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.. _sample_tutorial:
A sample tutorial
=================
This tutorial will show you how to use Boto3 with an AWS service. In this
sample tutorial, you will learn how to use Boto3 with
`Amazon Simple Queue Service (SQS) <http://aws.amazon.com/documentation/sqs/>`_
SQS
---
SQS allows you to queue and then process messages. This tutorial covers how to
create a new queue, get and use an existing queue, push new messages onto the
queue, and process messages from the queue by using
:ref:`guide_resources` and :ref:`guide_collections`.
Creating a queue
----------------
Queues are created with a name. You may also optionally set queue
attributes, such as the number of seconds to wait before an item may be
processed. The examples below will use the queue name ``test``.
Before creating a queue, you must first get the SQS service resource::
# Get the service resource
sqs = boto3.resource('sqs')
# Create the queue. This returns an SQS.Queue instance
queue = sqs.create_queue(QueueName='test', Attributes={'DelaySeconds': '5'})
# You can now access identifiers and attributes
print(queue.url)
print(queue.attributes.get('DelaySeconds'))
Reference: :py:meth:`SQS.ServiceResource.create_queue`
.. warning::
The code above may throw an exception if you already have a queue named
``test``.
Using an existing queue
-----------------------
It is possible to look up a queue by its name. If the queue does not exist,
then an exception will be thrown::
# Get the service resource
sqs = boto3.resource('sqs')
# Get the queue. This returns an SQS.Queue instance
queue = sqs.get_queue_by_name(QueueName='test')
# You can now access identifiers and attributes
print(queue.url)
print(queue.attributes.get('DelaySeconds'))
It is also possible to list all of your existing queues::
# Print out each queue name, which is part of its ARN
for queue in sqs.queues.all():
print(queue.url)
.. note::
To get the name from a queue, you must use its ARN, which is available
in the queue's ``attributes`` attribute. Using
``queue.attributes['QueueArn'].split(':')[-1]`` will return its name.
Reference: :py:meth:`SQS.ServiceResource.get_queue_by_name`,
:py:attr:`SQS.ServiceResource.queues`
Sending messages
----------------
Sending a message adds it to the end of the queue::
# Get the service resource
sqs = boto3.resource('sqs')
# Get the queue
queue = sqs.get_queue_by_name(QueueName='test')
# Create a new message
response = queue.send_message(MessageBody='world')
# The response is NOT a resource, but gives you a message ID and MD5
print(response.get('MessageId'))
print(response.get('MD5OfMessageBody'))
You can also create messages with custom attributes::
queue.send_message(MessageBody='boto3', MessageAttributes={
'Author': {
'StringValue': 'Daniel',
'DataType': 'String'
}
})
Messages can also be sent in batches. For example, sending the two messages
described above in a single request would look like the following::
response = queue.send_messages(Entries=[
{
'Id': '1',
'MessageBody': 'world'
},
{
'Id': '2',
'MessageBody': 'boto3',
'MessageAttributes': {
'Author': {
'StringValue': 'Daniel',
'DataType': 'String'
}
}
}
])
# Print out any failures
print(response.get('Failed'))
In this case, the response contains lists of ``Successful`` and ``Failed``
messages, so you can retry failures if needed.
Reference: :py:meth:`SQS.Queue.send_message`,
:py:meth:`SQS.Queue.send_messages`
Processing messages
-------------------
Messages are processed in batches::
# Get the service resource
sqs = boto3.resource('sqs')
# Get the queue
queue = sqs.get_queue_by_name(QueueName='test')
# Process messages by printing out body and optional author name
for message in queue.receive_messages(MessageAttributeNames=['Author']):
# Get the custom author message attribute if it was set
author_text = ''
if message.message_attributes is not None:
author_name = message.message_attributes.get('Author').get('StringValue')
if author_name:
author_text = ' ({0})'.format(author_name)
# Print out the body and author (if set)
print('Hello, {0}!{1}'.format(message.body, author_text))
# Let the queue know that the message is processed
message.delete()
Given *only* the messages that were sent in a batch with
:py:meth:`SQS.Queue.send_messages` in the previous section, the above code
will print out::
Hello, world!
Hello, boto3! (Daniel)
Reference: :py:meth:`SQS.Queue.receive_messages`,
:py:meth:`SQS.Message.delete`
|
