/*
Stream manufactures a `pkg/stream.Stream`, starts a worker pumping events out of decoding, and returns that.
The 'outputCh' parameter must be a sendable channel. The "zero"-values of channel's content type will be created and used in the deserialization, then sent.
The return values from `httpclient.RawReq` are probably a useful starting point for the 'res' parameter.
Closing the returned `stream.Stream` shuts down the worker.
*/
func Stream(res *http.Response, outputCh interface{}) stream.Stream {
stream := stream.New()
var chanValue reflect.Value
if v, ok := outputCh.(reflect.Value); ok {
chanValue = v
} else {
chanValue = reflect.ValueOf(outputCh)
}
stopChanValue := reflect.ValueOf(stream.StopCh)
msgType := chanValue.Type().Elem().Elem()
go func() {
done := make(chan struct{})
defer func() {
chanValue.Close()
close(done)
}()
go func() {
select {
case <-stream.StopCh:
case <-done:
}
res.Body.Close()
}()
r := bufio.NewReader(res.Body)
dec := sse.NewDecoder(r)
for {
msg := reflect.New(msgType)
if err := dec.Decode(msg.Interface()); err != nil {
if err != io.EOF {
stream.Error = err
}
break
}
chosen, _, _ := reflect.Select([]reflect.SelectCase{
{
Dir: reflect.SelectRecv,
Chan: stopChanValue,
},
{
Dir: reflect.SelectSend,
Chan: chanValue,
Send: msg,
},
})
switch chosen {
case 0:
return
default:
}
}
}()
return stream
}
func (s *service) Leaders(leaders chan *Instance) (stream.Stream, error) {
events := make(chan *Event)
eventStream, err := s.client.c.Stream("GET", fmt.Sprintf("/services/%s/leader", s.name), nil, events)
if err != nil {
return nil, err
}
stream := stream.New()
go func() {
defer func() {
eventStream.Close()
// wait for stream to close to prevent race with Err read
for range events {
}
if err := eventStream.Err(); err != nil {
stream.Error = err
}
close(leaders)
}()
for {
select {
case event, ok := <-events:
if !ok {
return
}
if event.Kind != EventKindLeader {
continue
}
select {
case leaders <- event.Instance:
case <-stream.StopCh:
return
}
case <-stream.StopCh:
return
}
}
}()
return stream, nil
}
func ResumingStream(connect func(int64) (*http.Response, error, bool), outputCh interface{}) (stream.Stream, error) {
stream := stream.New()
firstErr := make(chan error)
go func() {
var once sync.Once
var lastID int64
stopChanValue := reflect.ValueOf(stream.StopCh)
outValue := reflect.ValueOf(outputCh)
defer outValue.Close()
for {
var res *http.Response
// nonRetryableErr will be set if a connection attempt should not
// be retried (for example if a 404 is returned).
var nonRetryableErr error
err := connectAttempts.Run(func() (err error) {
var retry bool
res, err, retry = connect(lastID)
if !retry {
nonRetryableErr = err
return nil
}
return
})
if nonRetryableErr != nil {
err = nonRetryableErr
}
once.Do(func() { firstErr <- err })
if err != nil {
stream.Error = err
return
}
chanValue := reflect.MakeChan(outValue.Type(), 0)
s := Stream(res, chanValue)
loop:
for {
chosen, v, ok := reflect.Select([]reflect.SelectCase{
{
Dir: reflect.SelectRecv,
Chan: stopChanValue,
},
{
Dir: reflect.SelectRecv,
Chan: chanValue,
},
})
switch chosen {
case 0:
s.Close()
return
default:
if !ok {
// TODO: check s.Err() for a special error sent from the
// server indicating the stream should not be retried
break loop
}
id := v.Elem().FieldByName("ID")
if id.Kind() == reflect.Int64 {
lastID = id.Int()
}
outValue.Send(v)
}
}
}
}()
return stream, <-firstErr
}