/
message_dispatcher.go
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/
message_dispatcher.go
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/*
* Copyright 2020 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"
nethttp "net/http"
"net/url"
cloudevents "github.com/cloudevents/sdk-go/v2"
"github.com/cloudevents/sdk-go/v2/binding"
"github.com/cloudevents/sdk-go/v2/protocol/http"
"go.opencensus.io/trace"
"go.uber.org/zap"
"k8s.io/apimachinery/pkg/util/sets"
"knative.dev/eventing/pkg/kncloudevents"
"knative.dev/eventing/pkg/tracing"
"knative.dev/eventing/pkg/utils"
)
type MessageDispatcher interface {
// DispatchMessage dispatches an event to a destination over HTTP.
//
// The destination and reply are URLs.
DispatchMessage(ctx context.Context, message cloudevents.Message, additionalHeaders nethttp.Header, destination *url.URL, reply *url.URL, deadLetter *url.URL) error
}
// MessageDispatcherImpl is the 'real' MessageDispatcher used everywhere except unit tests.
var _ MessageDispatcher = &MessageDispatcherImpl{}
// MessageDispatcherImpl dispatches events to a destination over HTTP.
type MessageDispatcherImpl struct {
sender *kncloudevents.HttpMessageSender
supportedSchemes sets.String
logger *zap.Logger
}
// NewMessageDispatcher creates a new event dispatcher that can dispatch
// events to HTTP destinations.
func NewMessageDispatcher(logger *zap.Logger) *MessageDispatcherImpl {
return NewMessageDispatcherFromConfig(logger, defaultEventDispatcherConfig)
}
// NewMessageDispatcherFromConfig creates a new event dispatcher based on config.
func NewMessageDispatcherFromConfig(logger *zap.Logger, config EventDispatcherConfig) *MessageDispatcherImpl {
sender, err := kncloudevents.NewHttpMessageSender(&config.ConnectionArgs, "")
if err != nil {
logger.Fatal("Unable to create cloudevents binding sender", zap.Error(err))
return nil
}
return &MessageDispatcherImpl{
sender: sender,
supportedSchemes: sets.NewString("http", "https"),
logger: logger,
}
}
func (d *MessageDispatcherImpl) DispatchMessage(ctx context.Context, initialMessage cloudevents.Message, initialAdditionalHeaders nethttp.Header, destination *url.URL, reply *url.URL, deadLetter *url.URL) error {
// All messages that should be finished at the end of this function
// are placed in this slice
var messagesToFinish []binding.Message
defer func() {
for _, msg := range messagesToFinish {
_ = msg.Finish(nil)
}
}()
// sanitize eventual host-only URLs
destination = d.sanitizeURL(destination)
reply = d.sanitizeURL(reply)
deadLetter = d.sanitizeURL(deadLetter)
// If there is a destination, variables response* are filled with the response of the destination
// Otherwise, they are filled with the original message
var responseMessage cloudevents.Message
var responseAdditionalHeaders nethttp.Header
if destination != nil {
var err error
// Try to send to destination
messagesToFinish = append(messagesToFinish, initialMessage)
ctx, responseMessage, responseAdditionalHeaders, err = d.executeRequest(ctx, destination, initialMessage, initialAdditionalHeaders)
if err != nil {
// DeadLetter is configured, send the message to it
if deadLetter != nil {
_, deadLetterResponse, _, deadLetterErr := d.executeRequest(ctx, deadLetter, initialMessage, initialAdditionalHeaders)
if deadLetterErr != nil {
return fmt.Errorf("unable to complete request to either %s (%v) or %s (%v)", destination, err, deadLetter, deadLetterErr)
}
if deadLetterResponse != nil {
messagesToFinish = append(messagesToFinish, deadLetterResponse)
}
return nil
}
// No DeadLetter, just fail
return fmt.Errorf("unable to complete request to %s: %v", destination, err)
}
} else {
// No destination url, try to send to reply if available
responseMessage = initialMessage
responseAdditionalHeaders = initialAdditionalHeaders
}
// No response, dispatch completed
if responseMessage == nil {
return nil
}
messagesToFinish = append(messagesToFinish, responseMessage)
if reply == nil {
d.logger.Debug("cannot forward response as reply is empty")
return nil
}
ctx, responseResponseMessage, _, err := d.executeRequest(ctx, reply, responseMessage, responseAdditionalHeaders)
if err != nil {
// DeadLetter is configured, send the message to it
if deadLetter != nil {
_, deadLetterResponse, _, deadLetterErr := d.executeRequest(ctx, deadLetter, initialMessage, responseAdditionalHeaders)
if deadLetterErr != nil {
return fmt.Errorf("failed to forward reply to %s (%v) and failed to send it to the dead letter sink %s (%v)", reply, err, deadLetter, deadLetterErr)
}
if deadLetterResponse != nil {
messagesToFinish = append(messagesToFinish, deadLetterResponse)
}
return nil
}
// No DeadLetter, just fail
return fmt.Errorf("failed to forward reply to %s: %v", reply, err)
}
if responseResponseMessage != nil {
messagesToFinish = append(messagesToFinish, responseResponseMessage)
}
return nil
}
func (d *MessageDispatcherImpl) executeRequest(ctx context.Context, url *url.URL, message cloudevents.Message, additionalHeaders nethttp.Header) (context.Context, cloudevents.Message, nethttp.Header, error) {
d.logger.Debug("Dispatching event", zap.String("url", url.String()))
ctx, span := trace.StartSpan(ctx, "knative.dev", trace.WithSpanKind(trace.SpanKindClient))
defer span.End()
req, err := d.sender.NewCloudEventRequestWithTarget(ctx, url.String())
if err != nil {
return ctx, nil, nil, err
}
if span.IsRecordingEvents() {
err = kncloudevents.WriteHttpRequestWithAdditionalHeaders(ctx, message, req, additionalHeaders, tracing.PopulateSpan(span))
} else {
err = kncloudevents.WriteHttpRequestWithAdditionalHeaders(ctx, message, req, additionalHeaders)
}
if err != nil {
return ctx, nil, nil, err
}
response, err := d.sender.Send(req)
if err != nil {
return ctx, nil, nil, err
}
if isFailure(response.StatusCode) {
_ = response.Body.Close()
// Reject non-successful responses.
return ctx, nil, nil, fmt.Errorf("unexpected HTTP response, expected 2xx, got %d", response.StatusCode)
}
responseMessage := http.NewMessageFromHttpResponse(response)
if responseMessage.ReadEncoding() == binding.EncodingUnknown {
_ = response.Body.Close()
d.logger.Debug("Response is a non event, discarding it", zap.Int("status_code", response.StatusCode))
return ctx, nil, nil, nil
}
return ctx, responseMessage, utils.PassThroughHeaders(response.Header), nil
}
func (d *MessageDispatcherImpl) sanitizeURL(u *url.URL) *url.URL {
if u == nil {
return nil
}
if d.supportedSchemes.Has(u.Scheme) {
// Already a URL with a known scheme.
return u
}
return &url.URL{
Scheme: "http",
Host: u.Host,
Path: "/",
}
}