Implementing Queue Expiration w/RabbitMQ

The latest versions of RabbitMQ support a feature where idle queues can be automatically deleted from the server.  For queues used in an RPC or workflow model this can save a lot of grief - as the consumers for these queues typically vanish leaving the queue behind. Over time these unused queues accumulate and consume resources on the server(s). If you are using pyamqplib setting the expiration on a queue is as simple as:

import amqplib.client_0_8 as amq
connection = amq.Connection(host="localhost:5672", userid=*, password=*, virtual_host="/", insist=False)
channel = connection.channel()
queue = channel.queue_declare(queue="testQueue", durable=True, exclusive=False, auto_delete=False, arguments={'x-expires': 9000})
channel.exchange_declare(exchange='testExchange', type="fanout", durable=False, auto_delete=False)
channel.queue_bind(queue="testQueue", exchange='exchange')

Now if that queue goes unused for 9 seconds it will be dropped by the server [the value is in milliseconds]. So long as the queue has consumers it will persist, but once the last consumer has disconnected and no further operations have occurred - poof, you get your resources back.


Finding Address Coordinates using Python, SOAP, & the Bing Maps API

Bing maps provides a SOAP API that can be easily accessed via the Python suds module.  Using the API it is trivial to retrieve the coordinates of a postal address.  The only requirement is to acquire a Bing API application key; this process is free, quick, and simple.

import sys, urllib2, suds

if __name__ == '__main__':  
    url = 'http://dev.virtualearth.net/webservices/v1/geocodeservice/geocodeservice.svc?wsdl'
    client = suds.client.Client(url)
    request = client.factory.create('GeocodeRequest')

    credentials = client.factory.create('ns0:Credentials')
    credentials.ApplicationId = 'YOUR-APPLICATION-KEY'
    request.Credentials = credentials

    address = client.factory.create('ns0:Address')
    address.AddressLine = "535 Shirley St. NE"
    address.AdminDistrict = "Michigan"
    address.Locality = "Grand Rapids"      
    address.CountryRegion = "United States"
    request.Address = address

        response = client.service.Geocode(request)    
    except suds.client.WebFault, e:        
        print "ERROR!"        

    locations = response['Results']['GeocodeResult'][0]['Locations']['GeocodeLocation']
    for location in locations:        

If you need to make the request via an HTTP proxy server expand the line client = suds.client.Client(url) to:

    proxy = urllib2.ProxyHandler({'http': 'http://YOUR-PROXY-SERVER:3128'})\
    transport = suds.transport.http.HttpTransport()
    transport.urlopener = urllib2.build_opener(proxy)
    client = suds.client.Client(url, transport=transport)

The results will be Bing API GeocodeLocation objects that have an Longitude and Latitude properties.  Note that you may receive multiple coordinates for an address as there are multiple mechanism for locating an address; the method corresponding to the coordinates is a string in the CalculationMethod property of the GeocodeLocation objects.