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stream.go
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stream.go
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package service
import (
"io"
"io/ioutil"
"net/http"
"time"
"github.com/gorilla/websocket"
"github.com/NYTimes/gizmo/pubsub"
"github.com/NYTimes/gizmo/pubsub/kafka"
"github.com/NYTimes/gizmo/server"
"github.com/NYTimes/gizmo/web"
)
var (
upgrader = websocket.Upgrader{
ReadBufferSize: 1024,
WriteBufferSize: 1024,
CheckOrigin: func(r *http.Request) bool {
return true
},
}
)
func zeroOffset() int64 { return 0 }
func discardOffset(offset int64) {}
// Stream will init a new pubsub.Publisher and pubsub.Subscriber
// then upgrade the current request to a websocket connection. Any messages
// consumed from Kafka will be published to the web socket and vice versa.
func (s *StreamService) Stream(w http.ResponseWriter, r *http.Request) {
cfg := *s.cfg
cfg.Topic = topicName(web.GetInt64Var(r, "stream_id"))
server.LogWithFields(r).WithField("topic", cfg.Topic).Info("new stream req")
sub, err := kafka.NewSubscriber(&cfg, zeroOffset, discardOffset)
if err != nil {
server.LogWithFields(r).WithField("error", err).Error("unable to create sub")
http.Error(w, "unable to create subscriber: "+err.Error(), http.StatusBadRequest)
return
}
defer func() {
if err := sub.Stop(); err != nil {
server.LogWithFields(r).WithField("error", err).Error("unable to stop sub")
}
}()
var pub pubsub.Publisher
pub, err = kafka.NewPublisher(&cfg)
if err != nil {
server.LogWithFields(r).WithField("error", err).Error("unable to create pub")
http.Error(w, "unable to create publisher: "+err.Error(), http.StatusBadRequest)
return
}
defer func() {
kpub, ok := pub.(*kafka.Publisher)
if ok {
if err := kpub.Stop(); err != nil {
server.LogWithFields(r).WithField("error", err).Error("unable to stop pub")
}
}
}()
var ws *websocket.Conn
ws, err = upgrader.Upgrade(w, r, nil)
if err != nil {
server.LogWithFields(r).WithField("error", err).Error("unable to create websocket")
http.Error(w, "unable to create websocket: "+err.Error(), http.StatusBadRequest)
return
}
defer func() {
if err := ws.Close(); err != nil {
server.LogWithFields(r).WithField("error", err).Error("unable to close ws")
}
}()
// start consumer, emit to ws
noopTicker := time.NewTicker(time.Second * 5)
subscriberDone := make(chan bool, 1)
stopSubscriber := make(chan bool, 1)
go func() {
defer func() { subscriberDone <- true }()
var (
payload []byte
msgs = sub.Start()
)
for {
select {
case msg := <-msgs:
payload = msg.Message()
err = ws.SetWriteDeadline(time.Now().Add(time.Second * 30))
if err != nil {
server.LogWithFields(r).WithField("error", err).Error("unable to write deadline")
}
err = ws.WriteMessage(websocket.TextMessage, payload)
if err != nil {
server.LogWithFields(r).WithField("error", err).Error("unable to write ws message")
}
err = msg.Done()
if err != nil {
server.LogWithFields(r).WithField("error", err).Error("unable to mark gizmo message as done")
}
case <-noopTicker.C:
err = ws.SetWriteDeadline(time.Now().Add(time.Second * 30))
if err != nil {
server.LogWithFields(r).WithField("error", err).Error("unable to write deadline")
}
if err := ws.WriteMessage(websocket.PingMessage, []byte("ping")); err != nil {
server.LogWithFields(r).WithField("error", err).Error("error writing ws message")
return
}
case <-stopSubscriber:
return
}
}
}()
// start producer, emit to kafka
producerDone := make(chan bool, 1)
go func() {
defer func() {
producerDone <- true
stopSubscriber <- true
server.LogWithFields(r).WithField("topic", cfg.Topic).Info("closing stream req")
}()
var (
messageType int
payload []byte
err error
read io.Reader
)
for {
messageType, read, err = ws.NextReader()
if err != nil {
if err != io.EOF {
server.LogWithFields(r).WithField("error", err).Error("error reading message")
}
return
}
switch messageType {
case websocket.TextMessage:
payload, err = ioutil.ReadAll(read)
if err != nil {
server.LogWithFields(r).WithField("error", err).Error("unable to read payload")
return
}
err = pub.PublishRaw(nil, cfg.Topic, payload)
if err != nil {
server.LogWithFields(r).WithField("error", err).Error("unable to publish payload")
return
}
case websocket.PingMessage, websocket.PongMessage, websocket.BinaryMessage:
server.LogWithFields(r).Info("discarding message type: ", messageType)
case websocket.CloseMessage:
server.LogWithFields(r).Info("closing websocket")
return
}
}
}()
<-subscriberDone
<-producerDone
noopTicker.Stop()
server.LogWithFields(r).WithField("topic", cfg.Topic).Info("leaving stream req")
}