CPSC 4820 - DAY 13
MARCH 13, 2018

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Understanding the Properties of Distributed Queues
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Message Order
At least once delivery
message sample

Amazon SQS Features
-------------------

	-Visibility timeout prevents multiple components from processing the 
	same message.

	-When a message is received, it becomes "locked" while being processed.
	This prevents it from being processes by other computers.

	-The component that receives the message processes it and then deletes
	it from the queue.

	-If the message processing fails, the lock will expire and the message
	will be available again (fault tolerance).

	A dead letter queue is a list of messages that cannot be processed.
	It is used to sideline and isolate unsuccessfully processed messages.


Amazon SQS Use Cases
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	-Work Queue
	-Buffering Batch operations
	-Request offloading
	-Fan-out
	-Auto Scaling

Amazon Simple Notification Service (SNS)
----------------------------------------

Amazon SNS enables you to set up, operate and send notifications to subscribing
services and other applications.

Types:

	-Email
	-HTTP/HTTPS
	-Short Message Service (SMS) clients
	-Amazon SQS queues
	-Mobile push messaging
	-AWS Lambda function

+--------------------------+----------------------------+---------------------+
| 			   | Amazon SNS			| Amazon SQS	      |
+--------------------------+----------------------------+---------------------+
| Message persisitence     | 		No		|	Yes	      |
| Delivery Mechanism	   |	Push (passive)		|   Poll (Active)     |
| Producer/consumer	   |  Publish / subscribe	|  Send / receive     |
+--------------------------+----------------------------+---------------------+

Amazon API Gateway
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Allows you to create APIs that act as front doors for your applications to 
access data, business logic, or functionality from your back-end services.

Fully managed and handles all tasks involved in accepting and processing up to
hundreds of thousands of concurrent API calls

Can handle workloads running on:

	-Amazon EC2
	-Amazon Lambda
	-Any web app.

Use AWS Lambda to Decouple your infrastructure

	-AWS Lambda is a good solution for processing data with high
	availability and limited cost footprint.

	-AWS Lambda allows you to further decouple your infrastructure by
	replacing traditional servers with simple microprocesses.

How to use AWS Lambda
---------------------

	1. Upload your code to AWS Lambda in .zip form.
	2. Scheduled function / Event driven function
	3. Specify its necessary compute resources.
	4. Specify its timeout period
	5. Specify the VPC whose resources it needs to access
	6. Launch the function.