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protocol.go
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protocol.go
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/*
Copyright 2021 The CloudEvents Authors
SPDX-License-Identifier: Apache-2.0
*/
package http
import (
"bytes"
"context"
"errors"
"fmt"
"io"
"net/http"
"net/url"
"strconv"
"sync"
"sync/atomic"
"time"
"github.com/cloudevents/sdk-go/v2/binding"
cecontext "github.com/cloudevents/sdk-go/v2/context"
"github.com/cloudevents/sdk-go/v2/event"
"github.com/cloudevents/sdk-go/v2/protocol"
)
const (
// DefaultShutdownTimeout defines the default timeout given to the http.Server when calling Shutdown.
DefaultShutdownTimeout = time.Minute * 1
)
type msgErr struct {
msg *Message
respFn protocol.ResponseFn
err error
}
// Default error codes that we retry on - string isn't used, it's just there so
// people know what each error code's title is.
// To modify this use Option
var defaultRetriableErrors = map[int]string{
404: "Not Found",
413: "Payload Too Large",
425: "Too Early",
429: "Too Many Requests",
502: "Bad Gateway",
503: "Service Unavailable",
504: "Gateway Timeout",
}
// Protocol acts as both a http client and a http handler.
type Protocol struct {
Target *url.URL
RequestTemplate *http.Request
Client *http.Client
incoming chan msgErr
// OptionsHandlerFn handles the OPTIONS method requests and is intended to
// implement the abuse protection spec:
// https://github.com/cloudevents/spec/blob/v1.0/http-webhook.md#4-abuse-protection
OptionsHandlerFn http.HandlerFunc
WebhookConfig *WebhookConfig
GetHandlerFn http.HandlerFunc
DeleteHandlerFn http.HandlerFunc
// To support Opener:
// ShutdownTimeout defines the timeout given to the http.Server when calling Shutdown.
// If 0, DefaultShutdownTimeout is used.
ShutdownTimeout time.Duration
// Port is the port configured to bind the receiver to. Defaults to 8080.
// If you want to know the effective port you're listening to, use GetListeningPort()
Port int
// Path is the path to bind the receiver to. Defaults to "/".
Path string
// Receive Mutex
reMu sync.Mutex
// Handler is the handler the http Server will use. Use this to reuse the
// http server. If nil, the Protocol will create a one.
Handler *http.ServeMux
listener atomic.Value
roundTripper http.RoundTripper
server *http.Server
handlerRegistered bool
middleware []Middleware
limiter RateLimiter
isRetriableFunc IsRetriable
}
func New(opts ...Option) (*Protocol, error) {
p := &Protocol{
incoming: make(chan msgErr),
Port: -1,
}
if err := p.applyOptions(opts...); err != nil {
return nil, err
}
if p.Client == nil {
p.Client = http.DefaultClient
}
if p.roundTripper != nil {
p.Client.Transport = p.roundTripper
}
if p.ShutdownTimeout == 0 {
p.ShutdownTimeout = DefaultShutdownTimeout
}
if p.isRetriableFunc == nil {
p.isRetriableFunc = defaultIsRetriableFunc
}
if p.limiter == nil {
p.limiter = noOpLimiter{}
}
return p, nil
}
// NewObserved creates an HTTP protocol with trace propagating middleware.
// Deprecated: now this behaves like New and it will be removed in future releases,
// setup the http observed protocol using the opencensus separate module NewObservedHttp
var NewObserved = New
func (p *Protocol) applyOptions(opts ...Option) error {
for _, fn := range opts {
if err := fn(p); err != nil {
return err
}
}
return nil
}
// Send implements binding.Sender
func (p *Protocol) Send(ctx context.Context, m binding.Message, transformers ...binding.Transformer) error {
if ctx == nil {
return fmt.Errorf("nil Context")
} else if m == nil {
return fmt.Errorf("nil Message")
}
msg, err := p.Request(ctx, m, transformers...)
if msg != nil {
defer func() { _ = msg.Finish(err) }()
}
if err != nil && !protocol.IsACK(err) {
var res *Result
if protocol.ResultAs(err, &res) {
if message, ok := msg.(*Message); ok {
buf := new(bytes.Buffer)
buf.ReadFrom(message.BodyReader)
errorStr := buf.String()
// If the error is not wrapped, then append the original error string.
if og, ok := err.(*Result); ok {
og.Format = og.Format + "%s"
og.Args = append(og.Args, errorStr)
err = og
} else {
err = NewResult(res.StatusCode, "%w: %s", err, errorStr)
}
}
}
}
return err
}
// Request implements binding.Requester
func (p *Protocol) Request(ctx context.Context, m binding.Message, transformers ...binding.Transformer) (binding.Message, error) {
if ctx == nil {
return nil, fmt.Errorf("nil Context")
} else if m == nil {
return nil, fmt.Errorf("nil Message")
}
var err error
defer func() { _ = m.Finish(err) }()
req := p.makeRequest(ctx)
if p.Client == nil || req == nil || req.URL == nil {
return nil, fmt.Errorf("not initialized: %#v", p)
}
if err = WriteRequest(ctx, m, req, transformers...); err != nil {
return nil, err
}
return p.do(ctx, req)
}
func (p *Protocol) makeRequest(ctx context.Context) *http.Request {
req := &http.Request{
Method: http.MethodPost,
Header: HeaderFrom(ctx),
}
if p.RequestTemplate != nil {
req.Method = p.RequestTemplate.Method
req.URL = p.RequestTemplate.URL
req.Close = p.RequestTemplate.Close
req.Host = p.RequestTemplate.Host
copyHeadersEnsure(p.RequestTemplate.Header, &req.Header)
}
if p.Target != nil {
req.URL = p.Target
}
// Override the default request with target from context.
if target := cecontext.TargetFrom(ctx); target != nil {
req.URL = target
}
return req.WithContext(ctx)
}
// Ensure to is a non-nil map before copying
func copyHeadersEnsure(from http.Header, to *http.Header) {
if len(from) > 0 {
if *to == nil {
*to = http.Header{}
}
copyHeaders(from, *to)
}
}
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)
}
}
}
// Receive the next incoming HTTP request as a CloudEvent.
// Returns non-nil error if the incoming HTTP request fails to parse as a CloudEvent
// Returns io.EOF if the receiver is closed.
func (p *Protocol) Receive(ctx context.Context) (binding.Message, error) {
if ctx == nil {
return nil, fmt.Errorf("nil Context")
}
msg, fn, err := p.Respond(ctx)
// No-op the response when finish is invoked.
if msg != nil {
return binding.WithFinish(msg, func(err error) {
if fn != nil {
_ = fn(ctx, nil, nil)
}
}), err
} else {
return nil, err
}
}
// Respond receives the next incoming HTTP request as a CloudEvent and waits
// for the response callback to invoked before continuing.
// Returns non-nil error if the incoming HTTP request fails to parse as a CloudEvent
// Returns io.EOF if the receiver is closed.
func (p *Protocol) Respond(ctx context.Context) (binding.Message, protocol.ResponseFn, error) {
if ctx == nil {
return nil, nil, fmt.Errorf("nil Context")
}
select {
case in, ok := <-p.incoming:
if !ok {
return nil, nil, io.EOF
}
if in.msg == nil {
return nil, in.respFn, in.err
}
return in.msg, in.respFn, in.err
case <-ctx.Done():
return nil, nil, io.EOF
}
}
// ServeHTTP implements http.Handler.
// Blocks until ResponseFn is invoked.
func (p *Protocol) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
// always apply limiter first using req context
ok, reset, err := p.limiter.Allow(req.Context(), req)
if err != nil {
p.incoming <- msgErr{msg: nil, err: fmt.Errorf("unable to acquire rate limit token: %w", err)}
rw.WriteHeader(http.StatusInternalServerError)
return
}
if !ok {
rw.Header().Add("Retry-After", strconv.Itoa(int(reset)))
http.Error(rw, "limit exceeded", 429)
return
}
// Filter the GET style methods:
switch req.Method {
case http.MethodOptions:
if p.OptionsHandlerFn == nil {
rw.WriteHeader(http.StatusMethodNotAllowed)
return
}
p.OptionsHandlerFn(rw, req)
return
case http.MethodGet:
if p.GetHandlerFn == nil {
rw.WriteHeader(http.StatusMethodNotAllowed)
return
}
p.GetHandlerFn(rw, req)
return
case http.MethodDelete:
if p.DeleteHandlerFn == nil {
rw.WriteHeader(http.StatusMethodNotAllowed)
return
}
p.DeleteHandlerFn(rw, req)
return
}
m := NewMessageFromHttpRequest(req)
if m == nil {
// Should never get here unless ServeHTTP is called directly.
p.incoming <- msgErr{msg: nil, err: binding.ErrUnknownEncoding}
rw.WriteHeader(http.StatusBadRequest)
return // if there was no message, return.
}
var finishErr error
m.OnFinish = func(err error) error {
finishErr = err
return nil
}
wg := sync.WaitGroup{}
wg.Add(1)
var fn protocol.ResponseFn = func(ctx context.Context, respMsg binding.Message, res protocol.Result, transformers ...binding.Transformer) error {
// Unblock the ServeHTTP after the reply is written
defer func() {
wg.Done()
}()
if finishErr != nil {
http.Error(rw, fmt.Sprintf("Cannot forward CloudEvent: %s", finishErr), http.StatusInternalServerError)
return finishErr
}
status := http.StatusOK
var errMsg string
if res != nil {
var result *Result
switch {
case protocol.ResultAs(res, &result):
if result.StatusCode > 100 && result.StatusCode < 600 {
status = result.StatusCode
}
errMsg = fmt.Errorf(result.Format, result.Args...).Error()
case !protocol.IsACK(res):
// Map client errors to http status code
validationError := event.ValidationError{}
if errors.As(res, &validationError) {
status = http.StatusBadRequest
rw.Header().Set("content-type", "text/plain")
rw.WriteHeader(status)
_, _ = rw.Write([]byte(validationError.Error()))
return validationError
} else if errors.Is(res, binding.ErrUnknownEncoding) {
status = http.StatusUnsupportedMediaType
} else {
status = http.StatusInternalServerError
}
}
}
if respMsg != nil {
err := WriteResponseWriter(ctx, respMsg, status, rw, transformers...)
return respMsg.Finish(err)
}
rw.WriteHeader(status)
if _, err := rw.Write([]byte(errMsg)); err != nil {
return err
}
return nil
}
p.incoming <- msgErr{msg: m, respFn: fn} // Send to Request
// Block until ResponseFn is invoked
wg.Wait()
}
func defaultIsRetriableFunc(sc int) bool {
_, ok := defaultRetriableErrors[sc]
return ok
}