Section 10 - AWS SQS

Question 1

What is Amazon SQS?

Answer 1

Amazon SQS:

• A message queue service
• decouple applciation components
• messages can be up to 256kb
• pull-based (Not push)
• rmessages can be kept in the queue from one minute to 14 days (The default retention period is four days)

Question 2

What types of Queue are Available?

Answer 2

Two types of Queue:

• Standard queues are default, which privide bets-effort ordering.
  
  • Unlimited Transactions
  • Guarantee
    
    • Guarantees that a message is delivered at least once
  • best-effort ordering which ensures that messages are generally delivered in the same order as they are sent.
  • occasional duplicates
• FIFO (First-in-first-out) queues
  
  • The order in which messages are sent and received is strictly preserved
  • a massage is delivered once and remains available until a consumer processes and deletes it. Duplicates are not introduced.
  • there is a limit of 300 Transactions per second (TPS limit)

Question 3

Amazon SQS Settings?

Answer 3

• Visibility timeout
  
  • Visibility timeout is the amount of time that the message is invisible in the SQS queue after a reader picks up that message.
  • default timeout is 30 seconds for a message to be invisible.
  • the visibility timeout can be changed (Maximum 12 hours)
• Short Polling
  
  • Returns a response immediately even if there message queue is being polled is empty.
  • This can result in a lot of empty responses if nothing is in the queue.
  • you will still pay for these response.
• Long Polling
  
  • Periodically polls the queue
  • Doesn’t return a response until a message arrives in the message queue or the long poll times out.
  • Can save money
  • Long polling is generally preferable to short polling.

Question 4

Amazon SQS Delay Queues?

Answer 4

SQS Delay Queues - postpone delivery of new messages

• Postpone delivery of new messages to a queue for a number of seconds
• Messages sent to the Delay Queue remian invisible to consumers for a duration of the delay period
• Default delay is 0 seconds, maximum is 900 (15 minutes)
• For Standard Queues, changing the setting does’nt affect the delay of messages already in the queue, only new messages
• For FIFO Queues, this affects the delay of messages already in the queue

Question 5

Amazon SQS Large Messages?

Answer 5

Best Practice for Managing Large SQS messages using AWS S3

• For large SQS messages - 256KB up to 2GB in size
• Use S3 to store the messages
• Use Amazon SQS Extended Client Library for Java to manage them
• Cannot use the AWS CLI,AWS Management Cosole, SQS Console, SQS API