AWS Simple Queue Service
Amazon is a web service that gives you access to a message queue, that can be used to store messages while waiting for a computer to proccess them. Amazon SQS is a distributed messaging queue (one component generates and another component consumes).
- EC2 instances poll SQS for work.
- SQS is a pull base system (SNS is push base system)
- SQS is a great way to decouple your infra.
- Up to 256KB of messages in any format.
- Messages are retrieved using the SQS API
You can build auto scaling groups to handle messages (queue acts as a buffer)
Queue Types
- Standard Queue (default)
- Nearly unlimited number of messages
- Guarantee that the messages will be delivered at least one.
- Best Effort Ordering
- Fifo (good for strict order)
- First In/First Out
- No duplicates
- Message groups
- 300 transactions per second
SQS Key Facts
- Up to 256KB of messages in any format.
- SQS is a pull base system
- Default message retention is 4 days
- Messages can be kept from 1 minute to 14 days
- Guarantees that your messages will be processed at least once.
Visibility Timeout
Visibility timeout is the amount of time that a message is invisible in the queue after a reader picks it up. If the job is not processed within this time the message will become visible again.
- Default Visibility Timeout is 30 seconds
- Maximum is 12 hours
SQS Long Polling
Long polling doesn't return a response until a message arrives in the queue, or the long poll times out
Long polling can save your money
