adjust the behavior of the
+// circuit breaker.
+func NewRetryingSink(sink Sink, strategy RetryStrategy) *RetryingSink {
+	rs := &RetryingSink{
+		sink:     sink,
+		strategy: strategy,
+		closed:   make(chan struct{}),
+	}
+
+	return rs
+}
+
+// Write attempts to flush the events to the downstream sink until it succeeds
+// or the sink is closed.
+func (rs *RetryingSink) Write(event Event) error {
+	logger := logrus.WithField("event", event)
+
+retry:
+	select {
+	case <-rs.closed:
+		return ErrSinkClosed
+	default:
+	}
+
+	if backoff := rs.strategy.Proceed(event); backoff > 0 {
+		select {
+		case <-time.After(backoff):
+			// TODO(stevvooe): This branch holds up the next try. Before, we
+			// would simply break to the "retry" label and then possibly wait
+			// again. However, this requires all retry strategies to have a
+			// large probability of probing the sync for success, rather than
+			// just backing off and sending the request.
+		case <-rs.closed:
+			return ErrSinkClosed
+		}
+	}
+
+	if err := rs.sink.Write(event); err != nil {
+		if err == ErrSinkClosed {
+			// terminal!
+			return err
+		}
+
+		logger := logger.WithError(err) // shadow!!
+
+		if rs.strategy.Failure(event, err) {
+			logger.Errorf("retryingsink: dropped event")
+			return nil
+		}
+
+		logger.Errorf("retryingsink: error writing event, retrying")
+		goto retry
+	}
+
+	rs.strategy.Success(event)
+	return nil
+}
+
+// Close closes the sink and the underlying sink.
+func (rs *RetryingSink) Close() error {
+	rs.once.Do(func() {
+		close(rs.closed)
+	})
+
+	return nil
+}
+
+func (rs *RetryingSink) String() string {
+	// Serialize a copy of the RetryingSink without the sync.Once, to avoid
+	// a data race.
+	rs2 := map[string]interface{}{
+		"sink":     rs.sink,
+		"strategy": rs.strategy,
+		"closed":   rs.closed,
+	}
+	return fmt.Sprint(rs2)
+}
+
+// RetryStrategy defines a strategy for retrying event sink writes.
+//
+// All methods should be goroutine safe.
+type RetryStrategy interface {
+	// Proceed is called before every event send. If proceed returns a
+	// positive, non-zero integer, the retryer will back off by the provided
+	// duration.
+	//
+	// An event is provided, by may be ignored.
+	Proceed(event Event) time.Duration
+
+	// Failure reports a failure to the strategy. If this method returns true,
+	// the event should be dropped.
+	Failure(event Event, err error) bool
+
+	// Success should be called when an event is sent successfully.
+	Success(event Event)
+}
+
+// Breaker implements a circuit breaker retry strategy.
+//
+// The current implementation never drops events.
+type Breaker struct {
+	threshold int
+	recent    int
+	last      time.Time
+	backoff   time.Duration // time after which we retry after failure.
+	mu        sync.Mutex
+}
+
+var _ RetryStrategy = &Breaker{}
+
+// NewBreaker returns a breaker that will backoff after the threshold has been
+// tripped. A Breaker is thread safe and may be shared by many goroutines.
+func NewBreaker(threshold int, backoff time.Duration) *Breaker {
+	return &Breaker{
+		threshold: threshold,
+		backoff:   backoff,
+	}
+}
+
+// Proceed checks the failures against the threshold.
+func (b *Breaker) Proceed(event Event) time.Duration {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	if b.recent < b.threshold {
+		return 0
+	}
+
+	return b.last.Add(b.backoff).Sub(time.Now())
+}
+
+// Success resets the breaker.
+func (b *Breaker) Success(event Event) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	b.recent = 0
+	b.last = time.Time{}
+}
+
+// Failure records the failure and latest failure time.
+func (b *Breaker) Failure(event Event, err error) bool {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	b.recent++
+	b.last = time.Now().UTC()
+	return false // never drop events.
+}
+
+var (
+	// DefaultExponentialBackoffConfig provides a default configuration for
+	// exponential backoff.
+	DefaultExponentialBackoffConfig = ExponentialBackoffConfig{
+		Base:   time.Second,
+		Factor: time.Second,
+		Max:    20 * time.Second,
+	}
+)
+
+// ExponentialBackoffConfig configures backoff parameters.
+//
+// Note that these parameters operate on the upper bound for choosing a random
+// value. For example, at Base=1s, a random value in [0,1s) will be chosen for
+// the backoff value.
+type ExponentialBackoffConfig struct {
+	// Base is the minimum bound for backing off after failure.
+	Base time.Duration
+
+	// Factor sets the amount of time by which the backoff grows with each
+	// failure.
+	Factor time.Duration
+
+	// Max is the absolute maxiumum bound for a single backoff.
+	Max time.Duration
+}
+
+// ExponentialBackoff implements random backoff with exponentially increasing
+// bounds as the number consecutive failures increase.
+type ExponentialBackoff struct {
+	failures uint64 // consecutive failure counter (needs to be 64-bit aligned)
+	config   ExponentialBackoffConfig
+}
+
+// NewExponentialBackoff returns an exponential backoff strategy with the
+// desired config. If config is nil, the default is returned.
+func NewExponentialBackoff(config ExponentialBackoffConfig) *ExponentialBackoff {
+	return &ExponentialBackoff{
+		config: config,
+	}
+}
+
+// Proceed returns the next randomly bound exponential backoff time.
+func (b *ExponentialBackoff) Proceed(event Event) time.Duration {
+	return b.backoff(atomic.LoadUint64(&b.failures))
+}
+
+// Success resets the failures counter.
+func (b *ExponentialBackoff) Success(event Event) {
+	atomic.StoreUint64(&b.failures, 0)
+}
+
+// Failure increments the failure counter.
+func (b *ExponentialBackoff) Failure(event Event, err error) bool {
+	atomic.AddUint64(&b.failures, 1)
+	return false
+}
+
+// backoff calculates the amount of time to wait based on the number of
+// consecutive failures.
+func (b *ExponentialBackoff) backoff(failures uint64) time.Duration {
+	if failures <= 0 {
+		// proceed normally when there are no failures.
+		return 0
+	}
+
+	factor := b.config.Factor
+	if factor <= 0 {
+		factor = DefaultExponentialBackoffConfig.Factor
+	}
+
+	backoff := b.config.Base + factor*time.Duration(1<<(failures-1))
+
+	max := b.config.Max
+	if max <= 0 {
+		max = DefaultExponentialBackoffConfig.Max
+	}
+
+	if backoff > max || backoff < 0 {
+		backoff = max
+	}
+
+	// Choose a uniformly distributed value from [0, backoff).
+	return time.Duration(rand.Int63n(int64(backoff)))
+}

vendor/modules.txt

@@ -61,6 +61,8 @@ github.com/denverdino/aliyungo/oss
 github.com/denverdino/aliyungo/util
 # github.com/dgrijalva/jwt-go v0.0.0-20170104182250-a601269ab70c
 github.com/dgrijalva/jwt-go
+# github.com/docker/go-events v0.0.0-20190806004212-e31b211e4f1c
+github.com/docker/go-events
 # github.com/docker/go-metrics v0.0.1
 github.com/docker/go-metrics
 # github.com/docker/libtrust v0.0.0-20150114040149-fa567046d9b1