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event_dispatcher.go
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/
event_dispatcher.go
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/*
* Copyright 2018 The Knative Authors
*
* 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.
*/
package channel
import (
"context"
"fmt"
"net/http"
"net/url"
cloudevents "github.com/cloudevents/sdk-go"
cehttp "github.com/cloudevents/sdk-go/pkg/cloudevents/transport/http"
"go.opencensus.io/plugin/ochttp/propagation/b3"
"go.uber.org/zap"
"k8s.io/apimachinery/pkg/util/sets"
pkgtracing "knative.dev/pkg/tracing"
"knative.dev/eventing/pkg/kncloudevents"
"knative.dev/eventing/pkg/tracing"
"knative.dev/eventing/pkg/utils"
)
const (
correlationIDHeaderName = "Knative-Correlation-Id"
// TODO make these constants configurable (either as env variables, config map).
// Issue: https://github.com/knative/eventing/issues/1777
// Constants for the underlying HTTP Client transport. These would enable better connection reuse.
// Set them on a 10:1 ratio, but this would actually depend on the Subscriptions' subscribers and the workload itself.
// These are magic numbers, partly set based on empirical evidence running performance workloads, and partly
// based on what serving is doing. See https://github.com/knative/serving/blob/master/pkg/network/transports.go.
defaultMaxIdleConnections = 1000
defaultMaxIdleConnectionsPerHost = 100
)
type Dispatcher interface {
// DispatchEvent dispatches an event to a destination over HTTP.
//
// The destination and reply are URLs.
DispatchEvent(ctx context.Context, event cloudevents.Event, destination, reply string) error
// DispatchEventWithDelivery dispatches an event to a destination over HTTP with delivery options
//
// The destination and reply are URLs.
DispatchEventWithDelivery(ctx context.Context, event cloudevents.Event, destination, reply string, delivery *DeliveryOptions) error
}
// DeliveryOptions are the delivery options supported by this dispatcher
type DeliveryOptions struct {
// DeadLetterSink is the sink receiving events that could not be dispatched.
DeadLetterSink string
}
// EventDispatcher is the 'real' Dispatcher used everywhere except unit tests.
var _ Dispatcher = &EventDispatcher{}
var propagation = &b3.HTTPFormat{}
// EventDispatcher dispatches events to a destination over HTTP.
type EventDispatcher struct {
ceClient cloudevents.Client
supportedSchemes sets.String
logger *zap.Logger
}
// NewEventDispatcher creates a new event dispatcher that can dispatch
// events to HTTP destinations.
func NewEventDispatcher(logger *zap.Logger) *EventDispatcher {
httpTransport, err := cloudevents.NewHTTPTransport(
cloudevents.WithBinaryEncoding(),
cloudevents.WithMiddleware(pkgtracing.HTTPSpanMiddleware))
if err != nil {
logger.Fatal("Unable to create CE transport", zap.Error(err))
}
cArgs := kncloudevents.ConnectionArgs{
MaxIdleConns: defaultMaxIdleConnections,
MaxIdleConnsPerHost: defaultMaxIdleConnectionsPerHost,
}
ceClient, err := kncloudevents.NewDefaultClientGivenHttpTransport(httpTransport, &cArgs)
if err != nil {
logger.Fatal("failed to create cloudevents client", zap.Error(err))
}
return &EventDispatcher{
ceClient: ceClient,
supportedSchemes: sets.NewString("http", "https"),
logger: logger,
}
}
// DispatchEvent dispatches an event to a destination over HTTP.
//
// The destination and reply are URLs.
func (d *EventDispatcher) DispatchEvent(ctx context.Context, event cloudevents.Event, destination, reply string) error {
return d.DispatchEventWithDelivery(ctx, event, destination, reply, nil)
}
// DispatchEventWithDelivery dispatches an event to a destination over HTTP with delivery options
//
// The destination and reply are URLs.
func (d *EventDispatcher) DispatchEventWithDelivery(ctx context.Context, event cloudevents.Event, destination, reply string, delivery *DeliveryOptions) error {
var err error
// Default to replying with the original event. If there is a destination, then replace it
// with the response from the call to the destination instead.
response := &event
var nonerrctx context.Context = ctx
if destination != "" {
destinationURL := d.resolveURL(destination)
nonerrctx, response, err = d.executeRequest(ctx, destinationURL, event)
if err != nil {
if delivery != nil && delivery.DeadLetterSink != "" {
deadLetterURL := d.resolveURL(delivery.DeadLetterSink)
// TODO: decorate event with deadletter attributes
_, _, err2 := d.executeRequest(ctx, deadLetterURL, event)
if err2 != nil {
return fmt.Errorf("unable to complete request to either %s (%v) or %s (%v)", destinationURL, err, deadLetterURL, err2)
}
// Do not send event to reply
return nil
}
return fmt.Errorf("unable to complete request to %s: %v", destinationURL, err)
}
}
if reply == "" && response != nil {
d.logger.Debug("cannot forward response as reply is empty", zap.Any("response", response))
return nil
}
if reply != "" && response != nil {
replyURL := d.resolveURL(reply)
_, _, err = d.executeRequest(nonerrctx, replyURL, *response)
if err != nil {
if delivery != nil && delivery.DeadLetterSink != "" {
deadLetterURL := d.resolveURL(delivery.DeadLetterSink)
// TODO: decorate event with deadletter attributes
_, _, err2 := d.executeRequest(nonerrctx, deadLetterURL, event)
if err2 != nil {
return fmt.Errorf("failed to forward reply to %s (%v) and failed to send it to the dead letter sink %s (%v)", replyURL, err, deadLetterURL, err2)
}
} else {
return fmt.Errorf("failed to forward reply to %s: %v", replyURL, err)
}
}
}
return nil
}
func (d *EventDispatcher) executeRequest(ctx context.Context, url *url.URL, event cloudevents.Event) (context.Context, *cloudevents.Event, error) {
d.logger.Debug("Dispatching event", zap.String("event.id", event.ID()), zap.String("url", url.String()))
originalTransportCTX := cloudevents.HTTPTransportContextFrom(ctx)
sendingCTX := d.generateSendingContext(originalTransportCTX, url, event)
replyCTX, reply, err := d.ceClient.Send(sendingCTX, event)
if err != nil {
return nil, nil, err
}
replyCTX, err = generateReplyContext(replyCTX, originalTransportCTX)
if err != nil {
return nil, nil, err
}
return replyCTX, reply, nil
}
func (d *EventDispatcher) generateSendingContext(originalTransportCTX cehttp.TransportContext, url *url.URL, event cloudevents.Event) context.Context {
sctx := utils.ContextFrom(originalTransportCTX, url)
sctx, err := tracing.AddSpanFromTraceparentAttribute(sctx, url.Path, event)
if err != nil {
d.logger.Info("Unable to connect outgoing span", zap.Error(err))
}
return sctx
}
func generateReplyContext(rctx context.Context, originalTransportCTX cehttp.TransportContext) (context.Context, error) {
// rtctx = Reply transport context
rtctx := cloudevents.HTTPTransportContextFrom(rctx)
if isFailure(rtctx.StatusCode) {
// Reject non-successful responses.
return rctx, fmt.Errorf("unexpected HTTP response, expected 2xx, got %d", rtctx.StatusCode)
}
headers := utils.PassThroughHeaders(rtctx.Header)
if correlationID, ok := originalTransportCTX.Header[correlationIDHeaderName]; ok {
headers[correlationIDHeaderName] = correlationID
}
rtctx.Header = http.Header(headers)
rctx = cehttp.WithTransportContext(rctx, rtctx)
return rctx, nil
}
// isFailure returns true if the status code is not a successful HTTP status.
func isFailure(statusCode int) bool {
return statusCode < http.StatusOK /* 200 */ ||
statusCode >= http.StatusMultipleChoices /* 300 */
}
func (d *EventDispatcher) resolveURL(destination string) *url.URL {
if u, err := url.Parse(destination); err == nil && d.supportedSchemes.Has(u.Scheme) {
// Already a URL with a known scheme.
return u
}
return &url.URL{
Scheme: "http",
Host: destination,
Path: "/",
}
}