How to setup RabbitMQ

The RabbitMQ configuration used in this project is simple. We have a shell script that can be run that adds the new user: Usage with password team15. It also sets up a new vhost usage_vhost that can be specified. Finally, it adds the proper permissions for the new user and vhost as well as the guest and default vhost.

IMPORTANT One final note is that this setup requires that the consumers as defined in the RabbitMWClient package be connected prior to the publisher's first use. This allows the proper queues to be setup in order to allow persistant messages. This can be acheived by modifying and running the TestConsumer.py script.

How to use the RabbitMQClient package

First of all, the package includes:

1. MQClient Class
2. Connection Type - Connection SubTypes: Consumer and Publisher - Each SubType can hold value Normal or value Debug

Just use a simple import statement like so:

from RabbitMQClient import MQClient, Connection, Consumer, Publisher

MQClient Class

The constructor of the MQClient class is as such:

MQClient(
    hostname,
    queue_name,
    user='Usage',
    password='team15',
    vhost='/',
    connection_type=Publisher.Normal)

Where hostname is the IP address or hostname of the RabbitMQ server, queue_name is the name of the queue you want to interact with, user is the RabbitMQ username, password is the User's password, vhost is the virtual host to use, and connection_type is the type of client you want. For connection_type you must choose one of the Connection SubTypes and then choose whether to use the Normal or Debug version. In general, Normal will suffice.

Exceptions

The MQClient constructor will raise ValueError exception is you pass in an invalid argument or something else happens. Be sure to handle this in your code.

Consumer Usage

The Consumer connection type of MQClient can be used to listen to the specified message queue and do something on each message received.

This is done by calling the blocking method MQClient#subscribe like so:

test = MQClient('localhost','example','Usage','team15','usage_vhost',Consumer.Normal)
test.subscribe(callback)

The important part to note is the use of a callback function to handle the messages. As such, you must create or have access to a method to handle the messages you receive with the signature: func(message) where message is a raw string. A simple example is:

def example_handler(msg):
  print("GOT: %s"%(str(msg))

Additionally, note that the subscribe method is blocking so your program cannot execute while this is running. As such, all functionality must be called from your callback function.

Publisher Usage

The Publisher connection type is even easier to use. Once you have you MQClient object, you simple have to call the MQClient#send_message method like so:

test = MQClient('localhost','example','Usage','team15','usage_vhost',Publisher.Normal)
test.send_message(callback)

It is important to note that this method is non-blocking, so once the message is sent you should see a message on the console saying your message is sent. After that, you may call send_message as many times as you need.

Examples

Fully functioning examples are included in the Test*.py files.

Host & Monitor

For bost host and monitor, we have the similar usage as following. When we use it, we have to make sure they are same.

Usage: python pistatd.py [-h] -b MSGBROKER [-p P] [-c C] -k ROUTKEY

Example: pistatd.py -b 127.0.0.1 [-p usage_vhost] [-c Usage:team15] -k host_1

optional arguments:

-h, --help    show this help message and exit
-b MSGBROKER  This is the IP address or named address of the message broker
              to connect to
 -p P         This is the virtual host to connect to on the message broker.
              If not specified, should default to the root virtual host
              (i.e. ‘/’)
 -c C         Use the given credentials when connecting to the message
              broker. If not specified,should default to a guest login
 -k ROUTKEY   The routing key to use for filtering when subscribing to the
              pi_utilization exchange on the message broker