QPID-529: Priority queue implementation

QPID-2104: LVQ enhancement

These both required some refactoring of the Queue class to allow cleaner implementation of different types of behaviour. The in-memory storage of messages is now abstracted out behind an interface specified by qpid::broker::Messages which qpid::broker::Queue uses. Different implementations of that are available for the standard FIFO queue, priority queues and LVQ (I have also separated out the 'legacy' implementation of LVQ from the new version driven by QPID-2104).



git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk/qpid@1069322 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 211 insertions, 0 deletions

diff --git a/cpp/src/qpid/broker/PriorityQueue.cpp b/cpp/src/qpid/broker/PriorityQueue.cpp
new file mode 100644
index 0000000000..0272e968ec
--- /dev/null
+++ b/cpp/src/qpid/broker/PriorityQueue.cpp
@@ -0,0 +1,211 @@
+/*
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ * 
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ *
+ */
+#include "qpid/broker/PriorityQueue.h"
+#include "qpid/broker/Queue.h"
+#include "qpid/broker/QueuedMessage.h"
+#include "qpid/framing/reply_exceptions.h"
+
+namespace qpid {
+namespace broker {
+
+PriorityQueue::PriorityQueue(int l) : 
+    levels(l),
+    messages(levels, Deque()),
+    frontLevel(0), haveFront(false), cached(false) {}
+
+size_t PriorityQueue::size()
+{
+    size_t total(0);
+    for (int i = 0; i < levels; ++i) {
+        total += messages[i].size();
+    }
+    return total;
+}
+
+bool PriorityQueue::empty()
+{
+    for (int i = 0; i < levels; ++i) {
+        if (!messages[i].empty()) return false;
+    }
+    return true;
+}
+
+void PriorityQueue::reinsert(const QueuedMessage& message)
+{
+    uint p = getPriorityLevel(message);
+    messages[p].insert(lower_bound(messages[p].begin(), messages[p].end(), message), message);
+    clearCache();
+}
+
+bool PriorityQueue::find(const framing::SequenceNumber& position, QueuedMessage& message, bool remove)
+{
+    QueuedMessage comp;
+    comp.position = position;
+    for (int i = 0; i < levels; ++i) {
+        if (!messages[i].empty()) {
+            unsigned long diff = position.getValue() - messages[i].front().position.getValue();
+            long maxEnd = diff < messages[i].size() ? diff : messages[i].size();        
+            Deque::iterator l = lower_bound(messages[i].begin(),messages[i].begin()+maxEnd,comp);
+            if (l != messages[i].end() && l->position == position) {
+                message = *l;
+                if (remove) {
+                    messages[i].erase(l);
+                    clearCache();
+                }
+                return true;
+            }
+        }
+    }
+    return false;
+}
+
+bool PriorityQueue::remove(const framing::SequenceNumber& position, QueuedMessage& message)
+{
+    return find(position, message, true);
+}
+
+bool PriorityQueue::find(const framing::SequenceNumber& position, QueuedMessage& message)
+{
+    return find(position, message, false);
+}
+
+bool PriorityQueue::next(const framing::SequenceNumber& position, QueuedMessage& message)
+{
+    QueuedMessage match;
+    match.position = position+1;
+    Deque::iterator lowest;
+    bool found = false;
+    for (int i = 0; i < levels; ++i) {
+        Deque::iterator m = lower_bound(messages[i].begin(), messages[i].end(), match); 
+        if (m != messages[i].end()) {
+            if (m->position == match.position) {
+                message = *m;
+                return true;
+            } else if (!found || m->position < lowest->position) {
+                lowest = m;
+                found = true;
+            }
+        }
+    }
+    if (found) {
+        message = *lowest;
+    }
+    return found;
+}
+
+QueuedMessage& PriorityQueue::front()
+{
+    if (checkFront()) {
+        return messages[frontLevel].front();
+    } else {
+        throw qpid::framing::InternalErrorException(QPID_MSG("No message available"));
+    }
+}
+
+bool PriorityQueue::pop(QueuedMessage& message)
+{
+    if (checkFront()) {
+        message = messages[frontLevel].front();
+        messages[frontLevel].pop_front();
+        clearCache();
+        return true;
+    } else {
+        return false;
+    }
+}
+
+void PriorityQueue::pop()
+{
+    QueuedMessage dummy;
+    pop(dummy);
+}
+
+bool PriorityQueue::push(const QueuedMessage& added, QueuedMessage& /*not needed*/)
+{
+    messages[getPriorityLevel(added)].push_back(added);
+    clearCache();
+    return false;//adding a message never causes one to be removed for deque
+}
+
+void PriorityQueue::foreach(Functor f)
+{
+    for (int i = 0; i < levels; ++i) {
+        std::for_each(messages[i].begin(), messages[i].end(), f);
+    }
+}
+
+void PriorityQueue::removeIf(Predicate p)
+{
+    for (int priority = 0; priority < levels; ++priority) {
+        for (Deque::iterator i = messages[priority].begin(); i != messages[priority].end();) {
+            if (p(*i)) {
+                i = messages[priority].erase(i);
+                clearCache();
+            } else {
+                ++i;
+            }
+        }
+    }
+}
+
+uint PriorityQueue::getPriorityLevel(const QueuedMessage& m) const
+{
+    uint priority = m.payload->getPriority();
+    //Use AMQP 0-10 approach to mapping priorities to a fixed level
+    //(see rule priority-level-implementation)
+    const uint firstLevel = 5 - std::min(5.0, ceil((double) levels/2.0));
+    if (priority <= firstLevel) return 0;
+    return std::min(priority - firstLevel, (uint)levels-1);
+}
+
+void PriorityQueue::clearCache()
+{
+    cached = false;
+}
+
+bool PriorityQueue::findFrontLevel(uint& l, PriorityLevels& m)
+{
+    for (int p = levels-1; p >= 0; --p) {
+        if (!m[p].empty()) {
+            l = p;
+            return true;
+        }
+    }
+    return false;
+}
+
+bool PriorityQueue::checkFront()
+{
+    if (!cached) {
+        haveFront = findFrontLevel(frontLevel, messages);
+        cached = true;
+    }
+    return haveFront;
+}
+
+uint PriorityQueue::getPriority(const QueuedMessage& message)
+{
+    const PriorityQueue* queue = dynamic_cast<const PriorityQueue*>(&(message.queue->getMessages()));
+    if (queue) return queue->getPriorityLevel(message);
+    else return 0;
+}
+
+}} // namespace qpid::broker