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|
package eventsource
import (
"log"
"net/http"
"strings"
"sync"
)
type subscription struct {
channel string
lastEventId string
out chan Event
}
type outbound struct {
channels []string
event Event
}
type registration struct {
channel string
repository Repository
}
type Server struct {
AllowCORS bool // Enable all handlers to be accessible from any origin
ReplayAll bool // Replay repository even if there's no Last-Event-Id specified
BufferSize int // How many messages do we let the client get behind before disconnecting
Gzip bool // Enable compression if client can accept it
Logger *log.Logger // Logger is a logger that, when set, will be used for logging debug messages
registrations chan *registration
pub chan *outbound
subs chan *subscription
unregister chan *subscription
quit chan bool
isClosed bool
isClosedMutex sync.RWMutex
}
// Create a new Server ready for handler creation and publishing events
func NewServer() *Server {
srv := &Server{
registrations: make(chan *registration),
pub: make(chan *outbound),
subs: make(chan *subscription),
unregister: make(chan *subscription, 2),
quit: make(chan bool),
BufferSize: 128,
}
go srv.run()
return srv
}
// Stop handling publishing
func (srv *Server) Close() {
srv.quit <- true
srv.markServerClosed()
}
// Create a new handler for serving a specified channel
func (srv *Server) Handler(channel string) http.HandlerFunc {
return func(w http.ResponseWriter, req *http.Request) {
h := w.Header()
h.Set("Content-Type", "text/event-stream; charset=utf-8")
h.Set("Cache-Control", "no-cache, no-store, must-revalidate")
h.Set("Connection", "keep-alive")
if srv.AllowCORS {
h.Set("Access-Control-Allow-Origin", "*")
}
useGzip := srv.Gzip && strings.Contains(req.Header.Get("Accept-Encoding"), "gzip")
if useGzip {
h.Set("Content-Encoding", "gzip")
}
w.WriteHeader(http.StatusOK)
// If the Handler is still active even though the server is closed, stop here.
// Otherwise the Handler will block while publishing to srv.subs indefinitely.
if srv.isServerClosed() {
return
}
sub := &subscription{
channel: channel,
lastEventId: req.Header.Get("Last-Event-ID"),
out: make(chan Event, srv.BufferSize),
}
srv.subs <- sub
flusher := w.(http.Flusher)
notifier := w.(http.CloseNotifier)
flusher.Flush()
enc := NewEncoder(w, useGzip)
for {
select {
case <-notifier.CloseNotify():
srv.unregister <- sub
return
case ev, ok := <-sub.out:
if !ok {
return
}
if err := enc.Encode(ev); err != nil {
srv.unregister <- sub
if srv.Logger != nil {
srv.Logger.Println(err)
}
return
}
flusher.Flush()
}
}
}
}
// Register the repository to be used for the specified channel
func (srv *Server) Register(channel string, repo Repository) {
srv.registrations <- ®istration{
channel: channel,
repository: repo,
}
}
// Publish an event with the specified id to one or more channels
func (srv *Server) Publish(channels []string, ev Event) {
srv.pub <- &outbound{
channels: channels,
event: ev,
}
}
func replay(repo Repository, sub *subscription) {
for ev := range repo.Replay(sub.channel, sub.lastEventId) {
sub.out <- ev
}
}
func (srv *Server) run() {
subs := make(map[string]map[*subscription]struct{})
repos := make(map[string]Repository)
for {
select {
case reg := <-srv.registrations:
repos[reg.channel] = reg.repository
case sub := <-srv.unregister:
delete(subs[sub.channel], sub)
case pub := <-srv.pub:
for _, c := range pub.channels {
for s := range subs[c] {
select {
case s.out <- pub.event:
default:
srv.unregister <- s
close(s.out)
}
}
}
case sub := <-srv.subs:
if _, ok := subs[sub.channel]; !ok {
subs[sub.channel] = make(map[*subscription]struct{})
}
subs[sub.channel][sub] = struct{}{}
if srv.ReplayAll || len(sub.lastEventId) > 0 {
repo, ok := repos[sub.channel]
if ok {
go replay(repo, sub)
}
}
case <-srv.quit:
for _, sub := range subs {
for s := range sub {
close(s.out)
}
}
return
}
}
}
func (srv *Server) isServerClosed() bool {
srv.isClosedMutex.RLock()
defer srv.isClosedMutex.RUnlock()
return srv.isClosed
}
func (srv *Server) markServerClosed() {
srv.isClosedMutex.Lock()
defer srv.isClosedMutex.Unlock()
srv.isClosed = true
}
|
