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mock_stream.go
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mock_stream.go
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package mocknet
import (
"bytes"
"io"
"time"
process "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/goprocess"
inet "github.com/ipfs/go-ipfs/p2p/net"
)
// stream implements inet.Stream
type stream struct {
io.Reader
io.Writer
conn *conn
toDeliver chan *transportObject
proc process.Process
}
type transportObject struct {
msg []byte
arrivalTime time.Time
}
func NewStream(w io.Writer, r io.Reader) *stream {
s := &stream{
Reader: r,
Writer: w,
toDeliver: make(chan *transportObject),
}
s.proc = process.WithTeardown(s.teardown)
s.proc.Go(s.transport)
return s
}
// How to handle errors with writes?
func (s *stream) Write(p []byte) (n int, err error) {
l := s.conn.link
delay := l.GetLatency() + l.RateLimit(len(p))
t := time.Now().Add(delay)
select {
case <-s.proc.Closing(): // bail out if we're closing.
return 0, io.ErrClosedPipe
case s.toDeliver <- &transportObject{msg: p, arrivalTime: t}:
}
return len(p), nil
}
func (s *stream) Close() error {
return s.proc.Close()
}
// teardown shuts down the stream. it is called by s.proc.Close()
// after all the children of this s.proc (i.e. transport's proc)
// are done.
func (s *stream) teardown() error {
// at this point, no streams are writing.
s.conn.removeStream(s)
if r, ok := (s.Reader).(io.Closer); ok {
r.Close()
}
if w, ok := (s.Writer).(io.Closer); ok {
w.Close()
}
s.conn.net.notifyAll(func(n inet.Notifiee) {
n.ClosedStream(s.conn.net, s)
})
return nil
}
func (s *stream) Conn() inet.Conn {
return s.conn
}
// transport will grab message arrival times, wait until that time, and
// then write the message out when it is scheduled to arrive
func (s *stream) transport(proc process.Process) {
bufsize := 256
buf := new(bytes.Buffer)
ticker := time.NewTicker(time.Millisecond * 4)
// writeBuf writes the contents of buf through to the s.Writer.
// done only when arrival time makes sense.
drainBuf := func() {
if buf.Len() > 0 {
_, err := s.Writer.Write(buf.Bytes())
if err != nil {
return
}
buf.Reset()
}
}
// deliverOrWait is a helper func that processes
// an incoming packet. it waits until the arrival time,
// and then writes things out.
deliverOrWait := func(o *transportObject) {
buffered := len(o.msg) + buf.Len()
now := time.Now()
if now.Before(o.arrivalTime) {
if buffered < bufsize {
buf.Write(o.msg)
return
}
// we do not buffer + return here, instead hanging the
// call (i.e. not accepting any more transportObjects)
// so that we apply back-pressure to the sender.
// this sleep should wake up same time as ticker.
time.Sleep(o.arrivalTime.Sub(now))
}
// ok, we waited our due time. now rite the buf + msg.
// drainBuf first, before we write this message.
drainBuf()
// write this message.
_, err := s.Writer.Write(o.msg)
if err != nil {
log.Error("mock_stream", err)
}
}
for {
select {
case <-proc.Closing():
return // bail out of here.
case o, ok := <-s.toDeliver:
if !ok {
return
}
deliverOrWait(o)
case <-ticker.C: // ok, due to write it out.
drainBuf()
}
}
}