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Posted to commits@qpid.apache.org by ro...@apache.org on 2016/05/13 21:45:40 UTC
svn commit: r1743759 [2/2] - in /qpid/java/trunk/doc/jms-client-0-10: ./
src/ src/docbkx/ src/docbkx/JMS-Client-0-10-Book.xml
Added: qpid/java/trunk/doc/jms-client-0-10/src/docbkx/JMS-Client-0-10-Book.xml
URL: http://svn.apache.org/viewvc/qpid/java/trunk/doc/jms-client-0-10/src/docbkx/JMS-Client-0-10-Book.xml?rev=1743759&view=auto
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--- qpid/java/trunk/doc/jms-client-0-10/src/docbkx/JMS-Client-0-10-Book.xml (added)
+++ qpid/java/trunk/doc/jms-client-0-10/src/docbkx/JMS-Client-0-10-Book.xml Fri May 13 21:45:40 2016
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+<?xml version='1.0' encoding='utf-8' ?>
+<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
+
+<!--
+
+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.
+
+-->
+
+<book id="client-api-tutorial">
+ <title>Programming in Apache Qpid</title>
+ <subtitle>Cross-Platform AMQP Messaging in Java JMS, .NET, C++, and Python</subtitle>
+
+ <chapter>
+ <title>Introduction</title>
+
+ <para>Apache Qpid is a reliable, asynchronous messaging system that
+ supports the AMQP messaging protocol in several common programming
+ languages. Qpid is supported on most common platforms.
+ </para>
+
+ <itemizedlist>
+ <listitem>
+ <para>
+ On the Java platform, Qpid uses the
+ established <ulink url="http://java.sun.com/products/jms/">Java JMS
+ API</ulink>.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ For Python, C++, and .NET, Qpid defines its own messaging API, the
+ <firstterm>Qpid Messaging API</firstterm>, which is
+ conceptually similar in each.
+ </para>
+ <para>
+ On the .NET platform, Qpid also provides a WCF binding.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ Ruby will also use the Qpid Messaging API, which will soon
+ be implemented. (Ruby currently uses an API that is closely
+ tied to the AMQP version).
+ </para>
+ </listitem>
+ </itemizedlist>
+
+ </chapter>
+
+ <chapter>
+ <title>Using the Qpid Messaging API</title>
+
+ <para>The Qpid Messaging API is quite simple, consisting of only a
+ handful of core classes.
+ </para>
+
+ <itemizedlist>
+
+ <listitem>
+ <para>
+ A <firstterm>message</firstterm> consists of a standard set
+ of fields (e.g. <literal>subject</literal>,
+ <literal>reply-to</literal>), an application-defined set of
+ properties, and message content (the main body of the
+ message).
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ A <firstterm>connection</firstterm> represents a network
+ connection to a remote endpoint.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ A <firstterm>session</firstterm> provides a sequentially
+ ordered context for sending and receiving
+ <emphasis>messages</emphasis>. A session is obtained from a
+ connection.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ A <firstterm>sender</firstterm> sends messages to a target
+ using the <literal>sender.send</literal> method. A sender is
+ obtained from a session for a given target address.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ A <firstterm>receiver</firstterm> receives messages from a
+ source using the <literal>receiver.fetch</literal> method.
+ A receiver is obtained from a session for a given source
+ address.
+ </para>
+ </listitem>
+
+ </itemizedlist>
+
+ <para>
+ The following sections show how to use these classes in a
+ simple messaging program.
+ </para>
+
+ <section>
+ <title>A Simple Messaging Program in C++</title>
+
+ <para>The following C++ program shows how to create a connection,
+ create a session, send messages using a sender, and receive
+ messages using a receiver.</para>
+
+ <example>
+ <title>"Hello world!" in C++</title>
+ <programlisting lang="c++"><![CDATA[
+ #include <qpid/messaging/Connection.h>
+ #include <qpid/messaging/Message.h>
+ #include <qpid/messaging/Receiver.h>
+ #include <qpid/messaging/Sender.h>
+ #include <qpid/messaging/Session.h>
+
+ #include <iostream>]]>
+
+ using namespace qpid::messaging;
+
+ int main(int argc, char** argv) {
+ std::string broker = argc > 1 ? argv[1] : "localhost:5672";
+ std::string address = argc > 2 ? argv[2] : "amq.topic";
+ std::string connectionOptions = argc > 3 ? argv[3] : "";
+
+ Connection connection(broker, connectionOptions);
+ try {
+ connection.open(); <co id="hello-cpp-open" linkends="callout-cpp-open"/>
+ Session session = connection.createSession(); <co id="hello-cpp-session" linkends="callout-cpp-session"/>
+
+ Receiver receiver = session.createReceiver(address); <co id="hello-cpp-receiver" linkends="callout-cpp-receiver"/>
+ Sender sender = session.createSender(address); <co id="hello-cpp-sender" linkends="callout-cpp-sender"/>
+
+ sender.send(Message("Hello world!"));
+
+ Message message = receiver.fetch(Duration::SECOND * 1); <co id="hello-cpp-fetch" linkends="callout-cpp-fetch"/>
+ <![CDATA[std::cout << message.getContent() << std::endl;]]>
+ session.acknowledge(); <co id="hello-cpp-acknowledge" linkends="callout-cpp-acknowledge"/>
+
+ connection.close(); <co id="hello-cpp-close" linkends="callout-cpp-close"/>
+ return 0;
+ } catch(const std::exception& error) {
+ <![CDATA[std::cerr << error.what() << std::endl;]]>
+ connection.close();
+ return 1;
+ }
+ }</programlisting>
+
+ <calloutlist>
+ <callout id="callout-cpp-open" arearefs="hello-cpp-open">
+ <para>Establishes the connection with the messaging broker.</para>
+ </callout>
+ <callout id="callout-cpp-session" arearefs="hello-cpp-session">
+ <para>Creates a session object on which messages will be sent and received.</para>
+ </callout>
+ <callout id="callout-cpp-receiver" arearefs="hello-cpp-receiver">
+ <para>Creates a receiver that receives messages from the given address.</para>
+ </callout>
+ <callout id="callout-cpp-sender" arearefs="hello-cpp-sender">
+ <para>Creates a sender that sends to the given address.</para>
+ </callout>
+ <callout id="callout-cpp-fetch" arearefs="hello-cpp-fetch">
+ <para>Receives the next message. The duration is optional, if omitted, will wait indefinitely for the next message.</para>
+ </callout>
+ <callout id="callout-cpp-acknowledge" arearefs="hello-cpp-acknowledge">
+ <para>Acknowledges receipt of all fetched messages on the
+ session. This informs the broker that the messages were
+ transferred and processed by the client successfully.</para>
+ </callout>
+ <callout id="callout-cpp-close" arearefs="hello-cpp-close">
+ <para>Closes the connection, all sessions managed by the connection, and all senders and receivers managed by each session.</para>
+ </callout>
+ </calloutlist>
+ </example>
+
+
+ </section>
+
+ <section>
+ <title>A Simple Messaging Program in Python</title>
+
+ <para>The following Python program shows how to create a
+ connection, create a session, send messages using a sender, and
+ receive messages using a receiver.</para>
+
+ <example>
+ <title>"Hello world!" in Python</title>
+ <programlisting lang="python"><![CDATA[
+ import sys
+ from qpid.messaging import *
+
+ broker = "localhost:5672" if len(sys.argv)<2 else sys.argv[1]
+ address = "amq.topic" if len(sys.argv)<3 else sys.argv[2]]]>
+
+ connection = Connection(broker)
+
+ try:
+ connection.open() <co id="hello-python-open" linkends="callout-python-open"/>
+ session = connection.session() <co id="hello-python-session" linkends="callout-python-session"/>
+
+ sender = session.sender(address) <co id="hello-python-sender" linkends="callout-python-sender"/>
+ receiver = session.receiver(address) <co id="hello-python-receiver" linkends="callout-python-receiver"/>
+
+ sender.send(Message("Hello world!"));
+
+ message = receiver.fetch(timeout=1) <co id="hello-python-fetch" linkends="callout-python-fetch"/>
+ print message.content
+ session.acknowledge() <co id="hello-python-acknowledge" linkends="callout-python-acknowledge"/>
+
+ except MessagingError,m:
+ print m
+ finally:
+ connection.close() <co id="hello-python-close" linkends="callout-python-close"/>
+ </programlisting>
+
+ <calloutlist>
+ <callout id="callout-python-open" arearefs="hello-python-open">
+ <para>Establishes the connection with the messaging broker.</para>
+ </callout>
+ <callout id="callout-python-session" arearefs="hello-python-session">
+ <para>Creates a session object on which messages will be sent and received.</para>
+ </callout>
+ <callout id="callout-python-receiver" arearefs="hello-python-receiver">
+ <para>Creates a receiver that receives messages from the given address.</para>
+ </callout>
+ <callout id="callout-python-sender" arearefs="hello-python-sender">
+ <para>Creates a sender that sends to the given address.</para>
+ </callout>
+ <callout id="callout-python-fetch" arearefs="hello-python-fetch">
+ <para>Receives the next message. The duration is optional, if omitted, will wait indefinitely for the next message.</para>
+ </callout>
+ <callout id="callout-python-acknowledge" arearefs="hello-python-acknowledge">
+ <para>Acknowledges receipt of all fetched messages on
+ the session. This informs the broker that the messages were
+ transfered and processed by the client successfully.</para>
+ </callout>
+ <callout id="callout-python-close" arearefs="hello-python-close">
+ <para>Closes the connection, all sessions managed by the connection, and all senders and receivers managed by each session.</para>
+ </callout>
+ </calloutlist>
+
+ </example>
+
+ </section>
+
+
+
+
+ <section>
+ <title>A Simple Messaging Program in .NET C#</title>
+
+ <para>The following .NET C#
+ <footnote>
+ <para>
+ The .NET binding for the Qpid C++ Messaging API
+ applies to all .NET Framework managed code languages. C# was chosen
+ for illustration purposes only.
+ </para>
+ </footnote>
+ program shows how to create a connection,
+ create a session, send messages using a sender, and receive
+ messages using a receiver.
+ </para>
+
+ <example>
+ <title>"Hello world!" in .NET C#</title>
+ <programlisting lang="c++">
+ using System;
+ using Org.Apache.Qpid.Messaging; <co id="hello-csharp-using" linkends="callout-csharp-using"/>
+
+ namespace Org.Apache.Qpid.Messaging {
+ class Program {
+ static void Main(string[] args) {
+ String broker = args.Length > 0 ? args[0] : "localhost:5672";
+ String address = args.Length > 1 ? args[1] : "amq.topic";
+
+ Connection connection = null;
+ try {
+ connection = new Connection(broker);
+ connection.Open(); <co id="hello-csharp-open" linkends="callout-csharp-open"/>
+ Session session = connection.CreateSession(); <co id="hello-csharp-session" linkends="callout-csharp-session"/>
+
+ Receiver receiver = session.CreateReceiver(address); <co id="hello-csharp-receiver" linkends="callout-csharp-receiver"/>
+ Sender sender = session.CreateSender(address); <co id="hello-csharp-sender" linkends="callout-csharp-sender"/>
+
+ sender.Send(new Message("Hello world!"));
+
+ Message message = new Message();
+ message = receiver.Fetch(DurationConstants.SECOND * 1); <co id="hello-csharp-fetch" linkends="callout-csharp-fetch"/>
+ Console.WriteLine("{0}", message.GetContent());
+ session.Acknowledge(); <co id="hello-csharp-acknowledge" linkends="callout-csharp-acknowledge"/>
+
+ connection.Close(); <co id="hello-csharp-close" linkends="callout-csharp-close"/>
+ } catch (Exception e) {
+ Console.WriteLine("Exception {0}.", e);
+ if (null != connection)
+ connection.Close();
+ }
+ }
+ }
+ }
+
+ </programlisting>
+
+ <calloutlist>
+ <callout id="callout-csharp-using" arearefs="hello-csharp-using">
+ <para> Permits use of Org.Apache.Qpid.Messaging types and methods without explicit namespace qualification. Any .NET project must have a project reference to the assembly file <literal>Org.Apache.Qpid.Messaging.dll</literal> in order to obtain the definitions of the .NET Binding for Qpid Messaging namespace.</para>
+ </callout>
+ <callout id="callout-csharp-open" arearefs="hello-csharp-open">
+ <para>Establishes the connection with the messaging broker.</para>
+ </callout>
+ <callout id="callout-csharp-session" arearefs="hello-csharp-session">
+ <para>Creates a session object on which messages will be sent and received.</para>
+ </callout>
+ <callout id="callout-csharp-receiver" arearefs="hello-csharp-receiver">
+ <para>Creates a receiver that receives messages from the given address.</para>
+ </callout>
+ <callout id="callout-csharp-sender" arearefs="hello-csharp-sender">
+ <para>Creates a sender that sends to the given address.</para>
+ </callout>
+ <callout id="callout-csharp-fetch" arearefs="hello-csharp-fetch">
+ <para>Receives the next message. The duration is optional, if omitted, will wait indefinitely for the next message.</para>
+ </callout>
+ <callout id="callout-csharp-acknowledge" arearefs="hello-csharp-acknowledge">
+ <para>Acknowledges receipt of all fetched messages on the
+ session. This informs the broker that the messages were
+ transfered and processed by the client successfully.</para>
+ </callout>
+ <callout id="callout-csharp-close" arearefs="hello-csharp-close">
+ <para>Closes the connection, all sessions managed by the connection, and all senders and receivers managed by each session.</para>
+ </callout>
+ </calloutlist>
+ </example>
+
+
+ </section>
+
+
+
+
+
+
+ <section id="section-addresses">
+ <title>Addresses</title>
+
+ <para>An <firstterm>address</firstterm> is the name of a message
+ target or message source.
+
+ <footnote><para>In the programs we have just seen, we used
+ <literal>amq.topic</literal> as the default address if none is
+ passed in. This is the name of a standard exchange that always
+ exists on an AMQP 0-10 messaging broker.</para></footnote>
+
+ The methods that create senders and receivers require an
+ address. The details of sending to a particular target or
+ receiving from a particular source are then handled by the
+ sender or receiver. A different target or source can be used
+ simply by using a different address.
+ </para>
+
+ <para>An address resolves to a <firstterm>node</firstterm>. The
+ Qpid Messaging API recognises two kinds of nodes,
+ <firstterm>queues</firstterm> and <firstterm>topics</firstterm>
+
+ <footnote><para>The terms <emphasis>queue</emphasis> and
+ <emphasis>topic</emphasis> here were chosen to align with
+ their meaning in JMS. These two addressing 'patterns',
+ queue and topic, are sometimes refered as point-to-point
+ and publish-subscribe. AMQP 0-10 has an exchange type
+ called a <emphasis>topic exchange</emphasis>. When the term
+ <emphasis>topic</emphasis> occurs alone, it refers to a
+ Messaging API topic, not the topic
+ exchange.</para></footnote>.
+
+ A queue stores each message until it has been received and
+ acknowledged, and only one receiver can receive a given message
+
+ <footnote><para>There are exceptions to this rule; for instance,
+ a receiver can use <literal>browse</literal> mode, which leaves
+ messages on the queue for other receivers to
+ read.</para></footnote>.
+
+ A topic immediately delivers a message to all eligible
+ receivers; if there are no eligible receivers, it discards the
+ message. In the AMQP 0-10 implementation of the API,
+
+ <footnote><para>The AMQP 0-10 implementation is the only one
+ that currently exists.</para></footnote>
+
+ queues map to AMQP queues, and topics map to AMQP exchanges.
+
+ <footnote><para>In AMQP 0-10, messages are sent to
+ exchanges, and read from queues. The Messaging API also
+ allows a sender to send messages to a queue; internally,
+ Qpid implements this by sending the message to the default
+ exchange, with the name of the queue as the routing key. The
+ Messaging API also allows a receiver to receive messages
+ from a topic; internally, Qpid implements this by setting up
+ a private subscription queue for the receiver and binding
+ the subscription queue to the exchange that corresponds to
+ the topic.</para></footnote>
+ </para>
+
+ <para>In the rest of this tutorial, we present many examples
+ using two programs that take an address as a command line
+ parameter. <command>spout</command> sends messages to the
+ target address, <command>drain</command> receives messages from
+ the source address. The source code is available in C++, Python, and
+ .NET C# and can be found in the examples directory for each
+ language. These programs can use any address string as a source
+ or a destination, and have many command line options to
+ configure behavior—use the <command>-h</command> option
+ for documentation on these options.
+
+ <footnote><para>Currently, the C++, Python, and .NET C#
+ implementations of <command>drain</command> and
+ <command>spout</command> have slightly different
+ options. This tutorial uses the C++ implementation. The
+ options will be reconciled in the near
+ future.</para></footnote>
+
+
+ The examples in this tutorial also use the
+ <command>qpid-config</command> utility to configure AMQP 0-10
+ queues and exchanges on a Qpid broker.
+ </para>
+
+
+ <example>
+ <title>Queues</title>
+
+ <para>Create a queue with <command>qpid-config</command>, send a message using
+ <command>spout</command>, and read it using <command>drain</command>:</para>
+
+ <screen>
+ $ qpid-config add queue hello-world
+ $ ./spout hello-world
+ $ ./drain hello-world
+
+ Message(properties={spout-id:c877e622-d57b-4df2-bf3e-6014c68da0ea:0}, content='')
+ </screen>
+
+ <para>The queue stored the message sent by <command>spout</command> and delivered
+ it to <command>drain</command> when requested.</para>
+
+ <para>Once the message has been delivered and and acknowledged
+ by <command>drain</command>, it is no longer available on the queue. If we run
+ <command>drain</command> one more time, no messages will be retrieved.</para>
+
+ <screen>
+ $ ./drain hello-world
+ $
+ </screen>
+
+ </example>
+
+ <example>
+ <title>Topics</title>
+
+ <para>This example is similar to the previous example, but it
+ uses a topic instead of a queue.</para>
+
+ <para>First, use <command>qpid-config</command> to remove the queue
+ and create an exchange with the same name:</para>
+
+ <screen>
+ $ qpid-config del queue hello-world
+ $ qpid-config add exchange topic hello-world
+ </screen>
+
+ <para>Now run <command>drain</command> and <command>spout</command> the same way we did in the previous example:</para>
+
+ <screen>
+ $ ./spout hello-world
+ $ ./drain hello-world
+ $
+ </screen>
+
+ <para>Topics deliver messages immediately to any interested
+ receiver, and do not store messages. Because there were no
+ receivers at the time <command>spout</command> sent the
+ message, it was simply discarded. When we ran
+ <command>drain</command>, there were no messages to
+ receive.</para>
+
+ <para>Now let's run <command>drain</command> first, using the
+ <literal>-t</literal> option to specify a timeout in seconds.
+ While <command>drain</command> is waiting for messages,
+ run <command>spout</command> in another window.</para>
+
+ <para><emphasis>First Window:</emphasis></para>
+
+ <screen>
+ $ ./drain -t 30 hello-word
+ </screen>
+
+
+ <para><emphasis>Second Window:</emphasis></para>
+
+ <screen>
+ $ ./spout hello-word
+ </screen>
+
+ <para>Once <command>spout</command> has sent a message, return
+ to the first window to see the output from
+ <command>drain</command>:</para>
+
+ <screen>
+ Message(properties={spout-id:7da2d27d-93e6-4803-8a61-536d87b8d93f:0}, content='')
+ </screen>
+
+ <para>You can run <command>drain</command> in several separate
+ windows; each creates a subscription for the exchange, and
+ each receives all messages sent to the exchange.</para>
+
+ </example>
+
+ <section>
+ <title>Address Strings</title>
+
+ <para>So far, our examples have used address strings that
+ contain only the name of a node. An <firstterm>address
+ string</firstterm> can also contain a
+ <firstterm>subject</firstterm> and
+ <firstterm>options</firstterm>.</para>
+
+ <para>The syntax for an address string is:</para>
+
+ <programlisting><![CDATA[
+ address_string ::= <address> [ / <subject> ] [ ; <options> ]
+ options ::= { <key> : <value>, ... }
+ ]]></programlisting>
+
+ <para>Addresses, subjects, and keys are strings. Values can
+ be numbers, strings (with optional single or double quotes),
+ maps, or lists. A complete BNF for address strings appears in
+ <xref linkend="section-address-string-bnf"/>.</para>
+
+
+ <para>So far, the address strings in this tutorial have only
+ used simple names. The following sections show how to use
+ subjects and options.</para>
+
+ </section>
+
+ <section>
+ <title>Subjects</title>
+
+
+ <para>Every message has a property called
+ <firstterm>subject</firstterm>, which is analogous to the
+ subject on an email message. If no subject is specified, the
+ message's subject is null. For convenience, address strings
+ also allow a subject. If a sender's address contains a
+ subject, it is used as the default subject for the messages
+ it sends.
+
+ If a receiver's address contains a subject, it is used to
+ select only messages that match the subject—the matching
+ algorithm depends on the message source.
+ </para>
+
+ <para>
+ In AMQP 0-10, each exchange type has its own matching
+ algorithm. This is discussed in
+ <xref linkend="section-amqp0-10-mapping"/>.
+ </para>
+
+ <note>
+ <para>
+ Currently, a receiver bound to a queue ignores subjects,
+ receiving messages from the queue without filtering. Support
+ for subject filtering on queues will be implemented soon.
+ </para>
+ </note>
+
+
+ <example>
+ <title>Using subjects</title>
+
+ <para>In this example we show how subjects affect message
+ flow.</para>
+
+ <para>First, let's use <command>qpid-config</command> to create a topic exchange.</para>
+
+ <screen>
+ $ qpid-config add exchange topic news-service
+ </screen>
+
+ <para>Now we use drain to receive messages from <literal>news-service</literal> that match the subject <literal>sports</literal>.</para>
+ <para><emphasis>First Window:</emphasis></para>
+ <screen>
+ $ ./drain -t 30 news-service/sports
+ </screen>
+
+ <para>In a second window, let's send messages to <literal>news-service</literal> using two different subjects:</para>
+
+ <para><emphasis>Second Window:</emphasis></para>
+ <screen>
+ $ ./spout news-service/sports
+ $ ./spout news-service/news
+ </screen>
+
+ <para>Now look at the first window, the message with the
+ subject <literal>sports</literal> has been received, but not
+ the message with the subject <literal>news</literal>:</para>
+
+ <screen>
+ Message(properties={qpid.subject:sports, spout-id:9441674e-a157-4780-a78e-f7ccea998291:0}, content='')
+ </screen>
+
+ <para>If you run <command>drain</command> in multiple
+ windows using the same subject, all instances of
+ <command>drain</command> receive the messages for that
+ subject.</para>
+ </example>
+
+
+ <para>The AMQP exchange type we are using here,
+ <literal>amq.topic</literal>, can also do more sophisticated
+ matching.
+
+ A sender's subject can contain multiple words separated by a
+ <quote>.</quote> delimiter. For instance, in a news
+ application, the sender might use subjects like
+ <literal>usa.news</literal>, <literal>usa.weather</literal>,
+ <literal>europe.news</literal>, or
+ <literal>europe.weather</literal>.
+
+ The receiver's subject can include wildcard characters—
+ <quote>#</quote> matches one or more words in the message's
+ subject, <quote>*</quote> matches a single word.
+
+ For instance, if the subject in the source address is
+ <literal>*.news</literal>, it matches messages with the
+ subject <literal>europe.news</literal> or
+ <literal>usa.news</literal>; if it is
+ <literal>europe.#</literal>, it matches messages with subjects
+ like <literal>europe.news</literal> or
+ <literal>europe.pseudo.news</literal>.</para>
+
+ <example>
+ <title>Subjects with multi-word keys</title>
+
+ <para>This example uses drain and spout to demonstrate the
+ use of subjects with two-word keys.</para>
+
+ <para>Let's use <command>drain</command> with the subject
+ <literal>*.news</literal> to listen for messages in which
+ the second word of the key is
+ <literal>news</literal>.</para>
+
+ <para><emphasis>First Window:</emphasis></para>
+
+ <screen>
+ $ ./drain -t 30 news-service/*.news
+ </screen>
+
+ <para>Now let's send messages using several different
+ two-word keys:</para>
+
+ <para><emphasis>Second Window:</emphasis></para>
+
+ <screen>
+ $ ./spout news-service/usa.news
+ $ ./spout news-service/usa.sports
+ $ ./spout news-service/europe.sports
+ $ ./spout news-service/europe.news
+ </screen>
+
+ <para>In the first window, the messages with
+ <literal>news</literal> in the second word of the key have
+ been received:</para>
+
+ <screen>
+ Message(properties={qpid.subject:usa.news, spout-id:73fc8058-5af6-407c-9166-b49a9076097a:0}, content='')
+ Message(properties={qpid.subject:europe.news, spout-id:f72815aa-7be4-4944-99fd-c64c9747a876:0}, content='')
+ </screen>
+
+
+ <para>Next, let's use <command>drain</command> with the
+ subject <literal>#.news</literal> to match any sequence of
+ words that ends with <literal>news</literal>.</para>
+
+ <para><emphasis>First Window:</emphasis></para>
+
+ <screen>
+ $ ./drain -t 30 news-service/#.news
+ </screen>
+
+ <para>In the second window, let's send messages using a
+ variety of different multi-word keys:</para>
+
+ <para><emphasis>Second Window:</emphasis></para>
+
+ <screen>
+ $ ./spout news-service/news
+ $ ./spout news-service/sports
+ $ ./spout news-service/usa.news
+ $ ./spout news-service/usa.sports
+ $ ./spout news-service/usa.faux.news
+ $ ./spout news-service/usa.faux.sports
+ </screen>
+
+ <para>In the first window, messages with
+ <literal>news</literal> in the last word of the key have been
+ received:</para>
+
+ <screen>
+ Message(properties={qpid.subject:news, spout-id:cbd42b0f-c87b-4088-8206-26d7627c9640:0}, content='')
+ Message(properties={qpid.subject:usa.news, spout-id:234a78d7-daeb-4826-90e1-1c6540781eac:0}, content='')
+ Message(properties={qpid.subject:usa.faux.news, spout-id:6029430a-cfcb-4700-8e9b-cbe4a81fca5f:0}, content='')
+ </screen>
+ </example>
+
+ </section>
+
+ <section>
+ <title>Address String Options</title>
+
+ <para>
+ The options in an address string can contain additional
+ information for the senders or receivers created for it,
+ including:
+ </para>
+ <itemizedlist>
+ <listitem>
+ <para>
+ Policies for assertions about the node to which an address
+ refers.
+ </para>
+ <para>
+ For instance, in the address string <literal>my-queue;
+ {assert: always, node:{ type: queue }}</literal>, the node
+ named <literal>my-queue</literal> must be a queue; if not,
+ the address does not resolve to a node, and an exception
+ is raised.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ Policies for automatically creating or deleting the node to which an address refers.
+ </para>
+ <para>
+ For instance, in the address string <literal>xoxox ; {create: always}</literal>,
+ the queue <literal>xoxox</literal> is created, if it does
+ not exist, before the address is resolved.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ Extension points that can be used for sender/receiver configuration.
+ </para>
+ <para>
+ For instance, if the address for a receiver is
+ <literal>my-queue; {mode: browse}</literal>, the receiver
+ works in <literal>browse</literal> mode, leaving messages
+ on the queue so other receivers can receive them.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ Extension points providing more direct control over the underlying protocol.
+ </para>
+ <para>
+ For instance, the <literal>x-bindings</literal> property
+ allows greater control over the AMQP 0-10 binding process
+ when an address is resolved.
+ </para>
+ </listitem>
+ </itemizedlist>
+
+
+ <para>
+ Let's use some examples to show how these different kinds of
+ address string options affect the behavior of senders and
+ receives.
+ </para>
+
+ <section>
+ <title>assert</title>
+ <para>
+ In this section, we use the <literal>assert</literal> option
+ to ensure that the address resolves to a node of the required
+ type.
+ </para>
+
+
+ <example>
+ <title>Assertions on Nodes</title>
+
+ <para>Let's use <command>qpid-config</command> to create a
+ queue and a topic.</para>
+
+ <screen>
+ $ qpid-config add queue my-queue
+ $ qpid-config add exchange topic my-topic
+ </screen>
+
+ <para>
+ We can now use the address specified to drain to assert that it is
+ of a particular type:
+ </para>
+
+ <screen>
+ $ ./drain 'my-queue; {assert: always, node:{ type: queue }}'
+ $ ./drain 'my-queue; {assert: always, node:{ type: topic }}'
+ 2010-04-20 17:30:46 warning Exception received from broker: not-found: not-found: Exchange not found: my-queue (../../src/qpid/broker/ExchangeRegistry.cpp:92) [caused by 2 \x07:\x01]
+ Exchange my-queue does not exist
+ </screen>
+
+ <para>
+ The first attempt passed without error as my-queue is indeed a
+ queue. The second attempt however failed; my-queue is not a
+ topic.
+ </para>
+
+ <para>
+ We can do the same thing for my-topic:
+ </para>
+
+ <screen>
+ $ ./drain 'my-topic; {assert: always, node:{ type: topic }}'
+ $ ./drain 'my-topic; {assert: always, node:{ type: queue }}'
+ 2010-04-20 17:31:01 warning Exception received from broker: not-found: not-found: Queue not found: my-topic (../../src/qpid/broker/SessionAdapter.cpp:754) [caused by 1 \x08:\x01]
+ Queue my-topic does not exist
+ </screen>
+ </example>
+
+ <para>Now let's use the <literal>create</literal> option to
+ create the queue <literal>xoxox</literal> if it does not already
+ exist:</para>
+
+ </section>
+
+ <section>
+ <title>create</title>
+
+ <para>In previous examples, we created the queue before
+ listening for messages on it. Using <literal>create:
+ always</literal>, the queue is automatically created if it
+ does not exist.</para>
+
+ <example>
+ <title>Creating a Queue Automatically</title>
+
+ <para><emphasis>First Window:</emphasis></para>
+ <screen>$ ./drain -t 30 "xoxox ; {create: always}"</screen>
+
+
+ <para>Now we can send messages to this queue:</para>
+
+ <para><emphasis>Second Window:</emphasis></para>
+ <screen>$ ./spout "xoxox ; {create: always}"</screen>
+
+ <para>Returning to the first window, we see that <command>drain</command> has received this message:</para>
+
+ <screen>Message(properties={spout-id:1a1a3842-1a8b-4f88-8940-b4096e615a7d:0}, content='')</screen>
+ </example>
+ <para>The details of the node thus created can be controlled by further options within the node. See <xref linkend="table-node-properties"/> for details.</para>
+ </section>
+
+ <section>
+ <title>browse</title>
+ <para>Some options specify message transfer semantics; for
+ instance, they may state whether messages should be consumed or
+ read in browsing mode, or specify reliability
+ characteristics. The following example uses the
+ <literal>browse</literal> option to receive messages without
+ removing them from a queue.</para>
+
+ <example>
+ <title>Browsing a Queue</title>
+ <para>
+ Let's use the browse mode to receive messages without
+ removing them from the queue. First we send three messages to the
+ queue:
+ </para>
+ <screen>
+ $ ./spout my-queue --content one
+ $ ./spout my-queue --content two
+ $ ./spout my-queue --content three
+ </screen>
+
+ <para>Now we use drain to get those messages, using the browse option:</para>
+ <screen>
+ $ ./drain 'my-queue; {mode: browse}'
+ Message(properties={spout-id:fbb93f30-0e82-4b6d-8c1d-be60eb132530:0}, content='one')
+ Message(properties={spout-id:ab9e7c31-19b0-4455-8976-34abe83edc5f:0}, content='two')
+ Message(properties={spout-id:ea75d64d-ea37-47f9-96a9-d38e01c97925:0}, content='three')
+ </screen>
+
+ <para>We can confirm the messages are still on the queue by repeating the drain:</para>
+ <screen>
+ $ ./drain 'my-queue; {mode: browse}'
+ Message(properties={spout-id:fbb93f30-0e82-4b6d-8c1d-be60eb132530:0}, content='one')
+ Message(properties={spout-id:ab9e7c31-19b0-4455-8976-34abe83edc5f:0}, content='two')
+ Message(properties={spout-id:ea75d64d-ea37-47f9-96a9-d38e01c97925:0}, content='three')
+ </screen>
+ </example>
+ </section>
+
+ <section>
+ <title>x-bindings</title>
+
+ <para>Greater control over the AMQP 0-10 binding process can
+ be achieved by including an <literal>x-bindings</literal>
+ option in an address string.
+
+ For instance, the XML Exchange is an AMQP 0-10 custom exchange
+ provided by the Apache Qpid C++ broker. It allows messages to
+ be filtered using XQuery; queries can address either message
+ properties or XML content in the body of the message. The
+ xquery is specified in the arguments field of the AMQP 0-10
+ command. When using the messaging API an xquery can be
+ specified in and address that resolves to an XML exchange by
+ using the x-bindings property.</para>
+
+
+ <para>An instance of the XML Exchange must be added before it
+ can be used:</para>
+
+ <programlisting>
+ $ qpid-config add exchange xml xml
+ </programlisting>
+
+ <para>When using the XML Exchange, a receiver provides an
+ XQuery as an x-binding argument. If the query contains a
+ context item (a path starting with <quote>.</quote>), then it
+ is applied to the content of the message, which must be
+ well-formed XML. For instance, <literal>./weather</literal> is
+ a valid XQuery, which matches any message in which the root
+ element is named <literal>weather</literal>. Here is an
+ address string that contains this query:</para>
+
+ <programlisting><![CDATA[
+ xml; {
+ link: {
+ x-bindings: [{exchange:xml, key:weather, arguments:{xquery:"./weather"} }]
+ }
+ }
+ ]]></programlisting>
+
+ <para>When using longer queries with <command>drain</command>,
+ it is often useful to place the query in a file, and use
+ <command>cat</command> in the command line. We do this in the
+ following example.</para>
+
+ <example>
+ <title>Using the XML Exchange</title>
+
+ <para>This example uses an x-binding that contains queries, which filter based on the content of XML messages. Here is an XQuery that we will use in this example:</para>
+
+ <programlisting>
+ <![CDATA[
+ let $w := ./weather
+ return $w/station = 'Raleigh-Durham International Airport (KRDU)'
+ and $w/temperature_f > 50
+ and $w/temperature_f - $w/dewpoint > 5
+ and $w/wind_speed_mph > 7
+ and $w/wind_speed_mph < 20 ]]>
+ </programlisting>
+
+ <para>We can specify this query in an x-binding to listen to messages that meet the criteria specified by the query:</para>
+
+ <para><emphasis>First Window:</emphasis></para>
+
+ <screen>
+ $ ./drain -f "xml; {link:{x-bindings:[{key:'weather',
+ arguments:{xquery:\"$(cat rdu.xquery )\"}}]}}"
+ </screen>
+
+ <para>In another window, let's create an XML message that meets the criteria in the query, and place it in the file <filename>rdu.xml</filename>:</para>
+
+ <programlisting>
+ <![CDATA[
+ <weather>
+ <station>Raleigh-Durham International Airport (KRDU)</station>
+ <wind_speed_mph>16</wind_speed_mph>
+ <temperature_f>70</temperature_f>
+ <dewpoint>35</dewpoint>
+ </weather>
+ ]]></programlisting>
+
+ <para>Now let's use <command>spout</command> to send this message to the XML exchange:</para>
+
+ <para><emphasis>Second Window:</emphasis></para>
+ <screen>
+ spout --content "$(cat rdu.xml)" xml/weather
+ </screen>
+
+ <para>Returning to the first window, we see that the message has been received:</para>
+
+ <screen><![CDATA[$ ./drain -f "xml; {link:{x-bindings:[{exchange:'xml', key:'weather', arguments:{xquery:\"$(cat rdu.xquery )\"}}]}}"
+ Message(properties={qpid.subject:weather, spout-id:31c431de-593f-4bec-a3dd-29717bd945d3:0},
+ content='<weather>
+ <station>Raleigh-Durham International Airport (KRDU)</station>
+ <wind_speed_mph>16</wind_speed_mph>
+ <temperature_f>40</temperature_f>
+ <dewpoint>35</dewpoint>
+ </weather>') ]]>
+ </screen>
+ </example>
+ </section>
+
+ <!--
+ <para>When sending data using <command>cat</command> to provide arguments to <command>spout</command>, you can use <command>sed</command> to change the values that are sent:</para>
+
+<screen>
+spout - -content "$(cat rdu.xml | sed -e 's/70/45/')" xml/weather
+</screen>
+ -->
+
+ <!--
+ TODO: Add some reliability option examples
+ -->
+
+ <section>
+ <title>Address String Options - Reference</title>
+
+ <table pgwide="1">
+ <title>Address String Options</title>
+ <tgroup cols="3">
+ <thead>
+ <colspec colnum="1" colwidth="1*"/>
+ <colspec colnum="2" colwidth="3*"/>
+ <colspec colnum="3" colwidth="3*"/>
+ <row>
+ <entry>option</entry>
+ <entry>value</entry>
+ <entry>semantics</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>
+ assert
+ </entry>
+ <entry>
+ one of: always, never, sender or receiver
+ </entry>
+ <entry>
+ Asserts that the properties specified in the node option
+ match whatever the address resolves to. If they do not,
+ resolution fails and an exception is raised. <!-- ###
+ Which exception -->
+ </entry>
+ </row>
+
+ <row>
+ <entry>
+ create
+ </entry>
+ <entry>
+ one of: always, never, sender or receiver
+ </entry>
+ <entry>
+ Creates the node to which an address refers if it does
+ not exist. No error is raised if the node does
+ exist. The details of the node may be specified in the
+ node option.
+ </entry>
+ </row>
+ <row>
+ <entry>
+ delete
+ </entry>
+ <entry>
+ one of: always, never, sender or receiver
+ </entry>
+ <entry>
+ Delete the node when the sender or receiver is closed.
+ </entry>
+ </row>
+ <row>
+ <entry>
+ node
+ </entry>
+ <entry>
+ A nested map containing the entries shown in <xref linkend="table-node-properties"/>.
+ </entry>
+ <entry>
+ Specifies properties of the node to which the address
+ refers. These are used in conjunction with the assert or
+ create options.
+ </entry>
+ </row>
+ <row>
+ <entry>
+ link
+ </entry>
+ <entry>
+ A nested map containing the entries shown in <xref linkend="table-link-properties"/>.
+ </entry>
+ <entry>
+ Used to control the establishment of a conceptual link
+ from the client application to or from the target/source
+ address.
+ </entry>
+ </row>
+ <row>
+ <entry>
+ mode
+ </entry>
+ <entry>
+ one of: browse, consume
+ </entry>
+ <entry>
+ This option is only of relevance for source addresses
+ that resolve to a queue. If browse is specified the
+ messages delivered to the receiver are left on the queue
+ rather than being removed. If consume is specified the
+ normal behaviour applies; messages are removed from the
+ queue once the client acknowledges their receipt.
+ </entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+
+ <table id="table-node-properties" pgwide="1">
+ <title>Node Properties</title>
+ <tgroup cols="3">
+ <thead>
+ <colspec colnum="1" colwidth="1*"/>
+ <colspec colnum="2" colwidth="3*"/>
+ <colspec colnum="3" colwidth="3*"/>
+ <row>
+ <entry>property</entry>
+ <entry>value</entry>
+ <entry>semantics</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>
+ type
+ </entry>
+ <entry>
+ topic, queue
+ </entry>
+ <entry>
+ Indicates the type of the node.
+ </entry>
+ </row>
+ <row>
+ <entry>
+ durable
+ </entry>
+ <entry>
+ True, False
+ </entry>
+ <entry>
+ Indicates whether the node survives a loss of
+ volatile storage e.g. if the broker is restarted.
+ </entry>
+ </row>
+ <row>
+ <entry>
+ x-declare
+ </entry>
+ <entry>
+ A nested map whose values correspond to the valid fields
+ on an AMQP 0-10 queue-declare or exchange-declare
+ command.
+ </entry>
+ <entry>
+ These values are used to fine tune the creation or
+ assertion process. Note however that they are protocol
+ specific.
+ </entry>
+ </row>
+ <row>
+ <entry>
+ x-bindings
+ </entry>
+ <entry>
+ A nested list in which each binding is represented by
+ a map. The entries of the map for a binding contain
+ the fields that describe an AMQP 0-10 binding. Here is
+ the format for x-bindings:
+
+ <programlisting><![CDATA[
+ [
+ {
+ exchange: <exchange>,
+ queue: <queue>,
+ key: <key>,
+ arguments: {
+ <key_1>: <value_1>,
+ ...,
+ <key_n>: <value_n> }
+ },
+ ...
+ ]
+ ]]></programlisting>
+ </entry>
+ <entry>
+ In conjunction with the create option, each of these
+ bindings is established as the address is resolved. In
+ conjunction with the assert option, the existence of
+ each of these bindings is verified during
+ resolution. Again, these are protocol specific.
+ </entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ <table id="table-link-properties" pgwide="1">
+ <title>Link Properties</title>
+ <tgroup cols="3">
+ <thead>
+ <colspec colnum="1" colwidth="1*"/>
+ <colspec colnum="2" colwidth="3*"/>
+ <colspec colnum="3" colwidth="3*"/>
+ <row>
+ <entry>option</entry>
+ <entry>value</entry>
+ <entry>semantics</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>
+ reliability
+ </entry>
+ <entry>
+ one of: unreliable, at-least-once, at-most-once, exactly-once
+ </entry>
+ <entry>
+ Reliability indicates the level of reliability that
+ the sender or receiver. <literal>unreliable</literal>
+ and <literal>at-most-once</literal> are currently
+ treated as synonyms, and allow messages to be lost if
+ a broker crashes or the connection to a broker is
+ lost. <literal>at-least-once</literal> guarantees that
+ a message is not lost, but duplicates may be
+ received. <literal>exactly-once</literal> guarantees
+ that a message is not lost, and is delivered precisely
+ once. Currently only <literal>unreliable</literal>
+ and <literal>at-least-once</literal> are supported.
+ <footnote><para>If at-most-once is requested,
+ unreliable will be used and for durable messages on
+ durable queues there is the possibility that messages
+ will be redelivered; if exactly-once is requested,
+ at-least-once will be used and the application needs to
+ be able to deal with duplicates.</para></footnote>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ durable
+ </entry>
+ <entry>
+ True, False
+ </entry>
+ <entry>
+ Indicates whether the link survives a loss of
+ volatile storage e.g. if the broker is restarted.
+ </entry>
+ </row>
+ <row>
+ <entry>
+ x-declare
+ </entry>
+ <entry>
+ A nested map whose values correspond to the valid fields
+ of an AMQP 0-10 queue-declare command.
+ </entry>
+ <entry>
+ These values can be used to customise the subscription
+ queue in the case of receiving from an exchange. Note
+ however that they are protocol specific.
+ </entry>
+ </row>
+ <row>
+ <entry>
+ x-subscribe
+ </entry>
+ <entry>
+ A nested map whose values correspond to the valid fields
+ of an AMQP 0-10 message-subscribe command.
+ </entry>
+ <entry>
+ These values can be used to customise the subscription.
+ </entry>
+ </row>
+ <row>
+ <entry>
+ x-bindings
+ </entry>
+ <entry>
+ A nested list each of whose entries is a map that may
+ contain fields (queue, exchange, key and arguments)
+ describing an AMQP 0-10 binding.
+ </entry>
+ <entry>
+ These bindings are established during resolution
+ independent of the create option. They are considered
+ logically part of the linking process rather than of
+ node creation.
+ </entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ </section>
+ </section>
+
+ <section id="section-address-string-bnf">
+ <title>Address String Grammar</title>
+
+ <para>This section provides a formal grammar for address strings.</para>
+
+ <formalpara>
+ <title>Tokens</title>
+ <para>The following regular expressions define the tokens used
+ to parse address strings:</para></formalpara>
+ <programlisting><![CDATA[
+ LBRACE: \\{
+ RBRACE: \\}
+ LBRACK: \\[
+ RBRACK: \\]
+ COLON: :
+ SEMI: ;
+ SLASH: /
+ COMMA: ,
+ NUMBER: [+-]?[0-9]*\\.?[0-9]+
+ ID: [a-zA-Z_](?:[a-zA-Z0-9_-]*[a-zA-Z0-9_])?
+ STRING: "(?:[^\\\\"]|\\\\.)*"|\'(?:[^\\\\\']|\\\\.)*\'
+ ESC: \\\\[^ux]|\\\\x[0-9a-fA-F][0-9a-fA-F]|\\\\u[0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F]
+ SYM: [.#*%@$^!+-]
+ WSPACE: [ \\n\\r\\t]+
+ ]]></programlisting>
+
+ <formalpara>
+ <title>Grammar</title>
+ <para>The formal grammar for addresses is given below:</para>
+ </formalpara>
+
+ <programlisting><![CDATA[
+ address := name [ SLASH subject ] [ ";" options ]
+ name := ( part | quoted )+
+ subject := ( part | quoted | SLASH )*
+ quoted := STRING / ESC
+ part := LBRACE / RBRACE / COLON / COMMA / NUMBER / ID / SYM
+ options := map
+ map := "{" ( keyval ( "," keyval )* )? "}"
+ keyval "= ID ":" value
+ value := NUMBER / STRING / ID / map / list
+ list := "[" ( value ( "," value )* )? "]"
+ ]]></programlisting>
+
+
+ <formalpara>
+ <title>Address String Options</title>
+ <para>The address string options map supports the following parameters:</para>
+ </formalpara>
+
+ <programlisting><![CDATA[
+ <name> [ / <subject> ] ; {
+ create: always | sender | receiver | never,
+ delete: always | sender | receiver | never,
+ assert: always | sender | receiver | never,
+ mode: browse | consume,
+ node: {
+ type: queue | topic,
+ durable: True | False,
+ x-declare: { ... <declare-overrides> ... },
+ x-bindings: [<binding_1>, ... <binding_n>]
+ },
+ link: {
+ name: <link-name>,
+ durable: True | False,
+ reliability: unreliable | at-most-once | at-least-once | exactly-once,
+ x-declare: { ... <declare-overrides> ... },
+ x-bindings: [<binding_1>, ... <binding_n>],
+ x-subscribe: { ... <subscribe-overrides> ... }
+ }
+ }
+ ]]></programlisting>
+
+
+ <itemizedlist>
+ <title>Create, Delete, and Assert Policies</title>
+ <para>The create, delete, and assert policies specify who should
+ perfom the associated action:</para>
+ <listitem><para><emphasis>always</emphasis>: the action is performed by any messaging client</para></listitem>
+ <listitem><para><emphasis>sender</emphasis>: the action is only performed by a sender</para></listitem>
+ <listitem><para><emphasis>receiver</emphasis>: the action is only performed by a receiver</para></listitem>
+ <listitem><para><emphasis>never</emphasis>: the action is never performed (this is the default)</para></listitem>
+ </itemizedlist>
+
+ <itemizedlist>
+ <title>Node-Type</title>
+ <para>The node-type is one of:</para>
+ <listitem><para><emphasis>topic</emphasis>: in the AMQP 0-10
+ mapping, a topic node defaults to the topic exchange, x-declare
+ may be used to specify other exchange types</para></listitem>
+ <listitem><para><emphasis>queue</emphasis>: this is the default node-type</para></listitem>
+ </itemizedlist>
+ </section>
+
+
+ </section>
+
+ <section id="replay">
+ <title>Sender Capacity and Replay</title>
+
+ <para>The send method of a sender has an optional second parameter
+ that controls whether the send call is synchronous or not. A
+ synchronous send call will block until the broker has confirmed
+ receipt of the message. An asynchronous send call will return
+ before the broker confirms receipt of the message, allowing for
+ example further send calls to be made without waiting for a
+ roundtrip to the broker for each message. This is desirable where
+ increased throughput is important.</para>
+
+ <para>The sender maintains a list of sent messages whose receipt
+ has yet to be confirmed by the broker. The maximum number of such
+ messages that it will hold is defined by the capacity of the
+ sender, which can be set by the application. If an application
+ tries to send with a sender whose capacity is already fully used
+ up, the send call will block waiting for capacity regardless of
+ the value of the sync flag.</para>
+
+ <para>The sender can be queried for the available space (i.e. the
+ unused capacity), and for the current count of unsettled messages
+ (i.e. those held in the replay list pending confirmation by the
+ server). When the unsettled count is zero, all messages on that
+ sender have been successfully sent.</para>
+
+ <para>If the connection fails and is transparently reconnected
+ (see <xref linkend="connection-options"/> for details on how to control
+ this feature), the unsettled messages for each sender over that
+ connection will be re-transmitted. This provides a transparent
+ level of reliability. This feature can be controlled through the
+ link's reliability as defined in the address (see
+ <xref linkend="table-link-properties"/>). At present only
+ at-least-once guarantees are offered. </para>
+ </section>
+
+ <section id="prefetch">
+ <title>Receiver Capacity (Prefetch)</title>
+
+ <para>By default, a receiver requests the next message from the
+ server in response to each fetch call, resulting in messages being
+ sent to the receiver one at a time. As in the case of sending, it
+ is often desirable to avoid this roundtrip for each message. This
+ can be achieved by allowing the receiver
+ to <firstterm>prefetch</firstterm> messages in anticipation of
+ fetch calls being made. The receiver needs to be able to store
+ these prefetched messages, the number it can hold is controlled by
+ the receivers capacity.</para>
+
+ </section>
+
+ <section id="acknowledgements">
+ <title>Acknowledging Received Messages</title>
+
+ <para>Applications that receive messages should acknowledge their
+ receipt by calling the session's acknowledge method. As in the
+ case of sending messages, acknowledged transfer of messages to
+ receivers provides at-least-once reliability, which means that the
+ loss of the connection or a client crash does not result in lost
+ messages; durable messages are not lost even if the broker is
+ restarted.
+
+ Some cases may not require this however and the reliability can be
+ controlled through a link property in the address options (see
+ <xref linkend="table-link-properties"/>).</para>
+
+ <para>The acknowledge call acknowledges all messages received on
+ the session (i.e. all message that have been returned from a fetch
+ call on a receiver created on that session).</para>
+
+ <para>The acknowledge call also support an optional parameter
+ controlling whether the call is synchronous or not. A synchronous
+ acknowledge will block until the server has confirmed that it has
+ received the acknowledgement. In the asynchronous case, when the
+ call returns there is not yet any guarantee that the server has
+ received and processed the acknowledgement. The session may be
+ queried for the number of unsettled acknowledgements; when that
+ count is zero all acknowledgements made for received messages have
+ been successful.</para>
+
+ </section>
+
+
+ <section>
+ <title>Receiving Messages from Multiple Sources</title>
+
+ <para>A receiver can only read from one source, but many
+ programs need to be able to read messages from many sources. In
+ the Qpid Messaging API, a program can ask a session for
+ the <quote>next receiver</quote>; that is, the receiver that is
+ responsible for the next available message. The following
+ examples show how this is done in C++, Python, and .NET C#.
+ </para>
+
+ <para>Note that to use this pattern you must enable prefetching
+ for each receiver of interest so that the broker will send
+ messages before a fetch call is made. See
+ <xref linkend="prefetch"/> for more on this.</para>
+
+ <example>
+ <title>Receiving Messages from Multiple Sources</title>
+
+ <para>C++:</para>
+
+ <programlisting><![CDATA[
+ Receiver receiver1 = session.createReceiver(address1);
+ receiver1.setCapacity(10);
+ Receiver receiver2 = session.createReceiver(address2);
+ receiver2.setCapacity(10);
+
+ Message message = session.nextReceiver().fetch();
+ std::cout << message.getContent() << std::endl;
+ session.acknowledge(); // acknowledge message receipt
+ ]]> </programlisting>
+
+ <para>Python:</para>
+ <programlisting><![CDATA[
+ receiver1 = session.receiver(address1)
+ receiver1.capacity = 10
+ receiver2 = session.receiver(address)
+ receiver2.capacity = 10
+ message = session.next_receiver().fetch()
+ print message.content
+ session.acknowledge()
+ ]]> </programlisting>
+
+ <para>.NET C#:</para>
+ <programlisting><![CDATA[
+ Receiver receiver1 = session.CreateReceiver(address1);
+ receiver1.Capacity = 10;
+ Receiver receiver2 = session.CreateReceiver(address2);
+ receiver2.Capacity = 10;
+
+ Message message = new Message();
+ message = session.NextReceiver().Fetch();
+ Console.WriteLine("{0}", message.GetContent());
+ session.Acknowledge();
+ ]]> </programlisting>
+
+ </example>
+ </section>
+
+ <section>
+ <title>Transactions</title>
+
+ <para>Sometimes it is useful to be able to group messages
+ transfers - sent and/or received - on a session into atomic
+ grouping. This can be done be creating the session as
+ transactional. On a transactional session sent messages only
+ become available at the target address on commit. Likewise any
+ received and acknowledged messages are only discarded at their
+ source on commit
+
+ <footnote><para>Note that this currently is only true for
+ messages received using a reliable mode
+ e.g. at-least-once. Messages sent by a broker to a receiver in
+ unreliable receiver will be discarded immediately regardless of
+ transctionality.</para></footnote>
+
+ .</para>
+
+ <example>
+ <title>Transactions</title>
+ <para>C++:</para>
+ <programlisting><![CDATA[
+ Connection connection(broker);
+ Session session = connection.createTransactionalSession();
+ ...
+ if (smellsOk())
+ session.commit();
+ else
+ session.rollback();
+ ]]></programlisting>
+ <para>
+ .NET C#:
+ </para>
+
+ <programlisting>
+ Connection connection = new Connection(broker);
+ Session session = connection.CreateTransactionalSession();
+ ...
+ if (smellsOk())
+ session.Commit();
+ else
+ session.Rollback();
+ </programlisting>
+ <!--
+ <para>Python</para>
+ <programlisting><![CDATA[
+ ### TODO
+ ]]></programlisting>
+ -->
+ </example>
+
+ </section>
+
+ <section id="connections">
+ <title>Connections</title>
+
+ <para>
+ Messaging connections are created by specifying a broker or a list of brokers, and
+ an optional set of connection options. The constructor prototypes for Connections
+ are:
+ </para>
+
+ <programlisting><![CDATA[
+ Connection connection();
+ Connection connection(const string url);
+ Connection connection(const string url, const string& options);
+ Connection connection(const string url, const Variant::Map& options);
+ ]]></programlisting>
+
+ <para>
+ Messaging connection URLs specify only the network host address(es). Connection
+ options are specified separately as an options string or map. This is different
+ from JMS Connection URLs that combine the network address and connection properties
+ in a single string.
+ </para>
+
+ <section id="connection-url">
+ <title>Connection URLs</title>
+ <para>
+ Connection URLs describe the broker or set of brokers to which the connection
+ is to attach. The format of the Connection URL is defined by AMQP 0.10
+ Domain:connection.amqp-host-url.
+ </para>
+
+ <programlisting><![CDATA[
+ amqp_url = "amqp:" prot_addr_list
+ prot_addr_list = [prot_addr ","]* prot_addr
+ prot_addr = tcp_prot_addr | tls_prot_addr
+
+ tcp_prot_addr = tcp_id tcp_addr
+ tcp_id = "tcp:" | ""
+ tcp_addr = [host [":" port] ]
+ host = <as per http://www.ietf.org/rfc/rfc3986.txt>
+ port = number ]]></programlisting>
+
+ <para>
+ Examples of Messaging Connection URLs
+ </para>
+
+ <programlisting><![CDATA[
+ localhost
+ localhost:5672
+ localhost:9999
+ 192.168.1.2:5672
+ mybroker.example.com:5672
+ amqp:tcp:localhost:5672
+ tcp:locahost:5672,localhost:5800
+ ]]></programlisting>
+
+ </section>
+
+ <section id="connection-options">
+ <title>Connection Options</title>
+
+ <para>
+ Aspects of the connections behaviour can be controlled through
+ specifying connection options. For example, connections can be
+ configured to automatically reconnect if the connection to a
+ broker is lost.
+ </para>
+
+ <example>
+ <title>Specifying Connection Options in C++, Python, and .NET</title>
+
+ <para>In C++, these options can be set using <function>Connection::setOption()</function> or by passing in a set of options to the constructor. The options can be passed in as a map or in string form:</para>
+
+
+ <para>or</para>
+
+ <programlisting><![CDATA[
+ Connection connection("localhost:5672");
+ connection.setOption("reconnect", true);
+ try {
+ connection.open();
+ !!! SNIP !!!
+ ]]></programlisting>
+
+ <para>In Python, these options can be set as attributes of the connection or using named arguments in
+ the <function>Connection</function> constructor:</para>
+
+ <programlisting><![CDATA[
+ connection = Connection("localhost:5672", reconnect=True)
+ try:
+ connection.open()
+ !!! SNIP !!!
+ ]]></programlisting>
+
+ <para>or</para>
+
+ <programlisting><![CDATA[
+ connection = Connection("localhost:5672")
+ connection.reconnect = True
+ try:
+ connection.open()
+ !!! SNIP !!!
+ ]]></programlisting>
+ <para>
+ In .NET, these options can be set using <function>Connection.SetOption()</function> or by passing in a set of options to the constructor. The options can be passed in as a map or in string form:
+ </para>
+
+ <programlisting>
+ Connection connection= new Connection("localhost:5672", "{reconnect: true}");
+ try {
+ connection.Open();
+ !!! SNIP !!!
+ </programlisting>
+ <para>
+ or
+ </para>
+
+ <programlisting>
+ Connection connection = new Connection("localhost:5672");
+ connection.SetOption("reconnect", true);
+ try {
+ connection.Open();
+ !!! SNIP !!!
+ </programlisting>
+
+ <para>See the reference documentation for details in each language.</para>
+ </example>
+
+ <para>The following table lists the supported connection options.</para>
+
+ <table pgwide="1">
+ <title>Connection Options</title>
+ <tgroup cols="3">
+ <thead>
+ <colspec colnum="1" colwidth="1*"/>
+ <colspec colnum="2" colwidth="1*"/>
+ <colspec colnum="3" colwidth="3*"/>
+ <row>
+ <entry>option name</entry>
+ <entry>value type</entry>
+ <entry>semantics</entry>
+ </row>
+ </thead>
+ <tbody>
+
+ <row>
+ <entry>
+ <literal>username</literal>
+ </entry>
+ <entry>
+ string
+ </entry>
+ <entry>
+ The username to use when authenticating to the broker.
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <literal>password</literal>
+ </entry>
+ <entry>
+ string
+ </entry>
+ <entry>
+ The password to use when authenticating to the broker.
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <literal>sasl_mechanisms</literal>
+ </entry>
+ <entry>
+ string
+ </entry>
+ <entry>
+ The specific SASL mechanisms to use with the python
+ client when authenticating to the broker. The value
+ is a space separated list.
+ </entry>
+ </row>
+
+
+ <row>
+ <entry>
+ <literal>reconnect</literal>
+ </entry>
+ <entry>
+ boolean
+ </entry>
+ <entry>
+ Transparently reconnect if the connection is lost.
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <literal>reconnect_timeout</literal>
+ </entry>
+ <entry>
+ integer
+ </entry>
+ <entry>
+ Total number of seconds to continue reconnection attempts before giving up and raising an exception.
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <literal>reconnect_limit</literal>
+ </entry>
+ <entry>
+ integer
+ </entry>
+ <entry>
+ Maximum number of reconnection attempts before giving up and raising an exception.
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <literal>reconnect_interval_min</literal>
+ </entry>
+ <entry>
+ integer representing time in seconds
+ </entry>
+ <entry>
+ Minimum number of seconds between reconnection attempts. The first reconnection attempt is made immediately; if that fails, the first reconnection delay is set to the value of <literal>reconnect_interval_min</literal>; if that attempt fails, the reconnect interval increases exponentially until a reconnection attempt succeeds or <literal>reconnect_interval_max</literal> is reached.
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <literal>reconnect_interval_max</literal>
+ </entry>
+ <entry>
+ integer representing time in seconds
+ </entry>
+ <entry>
+ Maximum reconnect interval.
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <literal>reconnect_interval</literal>
+ </entry>
+ <entry>
+ integer representing time in seconds
+ </entry>
+ <entry>
+ Sets both <literal>reconnection_interval_min</literal> and <literal>reconnection_interval_max</literal> to the same value.
+ </entry>
+ </row>
+
+ <row>
+ <entry>
+ <literal>heartbeat</literal>
+ </entry>
+ <entry>
+ integer representing time in seconds
+ </entry>
+ <entry>
+ Requests that heartbeats be sent every N seconds. If two
+ successive heartbeats are missed the connection is
+ considered to be lost.
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <literal>transport</literal>
+ </entry>
+ <entry>
+ string
+ </entry>
+ <entry>
+ Sets the underlying transport protocol used. The default option is 'tcp'. To enable ssl, set to 'ssl'. The C++ client additionally supports 'rdma'.
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <literal>tcp-nodelay</literal>
+ </entry>
+ <entry>
+ boolean
+ </entry>
+ <entry>
+ Set tcp no-delay, i.e. disable Nagle algorithm. [C++ only]
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <literal>protocol</literal>
+ </entry>
+ <entry>
+ string
+ </entry>
+ <entry>
+ Sets the application protocol used. The default option is 'amqp0-10'. To enable AMQP 1.0, set to 'amqp1.0'.
+ </entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ </section>
+ </section>
+
+ <section id="section-Maps">
+ <title>Maps and Lists in Message Content</title>
+
+ <para>Many messaging applications need to exchange data across
+ languages and platforms, using the native datatypes of each
+ programming language.</para>
+
+ <para>The Qpid Messaging API supports <classname>map</classname> and <classname>list</classname> in message content.
+
+ <footnote><para>Unlike JMS, there is not a specific message type for
+ map messages.</para></footnote>
+
+ <footnote>
+ <para>
+ Note that the Qpid JMS client supports MapMessages whose values can be nested maps or lists. This is not standard JMS behaviour.
+ </para>
+ </footnote>
+ Specific language support for <classname>map</classname> and <classname>list</classname> objects are shown in the following table.
+ </para>
+ <table id="tabl-Programming_in_Apache_Qpid-Qpid_Maps_in_Message_Content">
+ <title>Map and List Representation in Supported Languages</title>
+ <tgroup cols="3">
+ <thead>
+ <row>
+ <entry>Language</entry>
+ <entry>map</entry>
+ <entry>list</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>Python</entry>
+ <entry><classname>dict</classname></entry>
+ <entry><classname>list</classname></entry>
+ </row>
+ <row>
+ <entry>C++</entry>
+ <entry><classname>Variant::Map</classname></entry>
+ <entry><classname>Variant::List</classname></entry>
+ </row>
+ <row>
+ <entry>Java</entry>
+ <entry><classname>MapMessage</classname></entry>
+ <entry><classname> </classname></entry>
+ </row>
+ <row>
+ <entry>.NET</entry>
+ <entry><classname>Dictionary<string, object></classname></entry>
+ <entry><classname>Collection<object></classname></entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+ <para>
+ In all languages, messages are encoded using AMQP's portable datatypes.
+ </para>
+
+ <tip>
+ <para>Because of the differences in type systems among
+ languages, the simplest way to provide portable messages is to
+ rely on maps, lists, strings, 64 bit signed integers, and
+ doubles for messages that need to be exchanged across languages
+ and platforms.</para>
+ </tip>
+
+ <section id="section-Python-Maps">
+ <title>Qpid Maps and Lists in Python</title>
+
+ <para>In Python, Qpid supports the <classname>dict</classname> and <classname>list</classname> types directly in message content. The following code shows how to send these structures in a message:</para>
+
+ <example>
+ <title>Sending Qpid Maps and Lists in Python</title>
+ <programlisting><![CDATA[
+ from qpid.messaging import *
+ # !!! SNIP !!!
+
+ content = {'Id' : 987654321, 'name' : 'Widget', 'percent' : 0.99}
+ content['colours'] = ['red', 'green', 'white']
+ content['dimensions'] = {'length' : 10.2, 'width' : 5.1,'depth' : 2.0};
+ content['parts'] = [ [1,2,5], [8,2,5] ]
+ content['specs'] = {'colors' : content['colours'],
+ 'dimensions' : content['dimensions'],
+ 'parts' : content['parts'] }
+ message = Message(content=content)
+ sender.send(message)
+ ]]> </programlisting>
+ </example>
+
+
+ <para>The following table shows the datatypes that can be sent in a Python map message,
+ and the corresponding datatypes that will be received by clients in Java or C++.</para>
+
+
+ <table id="table-Python-Maps" >
+ <title>Python Datatypes in Maps</title>
+ <tgroup cols="3">
+ <thead>
+ <row>
+ <entry>Python Datatype</entry>
+ <entry>→ C++</entry>
+ <entry>→ Java</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row><entry>bool</entry><entry>bool</entry><entry>boolean</entry></row>
+ <row><entry>int</entry><entry>int64</entry><entry>long</entry></row>
+ <row><entry>long</entry><entry>int64</entry><entry>long</entry></row>
+ <row><entry>float</entry><entry>double</entry><entry>double</entry></row>
+ <row><entry>unicode</entry><entry>string</entry><entry>java.lang.String</entry></row>
+ <row><entry>uuid</entry><entry>qpid::types::Uuid</entry><entry>java.util.UUID</entry></row>
+ <row><entry>dict</entry><entry>Variant::Map</entry><entry>java.util.Map</entry></row>
+ <row><entry>list</entry><entry>Variant::List</entry><entry>java.util.List</entry></row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ </section>
+
+
+
+
+ <section id="section-cpp-Maps">
+ <title>Qpid Maps and Lists in C++</title>
+
+
+ <para>In C++, Qpid defines the the
+ <classname>Variant::Map</classname> and
+ <classname>Variant::List</classname> types, which can be
+ encoded into message content. The following code shows how to
+ send these structures in a message:</para>
+
+ <example>
+ <title>Sending Qpid Maps and Lists in C++</title>
+ <programlisting><![CDATA[
+ using namespace qpid::types;
+
+ // !!! SNIP !!!
+
+ Message message;
+ Variant::Map content;
+ content["id"] = 987654321;
+ content["name"] = "Widget";
+ content["percent"] = 0.99;
+ Variant::List colours;
+ colours.push_back(Variant("red"));
+ colours.push_back(Variant("green"));
+ colours.push_back(Variant("white"));
+ content["colours"] = colours;
+
+ Variant::Map dimensions;
+ dimensions["length"] = 10.2;
+ dimensions["width"] = 5.1;
+ dimensions["depth"] = 2.0;
+ content["dimensions"]= dimensions;
+
+ Variant::List part1;
+ part1.push_back(Variant(1));
+ part1.push_back(Variant(2));
+ part1.push_back(Variant(5));
+
+ Variant::List part2;
+ part2.push_back(Variant(8));
+ part2.push_back(Variant(2));
+ part2.push_back(Variant(5));
+
+ Variant::List parts;
+ parts.push_back(part1);
+ parts.push_back(part2);
+ content["parts"]= parts;
+
+ Variant::Map specs;
+ specs["colours"] = colours;
+ specs["dimensions"] = dimensions;
+ specs["parts"] = parts;
+ content["specs"] = specs;
+
+ encode(content, message);
+ sender.send(message, true);
+ ]]> </programlisting>
+ </example>
+
+ <para>The following table shows the datatypes that can be sent
+ in a C++ map message, and the corresponding datatypes that
+ will be received by clients in Java and Python.</para>
+
+ <table id="table-cpp-Maps">
+ <title>C++ Datatypes in Maps</title>
+ <tgroup cols="3">
+ <thead>
+ <row>
+ <entry>C++ Datatype</entry>
+ <entry>→ Python</entry>
+ <entry>→ Java</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row><entry>bool</entry><entry>bool</entry><entry>boolean</entry></row>
+ <row><entry>uint16</entry><entry>int | long</entry><entry>short</entry></row>
+ <row><entry>uint32</entry><entry>int | long</entry><entry>int</entry></row>
+ <row><entry>uint64</entry><entry>int | long</entry><entry>long</entry></row>
+ <row><entry>int16</entry><entry>int | long</entry><entry>short</entry></row>
+ <row><entry>int32</entry><entry>int | long</entry><entry>int</entry></row>
+ <row><entry>int64</entry><entry>int | long</entry><entry>long</entry></row>
+ <row><entry>float</entry><entry>float</entry><entry>float</entry></row>
+ <row><entry>double</entry><entry>float</entry><entry>double</entry></row>
+ <row><entry>string</entry><entry>unicode</entry><entry>java.lang.String</entry></row>
+ <row><entry>qpid::types::Uuid</entry><entry>uuid</entry><entry>java.util.UUID</entry></row>
+ <row><entry>Variant::Map</entry><entry>dict</entry><entry>java.util.Map</entry></row>
+ <row><entry>Variant::List</entry><entry>list</entry><entry>java.util.List</entry></row>
+ </tbody>
+ </tgroup>
+ </table>
+ </section>
+
+ <section id="section-dotnet-Maps">
+ <title>Qpid Maps and Lists in .NET</title>
+
+
+ <para>
+ The .NET binding for the Qpid Messaging API binds .NET managed data types
+ to C++ <classname>Variant</classname> data types. The following code shows how to
+ send Map and List structures in a message:
+ </para>
+
+ <example>
+ <?dbfo keep-together="auto" ?>
+ <title>Sending Qpid Maps and Lists in .NET C#</title>
+ <programlisting><![CDATA[
+ using System;
+ using Org.Apache.Qpid.Messaging;
+
+ // !!! SNIP !!!
+
+ Dictionary<string, object> content = new Dictionary<string, object>();
+ Dictionary<string, object> subMap = new Dictionary<string, object>();
+ Collection<object> colors = new Collection<object>();
+
+ // add simple types
+ content["id"] = 987654321;
+ content["name"] = "Widget";
+ content["percent"] = 0.99;
+
+ // add nested amqp/map
+ subMap["name"] = "Smith";
+ subMap["number"] = 354;
+ content["nestedMap"] = subMap;
+
+ // add an amqp/list
+ colors.Add("red");
+ colors.Add("green");
+ colors.Add("white");
+ content["colorsList"] = colors;
+
+ // add one of each supported amqp data type
+ bool mybool = true;
+ content["mybool"] = mybool;
+
+ byte mybyte = 4;
+ content["mybyte"] = mybyte;
+
+ UInt16 myUInt16 = 5;
+ content["myUInt16"] = myUInt16;
+
+ UInt32 myUInt32 = 6;
+ content["myUInt32"] = myUInt32;
+
+ UInt64 myUInt64 = 7;
+ content["myUInt64"] = myUInt64;
+
+ char mychar = 'h';
+ content["mychar"] = mychar;
+
+ Int16 myInt16 = 9;
+ content["myInt16"] = myInt16;
+
+ Int32 myInt32 = 10;
+ content["myInt32"] = myInt32;
+
+ Int64 myInt64 = 11;
+ content["myInt64"] = myInt64;
+
+ Single mySingle = (Single)12.12;
+ content["mySingle"] = mySingle;
+
+ Double myDouble = 13.13;
+ content["myDouble"] = myDouble;
+
+ Guid myGuid = new Guid("000102030405060708090a0b0c0d0e0f");
+ content["myGuid"] = myGuid;
+
+ Message message = new Message(content);
+ Send(message, true);
+ ]]> </programlisting>
+ </example>
+
+ <para>
+ The following table shows the mapping between datatypes in .NET and C++.
+ </para>
+
+ <table id="table-dotnet-Maps">
+ <title>Datatype Mapping between C++ and .NET binding</title>
+ <tgroup cols="2">
+ <thead>
+ <row>
+ <entry>C++ Datatype</entry>
+ <entry>→ .NET binding</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row><entry>void</entry><entry>nullptr</entry></row>
+ <row><entry>bool</entry><entry>bool</entry></row>
+ <row><entry>uint8</entry><entry>byte</entry></row>
+ <row><entry>uint16</entry><entry>UInt16</entry></row>
+ <row><entry>uint32</entry><entry>UInt32</entry></row>
+ <row><entry>uint64</entry><entry>UInt64</entry></row>
+ <row><entry>uint8</entry><entry>char</entry></row>
+ <row><entry>int16</entry><entry>Int16</entry></row>
+ <row><entry>int32</entry><entry>Int32</entry></row>
+ <row><entry>int64</entry><entry>Int64</entry></row>
+ <row><entry>float</entry><entry>Single</entry></row>
+ <row><entry>double</entry><entry>Double</entry></row>
+ <row><entry>string</entry><entry>string
+ <footnote id="callout-dotnet-string">
+ <para>Strings are currently interpreted only with UTF-8 encoding.</para>
+ </footnote></entry></row>
+ <row><entry>qpid::types::Uuid</entry><entry>Guid</entry></row>
+ <row><entry>Variant::Map</entry><entry><![CDATA[Dictionary<string, object>]]>
+ <footnoteref linkend="callout-dotnet-string"/></entry></row>
+ <row><entry>Variant::List</entry><entry><![CDATA[Collection<object>]]>
+ <footnoteref linkend="callout-dotnet-string"/></entry></row>
+ </tbody>
+ </tgroup>
+ </table>
+
+
+ </section>
+
+
+ </section>
+
+ <section>
+ <title>The Request / Response Pattern</title>
+ <para>Request / Response applications use the reply-to property,
+ described in <xref
+ linkend="table-amqp0-10-message-properties"/>, to allow a server
+ to respond to the client that sent a message. A server sets up a
+ service queue, with a name known to clients. A client creates a
+ private queue for the server's response, creates a message for a
+ request, sets the request's reply-to property to the address of
+ the client's response queue, and sends the request to the
+ service queue. The server sends the response to the address
+ specified in the request's reply-to property.
+ </para>
+ <example>
+ <title>Request / Response Applications in C++</title>
+
+ <para>This example shows the C++ code for a client and server
+ that use the request / response pattern.</para>
+
+ <para>The server creates a service queue and waits for a
+ message to arrive. If it receives a message, it sends a
+ message back to the sender.</para>
+
+ <programlisting><![CDATA[Receiver receiver = session.createReceiver("service_queue; {create: always}");
+
+ Message request = receiver.fetch();
+ const Address& address = request.getReplyTo(); // Get "reply-to" from request ...
+ if (address) {
+ Sender sender = session.createSender(address); // ... send response to "reply-to"
+ Message response("pong!");
+ sender.send(response);
+ session.acknowledge();
+ }
+ ]]></programlisting>
+
+ <para>The client creates a sender for the service queue, and
+ also creates a response queue that is deleted when the
+ client closes the receiver for the response queue. In the C++
+ client, if the address starts with the character
+ <literal>#</literal>, it is given a unique name.</para>
+
+ <programlisting><![CDATA[
+ Sender sender = session.createSender("service_queue");
+
+ Address responseQueue("#response-queue; {create:always, delete:always}");
+ Receiver receiver = session.createReceiver(responseQueue);
+
+ Message request;
+ request.setReplyTo(responseQueue);
+ request.setContent("ping");
+ sender.send(request);
+ Message response = receiver.fetch();
+ std::cout << request.getContent() << " -> " << response.getContent() << std::endl;
+ ]]> </programlisting>
+
+ <para>The client sends the string <literal>ping</literal> to
+ the server. The server sends the response
+ <literal>pong</literal> back to the same client, using the
+ <varname>replyTo</varname> property.</para>
+
+ </example>
+ <!--
+ <example>
+ <title>Request / Response Applications in Python</title>
+ <programlisting>### TODO</programlisting>
+ </example>
+ -->
+ </section>
+
+
+ <section>
+ <title>Performance Tips</title>
+
+ <itemizedlist>
+ <listitem>
+ <para>Consider prefetching messages for receivers (see
+ <xref linkend="prefetch"/>). This helps eliminate roundtrips
+ and increases throughput. Prefetch is disabled by default,
+ and enabling it is the most effective means of improving
+ throughput of received messages.</para>
+ </listitem>
+ <listitem>
+ <para>Send messages asynchronously. Again, this helps
+ eliminate roundtrips and increases throughput. The C++ and
+ .NET clients send asynchronously by default, however the
+ python client defaults to synchronous sends. </para>
+ </listitem>
+ <listitem>
+ <para>Acknowledge messages in batches (see
+ <xref linkend="acknowledgements"/>). Rather than
+ acknowledging each message individually, consider issuing
+ acknowledgements after n messages and/or after a particular
+ duration has elapsed.</para>
+ </listitem>
+ <listitem>
+ <para>Tune the sender capacity (see
+ <xref linkend="replay"/>). If the capacity is too low the
+ sender may block waiting for the broker to confirm receipt
+ of messages, before it can free up more capacity.</para>
+ </listitem>
+ <listitem>
+ <para>If you are setting a reply-to address on messages
+ being sent by the c++ client, make sure the address type is
+ set to either queue or topic as appropriate. This avoids the
+ client having to determine which type of node is being
+ refered to, which is required when hanling reply-to in AMQP
+ 0-10. </para>
+ </listitem>
+ <listitem>
+ <para>For latency sensitive applications, setting tcp-nodelay
+ on qpidd and on client connections can help reduce the
+ latency.</para>
+ </listitem>
+ </itemizedlist>
+ </section>
+
+ <section>
+ <title>Cluster Failover</title>
+
+ <para>The messaging broker can be run in clustering mode, which provides high reliability through replicating state between brokers in the cluster. If one broker in a cluster fails, clients can choose another broker in the cluster and continue their work. Each broker in the cluster also advertises the addresses of all known brokers
+
+ <footnote><para>This is done via the amq.failover exchange in AMQP 0-10</para></footnote>
+
+ . A client can use this information to dynamically keep the list of reconnection urls up to date.</para>
+
+ <para>In C++, the <classname>FailoverUpdates</classname> class provides this functionality:</para>
+
+ <example>
+ <title>Tracking cluster membership</title>
+
+ <para>In C++:</para>
+
+ <programlisting><![CDATA[
+ #include <qpid/messaging/FailoverUpdates.h>
+ ...
+ Connection connection("localhost:5672");
+ connection.setOption("reconnect", true);
+ try {
+ connection.open();
+ std::auto_ptr<FailoverUpdates> updates(new FailoverUpdates(connection));
+ ]]>
+ </programlisting>
+
+ <para>In python:</para>
+
+ <programlisting><![CDATA[
+ import qpid.messaging.util
+ ...
+ connection = Connection("localhost:5672")
+ connection.reconnect = True
+ try:
+ connection.open()
+ auto_fetch_reconnect_urls(connection)
+ ]]>
+ </programlisting>
+ <para>
+ In .NET C#:
+ </para>
+
+ <programlisting>
+ using Org.Apache.Qpid.Messaging;
+ ...
+ connection = new Connection("localhost:5672");
+ connection.SetOption("reconnect", true);
+ try {
+ connection.Open();
+ FailoverUpdates failover = new FailoverUpdates(connection);
+
+ </programlisting>
+
+
+ </example>
+ </section>
+
+
+
+ <section>
+ <title>Logging</title>
+
+ <para>To simplify debugging, Qpid provides a logging facility
+ that prints out messaging events.</para>
+
+ <section>
+ <title>Logging in C++</title>
+ <para>
+ The Qpidd broker and C++ clients can both use environment variables to enable logging. Linux and Windows systems use the same named environment variables and values.
+ </para>
+ <para>Use QPID_LOG_ENABLE to set the level of logging you are interested in (trace, debug, info, notice, warning, error, or critical):
+ </para>
+
+ <screen>
+ export QPID_LOG_ENABLE="warning+"
+ </screen>
+ <para>
+ The Qpidd broker and C++ clients use QPID_LOG_OUTPUT to determine where logging output should be sent. This is either a file name or the special values stderr, stdout, or syslog:
+ </para>
+
+ <screen>
+ export QPID_LOG_TO_FILE="/tmp/myclient.out"
+ </screen>
+
+ <para>
+ From a Windows command prompt, use the following command format to set the environment variables:
+ </para>
+
+ <screen>
+ set QPID_LOG_ENABLE=warning+
+ set QPID_LOG_TO_FILE=D:\tmp\myclient.out
+ </screen>
+ </section>
+
+ <section>
+ <title>Logging in Python</title>
+ <para>
+ The Python client library supports logging using the standard Python logging module. The easiest way to do logging is to use the <command>basicConfig()</command>, which reports all warnings and errors:
+ </para>
+
+ <programlisting>from logging import basicConfig
+ basicConfig()
+ </programlisting>
+ <para>
+ Qpidd also provides a convenience method that makes it easy to specify the level of logging desired. For instance, the following code enables logging at the <command>DEBUG</command> level:
+ </para>
+
+ <programlisting>from qpid.log import enable, DEBUG
+ enable("qpid.messaging.io", DEBUG)
+ </programlisting>
+ <para>
+ For more information on Python logging, see <ulink url="http://docs.python.org/lib/node425.html">http://docs.python.org/lib/node425.html</ulink>. For more information on Qpid logging, use <command>$ pydoc qpid.log</command>.
+ </para>
+ </section>
+ </section>
+
+
+
+ <section id="section-amqp0-10-mapping">
+ <title>The AMQP 0-10 mapping</title>
+
+ <para>
+ This section describes the AMQP 0-10 mapping for the Qpid
+ Messaging API.
+ </para>
+ <para>
+ The interaction with the broker triggered by creating a sender
+ or receiver depends on what the specified address resolves
+ to. Where the node type is not specified in the address, the
+ client queries the broker to determine whether it refers to a
+ queue or an exchange.
+ </para>
+ <para>
+ When sending to a queue, the queue's name is set as the
+ routing key and the message is transfered to the default (or
+ nameless) exchange. When sending to an exchange, the message
+ is transfered to that exchange and the routing key is set to
+ the message subject if one is specified. A default subject may
+ be specified in the target address. The subject may also be
+ set on each message individually to override the default if
+ required. In each case any specified subject is also added as
+ a qpid.subject entry in the application-headers field of the
+ message-properties.
+ </para>
+ <para>
+ When receiving from a queue, any subject in the source address
+ is currently ignored. The client sends a message-subscribe
+ request for the queue in question. The accept-mode is
+ determined by the reliability option in the link properties;
+ for unreliable links the accept-mode is none, for reliable
+ links it is explicit. The default for a queue is reliable. The
+ acquire-mode is determined by the value of the mode option. If
+ the mode is set to browse the acquire mode is not-acquired,
+ otherwise it is set to pre-acquired. The exclusive and
+ arguments fields in the message-subscribe command can be
+ controlled using the x-subscribe map.
+ </para>
+ <para>
+ When receiving from an exchange, the client creates a
+ subscription queue and binds that to the exchange. The
+ subscription queue's arguments can be specified using the
+ x-declare map within the link properties. The reliability
+ option determines most of the other parameters. If the
+ reliability is set to unreliable then an auto-deleted,
+ exclusive queue is used meaning that if the client or
+ connection fails messages may be lost. For exactly-once the
+ queue is not set to be auto-deleted. The durability of the
+ subscription queue is determined by the durable option in the
+ link properties. The binding process depends on the type of
+ the exchange the source address resolves to.
+ </para>
+
+ <itemizedlist>
+ <listitem>
+ <para>
+ For a topic exchange, if no subject is specified and no
+ x-bindings are defined for the link, the subscription
+ queue is bound using a wildcard matching any routing key
+ (thus satisfying the expectation that any message sent to
+ that address will be received from it). If a subject is
+ specified in the source address however, it is used for
+ the binding key (this means that the subject in the source
+ address may be a binding pattern including wildcards).
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ For a fanout exchange the binding key is irrelevant to
+ matching. A receiver created from a source address that
+ resolves to a fanout exchange receives all messages
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