Multi-hop REQ/REP, part X., optional delayed creation of pipes during connect

src/options.cpp

@@ -34,6 +34,7 @@ zmq::options_t::options_t () :
     rcvbuf (0),
     requires_in (false),
     requires_out (false),
+    immediate_connect (true),
     traceroute (false)
 {
 }

src/options.hpp

@@ -56,6 +56,12 @@ namespace zmq
         bool requires_in;
         bool requires_out;
 
+        //  If true, when connecting, pipes are created immediately without
+        //  waiting for the connection to be established. That way the socket
+        //  is not aware of the peer's identity, however, it is able to send
+        //  messages straight away.
+        bool immediate_connect;
+
         //  If true, socket requires tracerouting the messages.
         bool traceroute;
     };

src/rep.cpp

@@ -32,6 +32,11 @@ zmq::rep_t::rep_t (class app_thread_t *parent_) :
 {
     options.requires_in = true;
     options.requires_out = true;
+
+    //  We don't need immediate connect. We'll be able to send messages
+    //  (replies) only when connection is established and thus requests
+    //  can arrive anyway.
+    options.immediate_connect = false;
 }
 
 zmq::rep_t::~rep_t ()

src/session.cpp

@@ -220,33 +220,31 @@ void zmq::session_t::process_attach (i_engine *engine_,
         }
     }
 
-    //  If session is created by 'connect' function, it has the pipes set
-    //  already. Otherwise, it's being created by the listener and the pipes
-    //  are yet to be created.
-    if (!in_pipe && !out_pipe) {
+    //  Check whether the required pipes already exist. If not so, we'll
+    //  create them and bind them to the socket object.
+    reader_t *socket_reader = NULL;
+    writer_t *socket_writer = NULL;
 
-        pipe_t *inbound = NULL;
-        pipe_t *outbound = NULL;
-
-        if (options.requires_out) {
-            inbound = new (std::nothrow) pipe_t (this, owner,
+    if (options.requires_in && !out_pipe) {
+        pipe_t *pipe = new (std::nothrow) pipe_t (owner, this,
             options.hwm, options.lwm);
-            zmq_assert (inbound);
-            in_pipe = &inbound->reader;
-            in_pipe->set_endpoint (this);
+        zmq_assert (pipe);
+        out_pipe = &pipe->writer;
+        out_pipe->set_endpoint (this);
+        socket_reader = &pipe->reader;
     }
 
-        if (options.requires_in) {
-            outbound = new (std::nothrow) pipe_t (owner, this,
+    if (options.requires_out && !in_pipe) {
+        pipe_t *pipe = new (std::nothrow) pipe_t (this, owner,
             options.hwm, options.lwm);
-            zmq_assert (outbound);
-            out_pipe = &outbound->writer;
-            out_pipe->set_endpoint (this);
+        zmq_assert (pipe);
+        in_pipe = &pipe->reader;
+        in_pipe->set_endpoint (this);
+        socket_writer = &pipe->writer;
     }
 
-        send_bind (owner, outbound ? &outbound->reader : NULL,
-            inbound ? &inbound->writer : NULL, peer_identity);
-    }
+    if (socket_reader || socket_writer)
+        send_bind (owner, socket_reader, socket_writer, peer_identity);
 
     //  Plug in the engine.
     zmq_assert (!engine);

src/socket_base.cpp

@@ -141,6 +141,10 @@ int zmq::socket_base_t::connect (const char *addr_)
 
     if (addr_type == "inproc") {
 
+        //  TODO: inproc connect is specific with respect to creating pipes
+        //  as there's no 'reconnect' functionality implemented. Once that
+        //  is in place we should follow generic pipe creation algorithm.
+
         //  Find the peer socket.
         socket_base_t *peer = find_endpoint (addr_args.c_str ());
         if (!peer)
@@ -182,6 +186,11 @@ int zmq::socket_base_t::connect (const char *addr_)
         this, options);
     zmq_assert (session);
 
+    //  If 'immediate connect' feature is required, we'll created the pipes
+    //  to the session straight away. Otherwise, they'll be created by the
+    //  session once the connection is established.
+    if (options.immediate_connect) {
+
         pipe_t *in_pipe = NULL;
         pipe_t *out_pipe = NULL;
 
@@ -207,6 +216,7 @@ int zmq::socket_base_t::connect (const char *addr_)
         //  Attach the pipes to the session object.
         session->attach_pipes (out_pipe ? &out_pipe->reader : NULL,
             in_pipe ? &in_pipe->writer : NULL);
+    }
 
     //  Activate the session.
     send_plug (session);
@@ -215,6 +225,8 @@ int zmq::socket_base_t::connect (const char *addr_)
     if (addr_type == "tcp" || addr_type == "ipc") {
 
 #if defined ZMQ_HAVE_WINDOWS || defined ZMQ_HAVE_OPENVMS
+        //  Windows named pipes are not compatible with Winsock API.
+        //  There's no UNIX domain socket implementation on OpenVMS.
         if (addr_type == "ipc") {
             errno = EPROTONOSUPPORT;
             return -1;
@@ -254,6 +266,9 @@ int zmq::socket_base_t::connect (const char *addr_)
         if (addr_type == "udp")
             udp_encapsulation = true;
 
+        //  At this point we'll create message pipes to the session straight
+        //  away. There's no point in delaying it as no concept of 'connect'
+        //  exists with PGM anyway.
         if (options.requires_out) {
 
             //  PGM sender.

src/xrep.cpp

@@ -28,6 +28,10 @@ zmq::xrep_t::xrep_t (class app_thread_t *parent_) :
     options.requires_in = true;
     options.requires_out = true;
 
+    //  On connect, pipes are created only after initial handshaking.
+    //  That way we are aware of the peer's identity when binding to the pipes.
+    options.immediate_connect = false;
+
     //  XREP socket adds identity to inbound messages and strips identity
     //  from the outbound messages.
     options.traceroute = true;