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#ifndef QPID_BROKER_INDEXEDDEQUE_H
#define QPID_BROKER_INDEXEDDEQUE_H
/*
*
* 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/framing/SequenceNumber.h"
#include "qpid/broker/Message.h"
#include "qpid/broker/Messages.h"
#include "qpid/broker/QueueCursor.h"
#include "qpid/log/Statement.h"
#include <deque>
namespace qpid {
namespace broker {
/**
* Template for a deque whose contents can be refered to by
* QueueCursor
*/
template <typename T> class IndexedDeque
{
public:
typedef boost::function1<T, qpid::framing::SequenceNumber> Padding;
IndexedDeque(Padding p) : head(0), version(0), padding(p) {}
bool index(const QueueCursor& cursor, size_t& result)
{
return cursor.valid && index(qpid::framing::SequenceNumber(cursor.position + 1), result);
}
/**
* Finds the index for the message with the specified sequence number.
*
* @returns true if a message was found with the specified sequence,
* in which case the second parameter will be set to the index of that
* message; false if no message with that sequence exists, in which
* case the second parameter will be 0 if the sequence is less than
* that of the first message and non-zero if it is greater than that
* of the last message
*/
bool index(const qpid::framing::SequenceNumber& position, size_t& i)
{
//assuming a monotonic sequence, with no messages removed except
//from the ends of the deque, we can use the position to determine
//an index into the deque
if (messages.size()) {
qpid::framing::SequenceNumber front(messages.front().getSequence());
if (position < front) {
i = 0;
} else {
i = position - front;
return i < messages.size();
}
}
return false;
}
bool deleted(const QueueCursor& cursor)
{
size_t i;
if (cursor.valid && index(cursor.position, i)) {
messages[i].setState(DELETED);
clean();
return true;
} else {
return false;
}
}
T& publish(const T& added)
{
// QPID-4046: let producer help clean the backlog of deleted messages
clean();
//for ha replication, the queue can sometimes be reset by
//removing some of the more recent messages, in this case we
//need to ensure the DELETED records at the tail do not interfere with indexing
while (messages.size() && added.getSequence() <= messages.back().getSequence() && messages.back().getState() == DELETED)
messages.pop_back();
if (messages.size() && added.getSequence() <= messages.back().getSequence()) throw qpid::Exception(QPID_MSG("Index out of sequence!"));
//add padding to prevent gaps in sequence, which break the index
//calculation (needed for queue replication)
while (messages.size() && (added.getSequence() - messages.back().getSequence()) > 1)
messages.push_back(padding(messages.back().getSequence() + 1));
messages.push_back(added);
T& m = messages.back();
m.setState(AVAILABLE);
if (head >= messages.size()) head = messages.size() - 1;
QPID_LOG(debug, "Message " << &m << " published, state is " << m.getState() << " (head is now " << head << ")");
return m;
}
T* release(const QueueCursor& cursor)
{
size_t i;
if (cursor.valid && index(cursor.position, i) && messages[i].getState() == ACQUIRED) {
messages[i].setState(AVAILABLE);
++version;
QPID_LOG(debug, "Released message at position " << cursor.position << ", index " << i);
return &messages[i];
} else {
if (!cursor.valid) { QPID_LOG(debug, "Could not release message; cursor was invalid");}
else { QPID_LOG(debug, "Could not release message at position " << cursor.position); }
return 0;
}
}
bool reset(const QueueCursor& cursor)
{
return !cursor.valid || (cursor.type == CONSUMER && cursor.version != version);
}
T* next(QueueCursor& cursor)
{
size_t i = 0;
if (reset(cursor)) i = head; //start from head
else index(cursor, i); //get first message that is greater than position
if (cursor.valid) {
QPID_LOG(debug, "next() called for cursor at " << cursor.position << ", index set to " << i << " (of " << messages.size() << ")");
} else {
QPID_LOG(debug, "next() called for invalid cursor, index started at " << i << " (of " << messages.size() << ")");
}
while (i < messages.size()) {
T& m = messages[i++];
if (m.getState() == DELETED) continue;
cursor.setPosition(m.getSequence(), version);
QPID_LOG(debug, "in next(), cursor set to " << cursor.position);
if (cursor.check(m)) {
QPID_LOG(debug, "in next(), returning message at " << cursor.position);
return &m;
}
}
QPID_LOG(debug, "no message to return from next");
return 0;
}
size_t size()
{
size_t count(0);
for (size_t i = head; i < messages.size(); ++i) {
if (messages[i].getState() == AVAILABLE) ++count;
}
return count;
}
T* find(const qpid::framing::SequenceNumber& position, QueueCursor* cursor)
{
size_t i = 0;
if (index(position, i)){
T& m = messages[i];
if (cursor) cursor->setPosition(position, version);
if (m.getState() == AVAILABLE || m.getState() == ACQUIRED) {
return &m;
}
} else if (cursor) {
if (i >= messages.size()) cursor->setPosition(position, version);//haven't yet got a message with that seq no
else if (i == 0) cursor->valid = false;//reset
}
return 0;
}
T* find(const QueueCursor& cursor)
{
if (cursor.valid) return find(cursor.position, 0);
else return 0;
}
void clean()
{
// QPID-4046: If a queue has multiple consumers, then it is possible for a large
// collection of deleted messages to build up. Limit the number of messages cleaned
// up on each call to clean().
size_t count = 0;
while (messages.size() && messages.front().getState() == DELETED && count < 10) {
messages.pop_front();
count += 1;
}
head = (head > count) ? head - count : 0;
QPID_LOG(debug, "clean(): " << messages.size() << " messages remain; head is now " << head);
}
void foreach(Messages::Functor f)
{
for (typename Deque::iterator i = messages.begin(); i != messages.end(); ++i) {
if (i->getState() == AVAILABLE) {
f(*i);
}
}
clean();
}
void resetCursors()
{
++version;
}
typedef std::deque<T> Deque;
Deque messages;
size_t head;
int32_t version;
Padding padding;
};
}} // namespace qpid::broker
#endif /*!QPID_BROKER_INDEXEDDEQUE_H*/
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