Module 7, 8, 9, 10, 11 - Interprocess communication

Question 1

Why is there a need for interprocess communication

Answer 1

1. Exchange data with another microservice

2. Induce status change/invoke business logic in another microservice

Question 2

Types of communication pattern

Answer 2

1. How many receivers
   
   • 1 receiver = one-to-one
   • Many receivers = one-to-many
   • Selected receivers = one-to-selected
2. Does the sender expect a reply
   
   • No: Fire-and-forget
   • Yes: Request- reply

Question 3

Types of communication technologies

Answer 3

1. Invocation-based (HTTP Calls, function calls)

2. Messaging based (go through message broker)

Question 4

Characteristics of invocation-based

Answer 4

1. Tightly coupled (if one go down, cannot work)
2. Code dependencies
3. Don’t need to maintain broker
4. If receiver offline, sender cannot send data

Question 5

Characteristics of messaging-based

Answer 5

1. Single point of failure in the messaging broker
2. Less tightly coupled than invocation
3. Can help facilitate 1-many communication
4. Need to maintain broker
5. Even if receiver die, sender still can send data and data is stored in queue.

Question 6

For messaging-based, does the receiver need to attend to message immediately

Answer 6

No. Messages stored at the queue and the receiver listen to the queue whenever

Question 7

What is inside a message

Answer 7

1. Networking info
2. Properties
3. Message body

Question 8

What is AMQP, RabbitMQ, Pika

Answer 8

Advanced messaging queuing protocol
As long as both sides AMQP compliant, can use AMQP technologies

RabbitMQ is implementation of AMQP
Pika is python module that allows the use of RabbitMQ

Question 9

Types of exchange

Answer 9

1. Direct exchange
   - Deliver message whose routing key matches exactly the binding key of the queue
2. Topic exchange
   - Does wildcard matching between routing key of message and binding key of queue
   - * means exactly 1
   - # means 0 or many
3. Fanout exchange
   - Send the message to every queue bound to the exchange

Question 10

In a request reply, what does the sender need to send

Answer 10

1. Correlation ID

2. Reply-to-queue