Lazy channels (#78)

* Implemented lazy stream opening for mplex connections

* Properly fix newStream usage

* Make lazy channel open optional

* Add Lazy channel test

* Cleanup mplex test

* Move lazyness properly into LPChannel

* Connection writeLp back to proc

libp2p/connection.nim

@@ -28,22 +28,26 @@ type
 proc newInvalidVarintException*(): ref InvalidVarintException =
   newException(InvalidVarintException, "unable to prase varint")
 
-proc newConnection*(stream: LPStream): Connection =
+proc init*[T: Connection](self: var T, stream: LPStream) =
   ## create a new Connection for the specified async reader/writer
-  new result
-  result.stream = stream
-  result.closeEvent = newAsyncEvent()
+  new self
+  self.stream = stream
+  self.closeEvent = newAsyncEvent()
 
   # bind stream's close event to connection's close
   # to ensure correct close propagation
-  let this = result
-  if not isNil(result.stream.closeEvent):
-    result.stream.closeEvent.wait().
+  let this = self
+  if not isNil(self.stream.closeEvent):
+    self.stream.closeEvent.wait().
       addCallback do (udata: pointer):
         if not this.closed:
           trace "closing this connection because wrapped stream closed"
           asyncCheck this.close()
 
+proc newConnection*(stream: LPStream): Connection =
+  ## create a new Connection for the specified async reader/writer
+  result.init(stream)
+
 method read*(s: Connection, n = -1): Future[seq[byte]] {.gcsafe.} =
  s.stream.read(n)
 

libp2p/muxers/mplex/lpchannel.nim

@@ -26,6 +26,8 @@ type
     name*: string
     conn*: Connection
     initiator*: bool
+    isLazy*: bool
+    isOpen*: bool
     isReset*: bool
     closedLocal*: bool
     closedRemote*: bool
@@ -39,7 +41,8 @@ proc newChannel*(id: uint,
                  conn: Connection,
                  initiator: bool,
                  name: string = "",
-                 size: int = DefaultChannelSize): LPChannel =
+                 size: int = DefaultChannelSize,
+                 lazy: bool = false): LPChannel =
   new result
   result.id = id
   result.name = name
@@ -49,6 +52,7 @@ proc newChannel*(id: uint,
   result.closeCode = if initiator: MessageType.CloseOut else: MessageType.CloseIn
   result.resetCode = if initiator: MessageType.ResetOut else: MessageType.ResetIn
   result.asyncLock = newAsyncLock()
+  result.isLazy = lazy
 
   let chan = result
   proc writeHandler(data: seq[byte]): Future[void] {.async.} =
@@ -76,6 +80,7 @@ proc cleanUp*(s: LPChannel): Future[void] =
   result = procCall close(BufferStream(s))
 
 proc open*(s: LPChannel): Future[void] =
+  s.isOpen = true
   s.conn.writeMsg(s.id, MessageType.New, s.name)
 
 method close*(s: LPChannel) {.async, gcsafe.} =
@@ -142,19 +147,22 @@ method readUntil*(s: LPChannel,
     raise newLPStreamEOFError()
   result = procCall readOnce(BufferStream(s), pbytes, nbytes)
 
-method write*(s: LPChannel,
-              pbytes: pointer,
-              nbytes: int): Future[void] =
+template writePrefix: untyped =
+  if s.isLazy and not s.isOpen:
+    await s.open()
   if s.closedLocal or s.isReset:
     raise newLPStreamEOFError()
+
+method write*(s: LPChannel,
+              pbytes: pointer,
+              nbytes: int): Future[void] {.async.} =
+  writePrefix()
   result = procCall write(BufferStream(s), pbytes, nbytes)
 
 method write*(s: LPChannel, msg: string, msglen = -1) {.async.} =
-  if s.closedLocal or s.isReset:
-    raise newLPStreamEOFError()
+  writePrefix()
   result = procCall write(BufferStream(s), msg, msglen)
 
 method write*(s: LPChannel, msg: seq[byte], msglen = -1) {.async.} =
-  if s.closedLocal or s.isReset:
-    raise newLPStreamEOFError()
+  writePrefix()
   result = procCall write(BufferStream(s), msg, msglen)

libp2p/muxers/mplex/mplex.nim

@@ -41,12 +41,13 @@ proc getChannelList(m: Mplex, initiator: bool): var Table[uint, LPChannel] =
 proc newStreamInternal*(m: Mplex,
                         initiator: bool = true,
                         chanId: uint = 0,
-                        name: string = ""):
+                        name: string = "",
+                        lazy: bool = false):
                         Future[LPChannel] {.async, gcsafe.} =
   ## create new channel/stream
   let id = if initiator: m.currentId.inc(); m.currentId else: chanId
   trace "creating new channel", channelId = id, initiator = initiator
-  result = newChannel(id, m.connection, initiator, name)
+  result = newChannel(id, m.connection, initiator, name, lazy = lazy)
   m.getChannelList(initiator)[id] = result
 
 proc cleanupChann(m: Mplex, chann: LPChannel, initiator: bool) {.async, inline.} =
@@ -142,9 +143,9 @@ proc newMplex*(conn: Connection,
     trace "connection closed, cleaning up mplex"
     asyncCheck m.close()
     
-method newStream*(m: Mplex, name: string = ""): Future[Connection] {.async, gcsafe.} =
-  let channel = await m.newStreamInternal()
-  # TODO: open the channel (this should be lazy)
+method newStream*(m: Mplex, name: string = "", lazy: bool = false): Future[Connection] {.async, gcsafe.} =
+  let channel = await m.newStreamInternal(lazy = lazy)
+  if not lazy:
     await channel.open()
   result = newConnection(channel)
   result.peerInfo = m.connection.peerInfo

libp2p/muxers/muxer.nim

@@ -32,7 +32,7 @@ type
     muxerHandler*: MuxerHandler # triggered every time there is a new muxed connection created
 
 # muxer interface
-method newStream*(m: Muxer, name: string = ""): Future[Connection] {.base, async, gcsafe.} = discard
+method newStream*(m: Muxer, name: string = "", lazy: bool = false): Future[Connection] {.base, async, gcsafe.} = discard
 method close*(m: Muxer) {.base, async, gcsafe.} = discard
 method handle*(m: Muxer): Future[void] {.base, async, gcsafe.} = discard
 

tests/testmplex.nim

@@ -139,8 +139,41 @@ suite "Mplex":
 
       let mplexDial = newMplex(conn)
       let stream = await mplexDial.newStream()
+      let openState = cast[LPChannel](stream.stream).isOpen
       await stream.writeLp("Hello from stream!")
       await conn.close()
+      check openState # not lazy
+      result = true
+
+    check:
+      waitFor(testNewStream()) == true
+
+  test "e2e - read/write receiver lazy":
+    proc testNewStream(): Future[bool] {.async.} =
+      let ma: MultiAddress = Multiaddress.init("/ip4/0.0.0.0/tcp/0")
+
+      proc connHandler(conn: Connection) {.async, gcsafe.} =
+        proc handleMplexListen(stream: Connection) {.async, gcsafe.} =
+          let msg = await stream.readLp()
+          check cast[string](msg) == "Hello from stream!"
+          await stream.close()
+
+        let mplexListen = newMplex(conn)
+        mplexListen.streamHandler = handleMplexListen
+        discard mplexListen.handle()
+
+      let transport1: TcpTransport = newTransport(TcpTransport)
+      discard await transport1.listen(ma, connHandler)
+
+      let transport2: TcpTransport = newTransport(TcpTransport)
+      let conn = await transport2.dial(transport1.ma)
+
+      let mplexDial = newMplex(conn)
+      let stream = await mplexDial.newStream("", true)
+      let openState = cast[LPChannel](stream.stream).isOpen
+      await stream.writeLp("Hello from stream!")
+      await conn.close()
+      check not openState # assert lazy 
       result = true
 
     check: