L6 - Monolithic vs. Microservice Application Architecture 2/2

Question 1

Cons of client-side service discovery

Answer 1

• couples the client with the service registry
• implementation of client-side service discovery logic for each programming language and framework used by service clients

Question 2

What is server-side discovery?

Answer 2

• client requests a service via a load balancer
• the load balancer queries the service registry and routes each request to an available service instance

Question 3

Example of server-side service discovery

Answer 3

AWS Elastic LB

Question 4

Pros of server-side discovery

Answer 4

• details of the discovery are abstracted away from the client
• eliminates the need to implement discovery logic for each programming language and framework used by your service clients

Question 5

Cons of server-side discovery

Answer 5

• requires load balancer

Question 6

Immediate failure

Answer 6

Question 7

Timeout fialure

Answer 7

Question 8

Cascade failure

Answer 8

Question 9

Timeout Failure Solution

Answer 9

order service stops calling for some time. Then calls to the payment service are allowed partially.

Question 10

What is a circuit breaker?

Answer 10

It intercepts all requests from the order service to the payment service.

Question 11

How does the circuit breaker work?

Answer 11

Question 12

What is ramped - slow roll out?

Answer 12

the number of instances of the old version is decreased and the new version is increased until the correct number of service instances is reached

Question 13

Pros of ramped - slow roll out?

Answer 13

• version is slowly released across instances
• convenient for stateful applications that can handle rebalancing of the data

Question 14

What is a stateful application?

Answer 14

Stateful applications save data to persistent disk storage for use by the server, by clients, and by other applications.

Question 15

What are the cons of a ramped - slow roll out?

Answer 15

• rollout/rollback can take time
• supporting multiple APIs is hard
• no control over traffic

Question 16

What is Blue/Green?

Answer 16

• the green version of the application is deployed alongside the blue version. After testing the new version, update the load balancer to send traffic to the new version.

Question 17

Pros of Blue/Green?

Answer 17

• instant rollout/rollback
• avoid versioning issues

Question 18

Cons of Blue/Green?

Answer 18

• requires double the resources
• proper test of the entire platform should be done before releasing to production.

Question 19

What is canary deployment?

Answer 19

• a canary deployment consists of routing a subset of users to a new functionality
• e.g. 35% of traffic to new version

Question 20

Pros of Canary

Answer 20

• version released for a subset of users
• convenient for error rate and performance monitoring
• fast rollback

Question 21

Cons of Canary

Answer 21

• slow rollout
• fine-tuned traffic distribution can be expensive

Question 22

What is A/B testing?

Answer 22

• distributing traffic amongst versions based on a few parameters (cookie, user agent, etc.)

Question 23

Pros of A/B testing

Answer 23

• intelligent load balancing
• several versions running in parallel
• full control over the traffic distribution