forked from knative/eventing
/
message_receiver.go
171 lines (148 loc) · 5.66 KB
/
message_receiver.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"
"errors"
nethttp "net/http"
"time"
"github.com/cloudevents/sdk-go/v2/binding"
"github.com/cloudevents/sdk-go/v2/binding/transformer"
"github.com/cloudevents/sdk-go/v2/protocol/http"
"go.uber.org/zap"
"knative.dev/eventing/pkg/kncloudevents"
"knative.dev/eventing/pkg/utils"
)
var defaultTransformers = []binding.Transformer{
transformer.AddTimeNow,
}
// MessageReceiver starts a server to receive new events for the channel dispatcher. The new
// event is emitted via the receiver function.
type MessageReceiver struct {
httpBindingsReceiver *kncloudevents.HttpMessageReceiver
receiverFunc UnbufferedMessageReceiverFunc
logger *zap.Logger
hostToChannelFunc ResolveChannelFromHostFunc
}
// UnbufferedMessageReceiverFunc is the function to be called for handling the message.
// The provided message is not buffered, so it can't be safely read more times.
// When you perform the write (or the buffering) of the Message, you must use the transformers provided as parameters.
// This function is responsible for invoking Message.Finish().
type UnbufferedMessageReceiverFunc func(context.Context, ChannelReference, binding.Message, []binding.Transformer, nethttp.Header) error
// ReceiverOptions provides functional options to MessageReceiver function.
type MessageReceiverOptions func(*MessageReceiver) error
// ResolveMessageChannelFromHostHeader is a ReceiverOption for NewMessageReceiver which enables the caller to overwrite the
// default behaviour defined by ParseChannel function.
func ResolveMessageChannelFromHostHeader(hostToChannelFunc ResolveChannelFromHostFunc) MessageReceiverOptions {
return func(r *MessageReceiver) error {
r.hostToChannelFunc = hostToChannelFunc
return nil
}
}
// NewMessageReceiver creates an event receiver passing new events to the
// receiverFunc.
func NewMessageReceiver(receiverFunc UnbufferedMessageReceiverFunc, logger *zap.Logger, opts ...MessageReceiverOptions) (*MessageReceiver, error) {
bindingsReceiver := kncloudevents.NewHttpMessageReceiver(8080)
receiver := &MessageReceiver{
httpBindingsReceiver: bindingsReceiver,
receiverFunc: receiverFunc,
hostToChannelFunc: ResolveChannelFromHostFunc(ParseChannel),
logger: logger,
}
for _, opt := range opts {
if err := opt(receiver); err != nil {
return nil, err
}
}
return receiver, nil
}
// Start begins to receive events for the receiver.
//
// Only HTTP POST requests to the root path (/) are accepted. If other paths or
// methods are needed, use the HandleRequest method directly with another HTTP
// server.
func (r *MessageReceiver) Start(ctx context.Context) error {
ctx, cancel := context.WithCancel(ctx)
defer cancel()
errCh := make(chan error, 1)
go func() {
errCh <- r.httpBindingsReceiver.StartListen(ctx, r)
}()
// Stop either if the receiver stops (sending to errCh) or if the context Done channel is closed.
select {
case err := <-errCh:
return err
case <-ctx.Done():
break
}
// Done channel has been closed, we need to gracefully shutdown r.ceClient. The cancel() method will start its
// shutdown, if it hasn't finished in a reasonable amount of time, just return an error.
cancel()
select {
case err := <-errCh:
return err
case <-time.After(shutdownTimeout):
return errors.New("timeout shutting down http bindings receiver")
}
}
func (r *MessageReceiver) ServeHTTP(response nethttp.ResponseWriter, request *nethttp.Request) {
if request.Method != nethttp.MethodPost {
response.WriteHeader(nethttp.StatusMethodNotAllowed)
return
}
// tctx.URI is actually the path...
if request.URL.Path != "/" {
response.WriteHeader(nethttp.StatusNotFound)
return
}
// The response status codes:
// 202 - the event was sent to subscribers
// 404 - the request was for an unknown channel
// 500 - an error occurred processing the request
host := request.Host
r.logger.Debug("Received request", zap.String("host", host))
channel, err := r.hostToChannelFunc(host)
if err != nil {
if _, ok := err.(UnknownHostError); ok {
response.WriteHeader(nethttp.StatusNotFound)
r.logger.Info(err.Error())
} else {
r.logger.Info("Could not extract channel", zap.Error(err))
response.WriteHeader(nethttp.StatusInternalServerError)
}
return
}
r.logger.Debug("Request mapped to channel", zap.String("channel", channel.String()))
message := http.NewMessageFromHttpRequest(request)
if message.ReadEncoding() == binding.EncodingUnknown {
r.logger.Info("Cannot determine the cloudevent message encoding")
response.WriteHeader(nethttp.StatusBadRequest)
return
}
transformers := append(defaultTransformers, AddHistory(host))
err = r.receiverFunc(request.Context(), channel, message, transformers, utils.PassThroughHeaders(request.Header))
if err != nil {
if _, ok := err.(*UnknownChannelError); ok {
response.WriteHeader(nethttp.StatusNotFound)
} else {
r.logger.Info("Error in receiver", zap.Error(err))
response.WriteHeader(nethttp.StatusInternalServerError)
}
return
}
response.WriteHeader(nethttp.StatusAccepted)
}
var _ nethttp.Handler = (*MessageReceiver)(nil)