Amazon's SQS messaging service has been updated with some interesting new features, as announced in the AWS blog post Powerful New Amazon SQS Features.
The original release of SQS allowed users to set access permissions for their message queues so that third-parties could participate in their messaging system. This feature was deprecated by Amazon in the 2008-01-01 version of the service's API due to unspecified shortcomings in the way the access was handled. Since then, users who relied on queue sharing capabilities for their applications needed to continue using the older API which was due to expire on May 6 this year.
In the new SQS API version 2009-02-01, the service's ability to share queues has been reinstated along with a greatly improved access control model. The Shared Queues feature allows you to grant third-parties access to your message queues using either simple API calls to control principal-based permissions (for other AWS account-holders) or by writing more sophisticated rules using a new Access Policy Language. The policy language provides many more features, including the ability to grant public access or to limit access based on IP address ranges.
Another feature that was lost in the 2008-01-01 API update was the ChangeMessageVisibility operation, which allowed users to change the visibility timeout for a specific message on-demand as well as when the message was delivered. This feature was very useful for delaying the redelivery of a message when it turned out that your application would not be able to process the original message as quickly as expected, a common occurrence in applications that process work units with unpredictable processing times.
This feature too has been reinstated in the new API version under the same name: ChangeMessageVisibility. With this operation you can change/extend a message's visibility timeout up to 12 hours.
SQS has now joined the list of services with endpoints located in Europe, which will make the service perform better for users in that part of the world. This is particularly good news for anyone running EC2 instances in the EU region, because data traffic between these instances and EU-based SQS queues is free.
There is a lot to like in this service update. See the full list of changes, and detailed documentation, in the Amazon Simple Queue Service Developer Guide.