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transport.go
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transport.go
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package http
import (
"bytes"
"context"
"fmt"
"io/ioutil"
"net"
"net/http"
"strconv"
"strings"
"sync"
"time"
"go.uber.org/zap"
"github.com/cloudevents/sdk-go/pkg/cloudevents"
cecontext "github.com/cloudevents/sdk-go/pkg/cloudevents/context"
"github.com/cloudevents/sdk-go/pkg/cloudevents/observability"
"github.com/cloudevents/sdk-go/pkg/cloudevents/transport"
)
type EncodingSelector func(e cloudevents.Event) Encoding
// Transport adheres to transport.Transport.
var _ transport.Transport = (*Transport)(nil)
const (
// DefaultShutdownTimeout defines the default timeout given to the http.Server when calling Shutdown.
DefaultShutdownTimeout = time.Minute * 1
)
// Transport acts as both a http client and a http handler.
type Transport struct {
// The encoding used to select the codec for outbound events.
Encoding Encoding
// DefaultEncodingSelectionFn allows for other encoding selection strategies to be injected.
DefaultEncodingSelectionFn EncodingSelector
// ShutdownTimeout defines the timeout given to the http.Server when calling Shutdown.
// If nil, DefaultShutdownTimeout is used.
ShutdownTimeout *time.Duration
// Sending
// Client is the http client that will be used to send requests.
// If nil, the Transport will create a one.
Client *http.Client
// Req is the base http request that is used for http.Do.
// Only .Method, .URL, and .Header is considered.
// If not set, Req.Method defaults to POST.
// Req.URL or context.WithTarget(url) are required for sending.
Req *http.Request
// Receiving
// Receiver is invoked target for incoming events.
Receiver transport.Receiver
// Port is the port to bind the receiver to. Defaults to 8080.
Port *int
// Path is the path to bind the receiver to. Defaults to "/".
Path string
// Handler is the handler the http Server will use. Use this to reuse the
// http server. If nil, the Transport will create a one.
Handler *http.ServeMux
realPort int
server *http.Server
handlerRegistered bool
codec transport.Codec
// Create Mutex
crMu sync.Mutex
// Receive Mutex
reMu sync.Mutex
}
func New(opts ...Option) (*Transport, error) {
t := &Transport{
Req: &http.Request{
Method: http.MethodPost,
},
}
if err := t.applyOptions(opts...); err != nil {
return nil, err
}
return t, nil
}
func (t *Transport) applyOptions(opts ...Option) error {
for _, fn := range opts {
if err := fn(t); err != nil {
return err
}
}
return nil
}
func (t *Transport) loadCodec(ctx context.Context) bool {
if t.codec == nil {
t.crMu.Lock()
if t.DefaultEncodingSelectionFn != nil && t.Encoding != Default {
logger := cecontext.LoggerFrom(ctx)
logger.Warn("transport has a DefaultEncodingSelectionFn set but Encoding is not Default. DefaultEncodingSelectionFn will be ignored.")
t.codec = &Codec{
Encoding: t.Encoding,
}
} else {
t.codec = &Codec{
Encoding: t.Encoding,
DefaultEncodingSelectionFn: t.DefaultEncodingSelectionFn,
}
}
t.crMu.Unlock()
}
return true
}
func copyHeaders(from, to http.Header) {
if from == nil || to == nil {
return
}
for header, values := range from {
for _, value := range values {
to.Add(header, value)
}
}
}
// Send implements Transport.Send
func (t *Transport) Send(ctx context.Context, event cloudevents.Event) (*cloudevents.Event, error) {
ctx, r := observability.NewReporter(ctx, reportSend)
resp, err := t.obsSend(ctx, event)
if err != nil {
r.Error()
} else {
r.OK()
}
return resp, err
}
func (t *Transport) obsSend(ctx context.Context, event cloudevents.Event) (*cloudevents.Event, error) {
if t.Client == nil {
t.crMu.Lock()
t.Client = &http.Client{}
t.crMu.Unlock()
}
req := http.Request{
Header: HeaderFrom(ctx),
}
if t.Req != nil {
req.Method = t.Req.Method
req.URL = t.Req.URL
copyHeaders(t.Req.Header, req.Header)
}
// Override the default request with target from context.
if target := cecontext.TargetFrom(ctx); target != nil {
req.URL = target
}
if ok := t.loadCodec(ctx); !ok {
return nil, fmt.Errorf("unknown encoding set on transport: %d", t.Encoding)
}
msg, err := t.codec.Encode(event)
if err != nil {
return nil, err
}
if m, ok := msg.(*Message); ok {
copyHeaders(m.Header, req.Header)
req.Body = ioutil.NopCloser(bytes.NewBuffer(m.Body))
req.ContentLength = int64(len(m.Body))
req.Close = true
return httpDo(ctx, t.Client, &req, func(resp *http.Response, err error) (*cloudevents.Event, error) {
logger := cecontext.LoggerFrom(ctx)
if err != nil {
return nil, err
}
defer resp.Body.Close()
body, _ := ioutil.ReadAll(resp.Body)
msg := &Message{
Header: resp.Header,
Body: body,
}
var respEvent *cloudevents.Event
if msg.CloudEventsVersion() != "" {
if ok := t.loadCodec(ctx); !ok {
err := fmt.Errorf("unknown encoding set on transport: %d", t.Encoding)
logger.Error("failed to load codec", zap.Error(err))
}
if respEvent, err = t.codec.Decode(msg); err != nil {
logger.Error("failed to decode message", zap.Error(err))
}
}
if accepted(resp) {
return respEvent, nil
}
return respEvent, fmt.Errorf("error sending cloudevent: %s", resp.Status)
})
}
return nil, fmt.Errorf("failed to encode Event into a Message")
}
// SetReceiver implements Transport.SetReceiver
func (t *Transport) SetReceiver(r transport.Receiver) {
t.Receiver = r
}
// StartReceiver implements Transport.StartReceiver
// NOTE: This is a blocking call.
func (t *Transport) StartReceiver(ctx context.Context) error {
t.reMu.Lock()
defer t.reMu.Unlock()
if t.Handler == nil {
t.Handler = http.NewServeMux()
}
if !t.handlerRegistered {
// handler.Handle might panic if the user tries to use the same path as the sdk.
t.Handler.Handle(t.GetPath(), t)
t.handlerRegistered = true
}
addr := fmt.Sprintf(":%d", t.GetPort())
t.server = &http.Server{
Addr: addr,
Handler: t.Handler,
}
listener, err := net.Listen("tcp", addr)
if err != nil {
return err
}
t.realPort = listener.Addr().(*net.TCPAddr).Port
// Shutdown
defer func() {
t.realPort = 0
t.server.Close()
t.server = nil
}()
errChan := make(chan error, 1)
go func() {
errChan <- t.server.Serve(listener)
}()
// wait for the server to return or ctx.Done().
select {
case <-ctx.Done():
// Try a gracefully shutdown.
timeout := DefaultShutdownTimeout
if t.ShutdownTimeout != nil {
timeout = *t.ShutdownTimeout
}
ctx, cancel := context.WithTimeout(context.Background(), timeout)
defer cancel()
return t.server.Shutdown(ctx)
case err := <-errChan:
return err
}
}
type eventError struct {
event *cloudevents.Event
err error
}
func httpDo(ctx context.Context, client *http.Client, req *http.Request, fn func(*http.Response, error) (*cloudevents.Event, error)) (*cloudevents.Event, error) {
// Run the HTTP request in a goroutine and pass the response to fn.
c := make(chan eventError, 1)
req = req.WithContext(ctx)
go func() {
event, err := fn(client.Do(req))
c <- eventError{event: event, err: err}
}()
select {
case <-ctx.Done():
return nil, ctx.Err()
case ee := <-c:
return ee.event, ee.err
}
}
// accepted is a helper method to understand if the response from the target
// accepted the CloudEvent.
func accepted(resp *http.Response) bool {
if resp.StatusCode >= 200 && resp.StatusCode < 300 {
return true
}
return false
}
func (t *Transport) invokeReceiver(ctx context.Context, event cloudevents.Event) (*Response, error) {
ctx, r := observability.NewReporter(ctx, reportReceive)
resp, err := t.obsInvokeReceiver(ctx, event)
if err != nil {
r.Error()
} else {
r.OK()
}
return resp, err
}
func (t *Transport) obsInvokeReceiver(ctx context.Context, event cloudevents.Event) (*Response, error) {
logger := cecontext.LoggerFrom(ctx)
if t.Receiver != nil {
// Note: http does not use eventResp.Reason
eventResp := cloudevents.EventResponse{}
resp := Response{}
err := t.Receiver.Receive(ctx, event, &eventResp)
if err != nil {
logger.Warnw("got an error from receiver fn: %s", zap.Error(err))
resp.StatusCode = http.StatusInternalServerError
return &resp, err
}
if eventResp.Event != nil {
if t.loadCodec(ctx) {
if m, err := t.codec.Encode(*eventResp.Event); err != nil {
logger.Errorw("failed to encode response from receiver fn", zap.Error(err))
} else if msg, ok := m.(*Message); ok {
resp.Header = msg.Header
resp.Body = msg.Body
}
} else {
logger.Error("failed to load codec")
resp.StatusCode = http.StatusInternalServerError
return &resp, err
}
// Look for a transport response context
var trx *TransportResponseContext
if ptrTrx, ok := eventResp.Context.(*TransportResponseContext); ok {
// found a *TransportResponseContext, use it.
trx = ptrTrx
} else if realTrx, ok := eventResp.Context.(TransportResponseContext); ok {
// found a TransportResponseContext, make it a pointer.
trx = &realTrx
}
// If we found a TransportResponseContext, use it.
if trx != nil && trx.Header != nil && len(trx.Header) > 0 {
copyHeaders(trx.Header, resp.Header)
}
}
if eventResp.Status != 0 {
resp.StatusCode = eventResp.Status
} else {
resp.StatusCode = http.StatusAccepted // default is 202 - Accepted
}
return &resp, err
}
return nil, nil
}
// ServeHTTP implements http.Handler
func (t *Transport) ServeHTTP(w http.ResponseWriter, req *http.Request) {
ctx, r := observability.NewReporter(req.Context(), reportServeHTTP)
logger := cecontext.LoggerFrom(ctx)
body, err := ioutil.ReadAll(req.Body)
if err != nil {
logger.Errorw("failed to handle request", zap.Error(err))
w.WriteHeader(http.StatusBadRequest)
w.Write([]byte(`{"error":"Invalid request"}`))
r.Error()
return
}
msg := &Message{
Header: req.Header,
Body: body,
}
if ok := t.loadCodec(ctx); !ok {
err := fmt.Errorf("unknown encoding set on transport: %d", t.Encoding)
logger.Errorw("failed to load codec", zap.Error(err))
w.WriteHeader(http.StatusBadRequest)
w.Write([]byte(fmt.Sprintf(`{"error":%q}`, err.Error())))
r.Error()
return
}
event, err := t.codec.Decode(msg)
if err != nil {
logger.Errorw("failed to decode message", zap.Error(err))
w.WriteHeader(http.StatusBadRequest)
w.Write([]byte(fmt.Sprintf(`{"error":%q}`, err.Error())))
r.Error()
return
}
if req != nil {
ctx = WithTransportContext(ctx, NewTransportContext(req))
}
resp, err := t.invokeReceiver(ctx, *event)
if err != nil {
logger.Warnw("error returned from invokeReceiver", zap.Error(err))
w.WriteHeader(http.StatusBadRequest)
w.Write([]byte(fmt.Sprintf(`{"error":%q}`, err.Error())))
r.Error()
return
}
if resp != nil {
if t.Req != nil {
copyHeaders(t.Req.Header, w.Header())
}
if len(resp.Header) > 0 {
copyHeaders(resp.Header, w.Header())
}
w.Header().Add("Content-Length", strconv.Itoa(len(resp.Body)))
if len(resp.Body) > 0 {
if _, err := w.Write(resp.Body); err != nil {
r.Error()
return
}
}
status := http.StatusAccepted
if resp.StatusCode >= 200 && resp.StatusCode < 600 {
status = resp.StatusCode
}
w.WriteHeader(status)
r.OK()
return
}
w.WriteHeader(http.StatusNoContent)
r.OK()
}
// GetPort returns the port the transport is active on.
// .Port can be set to 0, which means the transport selects a port, GetPort
// allows the transport to report back the selected port.
func (t *Transport) GetPort() int {
if t.Port != nil && *t.Port == 0 && t.realPort != 0 {
return t.realPort
}
if t.Port != nil && *t.Port >= 0 { // 0 means next open port
return *t.Port
}
return 8080 // default
}
// GetPath returns the path the transport is hosted on. If the path is '/',
// the transport will handle requests on any URI. To discover the true path
// a request was received on, inspect the context from Receive(cxt, ...) with
// TransportContextFrom(ctx).
func (t *Transport) GetPath() string {
path := strings.TrimSpace(t.Path)
if len(path) > 0 {
return path
}
return "/" // default
}