path: root/qpid/doc/book/src/Cheat-Sheet-for-configuring-Queue-Options.xml

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<section><title>
      Cheat Sheet for configuring Queue Options
    </title>

    <section role="h2" id="CheatSheetforconfiguringQueueOptions-ConfiguringQueueOptions"><title>
            Configuring
            Queue Options
          </title>

	  <para>
            The C++ Broker M4 or later supports the following additional
            Queue constraints.
          </para>
            <itemizedlist>
              <listitem><para>
                <xref linkend="CheatSheetforconfiguringQueueOptions-ConfiguringQueueOptions"/>
              </para></listitem>
              <listitem><para>
                <itemizedlist>
                  <listitem><para>
                    <xref linkend="CheatSheetforconfiguringQueueOptions-ApplyingQueueSizingConstraints"/>
                  </para></listitem>
                  <listitem><para>
                    <xref linkend="CheatSheetforconfiguringQueueOptions-ChangingtheQueueorderingBehaviors-28FIFO-2FLVQ-29"/>
                  </para></listitem>
                  <listitem><para>
                    <xref linkend="CheatSheetforconfiguringQueueOptions-Settingadditionalbehaviors"/>
                  </para></listitem>
                  <listitem><para>
                    <itemizedlist>
                      <listitem><para>
                        <xref linkend="CheatSheetforconfiguringQueueOptions-PersistLastNode"/>
                      </para></listitem>
                      <listitem><para>
                        <xref linkend="CheatSheetforconfiguringQueueOptions-Queueeventgeneration"/>
                      </para></listitem>
                    </itemizedlist>
                  </para></listitem>
                  <listitem><para>
                    <xref linkend="CheatSheetforconfiguringQueueOptions-OtherClients"/>
                  </para></listitem>
                </itemizedlist>
              </para></listitem>
            </itemizedlist>

	  <para>
            The 0.10 C++ Broker supports the following additional Queue configuration options:
          </para>
          <itemizedlist>
            <listitem><para>
              <xref linkend="producer-flow-control"/>
            </para></listitem>
          </itemizedlist>

          <section role="h3" id="CheatSheetforconfiguringQueueOptions-ApplyingQueueSizingConstraints"><title>
            Applying Queue Sizing Constraints
          </title>

	  <para>
            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.
          </para><para>
            Once the Queue meets/ exceeds these constraints the follow
            policies can be applied
          </para><itemizedlist>
            <listitem><para>REJECT - Reject the published message
            </para></listitem>
            <listitem><para>FLOW_TO_DISK - Flow the messages to disk, to preserve memory
            </para></listitem>
            <listitem><para>RING - start overwriting messages in a ring based on sizing.
            If head meets tail, advance head
            </para></listitem>
            <listitem><para>RING_STRICT - start overwriting messages in a ring based on
            sizing. If head meets tail, AND the consumer has the tail message
            acquired it will reject
            </para></listitem>
          </itemizedlist><para>
            Examples:
          </para><para>
            Create a queue an auto delete queue that will support 100 000
            bytes, and then REJECT
          </para>
            <programlisting>
#include "qpid/client/QueueOptions.h"

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

    session.queueDeclare(arg::queue=queue, arg::autoDelete=true, arg::arguments=qo);
</programlisting>
          <para>
            Create a queue that will support 1000 messages into a RING buffer
          </para>
            <programlisting>
#include "qpid/client/QueueOptions.h"

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

    session.queueDeclare(arg::queue=queue, arg::arguments=qo);
</programlisting>
	  <!--h3--></section>
          <section role="h3" id="CheatSheetforconfiguringQueueOptions-ChangingtheQueueorderingBehaviors-28FIFO-2FLVQ-29"><title>
            Changing the Queue ordering Behaviors (FIFO/LVQ)
          </title>
          <para>
            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.
          </para><para>
            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.
          </para><para>
            Example:
          </para>
            <programlisting>
#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");
    
</programlisting>
          <para>
            Notes:
          </para><itemizedlist>
            <listitem><para>Messages that are dequeued and the re-queued will have the
            following exceptions. a.) if a new message has been queued with
            the same key, the re-queue from the consumer, will combine these
            two messages. b.) If an update happens for a message of the same
            key, after the re-queue, it will not update the re-queued
            message. This is done to protect a client from being able to
            adversely manipulate the queue.
            </para></listitem>
            <listitem><para>Acquire: When a message is acquired from the queue, no matter
            it's position, it will behave the same as a dequeue
            </para></listitem>
            <listitem><para>LVQ does not support durable messages. If the queue or
            messages are declared durable on an LVQ, the durability will be
            ignored.
            </para></listitem>
          </itemizedlist><para>
            A fully worked <xref linkend="LVQ-Examplesource"/> can be found here
          </para>
	  <!--h3--></section>
	  <section role="h3" id="CheatSheetforconfiguringQueueOptions-Settingadditionalbehaviors"><title>
            Setting additional behaviors
          </title>
          <section role="h4" id="CheatSheetforconfiguringQueueOptions-PersistLastNode"><title>
            Persist
            Last Node
          </title>
          <para>
            This option is used in conjunction with clustering. It allows for
            a queue configured with this option to persist transient messages
            if the cluster fails down to the last node. If additional nodes
            in the cluster are restored it will stop persisting transient
            messages.
          </para><para>
            Note
          </para><itemizedlist>
            <listitem><para>if a cluster is started with only one active node, this mode
            will not be triggered. It is only triggered the first time the
            cluster fails down to 1 node.
            </para></listitem>
            <listitem><para>The queue MUST be configured durable
            </para></listitem>
          </itemizedlist><para>
            Example:
          </para>
            <programlisting>
#include "qpid/client/QueueOptions.h"

    QueueOptions qo;
    qo.clearPersistLastNode();

    session.queueDeclare(arg::queue=queue, arg::durable=true, arg::arguments=qo);
</programlisting>
	  <!--h4--></section>
          <section role="h4" id="CheatSheetforconfiguringQueueOptions-Queueeventgeneration"><title>
            Queue
            event generation
          </title>
          <para>
            This option is used to determine whether enqueue/dequeue events
            representing changes made to queue state are generated. These
            events can then be processed by plugins such as that used for
            <xref linkend="queue-state-replication"/>.
          </para><para>
            Example:
          </para>
            <programlisting>
#include "qpid/client/QueueOptions.h"

    QueueOptions options;
    options.enableQueueEvents(1);
    session.queueDeclare(arg::queue="my-queue", arg::arguments=options);
</programlisting>
          <para>
            The boolean option indicates whether only enqueue events should
            be generated. The key set by this is
            'qpid.queue_event_generation' and the value is and integer value
            of 1 (to replicate only enqueue events) or 2 (to replicate both
            enqueue and dequeue events).
          </para>
	  <!--h3--></section>
	  <!--h4--></section>
	  <section role="h3" id="CheatSheetforconfiguringQueueOptions-OtherClients"><title>
            Other
            Clients
          </title>
          <para>
            Note that these options can be set from any client. QueueOptions
            just correctly formats the arguments passed to the QueueDeclare()
            method.
          </para>

	  <!--h3--></section>
	  
	<!--h2--></section>


</section>