amazonsqs

Simple Queue Service (Amazon SQS)

AWS Page

Example Usage

• As a queue of work where each message is a task that needs to be completed by a process. One or many computers can read tasks from the queue and perform them.
• A browser-based application receive notifications from a server. The application server can add the notifications to a queue, which the browser can poll – even if there is a firewall between them.
• Keeping notifications of significant events in a business process in an Amazon SQS queue. Each event can have a corresponding message in a queue, and applications that need to be aware of the event can read and process the messages.

Basic approach is to use SQS queues to hold requests for work to be done…You could have a variable number of worker servers (possibly EC2 instances?) that read messages from the queue and perform the actual work.You might want to have those servers store any results that are generated into some accessible and reliable storage service like S3…The very last actions the worker server should perform would be to write a message to a status queue describing the work it has just completed and then delete the request message from the input queue…You then need to process the status messages written by the workers, bundle up the results and send them to your clients (or report on failures).

Security

Queue owners can control which Amazon SQS users are allowed to write messages to or read messages from their queue – Access Keys or X.509 certificates. For additional security, the applications using Amazon SQS can be built to encrypt messages before they are placed in a queue.

Concurrent access

Every Amazon SQS queue has a configurable visibility timeout. For the designated amount of time after a message is read from a queue, it will not be visible to any other reader.In the event that the computer processing the message fails or becomes unavailable, the message will again become visible to any computer reading the queue once the visibility timeout ends. Amazon SQS users may keep their messages in a queue for up to 15 days, after which Amazon no longer guarantees that enqueued messages will remain available.

Limits

Amazon SQS messages can contain up to 256 KB of text data, including XML, JSON and unformatted text. A single queue may contain an unlimited number of messages, and a developer may create an unlimited number of queues.

Pricing

• Pay only for what you use. There is no minimum fee, and no start-up cost.
• $0.10 per 1,000 messages sent ($0.0001 per message sent)
• $0.20 per GB of data transferred