Support XPub socket send last value caching to last subscription pipe with…

 Support XPub socket send last value caching to last subscription pipe with ZMQ_XPUB_MANUAL_LAST_VALUE. (#3511)

* Add ZMQ_XPUB_MANUAL_LAST_VALUE

* Surpport xpub send last value caching to one pipe with ZMQ_XPUB_MANUAL_LAST_VALUE

* Add test_xpubub_manual_last_value

* Add relicense and doc

RELICENSE/imkcy9.md

+# Permission to Relicense under MPLv2 or any other OSI approved license chosen by the current ZeroMQ BDFL
+
+This is a statement by Chengye Ke
+that grants permission to relicense its copyrights in the libzmq C++
+library (ZeroMQ) under the Mozilla Public License v2 (MPLv2) or any other
+Open Source Initiative approved license chosen by the current ZeroMQ
+BDFL (Benevolent Dictator for Life).
+
+A portion of the commits made by the Github handle "imkcy9", with
+commit author "Chengye Ke <imkcy9@icloud.com>" or
+"Chengye Ke <imkcy9@gmail.com>", are copyright of Chengye Ke.
+This document hereby grants the libzmq project team to relicense libzmq,
+including all past, present and future contributions of the author listed above.
+
+Chengye Ke
+2019/05/18
\ No newline at end of file

doc/zmq_setsockopt.txt

@@ -1073,6 +1073,23 @@ Default value:: 0
 Applicable socket types:: ZMQ_XPUB
 
 
+ZMQ_XPUB_MANUAL_LAST_VALUE: change the subscription handling to manual
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+This option is similar to ZMQ_XPUB_MANUAL.
+What is the difference, ZMQ_XPUB_MANUAL_LAST_VALUE sets the 'XPUB' socket
+behaviour to send the first message to the last subscriber after the 'XPUB' socket
+recieve a subscription and call setsockopt with ZMQ_SUBSCRIBE on 'XPUB' socket.
+This prevent duplicated message when use last value caching(LVC).
+
+NOTE: in DRAFT state, not yet available in stable releases.
+
+[horizontal]
+Option value type:: int
+Option value unit:: 0, 1
+Default value:: 0
+Applicable socket types:: ZMQ_XPUB
+
+
 ZMQ_XPUB_NODROP: do not silently drop messages if SENDHWM is reached
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 Sets the 'XPUB' socket behaviour to return error EAGAIN if SENDHWM is

include/zmq.h

@@ -655,6 +655,7 @@ ZMQ_EXPORT void zmq_threadclose (void *thread_);
 #define ZMQ_METADATA 95
 #define ZMQ_MULTICAST_LOOP 96
 #define ZMQ_ROUTER_NOTIFY 97
+#define ZMQ_XPUB_MANUAL_LAST_VALUE 98
 
 /*  DRAFT Context options                                                     */
 #define ZMQ_ZERO_COPY_RECV 10

src/xpub.cpp

@@ -44,6 +44,9 @@ zmq::xpub_t::xpub_t (class ctx_t *parent_, uint32_t tid_, int sid_) :
     _more (false),
     _lossy (true),
     _manual (false),
+#ifdef ZMQ_BUILD_DRAFT_API
+    _send_last_pipe (false),
+#endif
     _pending_pipes (),
     _welcome_msg ()
 {
@@ -190,6 +193,9 @@ int zmq::xpub_t::xsetsockopt (int option_,
                               size_t optvallen_)
 {
     if (option_ == ZMQ_XPUB_VERBOSE || option_ == ZMQ_XPUB_VERBOSER
+#ifdef ZMQ_BUILD_DRAFT_API
+        || option_ == ZMQ_XPUB_MANUAL_LAST_VALUE
+#endif
         || option_ == ZMQ_XPUB_NODROP || option_ == ZMQ_XPUB_MANUAL) {
         if (optvallen_ != sizeof (int)
             || *static_cast<const int *> (optval_) < 0) {
@@ -202,6 +208,11 @@ int zmq::xpub_t::xsetsockopt (int option_,
         } else if (option_ == ZMQ_XPUB_VERBOSER) {
             _verbose_subs = (*static_cast<const int *> (optval_) != 0);
             _verbose_unsubs = _verbose_subs;
+#ifdef ZMQ_BUILD_DRAFT_API
+        } else if (option_ == ZMQ_XPUB_MANUAL_LAST_VALUE) {
+            _manual = (*static_cast<const int *> (optval_) != 0);
+            _send_last_pipe = _manual;
+#endif
         } else if (option_ == ZMQ_XPUB_NODROP)
             _lossy = (*static_cast<const int *> (optval_) == 0);
         else if (option_ == ZMQ_XPUB_MANUAL)
@@ -265,14 +276,33 @@ void zmq::xpub_t::mark_as_matching (pipe_t *pipe_, xpub_t *self_)
     self_->_dist.match (pipe_);
 }
 
+#ifdef ZMQ_BUILD_DRAFT_API
+void zmq::xpub_t::mark_last_pipe_as_matching (pipe_t *pipe_, xpub_t *self_)
+{
+    if (self_->_last_pipe == pipe_)
+        self_->_dist.match (pipe_);
+}
+#endif
+
 int zmq::xpub_t::xsend (msg_t *msg_)
 {
     bool msg_more = (msg_->flags () & msg_t::more) != 0;
 
     //  For the first part of multi-part message, find the matching pipes.
     if (!_more) {
+#ifdef ZMQ_BUILD_DRAFT_API
+        if (_manual && _last_pipe && _send_last_pipe) {
+            _subscriptions.match (static_cast<unsigned char *> (msg_->data ()),
+                                  msg_->size (), mark_last_pipe_as_matching,
+                                  this);
+            _last_pipe = NULL;
+        } else
+            _subscriptions.match (static_cast<unsigned char *> (msg_->data ()),
+                                  msg_->size (), mark_as_matching, this);
+#else
         _subscriptions.match (static_cast<unsigned char *> (msg_->data ()),
                               msg_->size (), mark_as_matching, this);
+#endif
         // If inverted matching is used, reverse the selection now
         if (options.invert_matching) {
             _dist.reverse_match ();

src/xpub.hpp

@@ -99,6 +99,14 @@ class xpub_t : public socket_base_t
     //  Subscriptions will not bed added automatically, only after calling set option with ZMQ_SUBSCRIBE or ZMQ_UNSUBSCRIBE
     bool _manual;
 
+#ifdef ZMQ_BUILD_DRAFT_API
+    //  Send message to the last pipe, only used if xpub is on manual and after calling set option with ZMQ_SUBSCRIBE
+    bool _send_last_pipe;
+
+    //  Function to be applied to match the last pipe.
+    static void mark_last_pipe_as_matching (zmq::pipe_t *pipe_, xpub_t *arg_);
+#endif
+
     //  Last pipe that sent subscription message, only used if xpub is on manual
     pipe_t *_last_pipe;
 

src/zmq_draft.h

@@ -52,6 +52,7 @@
 #define ZMQ_METADATA 95
 #define ZMQ_MULTICAST_LOOP 96
 #define ZMQ_ROUTER_NOTIFY 97
+#define ZMQ_XPUB_MANUAL_LAST_VALUE 98
 
 /*  DRAFT Context options                                                     */
 #define ZMQ_ZERO_COPY_RECV 10

tests/CMakeLists.txt

@@ -153,6 +153,7 @@ if(ENABLE_DRAFTS)
     test_dgram
     test_app_meta
     test_router_notify
+    test_xpub_manual_last_value
   )
 endif()