This document provides an overview of several AWS application services including SQS, SNS, Cognito, API Gateway, and WebSockets. It describes how SQS uses queues to asynchronously and reliably deliver messages between distributed components. SNS is a pub/sub messaging service that decouples systems using an event-driven model. Cognito provides authentication, authorization, and user management for web and mobile apps. API Gateway acts as a facade and endpoint for RESTful APIs. WebSockets in AWS can enable real-time communication using services like IoT and AppSync.

1. Ch7. Integrating
Application Services

2. Contents
• SQS
• SNS
• Cognito
• API Gateway
• WebSockets in AWS

3. 1. SQS (Simple Queue Service)

4. The problem of delivering a
letter
• Failed to find the recipient in time.
• lose the letter in the process.

5. Messaging services
• An intermediary that has the main responsibility of
delivering the message and guaranteeing the delivery.
• These systems are designed to provide a communication
buffer between distributed components.
• producers (senders) -> broker (queues) -> receivers

6. SQS
• Simple Queue Service (SQS，訊息佇列列服務)

7. Asynchrony
• send-and-forget (fire-and-forget) & store and forward (儲
存與轉發) approach.
• Can be used for batch processing (批次處理理) and
coordinating message processing in different schedules.
SQS can also be used for batch processing and coordinating message processing in
different schedules.

8. SQS
• SQS is designed with high scalability, availability, and
reliability.
• this service is vendor neutral.
• This service availability is achieved by storing every
received message in multiple availability zones.
• Allows multiple producers on the same queue and
multiple consumers on the same queue.

9. Security
• Transport Level Security (TLS)
• Encrypted with a unique cryptographic key
• IAM

10. Security - Encryption

11. Durability（持續性）
• Default: 4 days.
• Range: 1 minutes ~ 14 days

12. Multiple AZs & Weighted
Random Distribution

13. Queue Types
• Standard Queues:
• Unlimited Throughput
• At-Least-Once Delivery
• Best-Effort Ordering. (盡⼒力力按順序傳遞)
• FIFO Queues:
• High Throughput,
• Exactly-Once Processing
• First-In-First-Out Delivery.

14. Polling (輪輪詢)
• The way SQS retrieves messages depends on factors
such as the message volume (greater than 1,000) and the
polling (pooling) configuration specified at the message or
the queue level.
• Amazon SQS provides 2 kinds of polling to receive
messages from a queue:
• Short Polling (default)
• Long Polling

15. Short Polling (短輪輪詢)
• The ReceiveMessage request queries only a subset of
the servers (weighted random distribution) to find
messages that are available to include in the response.
• Amazon SQS sends the response right away, even if the
query found no messages.

16. Long Polling (長輪輪詢)
• The ReceiveMessage request queries all of the servers for
messages.
• Amazon SQS sends the response after it collects the
maximum number of messages for the response, or when
the ReceiveMessage polling wait time expires.
• Benefits:
• Minimize CPU client cycles and diminishing costs,
avoiding unnecessary requests to the service API.

17. Messaging patterns
• Queuing chain pattern（佇列列鏈表模式）:
• Problem to Be Solved:
• A tendency for performance bottlenecks to result from
having the systems tightly linked to each other.
• Hard to recover when there has been a failure.
• Solution:
• Loosely coupling the systems by between systems using
queues, and then exchanging messages that transfer jobs.

18. • image source: http://en.clouddesignpattern.org/index.php/CDP:Queuing_Chain_Pattern

19. Messaging patterns
• Benefits:
• Use asynchronous processing to return responses
quickly.
• Structure the system through loose coupling of simple
processes.
• You can increase or decrease the number of instances.
• Robust to failure.

20. Messaging patterns
• Job observer Pattern:
• Problem to Be Solved:
• Unanticipatedly large load on the batch system.
• Solution:
• Use tool such as CloudWatch to monitor the volume
of job requests (the number of SQS messages), so
that the batch servers can be added or deleted
automatically as required.

21. • image source: http://en.clouddesignpattern.org/index.php/CDP:Job_Observer_Pattern

22. Messaging patterns
• Priority queue pattern:
• Problem:
• There are cases where a large number of batch jobs
may need processing, and where the the jobs may
need to be re-prioritized.
• Solution:
• A queue is used in controlling batch jobs. The queue
need only be provided with priority numbers.

23. • source image: http://en.clouddesignpattern.org/index.php/CDP:Priority_Queue_Pattern

24. 2. SNS (Simple Notification Service)

25. SNS
• Simple Notification Service (SNS)
• A messaging service designed to work with publisher/
subscriber semantics by decoupling distributed system
components using an event model based on
asynchronous push messaging.
• Message:
• payload (can be encrypted) and attributes
• Maximum limit of 256 KB

26. SNS
• Publisher:
• Produce and send a message to a topic.
• Topic:
• A logical access point and communication channel.
• Subscribers:
• Consume or receive the message or notification over
one of the supported protocols (e.g. SNS) when they
are subscribed to the topic.

27. SNS
• 1 to N (one to many)
image source:https://aws.amazon.com/pub-sub-messaging/

28. SNS
• Messages will be delivered to all the channel's
subscribers, and subscribers who arrive late will lose their
sent messages.
• This kind of messaging is excellent for orchestrating
communications between micro services, and every
listening party chooses to process the message of drop it.
• Once a message has been sent, it cannot be sent again.

29. SNS
• Fanout (the number of inputs that can be connected to a
specified output) 廣播模式:
• A single published message can be copied on to
multiple destinations

30. SNS

31. 3. Cognito

32. Cognito
• Amazon Cognito provides authentication (認證),
authorization (授權), and user management for your web
and mobile apps.
• Your users can sign in directly with a user name and
password, or through a third party such as Facebook,
Amazon, Google or Apple.

33. Cognito
• Federation Identity (⾝身分識別聯聯盟):
• Use existing credentials in multiple authentication facades
• 1. Cognito user pools:
• A serverless managed database that you can use to
authenticate your web and mobile apps.
• 2. Cognito identity pools:
• Enable you to grant your users access to other AWS services.
You can use identity pools and user pools separately or
together.

34. Cognito
• Cognito user pools:
• Signing up and signing in
• Updating the user profile data via standard and custom
attributes
• Forgot password by providing challenges
• Token-based authentication for JSON Web Tokens
(JWTs)
• Email and SMS two-factor verification

35. Cognito
• image source: https://www.notsosecure.com/hacking-
aws-cognito-misconfigurations/

36. 4. API Gateway

37. API Gateway
• A service facade for RESTFul applications, the REST
architectural approach that integrates via web services.
• The API exposes a series of resources in a stateless
manner, and applications interact
with verbs (GET, POST, PUSH, DELETE), indicating the
server operation to be done.

38. API Gateway

39. API Gateway

40. API Gateway
• The endpoint can be configured with the following
scopes:

41. API Gateway
• The integration request can be made with one of the
following:
• Lambda function
• HTTP
• Mock
• AWS service
• VPC Link

42. 5. WebSockets in AWS

43. WebSocket
• Provide bi-directional communication between the client and the
server to reach real-time applications:
• AWS IoT:
• A service designed to connect objects to the IoT via the SDK;
you can use the WebSockets via MQTT to push messages
back to the client.
• AWS AppSync:
• Supports the WebSockets protocol, and it can push
messages published to subscribers listening to specific
topics.

44. Resources
• 程式設計冪等設計：資料最終⼀一致性的保證
• Amazon SQS Queue Types
• Amazon SQS short and long polling
• CDP:Queuing Chain Pattern
• CDP:Job Observer Pattern
• What Is Amazon Cognito?
• WS-Federation⼆二三事

45. Thank You