QPID-1660: If selected consumer can't take a message, ensure others are notified of message availability.

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk/qpid@743694 13f79535-47bb-0310-9956-ffa450edef68

4 files changed, 42 insertions, 9 deletions

diff --git a/cpp/src/qpid/broker/Queue.cpp b/cpp/src/qpid/broker/Queue.cpp
index f3cdc03f7d..c9ee7f394f 100644
--- a/cpp/src/qpid/broker/Queue.cpp
+++ b/cpp/src/qpid/broker/Queue.cpp
@@ -256,10 +256,30 @@ bool Queue::acquire(const QueuedMessage& msg) {
     return false;
 }
 
+void Queue::notifyListener()
+{
+    QueueListeners::NotificationSet set;
+    {
+        Mutex::ScopedLock locker(messageLock);
+        if (messages.size()) {
+            listeners.populate(set);
+        }
+    }
+    set.notify();
+}
+
 bool Queue::getNextMessage(QueuedMessage& m, Consumer::shared_ptr c)
 {
     if (c->preAcquires()) {
-        return consumeNextMessage(m, c);
+        switch (consumeNextMessage(m, c)) {
+          case CONSUMED:
+            return true;
+          case CANT_CONSUME:
+            notifyListener();//let someone else try
+          case NO_MESSAGES:
+          default:
+            return false;
+        }        
     } else {
         return browseNextMessage(m, c);
     }
@@ -291,14 +311,14 @@ bool Queue::checkForMessages(Consumer::shared_ptr c)
     }
 }
 
-bool Queue::consumeNextMessage(QueuedMessage& m, Consumer::shared_ptr c)
+Queue::ConsumeCode Queue::consumeNextMessage(QueuedMessage& m, Consumer::shared_ptr c)
 {
     while (true) {
         Mutex::ScopedLock locker(messageLock);
         if (messages.empty()) { 
             QPID_LOG(debug, "No messages to dispatch on queue '" << name << "'");
             listeners.addListener(c);
-            return false;
+            return NO_MESSAGES;
         } else {
             QueuedMessage msg = getFront();
             if (msg.payload->hasExpired()) {
@@ -311,16 +331,16 @@ bool Queue::consumeNextMessage(QueuedMessage& m, Consumer::shared_ptr c)
                 if (c->accept(msg.payload)) {            
                     m = msg;
                     popMsg(msg);
-                    return true;
+                    return CONSUMED;
                 } else {
                     //message(s) are available but consumer hasn't got enough credit
                     QPID_LOG(debug, "Consumer can't currently accept message from '" << name << "'");
-                    return false;
+                    return CANT_CONSUME;
                 }
             } else {
                 //consumer will never want this message
                 QPID_LOG(debug, "Consumer doesn't want message from '" << name << "'");
-                return false;
+                return CANT_CONSUME;
             } 
         }
     }
diff --git a/cpp/src/qpid/broker/Queue.h b/cpp/src/qpid/broker/Queue.h
index e4bcded8bd..61fbd45de8 100644
--- a/cpp/src/qpid/broker/Queue.h
+++ b/cpp/src/qpid/broker/Queue.h
@@ -68,6 +68,7 @@ namespace qpid {
 
             typedef std::deque<QueuedMessage> Messages;
             typedef std::map<string,boost::intrusive_ptr<Message> > LVQ;
+            enum ConsumeCode {NO_MESSAGES=0, CANT_CONSUME=1, CONSUMED=2};
 
             const string name;
             const bool autodelete;
@@ -104,8 +105,9 @@ namespace qpid {
             void setPolicy(std::auto_ptr<QueuePolicy> policy);
             bool seek(QueuedMessage& msg, Consumer::shared_ptr position);
             bool getNextMessage(QueuedMessage& msg, Consumer::shared_ptr c);
-            bool consumeNextMessage(QueuedMessage& msg, Consumer::shared_ptr c);
+            ConsumeCode consumeNextMessage(QueuedMessage& msg, Consumer::shared_ptr c);
             bool browseNextMessage(QueuedMessage& msg, Consumer::shared_ptr c);
+            void notifyListener();
 
             void removeListener(Consumer::shared_ptr);
 
diff --git a/cpp/src/qpid/broker/SemanticState.cpp b/cpp/src/qpid/broker/SemanticState.cpp
index 13a8c649d2..4f751e43b7 100644
--- a/cpp/src/qpid/broker/SemanticState.cpp
+++ b/cpp/src/qpid/broker/SemanticState.cpp
@@ -527,9 +527,19 @@ void SemanticState::ConsumerImpl::addMessageCredit(uint32_t value)
     }
 }
 
+bool SemanticState::ConsumerImpl::haveCredit()
+{
+    if (msgCredit) {
+        return true;
+    } else {
+        blocked = true;
+        return false;
+    }
+}
+
 void SemanticState::ConsumerImpl::flush()
 {
-    while(queue->dispatch(shared_from_this()))
+    while(haveCredit() && queue->dispatch(shared_from_this()))
         ;
     stop();
 }
@@ -587,7 +597,7 @@ bool SemanticState::ConsumerImpl::hasOutput() {
 
 bool SemanticState::ConsumerImpl::doOutput()
 {
-    return queue->dispatch(shared_from_this());
+    return haveCredit() && queue->dispatch(shared_from_this());
 }
 
 void SemanticState::ConsumerImpl::enableNotify()
diff --git a/cpp/src/qpid/broker/SemanticState.h b/cpp/src/qpid/broker/SemanticState.h
index a1bee23fd2..c31a6978c9 100644
--- a/cpp/src/qpid/broker/SemanticState.h
+++ b/cpp/src/qpid/broker/SemanticState.h
@@ -82,6 +82,7 @@ class SemanticState : public sys::OutputTask,
 
         bool checkCredit(boost::intrusive_ptr<Message>& msg);
         void allocateCredit(boost::intrusive_ptr<Message>& msg);
+        bool haveCredit();
 
       public:
         typedef boost::shared_ptr<ConsumerImpl> shared_ptr;