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Using the AMQ Python Client

Red Hat AMQ 7.6

For Use with AMQ Clients 2.7

Abstract

This guide describes how to install and configure the client, run hands-on examples, and use your client with other AMQ components.

Chapter 1. Overview

AMQ Python is a library for developing messaging applications. It enables you to write Python applications that send and receive AMQP messages.

AMQ Python is part of AMQ Clients, a suite of messaging libraries supporting multiple languages and platforms. For an overview of the clients, see AMQ Clients Overview. For information about this release, see AMQ Clients 2.7 Release Notes.

AMQ Python is based on the Proton API from Apache Qpid. For detailed API documentation, see the AMQ Python API reference.

1.1. Key features

  • An event-driven API that simplifies integration with existing applications
  • SSL/TLS for secure communication
  • Flexible SASL authentication
  • Automatic reconnect and failover
  • Seamless conversion between AMQP and language-native data types
  • Access to all the features and capabilities of AMQP 1.0
  • Distributed tracing based on the OpenTracing standard (RHEL 7 and 8)

    Important

    Distributed tracing in AMQ Clients is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process. For more information about the support scope of Red Hat Technology Preview features, see https://access.redhat.com/support/offerings/techpreview/.

1.2. Supported standards and protocols

AMQ Python supports the following industry-recognized standards and network protocols:

1.3. Supported configurations

AMQ Python supports the OS and language versions listed below. For more information, see Red Hat AMQ 7 Supported Configurations.

  • Red Hat Enterprise Linux 6 with Python 2.6
  • Red Hat Enterprise Linux 7 with Python 2.7
  • Red Hat Enterprise Linux 8 with Python 3.6
  • Microsoft Windows 10 Pro with Python 3.6
  • Microsoft Windows Server 2012 R2 and 2016 with Python 3.6

AMQ Python is supported in combination with the following AMQ components and versions:

  • All versions of AMQ Broker
  • All versions of AMQ Interconnect
  • All versions of AMQ Online
  • A-MQ 6 versions 6.2.1 and newer

1.4. Terms and concepts

This section introduces the core API entities and describes how they operate together.

Table 1.1. API terms

EntityDescription

Container

A top-level container of connections.

Connection

A channel for communication between two peers on a network. It contains sessions.

Session

A context for sending and receiving messages. It contains senders and receivers.

Sender

A channel for sending messages to a target. It has a target.

Receiver

A channel for receiving messages from a source. It has a source.

Source

A named point of origin for messages.

Target

A named destination for messages.

Message

An application-specific piece of information.

Delivery

A message transfer.

AMQ Python sends and receives messages. Messages are transferred between connected peers over senders and receivers. Senders and receivers are established over sessions. Sessions are established over connections. Connections are established between two uniquely identified containers. Though a connection can have multiple sessions, often this is not needed. The API allows you to ignore sessions unless you require them.

A sending peer creates a sender to send messages. The sender has a target that identifies a queue or topic at the remote peer. A receiving peer creates a receiver to receive messages. The receiver has a source that identifies a queue or topic at the remote peer.

The sending of a message is called a delivery. The message is the content sent, including all metadata such as headers and annotations. The delivery is the protocol exchange associated with the transfer of that content.

To indicate that a delivery is complete, either the sender or the receiver settles it. When the other side learns that it has been settled, it will no longer communicate about that delivery. The receiver can also indicate whether it accepts or rejects the message.

1.5. Document conventions

The sudo command

In this document, sudo is used for any command that requires root privileges. Exercise caution when using sudo because any changes can affect the entire system. For more information about sudo, see Using the sudo command.

File paths

In this document, all file paths are valid for Linux, UNIX, and similar operating systems (for example, /home/andrea). On Microsoft Windows, you must use the equivalent Windows paths (for example, C:\Users\andrea).

Variable text

This document contains code blocks with variables that you must replace with values specific to your environment. Variable text is enclosed in arrow braces and styled as italic monospace. For example, in the following command, replace <project-dir> with the value for your environment:

$ cd <project-dir>

Chapter 2. Installation

This chapter guides you through the steps to install AMQ Python in your environment.

2.1. Prerequisites

  • To use AMQ Python, you must install Python in your environment.

2.2. Installing on Red Hat Enterprise Linux

Procedure

  1. Use the subscription-manager command to subscribe to the required package repositories. If necessary, replace <variant> with the value for your variant of Red Hat Enterprise Linux (for example, server or workstation).

    Red Hat Enterprise Linux 6

    $ sudo subscription-manager repos --enable=amq-clients-2-for-rhel-6-<variant>-rpms

    Red Hat Enterprise Linux 7

    $ sudo subscription-manager repos --enable=amq-clients-2-for-rhel-7-<variant>-rpms

    Red Hat Enterprise Linux 8

    $ sudo subscription-manager repos --enable=amq-clients-2-for-rhel-8-x86_64-rpms

  2. Use the yum command to install the python-qpid-proton and python-qpid-proton-docs packages.

    $ sudo yum install python-qpid-proton python-qpid-proton-docs

For more information about using packages, see Appendix B, Using Red Hat Enterprise Linux packages.

2.3. Installing on Microsoft Windows

Procedure

  1. Open a browser and log in to the Red Hat Customer Portal Product Downloads page at access.redhat.com/downloads.
  2. Locate the Red Hat AMQ Clients entry in the INTEGRATION AND AUTOMATION category.
  3. Click Red Hat AMQ Clients. The Software Downloads page opens.
  4. Download the AMQ Clients 2.7.0 Python .whl file.
  5. Open a command prompt window and use the pip install command to install the .whl file.

    > pip install python_qpid_proton-0.31.0-cp36-cp36m-win_amd64.whl

Chapter 3. Getting started

This chapter guides you through the steps to set up your environment and run a simple messaging program.

3.1. Prerequisites

  • You must complete the installation procedure for your environment.
  • You must have an AMQP 1.0 message broker listening for connections on interface localhost and port 5672. It must have anonymous access enabled. For more information, see Starting the broker.
  • You must have a queue named examples. For more information, see Creating a queue.

3.2. Running Hello World on Red Hat Enterprise Linux

The Hello World example creates a connection to the broker, sends a message containing a greeting to the examples queue, and receives it back. On success, it prints the received message to the console.

Change to the examples directory and run the helloworld.py example.

$ cd /usr/share/proton/examples/python/
$ python helloworld.py
Hello World!

3.3. Running Hello World on Microsoft Windows

The Hello World example creates a connection to the broker, sends a message containing a greeting to the examples queue, and receives it back. On success, it prints the received message to the console.

Download and run the Hello World example.

> curl -o helloworld.py https://raw.githubusercontent.com/apache/qpid-proton/master/python/examples/helloworld.py
> python helloworld.py
Hello World!

Chapter 4. Examples

This chapter demonstrates the use of AMQ Python through example programs.

For more examples, see the AMQ Python example suite.

4.1. Sending messages

This client program connects to a server using <connection-url>, creates a sender for target <address>, sends a message containing <message-body>, closes the connection, and exits.

Example: Sending messages

from __future__ import print_function

import sys

from proton import Message
from proton.handlers import MessagingHandler
from proton.reactor import Container

class SendHandler(MessagingHandler):
    def __init__(self, conn_url, address, message_body):
        super(SendHandler, self).__init__()

        self.conn_url = conn_url
        self.address = address
        self.message_body = message_body

    def on_start(self, event):
        conn = event.container.connect(self.conn_url)

        # To connect with a user and password:
        # conn = event.container.connect(self.conn_url, user="<user>", password="<password>")

        event.container.create_sender(conn, self.address)

    def on_link_opened(self, event):
        print("SEND: Opened sender for target address '{0}'".format
              (event.sender.target.address))

    def on_sendable(self, event):
        message = Message(self.message_body)
        event.sender.send(message)

        print("SEND: Sent message '{0}'".format(message.body))

        event.sender.close()
        event.connection.close()

def main():
    try:
        conn_url, address, message_body = sys.argv[1:4]
    except ValueError:
        sys.exit("Usage: send.py <connection-url> <address> <message-body>")

    handler = SendHandler(conn_url, address, message_body)
    container = Container(handler)
    container.run()

if __name__ == "__main__":
    try:
        main()
    except KeyboardInterrupt:
        pass

Running the example

To run the example program, copy it to a local file and invoke it using the python command.

$ python send.py amqp://localhost queue1 hello

4.2. Receiving messages

This client program connects to a server using <connection-url>, creates a receiver for source <address>, and receives messages until it is terminated or it reaches <count> messages.

Example: Receiving messages

from __future__ import print_function

import sys

from proton.handlers import MessagingHandler
from proton.reactor import Container

class ReceiveHandler(MessagingHandler):
    def __init__(self, conn_url, address, desired):
        super(ReceiveHandler, self).__init__()

        self.conn_url = conn_url
        self.address = address
        self.desired = desired
        self.received = 0

    def on_start(self, event):
        conn = event.container.connect(self.conn_url)

        # To connect with a user and password:
        # conn = event.container.connect(self.conn_url, user="<user>", password="<password>")

        event.container.create_receiver(conn, self.address)

    def on_link_opened(self, event):
        print("RECEIVE: Created receiver for source address '{0}'".format
              (self.address))

    def on_message(self, event):
        message = event.message

        print("RECEIVE: Received message '{0}'".format(message.body))

        self.received += 1

        if self.received == self.desired:
            event.receiver.close()
            event.connection.close()

def main():
    try:
        conn_url, address = sys.argv[1:3]
    except ValueError:
        sys.exit("Usage: receive.py <connection-url> <address> [<message-count>]")

    try:
        desired = int(sys.argv[3])
    except (IndexError, ValueError):
        desired = 0

    handler = ReceiveHandler(conn_url, address, desired)
    container = Container(handler)
    container.run()

if __name__ == "__main__":
    try:
        main()
    except KeyboardInterrupt:
        pass

Running the example

To run the example program, copy it to a local file and invoke it using the python command.

$ python receive.py amqp://localhost queue1

Chapter 5. Using the API

For more information, see the AMQ Python API reference and AMQ Python example suite.

5.1. Handling messaging events

AMQ Python is an asynchronous event-driven API. To define how an application handles events, the user implements callback methods on the MessagingHandler class. These methods are then called as network activity or timers trigger new events.

Example: Handling messaging events

class ExampleHandler(MessagingHandler):
    def on_start(self, event):
        print("The container event loop has started")

    def on_sendable(self, event):
        print("A message can be sent")

    def on_message(self, event):
        print("A message is received")

These are only a few common-case events. The full set is documented in the API reference.

5.3. Creating a container

The container is the top-level API object. It is the entry point for creating connections, and it is responsible for running the main event loop. It is often constructed with a global event handler.

Example: Creating a container

handler = ExampleHandler()
container = Container(handler)
container.run()

5.4. Setting the container identity

Each container instance has a unique identity called the container ID. When AMQ Python makes a connection, it sends the container ID to the remote peer. To set the container ID, pass it to the Container constructor.

Example: Setting the container identity

container = Container(handler)
container.container_id = "job-processor-3"

If the user does not set the ID, the library will generate a UUID when the container is constucted.

Chapter 6. Network connections

6.1. Connection URLs

Connection URLs encode the information used to establish new connections.

Connection URL syntax

scheme://host[:port]

  • Scheme - The connection transport, either amqp for unencrypted TCP or amqps for TCP with SSL/TLS encryption.
  • Host - The remote network host. The value can be a hostname or a numeric IP address. IPv6 addresses must be enclosed in square brackets.
  • Port - The remote network port. This value is optional. The default value is 5672 for the amqp scheme and 5671 for the amqps scheme.

Connection URL examples

amqps://example.com
amqps://example.net:56720
amqp://127.0.0.1
amqp://[::1]:2000

6.2. Creating outgoing connections

To connect to a remote server, call the Container.connect() method with a connection URL. This is typically done inside the MessagingHandler.on_start() method.

Example: Creating outgoing connections

class ExampleHandler(MessagingHandler):
    def on_start(self, event):
        event.container.connect("amqp://example.com")

    def on_connection_opened(self, event):
        print("Connection", event.connection, "is open")

See the Chapter 7, Security section for information about creating secure connections.

6.3. Configuring reconnect

Reconnect allows a client to recover from lost connections. It is used to ensure that the components in a distributed system reestablish communication after temporary network or component failures.

AMQ Python enables reconnect by default. If a connection is lost or a connection attempt fails, the client will try again after a brief delay. The delay increases exponentially for each new attempt, up to a default maximum of 10 seconds.

To disable reconnect, set the reconnect connection option to False.

Example: Disabling reconnect

container.connect("amqp://example.com", reconnect=False)

To control the delays between connection attempts, define a class implementing the reset() and next() methods and set the reconnect connection option to an instance of that class.

Example: Configuring reconnect

class ExampleReconnect(object):
    def __init__(self):
        self.delay = 0

    def reset(self):
        self.delay = 0

    def next(self):
        if self.delay == 0:
            self.delay = 0.1
        else:
            self.delay = min(10, 2 * self.delay)

        return self.delay

container.connect("amqp://example.com", reconnect=ExampleReconnect())

The next method returns the next delay in seconds. The reset method is called once before the reconnect process begins.

6.4. Configuring failover

AMQ Python allows you to configure multiple connection endpoints. If connecting to one fails, the client attempts to connect to the next in the list. If the list is exhausted, the process starts over.

To specify multiple connection endpoints, set the urls connection option to a list of connection URLs.

Example: Configuring failover

urls = ["amqp://alpha.example.com", "amqp://beta.example.com"]
container.connect(urls=urls)

It is an error to use the url and urls options at the same time.

6.5. Accepting incoming connections

AMQ Python can accept inbound network connections, enabling you to build custom messaging servers.

To start listening for connections, use the Container.listen() method with a URL containing the local host address and port to listen on.

Example: Accepting incoming connections

class ExampleHandler(MessagingHandler):
    def on_start(self, event):
        event.container.listen("0.0.0.0")

    def on_connection_opened(self, event):
        print("New incoming connection", event.connection)

The special IP address 0.0.0.0 listens on all available IPv4 interfaces. To listen on all IPv6 interfaces, use [::0].

For more information, see the server receive.py example.

Chapter 7. Security

7.1. Securing connections with SSL/TLS

AMQ Python uses SSL/TLS to encrypt communication between clients and servers.

To connect to a remote server with SSL/TLS, use a connection URL with the amqps scheme.

Example: Enabling SSL/TLS

container.connect("amqps://example.com")

7.2. Connecting with a user and password

AMQ Python can authenticate connections with a user and password.

To specify the credentials used for authentication, set the user and password options on the connect() method.

Example: Connecting with a user and password

container.connect("amqps://example.com", user="alice", password="secret")

7.3. Configuring SASL authentication

AMQ Python uses the SASL protocol to perform authentication. SASL can use a number of different authentication mechanisms. When two network peers connect, they exchange their allowed mechanisms, and the strongest mechanism allowed by both is selected.

Note

The client uses Cyrus SASL to perform authentication. Cyrus SASL uses plug-ins to support specific SASL mechanisms. Before you can use a particular SASL mechanism, the relevant plug-in must be installed. For example, you need the cyrus-sasl-plain plug-in in order to use SASL PLAIN authentication.

To see a list of Cyrus SASL plug-ins in Red Hat Enterprise Linux, use the yum search cyrus-sasl command. To install a Cyrus SASL plug-in, use the yum install PLUG-IN command.

By default, AMQ Python allows all of the mechanisms supported by the local SASL library configuration. To restrict the allowed mechanisms and thereby control what mechanisms can be negotiated, use the allowed_mechs connection option. It takes a string containing a space-separated list of mechanism names.

Example: Configuring SASL authentication

container.connect("amqps://example.com", allowed_mechs="ANONYMOUS")

This example forces the connection to authenticate using the ANONYMOUS mechanism even if the server we connect to offers other options. Valid mechanisms include ANONYMOUS, PLAIN, SCRAM-SHA-256, SCRAM-SHA-1, GSSAPI, and EXTERNAL.

AMQ Python enables SASL by default. To disable it, set the sasl_enabled connection option to false.

Example: Disabling SASL

event.container.connect("amqps://example.com", sasl_enabled=False)

7.4. Authenticating using Kerberos

Kerberos is a network protocol for centrally managed authentication based on the exchange of encrypted tickets. See Using Kerberos for more information.

  1. Configure Kerberos in your operating system. See Configuring Kerberos to set up Kerberos on Red Hat Enterprise Linux.
  2. Enable the GSSAPI SASL mechanism in your client application.

    container.connect("amqps://example.com", allowed_mechs="GSSAPI")
  3. Use the kinit command to authenticate your user credentials and store the resulting Kerberos ticket.

    $ kinit <user>@<realm>
  4. Run the client program.

Chapter 8. Senders and receivers

The client uses sender and receiver links to represent channels for delivering messages. Senders and receivers are unidirectional, with a source end for the message origin, and a target end for the message destination.

Source and targets often point to queues or topics on a message broker. Sources are also used to represent subscriptions.

8.1. Creating queues and topics on demand

Some message servers support on-demand creation of queues and topics. When a sender or receiver is attached, the server uses the sender target address or the receiver source address to create a queue or topic with a name matching the address.

The message server typically defaults to creating either a queue (for one-to-one message delivery) or a topic (for one-to-many message delivery). The client can indicate which it prefers by setting the queue or topic capability on the source or target.

To select queue or topic semantics, follow these steps:

  1. Configure your message server for automatic creation of queues and topics. This is often the default configuration.
  2. Set either the queue or topic capability on your sender target or receiver source, as in the examples below.

Example: Sending to a queue created on demand

class CapabilityOptions(SenderOption):
    def apply(self, sender):
        sender.target.capabilities.put_object(symbol("queue"))

class ExampleHandler(MessagingHandler):
    def on_start(self, event):
        conn = event.container.connect("amqp://example.com")
        event.container.create_sender(conn, "jobs", options=CapabilityOptions())

Example: Receiving from a topic created on demand

class CapabilityOptions(ReceiverOption):
    def apply(self, receiver):
        receiver.source.capabilities.put_object(symbol("topic"))

class ExampleHandler(MessagingHandler):
    def on_start(self, event):
        conn = event.container.connect("amqp://example.com")
        event.container.create_receiver(conn, "notifications", options=CapabilityOptions())

For more information, see the following examples:

8.2. Creating durable subscriptions

A durable subscription is a piece of state on the remote server representing a message receiver. Ordinarily, message receivers are discarded when a client closes. However, because durable subscriptions are persistent, clients can detach from them and then re-attach later. Any messages received while detached are available when the client re-attaches.

Durable subscriptions are uniquely identified by combining the client container ID and receiver name to form a subscription ID. These must have stable values so that the subscription can be recovered.

To create a durable subscription, follow these steps:

  1. Set the connection container ID to a stable value, such as client-1:

    container = Container(handler)
    container.container_id = "client-1"
  2. Configure the receiver source for durability by setting the durability and expiry_policy properties:

    class SubscriptionOptions(ReceiverOption):
        def apply(self, receiver):
            receiver.source.durability = Terminus.DELIVERIES
            receiver.source.expiry_policy = Terminus.EXPIRE_NEVER
  3. Create a receiver with a stable name, such as sub-1, and apply the source properties:

    event.container.create_receiver(conn, "notifications",
                                    name="sub-1",
                                    options=SubscriptionOptions())

To detach from a subscription, use the Receiver.detach() method. To terminate the subscription, use the Receiver.close() method.

For more information, see the durable-subscribe.py example.

8.3. Creating shared subscriptions

A shared subscription is a piece of state on the remote server representing one or more message receivers. Because it is shared, multiple clients can consume from the same stream of messages.

The client configures a shared subscription by setting the shared capability on the receiver source.

Shared subscriptions are uniquely identified by combining the client container ID and receiver name to form a subscription ID. These must have stable values so that multiple client processes can locate the same subscription. If the global capability is set in addition to shared, the receiver name alone is used to identify the subscription.

To create a durable subscription, follow these steps:

  1. Set the connection container ID to a stable value, such as client-1:

    container = Container(handler)
    container.container_id = "client-1"
  2. Configure the receiver source for sharing by setting the shared capability:

    class SubscriptionOptions(ReceiverOption):
        def apply(self, receiver):
            receiver.source.capabilities.put_object(symbol("shared"))
  3. Create a receiver with a stable name, such as sub-1, and apply the source properties:

    event.container.create_receiver(conn, "notifications",
                                    name="sub-1",
                                    options=SubscriptionOptions())

To detach from a subscription, use the Receiver.detach() method. To terminate the subscription, use the Receiver.close() method.

For more information, see the shared-subscribe.py example.

Chapter 9. Message delivery

9.1. Sending messages

To send a message, override the on_sendable event handler and call the Sender.send() method. The sendable event fires when the Sender has enough credit to send at least one message.

Example: Sending messages

class ExampleHandler(MessagingHandler):
    def on_start(self, event):
        conn = event.container.connect("amqp://example.com")
        sender = event.container.create_sender(conn, "jobs")

    def on_sendable(self, event):
        message = Message("job-content")
        event.sender.send(message)

For more information, see the send.py example.

9.2. Tracking sent messages

When a message is sent, the sender can keep a reference to the delivery object representing the transfer. After the message is delivered, the receiver accepts or rejects it. The sender is notified of the outcome for each delivery.

To monitor the outcome of a sent message, override the on_accepted and on_rejected event handlers and map the delivery state update to the delivery returned from send().

Example: Tracking sent messages

def on_sendable(self, event):
    message = Message(self.message_body)
    delivery = event.sender.send(message)

def on_accepted(self, event):
    print("Delivery", event.delivery, "is accepted")

def on_rejected(self, event):
    print("Delivery", event.delivery, "is rejected")

9.3. Receiving messages

To receive a message, create a receiver and override the on_message event handler.

Example: Receiving messages

class ExampleHandler(MessagingHandler):
    def on_start(self, event):
        conn = event.container.connect("amqp://example.com")
        receiver = event.container.create_receiver(conn, "jobs")

    def on_message(self, event):
        print("Received message", event.message, "from", event.receiver)

For more information, see the receive.py example.

9.4. Acknowledging received messages

To explicitly accept or reject a delivery, use the Delivery.update() method with the ACCEPTED or REJECTED state in the on_message event handler.

Example: Acknowledging received messages

def on_message(self, event):
    try:
        process_message(event.message)
        event.delivery.update(ACCEPTED)
    except:
        event.delivery.update(REJECTED)

By default, if you do not explicity acknowledge a delivery, then the library accepts it after on_message returns. To disable this behavior, set the auto_accept receiver option to false.

Chapter 10. Logging and tracing

10.1. Enabling protocol logging

The client can log AMQP protocol frames to the console. This data is often critical when diagnosing problems.

To enable protocol logging, set the PN_TRACE_FRM environment variable to 1:

Example: Enabling protocol logging

$ export PN_TRACE_FRM=1
$ <your-client-program>

To disable protocol logging, unset the PN_TRACE_FRM environment variable.

10.2. Enabling distributed tracing

The client offers distributed tracing based on the Jaeger implementation of the OpenTracing standard. Use the following steps to enable tracing in your application:

  1. Install the tracing dependencies.

    Red Hat Enterprise Linux 7

    $ sudo yum install https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
    $ sudo yum install python2-pip
    $ pip install --user --upgrade setuptools
    $ pip install --user opentracing jaeger-client

    Red Hat Enterprise Linux 8

    $ sudo dnf install python3-pip
    $ pip3 install --user opentracing jaeger-client

  2. Register the global tracer in your program.

    Example: Global tracer configuration

    from proton.tracing import init_tracer
    
    tracer = init_tracer("<service-name>")

For more information about Jaeger configuration, see Jaeger Sampling.

When testing or debugging, you may want to force Jaeger to trace a particular operation. See the Jaeger Python client documentation for more information.

To view the traces your application captures, use the Jaeger Getting Started to run the Jaeger infrastructure and console.

Chapter 11. File-based configuration

AMQ Python can read the configuration options used to establish connections from a local file named connect.json. This enables you to configure connections in your application at the time of deployment.

The library attempts to read the file when the application calls the container connect method without supplying any connection options.

11.1. File locations

If set, AMQ Python uses the value of the MESSAGING_CONNECT_FILE environment variable to locate the configuration file.

If MESSAGING_CONNECT_FILE is not set, AMQ Python searches for a file named connect.json at the following locations and in the order shown. It stops at the first match it encounters.

On Linux:

  1. $PWD/connect.json, where $PWD is the current working directory of the client process
  2. $HOME/.config/messaging/connect.json, where $HOME is the current user home directory
  3. /etc/messaging/connect.json

On Windows:

  1. %cd%/connect.json, where %cd% is the current working directory of the client process

If no connect.json file is found, the library uses default values for all options.

11.2. The file format

The connect.json file contains JSON data, with additional support for JavaScript comments.

All of the configuration attributes are optional or have default values, so a simple example need only provide a few details:

Example: A simple connect.json file

{
    "host": "example.com",
    "user": "alice",
    "password": "secret"
}

SASL and SSL/TLS options are nested under "sasl" and "tls" namespaces:

Example: A connect.json file with SASL and SSL/TLS options

{
    "host": "example.com",
    "user": "ortega",
    "password": "secret",
    "sasl": {
        "mechanisms": ["SCRAM-SHA-1", "SCRAM-SHA-256"]
    },
    "tls": {
        "cert": "/home/ortega/cert.pem",
        "key": "/home/ortega/key.pem"
    }
}

11.3. Configuration options

The option keys containing a dot (.) represent attributes nested inside a namespace.

Table 11.1. Configuration options in connect.json

KeyValue typeDefault valueDescription

scheme

string

"amqps"

"amqp" for cleartext or "amqps" for SSL/TLS

host

string

"localhost"

The hostname or IP address of the remote host

port

string or number

"amqps"

A port number or port literal

user

string

None

The user name for authentication

password

string

None

The password for authentication

sasl.mechanisms

list or string

None (system defaults)

A JSON list of enabled SASL mechanisms. A bare string represents one mechanism. If none are specified, the client uses the default mechanisms provided by the system.

sasl.allow_insecure

boolean

false

Enable mechanisms that send cleartext passwords

tls.cert

string

None

The filename or database ID of the client certificate

tls.key

string

None

The filename or database ID of the private key for the client certificate

tls.ca

string

None

The filename, directory, or database ID of the CA certificate

tls.verify

boolean

true

Require a valid server certificate with a matching hostname

Chapter 12. Interoperability

This chapter discusses how to use AMQ Python in combination with other AMQ components. For an overview of the compatibility of AMQ components, see the product introduction.

12.1. Interoperating with other AMQP clients

AMQP messages are composed using the AMQP type system. This common format is one of the reasons AMQP clients in different languages are able to interoperate with each other.

When sending messages, AMQ Python automatically converts language-native types to AMQP-encoded data. When receiving messages, the reverse conversion takes place.

Note

More information about AMQP types is available at the interactive type reference maintained by the Apache Qpid project.

Table 12.1. AMQP types

AMQP typeDescription

null

An empty value

boolean

A true or false value

char

A single Unicode character

string

A sequence of Unicode characters

binary

A sequence of bytes

byte

A signed 8-bit integer

short

A signed 16-bit integer

int

A signed 32-bit integer

long

A signed 64-bit integer

ubyte

An unsigned 8-bit integer

ushort

An unsigned 16-bit integer

uint

An unsigned 32-bit integer

ulong

An unsigned 64-bit integer

float

A 32-bit floating point number

double

A 64-bit floating point number

array

A sequence of values of a single type

list

A sequence of values of variable type

map

A mapping from distinct keys to values

uuid

A universally unique identifier

symbol

A 7-bit ASCII string from a constrained domain

timestamp

An absolute point in time

Table 12.2. AMQ Python types before encoding and after decoding

AMQP typeAMQ Python type before encodingAMQ Python type after decoding

null

None

None

boolean

bool

bool

char

proton.char

unicode

string

unicode

unicode

binary

bytes

bytes

byte

proton.byte

int

short

proton.short

int

int

proton.int32

long

long

long

long

ubyte

proton.ubyte

long

ushort

proton.ushort

long

uint

proton.uint

long

ulong

proton.ulong

long

float

proton.float32

float

double

float

float

array

proton.Array

proton.Array

list

list

list

map

dict

dict

symbol

proton.symbol

str

timestamp

proton.timestamp

long

Table 12.3. AMQ Python and other AMQ client types (1 of 2)

AMQ Python type before encodingAMQ C++ typeAMQ JavaScript type

None

nullptr

null

bool

bool

boolean

proton.char

wchar_t

number

unicode

std::string

string

bytes

proton::binary

string

proton.byte

int8_t

number

proton.short

int16_t

number

proton.int32

int32_t

number

long

int64_t

number

proton.ubyte

uint8_t

number

proton.ushort

uint16_t

number

proton.uint

uint32_t

number

proton.ulong

uint64_t

number

proton.float32

float

number

float

double

number

proton.Array

-

Array

list

std::vector

Array

dict

std::map

object

uuid.UUID

proton::uuid

number

proton.symbol

proton::symbol

string

proton.timestamp

proton::timestamp

number

Table 12.4. AMQ Python and other AMQ client types (2 of 2)

AMQ Python type before encodingAMQ .NET typeAMQ Ruby type

None

null

nil

bool

System.Boolean

true, false

proton.char

System.Char

String

unicode

System.String

String

bytes

System.Byte[]

String

proton.byte

System.SByte

Integer

proton.short

System.Int16

Integer

proton.int32

System.Int32

Integer

long

System.Int64

Integer

proton.ubyte

System.Byte

Integer

proton.ushort

System.UInt16

Integer

proton.uint

System.UInt32

Integer

proton.ulong

System.UInt64

Integer

proton.float32

System.Single

Float

float

System.Double

Float

proton.Array

-

Array

list

Amqp.List

Array

dict

Amqp.Map

Hash

uuid.UUID

System.Guid

-

proton.symbol

Amqp.Symbol

Symbol

proton.timestamp

System.DateTime

Time

12.2. Interoperating with AMQ JMS

AMQP defines a standard mapping to the JMS messaging model. This section discusses the various aspects of that mapping. For more information, see the AMQ JMS Interoperability chapter.

JMS message types

AMQ Python provides a single message type whose body type can vary. By contrast, the JMS API uses different message types to represent different kinds of data. The table below indicates how particular body types map to JMS message types.

For more explicit control of the resulting JMS message type, you can set the x-opt-jms-msg-type message annotation. See the AMQ JMS Interoperability chapter for more information.

Table 12.5. AMQ Python and JMS message types

AMQ Python body typeJMS message type

unicode

TextMessage

None

TextMessage

bytes

BytesMessage

Any other type

ObjectMessage

12.3. Connecting to AMQ Broker

AMQ Broker is designed to interoperate with AMQP 1.0 clients. Check the following to ensure the broker is configured for AMQP messaging:

  • Port 5672 in the network firewall is open.
  • The AMQ Broker AMQP acceptor is enabled. See Default acceptor settings.
  • The necessary addresses are configured on the broker. See Addresses, Queues, and Topics.
  • The broker is configured to permit access from your client, and the client is configured to send the required credentials. See Broker Security.

12.4. Connecting to AMQ Interconnect

AMQ Interconnect works with any AMQP 1.0 client. Check the following to ensure the components are configured correctly:

  • Port 5672 in the network firewall is open.
  • The router is configured to permit access from your client, and the client is configured to send the required credentials. See Securing network connections.

Appendix A. Using your subscription

AMQ is provided through a software subscription. To manage your subscriptions, access your account at the Red Hat Customer Portal.

A.1. Accessing your account

Procedure

  1. Go to access.redhat.com.
  2. If you do not already have an account, create one.
  3. Log in to your account.

A.2. Activating a subscription

Procedure

  1. Go to access.redhat.com.
  2. Navigate to My Subscriptions.
  3. Navigate to Activate a subscription and enter your 16-digit activation number.

A.3. Downloading release files

To access .zip, .tar.gz, and other release files, use the customer portal to find the relevant files for download. If you are using RPM packages or the Red Hat Maven repository, this step is not required.

Procedure

  1. Open a browser and log in to the Red Hat Customer Portal Product Downloads page at access.redhat.com/downloads.
  2. Locate the Red Hat AMQ entries in the INTEGRATION AND AUTOMATION category.
  3. Select the desired AMQ product. The Software Downloads page opens.
  4. Click the Download link for your component.

A.4. Registering your system for packages

To install RPM packages on Red Hat Enterprise Linux, your system must be registered. If you are using downloaded release files, this step is not required.

Procedure

  1. Go to access.redhat.com.
  2. Navigate to Registration Assistant.
  3. Select your OS version and continue to the next page.
  4. Use the listed command in your system terminal to complete the registration.

For more information, see How to Register and Subscribe a System to the Red Hat Customer Portal.

Appendix B. Using Red Hat Enterprise Linux packages

This section describes how to use software delivered as RPM packages for Red Hat Enterprise Linux.

B.1. Overview

A component such as a library or server often has multiple packages associated with it. You do not have to install them all. You can install only the ones you need.

The primary package typically has the simplest name, without additional qualifiers. This package provides all the required interfaces for using the component at program run time.

Packages with names ending in -devel contain headers for C and C++ libraries. These are required at compile time to build programs that depend on this package.

Packages with names ending in -docs contain documentation and example programs for the component.

For more information about using RPM packages, see one of the following resources:

B.2. Searching for packages

To search for packages, use the yum search command. The search results include package names, which you can use as the value for <package> in the other commands listed in this section.

$ yum search <keyword>...

B.3. Installing packages

To install packages, use the yum install command.

$ sudo yum install <package>...

B.4. Querying package information

To list the packages installed in your system, use the rpm -qa command.

$ rpm -qa

To get information about a particular package, use the rpm -qi command.

$ rpm -qi <package>

To list all the files associated with a package, use the rpm -ql command.

$ rpm -ql <package>

Appendix C. Using AMQ Broker with the examples

The AMQ Python examples require a running message broker with a queue named examples. Use the procedures below to install and start the broker and define the queue.

C.1. Installing the broker

Follow the instructions in Getting Started with AMQ Broker to install the broker and create a broker instance. Enable anonymous access.

The following procedures refer to the location of the broker instance as <broker-instance-dir>.

C.2. Starting the broker

Procedure

  1. Use the artemis run command to start the broker.

    $ <broker-instance-dir>/bin/artemis run
  2. Check the console output for any critical errors logged during startup. The broker logs Server is now live when it is ready.

    $ example-broker/bin/artemis run
               __  __  ____    ____            _
         /\   |  \/  |/ __ \  |  _ \          | |
        /  \  | \  / | |  | | | |_) |_ __ ___ | | _____ _ __
       / /\ \ | |\/| | |  | | |  _ <| '__/ _ \| |/ / _ \ '__|
      / ____ \| |  | | |__| | | |_) | | | (_) |   <  __/ |
     /_/    \_\_|  |_|\___\_\ |____/|_|  \___/|_|\_\___|_|
    
     Red Hat AMQ <version>
    
    2020-06-03 12:12:11,807 INFO  [org.apache.activemq.artemis.integration.bootstrap] AMQ101000: Starting ActiveMQ Artemis Server
    ...
    2020-06-03 12:12:12,336 INFO  [org.apache.activemq.artemis.core.server] AMQ221007: Server is now live
    ...

C.3. Creating a queue

In a new terminal, use the artemis queue command to create a queue named examples.

$ <broker-instance-dir>/bin/artemis queue create --name examples --address examples --auto-create-address --anycast

You are prompted to answer a series of yes or no questions. Answer N for no to all of them.

Once the queue is created, the broker is ready for use with the example programs.

C.4. Stopping the broker

When you are done running the examples, use the artemis stop command to stop the broker.

$ <broker-instance-dir>/bin/artemis stop

Revised on 2020-06-16 17:53:14 UTC

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