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subscribe.go
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subscribe.go
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package mercure
import (
"encoding/json"
"errors"
"net/http"
"time"
"go.uber.org/zap"
)
type responseController struct {
http.ResponseController
rw http.ResponseWriter
// disconnectionTime is the JWT expiration date minus hub.dispatchTimeout, or time.Now() plus hub.writeTimeout minus hub.dispatchTimeout
disconnectionTime time.Time
// writeDeadline is the JWT expiration date or time.Now() + hub.writeTimeout
writeDeadline time.Time
hub *Hub
subscriber *Subscriber
}
func (rc *responseController) setDispatchWriteDeadline() bool {
if rc.hub.dispatchTimeout == 0 {
return true
}
deadline := time.Now().Add(rc.hub.dispatchTimeout)
if deadline.After(rc.writeDeadline) {
return true
}
if err := rc.SetWriteDeadline(deadline); err != nil {
if c := rc.hub.logger.Check(zap.ErrorLevel, "Unable to set dispatch write deadline"); c != nil {
c.Write(zap.Object("subscriber", rc.subscriber), zap.Error(err))
}
return false
}
return true
}
func (rc *responseController) setDefaultWriteDeadline() bool {
if err := rc.SetWriteDeadline(rc.writeDeadline); err != nil {
if errors.Is(err, http.ErrNotSupported) {
panic(err)
}
if c := rc.hub.logger.Check(zap.InfoLevel, "Error while setting default write deadline"); c != nil {
c.Write(zap.Object("subscriber", rc.subscriber), zap.Error(err))
}
return false
}
return true
}
func (rc *responseController) flush() bool {
if err := rc.Flush(); err != nil {
if errors.Is(err, http.ErrNotSupported) {
panic(err)
}
if c := rc.hub.logger.Check(zap.InfoLevel, "Unable to flush"); c != nil {
c.Write(zap.Object("subscriber", rc.subscriber), zap.Error(err))
}
return false
}
return true
}
func (h *Hub) newResponseController(w http.ResponseWriter, s *Subscriber) *responseController {
wd := h.getWriteDeadline(s)
return &responseController{*http.NewResponseController(w), w, wd.Add(-h.dispatchTimeout), wd, h, s} // nolint:bodyclose
}
func (h *Hub) getWriteDeadline(s *Subscriber) (deadline time.Time) {
if h.writeTimeout != 0 {
deadline = time.Now().Add(h.writeTimeout)
}
if s.Claims != nil && s.Claims.ExpiresAt != nil && (deadline == time.Time{} || s.Claims.ExpiresAt.Time.Before(deadline)) {
deadline = s.Claims.ExpiresAt.Time
}
return
}
// SubscribeHandler creates a keep alive connection and sends the events to the subscribers.
//
//nolint:funlen,gocognit
func (h *Hub) SubscribeHandler(w http.ResponseWriter, r *http.Request) {
s, rc := h.registerSubscriber(w, r)
if s == nil {
return
}
defer h.shutdown(s)
rc.setDefaultWriteDeadline()
var (
heartbeatTimer *time.Timer
heartbeatTimerC <-chan time.Time
disconnectionTimerC <-chan time.Time
)
if h.heartbeat != 0 {
heartbeatTimer = time.NewTimer(h.heartbeat)
defer heartbeatTimer.Stop()
heartbeatTimerC = heartbeatTimer.C
}
if h.writeTimeout != 0 {
disconnectionTimer := time.NewTimer(time.Until(rc.disconnectionTime))
defer disconnectionTimer.Stop()
disconnectionTimerC = disconnectionTimer.C
}
for {
select {
case <-r.Context().Done():
if c := h.logger.Check(zap.DebugLevel, "Connection closed by the client"); c != nil {
c.Write(zap.Object("subscriber", s))
}
return
case <-heartbeatTimerC:
// Send a SSE comment as a heartbeat, to prevent issues with some proxies and old browsers
if !h.write(rc, ":\n") {
return
}
heartbeatTimer.Reset(h.heartbeat)
case <-disconnectionTimerC:
// Cleanly close the HTTP connection before the write deadline to prevent client-side errors
return
case update, ok := <-s.Receive():
h.logger.Info("Subscriber:received update")
if !ok || !h.write(rc, newSerializedUpdate(update).event) {
h.logger.Info("Subscriber:received not ok")
return
}
if heartbeatTimer != nil {
if !heartbeatTimer.Stop() {
<-heartbeatTimer.C
}
heartbeatTimer.Reset(h.heartbeat)
}
if c := h.logger.Check(zap.DebugLevel, "Update sent"); c != nil {
c.Write(zap.Object("subscriber", s), zap.Object("update", update))
}
}
}
}
// registerSubscriber initializes the connection.
func (h *Hub) registerSubscriber(w http.ResponseWriter, r *http.Request) (*Subscriber, *responseController) {
s := NewSubscriber(retrieveLastEventID(r, h.opt, h.logger), h.logger)
s.Debug = h.debug
s.RemoteAddr = r.RemoteAddr
var privateTopics []string
var claims *claims
if h.subscriberJWTKeyFunc != nil {
var err error
claims, err = authorize(r, h.subscriberJWTKeyFunc, nil, h.cookieName)
if claims != nil {
s.Claims = claims
privateTopics = claims.Mercure.Subscribe
}
if err != nil || (claims == nil && !h.anonymous) {
http.Error(w, http.StatusText(http.StatusUnauthorized), http.StatusUnauthorized)
if c := h.logger.Check(zap.DebugLevel, "Subscriber unauthorized"); c != nil {
c.Write(zap.Object("subscriber", s), zap.Error(err))
}
return nil, nil
}
}
topics := r.URL.Query()["topic"]
if len(topics) == 0 {
http.Error(w, "Missing \"topic\" parameter.", http.StatusBadRequest)
return nil, nil
}
s.SetTopics(topics, privateTopics)
h.dispatchSubscriptionUpdate(s, true)
if err := h.transport.AddSubscriber(s); err == nil {
h.dispatchSubscriptionUpdate(s, true)
} else {
http.Error(w, http.StatusText(http.StatusServiceUnavailable), http.StatusServiceUnavailable)
h.dispatchSubscriptionUpdate(s, false)
if c := h.logger.Check(zap.ErrorLevel, "Unable to add subscriber"); c != nil {
c.Write(zap.Object("subscriber", s), zap.Error(err))
}
return nil, nil
}
h.sendHeaders(w, s)
rc := h.newResponseController(w, s)
rc.flush()
if c := h.logger.Check(zap.InfoLevel, "New subscriber"); c != nil {
fields := []LogField{zap.Object("subscriber", s)}
if claims != nil && h.logger.Level() == zap.DebugLevel {
fields = append(fields, zap.Reflect("payload", claims.Mercure.Payload))
}
c.Write(fields...)
}
h.metrics.SubscriberConnected(s)
return s, rc
}
// sendHeaders sends correct HTTP headers to create a keep-alive connection.
func (h *Hub) sendHeaders(w http.ResponseWriter, s *Subscriber) {
// Keep alive, useful only for HTTP 1 clients https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Keep-Alive
w.Header().Set("Connection", "keep-alive")
// Server-sent events https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events/Using_server-sent_events#Sending_events_from_the_server
w.Header().Set("Content-Type", "text/event-stream")
// Disable cache, even for old browsers and proxies
w.Header().Set("Cache-Control", "private, no-cache, no-store, must-revalidate, max-age=0")
w.Header().Set("Pragma", "no-cache")
w.Header().Set("Expire", "0")
// NGINX support https://www.nginx.com/resources/wiki/start/topics/examples/x-accel/#x-accel-buffering
w.Header().Set("X-Accel-Buffering", "no")
if s.RequestLastEventID != "" {
w.Header().Set("Last-Event-ID", <-s.responseLastEventID)
}
// Write a comment in the body
// Go currently doesn't provide a better way to flush the headers
w.Write([]byte{':', '\n'})
}
// retrieveLastEventID extracts the Last-Event-ID from the corresponding HTTP header with a fallback on the query parameter.
func retrieveLastEventID(r *http.Request, opt *opt, logger Logger) string {
if id := r.Header.Get("Last-Event-ID"); id != "" {
return id
}
query := r.URL.Query()
if id := query.Get("lastEventID"); id != "" {
return id
}
if legacyEventIDValues, present := query["Last-Event-ID"]; present {
if opt.isBackwardCompatiblyEnabledWith(7) {
logger.Info("Deprecated: the 'Last-Event-ID' query parameter is deprecated since the version 8 of the protocol, use 'lastEventID' instead.")
if len(legacyEventIDValues) != 0 {
return legacyEventIDValues[0]
}
} else {
logger.Info("Unsupported: the 'Last-Event-ID' query parameter is not supported anymore, use 'lastEventID' instead or enable backward compatibility with version 7 of the protocol.")
}
}
return ""
}
// Write sends the given string to the client.
// It returns false if the subscriber has been disconnected (e.g. timeout).
func (h *Hub) write(rc *responseController, data string) bool {
if !rc.setDispatchWriteDeadline() {
return false
}
if _, err := rc.rw.Write([]byte(data)); err != nil {
if c := h.logger.Check(zap.DebugLevel, "Error writing to client"); c != nil {
c.Write(zap.Object("subscriber", rc.subscriber), zap.Error(err))
}
return false
}
return rc.flush() && rc.setDefaultWriteDeadline()
}
func (h *Hub) shutdown(s *Subscriber) {
// Notify that the client is closing the connection
s.Disconnect()
h.transport.RemoveSubscriber(s)
h.dispatchSubscriptionUpdate(s, false)
if c := h.logger.Check(zap.InfoLevel, "Subscriber disconnected"); c != nil {
c.Write(zap.Object("subscriber", s))
}
h.metrics.SubscriberDisconnected(s)
}
func (h *Hub) dispatchSubscriptionUpdate(s *Subscriber, active bool) {
if !h.subscriptions {
return
}
for _, subscription := range s.getSubscriptions("", jsonldContext, active) {
json, err := json.MarshalIndent(subscription, "", " ")
if err != nil {
panic(err)
}
u := &Update{
Topics: []string{subscription.ID},
Private: true,
Debug: h.debug,
Event: Event{Data: string(json)},
}
h.transport.Dispatch(u)
}
}