This allows to specify how to size a queue and what to do when the sizing constraints have been reached. The queue size can be limited by the number messages (message depth) or byte depth on the queue.

Once the Queue meets/ exceeds these constraints the follow policies can be applied

Examples:

Create a queue an auto delete queue that will support 100 000 bytes, and then REJECT

#include "qpid/client/QueueOptions.h"

    QueueOptions qo;
    qo.setSizePolicy(REJECT,100000,0);

    session.queueDeclare(arg::queue=queue, arg::autoDelete=true, arg::arguments=qo);

Create a queue that will support 1000 messages into a RING buffer

#include "qpid/client/QueueOptions.h"

    QueueOptions qo;
    qo.setSizePolicy(RING,0,1000);

    session.queueDeclare(arg::queue=queue, arg::arguments=qo);

The default ordering in a queue in Qpid is FIFO. However additional ordering semantics can be used namely LVQ (Last Value Queue). Last Value Queue is define as follows.

If I publish symbols RHT, IBM, JAVA, MSFT, and then publish RHT before the consumer is able to consume RHT, that message will be over written in the queue and the consumer will receive the last published value for RHT.

Example:

#include "qpid/client/QueueOptions.h"

    QueueOptions qo;
    qo.setOrdering(LVQ);

    session.queueDeclare(arg::queue=queue, arg::arguments=qo);

    .....
    string key;
    qo.getLVQKey(key);

    ....
    for each message, set the into application headers before transfer
    message.getHeaders().setString(key,"RHT");
    

Notes:

A fully worked Section 1.6.3, “LVQ Example” can be found here

Note that these options can be set from any client. QueueOptions just correctly formats the arguments passed to the QueueDeclare() method.