Module W5.4 Communication Technologies-AMQP
Communication Technologies
--- AMQP
Items in this lesson
Communication Technologies
--- AMQP
Module Outline
Objectives
On completing this module, you will be able to:
Identify the communication patterns which are suitable for a given scenario
Implement the communication patterns in a given scenario by using different communication technologies
Topics
Implementation of communication patterns
AMQP
Bookstore Scenario
Order
Shipping Record
5. Send the newly created order
{ order }
1. Send the order information
{cart items}
4. Send the ordering activity
Example: Microservice Interaction Diagram
– A customer places an order: Communication via HTTP & Messaging
Activity Log
Error
6. Return the created shipping record or error
4
Select the books to order and see the ordering results
Place an Order
7. Return the created order and shipping record and/or error
2. Send the order information
{cart items}
3. Return the newly created order
{ order }
3. or 6. If error from any service, send error
Producer/sender of request data
Consumer/receiver of request data
HTTP
HTTP
HTTP
Messaging
Choices of Communication Technologies
P1 – If a process or a user needs an immediate response, then the communication with all the relevant underlying microservices should use invocation-based, synchronous communication.
To make it straightforward in receiving a response and avoid the perception of no reaction or slow performance
P2 – If a process or a user does not need an immediate response (i.e., the process may be long-running or the user may interact at later time), then the communication with all the relevant underlying microservices should use message-based, asynchronous communication.
Order
Shipping Record
5. Send the newly created order
{ order }
1. Send the order information
{cart items}
4. Send the ordering activity
Example: Microservice Interaction Diagram
– A customer places an order: Communication via HTTP & AMQP
Activity Log
Error
6. Return the created shipping record or error
6
Select the books to order and see the ordering results
Place an Order
7. Return the created order and shipping record and/or error
2. Send the order information
{cart items}
3. Return the newly created order
{ order }
3. or 6. If error from any service, send error
Producer/sender of request data
Consumer/receiver of request data
HTTP
HTTP
HTTP
AMQP
AMQP
Scenario Diagram - Sample Communication Patterns
If Order creation succeeds and Shipping Record creation succeeds:
"Place an Order" -> "Activity Log": One-to-one, fire-forget
If Order creation succeeds and Shipping Record creation fails:
"Place an Order" -> "Activity Log": One-to-one, fire-forget
"Place an Order" -> "Error": One-to-one, fire-forget
If Order creation fails:
"Place an Order" -> "Activity Log" and "Error": One-to-two, fire-forget
Place an Order
Activity Log
Error
If error from any service, activate the error handler
4. Send the order activity for recording
AMQP
AMQP
Implementation: AMQP with Direct Exchange
Place an Order
Activity
Log
Error
Sender
Receiver
Receiver
AMQP Code
AMQP Code
AMQP Code
order.error
order.info
shipping.error
Error
Activity_Log
The queue(s) are bound to a direct exchange with specific binding key(s);
The receiver(s) connect to the broker and wait for messages from specific queue(s);
Data is passed in the form of AMQP messages;
When sending a message to the broker, the sender sets the routing key of the message according to the binding key of intended receiving queue(s);
After sending a message to the broker, the sender doesn't have to wait for a reply before doing other things;
connect & subscribe
connect & subscribe
connect & publish
Implementation: AMQP with Fanout Exchange
Place an Order
Activity
Log
Error
Sender
Receiver
Receiver
AMQP Code
AMQP Code
AMQP Code
The queue(s) are bound to a fanout exchange with no binding key;
The receiver(s) connect to the broker and wait for messages from specific queue(s);
Every queue bound to the exchange gets every message sent to the exchange;
Error
Activity_Log
connect & subscribe
connect & subscribe
connect & publish
Implementation: AMQP with Topic Exchange
Place an Order
Activity
Log
Error
Receiver
Receiver
AMQP Code
AMQP Code
AMQP Code
*.error
#
The queue(s) are bound to a topic exchange with binding key(s) or pattern(s);
The receiver(s) connect to the broker and wait for messages from specific queue(s);
A message is routed to the queue(s) whose binding key/pattern matches the routing key of the message.
Error
Activity_Log
connect & subscribe
connect & subscribe
connect & publish
Sender
Implementation: Load Balancing among AMQP Consumers
Place an Order
Error
Error
Error
Sender
All receivers subscribed to the same queue take turns to retrieve a message from the queue; this is a round-robin mode
The workload of receiving and processing data is thus (often) evenly distributed among all the receivers, which is known as load balancing, and the queue acts as a load balancer
AMQP Code
AMQP Code
AMQP Code
AMQP Code
load balancing
Receiver (instance 1)
Receiver (instance 2)
Receiver (instance …)
*.error
Error
Order
Shipping Record
5. Send the newly created order
{ order }
1. Send the order information
{cart items}
Example: Microservice Interaction Diagram
– A customer places an order: Communication via HTTP & AMQP
Activity Log
Error
6. Return the created shipping record or error
12
Place an Order
7. Return the created order and shipping record and/or error
2. Send the order information
{cart items}
3. Return the newly created order
{ order }
Producer/sender of request data
Consumer/receiver of request data
HTTP
HTTP
HTTP
4. Send the ordering activity
3. or 6. If error from any service, send error
key = *.error
key = order.*
